locating PONPC on return side, air elimination and zone valve location

archibald tuttle

i've read on a few threads that some hyrdonic boilers, maybe burnham . . . and?? are designed to separate air in the boiler and have a separate small outlet adjacent to the main outlet. i'm realized after looking at one today and checking old threads this might be one. it is a burnham. i didn't inquire into the fine print but it has an additional 3/4" line from the top of the boiler adjacent to the supply. And that mounts both the pressure relief and a spirotop . my first instinct was to move the pump to to the supply side since we will have the mains broken open for some new zone valves.

Aalthough since we what we need to do is pump away from point of no pressure change (PONPC) couldn't i instead leave the pump where it's at and just move the expansion tank which was on the outlet to the return upstream 10 pipe diameters or so from the pump inlet? While i'm aware that the pumps operate fine in the higher temp. environment, jon seignethaler's review on this in plumbing and mech magazine or something like that shows a variant with the expansion tank on the return side of a low loss boiler with the benefit of potentially longer diapraghm life. I haven't gotten scientific doing my own side by sides with pumps on feeds and returns but stands to reason it wouldn't hurt as long as it observes the pump away from PONPC convention.

And as to venting of trapped air, are these air separation boiler designs good enough to fughetaboutit or would this be well served by adding a separator/eliminator on the outlet piping prior to the manifold for various zones.

and, in the same vein, is there any hydraulic or hyrdronic reason why i should prefer zone valves on the feeds vs. returns.

thanks,

brian

Ironman

What type of xtank do you have? If it's the old style open compression tank, then you should NOT have any air separator. The tank receives the air from the top of the boiler and is your means of air removal as well as maintaining the air cushion in the tank. If this is your setup, under no circumstances should you connect the xtank to the return. It must remain connected to the top of the boiler or the top of the supply riser coming out of the boiler.
If you have a diaphragm tank, then you need an MBR (micro bubble resorber) and you could connect to the return, up stream of the pump.

unclejohn

You gave just enough info to keep every one guessing. If you have a old style ceiling mounted expansion tank get rid of it now and replace with a extrol tank. Now where does your feed water enter. It should be right at the extrol tank. If you look at that simple pumping away pipe diagram. If you have the pump on your return and you just move the tank downstream of the pump you will lower the system pressure and add water when the pump starts up the first time. And then instead of a system running pressure of around 18psig you will be around 24 psig. If your boiler is drained and pipes open do it right now you will be happy for every.

Paul48

I'm more inclined to believe that the addition of air removal at the top of the boiler, was more an "oh crap" moment, than any design feature. It is not intended to take the place of an MBR in a system using a diaphragm expansion tank.

archibald tuttle

sorry I wasn't back earlier ( I wish it were easier to do whatever i have to do to get notification of responses.)

i thought when i talked about diaphragm life that you would think i was dealing with a modern expansion tank and not discussing pregnancy prevention. but i did bury the lead on that score.

re uncle john's band . . . eer diagram, this is in low ceiling hemmed by walls and pipes. currently the pump is low on the return just above the drain valve and the expansion tank is located just where it is on the diagram -- meaning things are essentially reversed from where they ought to be.

So I pulled the main feed coming from the top of the boiler and the tank which was a couple feet about the boiler in a tee from that main. my plan was to put the pump on a 12" riser from the boiler but this doesn't leave me the recommending 10 pipe diameters upstream for a tee for the expansion tank.

Nor does it leave me room for an air separator and vent.

archibald tuttle

sorry my computer crashed so i'll pick up where i left off. on the seigenthaler diagram i found linked from an article on an old thread he offered option 2 which had the expansion tank on the return just before the boiler and discussing this in the article pointed out that as long as the boiler did not present significant head loss this was essentially pumping away from the PONPC since the boiler didn't represent a lot of feet of piping and thus the pump was still hyrdraulically close to PONPC even though the boiler intervened.

Then there was a discussion of how this exposed the diaphragm of the expansion tank to lower temps and so you might get a longer life. Don't know if that was apocryphal, evidence based or reasonable supposition. And i wonder how it applies to other components.

Again, on the apocryphal to anecdotal scale, my understanding was the older pumps always went on the return for the same reason (although if the expansion tank was just upstream it seems like that didn't matter so much, the mistake was where the PONPC went and not where the pump went).

so his diagram still had the pump near the exit of the feed and the tank connected near the entry of the return.

but then what occurred to me is, what's the difference in leaving the pump on the return but moving the expansion tank tee to be 10 pipe diameters or so upstream of that on the return just a little further from the boiler?

then I have room on the feed side to put a vertical mounted vent on the 12" nipple from the main and then i jump 12" to an elbow and start the manifold.

and my plan is to put the zone valves on the feed side since I had it open and was reconfiguring, but all the talk about extension of service life with the lower temperatures of the return relative to various parts of the system makes me wonder if i should throw the zones valves on the returns as well.

Thanks,

and i'll try to check back in case there is something i left out about the system that would be useful.

Techman

Curious, in a given 30 year period,and system. How many "old" style ceiling mounted expansion tanks are replaced as compared to, if, the x-tank was the "new" diaphragm style. I'm missing the reason why the new x-tanks are "better" for the system. Tks.

Gordy

I agree with Tech man. I have the steel compression tank with an air trol tank fitting works great. The air baffle at least in the WM is thought out , and does work. I believe Dan our host of this site still has his steel tank.

Now days the diaphram and bladder tanks take up less room in the mechanical room, and it's the modern method. But you can't beat the service life of a steel compression tank.

As far as pumping away on the return side of the boiler it can be done, but it is possible if the system pressure is high due to over the top elevation requiring higher pressure that the circ could pop the relief valve.

As far as uncle johns comment on sucking water in the system. Yes it could but then once system is filled purged I'm in the camp of keeping the fill supply shut off. Then this could not happen.

icesailor

Progress. Not Perfection.

Some live in a perfect world. Others don't.

I can't believe my old dead boss and all the boilers he put in improperly when he worked for someone else and then, when I worked for him. All those HB Smith 2000 and 2500 series boilers done wrong that always worked flawlessly. If they didn't work, I would have been elected to figure out why. All designed and laid out by Reg. Mechanical Engineer that owned the supply company. That supplied all the mills in SE Mass and New Bedford, MA. Those Taco 110's and B&G Series 100's didn't last for squat. on the supply side. And all those package boilers that came from the factory piped wrong with the circulator installed (for convenience I suppose) on the return.

Anyone priced a 30 gallon (12" Diameter X 60" Long) lately? Tucked up tightly up in the ceiling surrounded by pipes. Some of us have found that you can take a #30 or #60 Extrol and add it anywhere you can find to put it near the boiler and oh wondrous of wonders, nothing happens but good.

If the PONC is what is going to send the system down the white porcelain throne with the writing paper from the roll beside it, there are other larger issues to be attended to.

KISS or it might become FUBAR.

That's what I learned by watching and figuring out what the old dead guys did. The number one problem I ever found was lack of adequate system pressure. Pressure equals altitude or head in feet. Maybe those old dead guys would say that the worst thing to happen in modern hydronic systems was the elimination of the high tank in the attic or second floor closet that always kept adequate head pressure on a heating system. As long as the red altitude arrow was on the black mark where the height of the tank was, the system worked. I can't remember any system with adequate pressure for the conditions that wasn't working spiffily. Then, there's the ones that were running less than 10# in a 2 story house with the boiler in the basement.

archibald tuttle

Samuel Johnson's right about Olson Johnson being right . . . eer roger that icesailor. There never was a system i couldn't get working, even with the pump on the return and the expansion tank on the theoretical wrong side of the circulator, by simply increasing the system pressure. three story houses i had to carry it up there to about as high pressure as you could run without tripping the relief or adding additional expansion. every once in a while on the most challenging systems a loop would air up but mostly because pressure went low (thanks to none of the pressure reducing valves ever lasting very long and delivering very accurately.

so, i guess i could have as easily asked, why should bother to change anything given that it has been working fine. (It is the reconfiguring of zones that has me opening it in the first place and there is limited space to work on the supply side of the boiler. This isn't a system that wasn't working well and it is two story, but with low ceilings in basement and upper floors it presents not a lot more head challenge than a raised ranch.)

I've got some Gordy kind of systems where the feed valve is off because it doesn't shut off positively and pressure keeps creeping up over time so the system is tripping the relief. And I've got a few hydronic systems running where there is no make up water. I have to bring it in barrels and pump it into the system.

And now that have that new innovation, the low water cutoff for hydronic installations, love the new TACOs BTW, so this is little less dicey than it might otherwise have been. Although i'm always open to recommendations for a kick **** pressure reducing valve that gives long and accurate service. While in theory the purged system with adequate expansion shouldn't need make-up water, i've got some systems that seem to disappear or seep water that never shows up anywhere as a problem, but the pressure goes low if the feed is off.

never considered that the old style tanks were a 'better' solution. My instinct was that they were a source of air in the system rather than help in removing it. So my instinct was to love the bladder. Maybe there is a 12 step program for that. But bladder tanks were the preemptive norm here when i started on this stuff 40 years ago.

i'm the first guy to buck the conventional wisdom but i was impressionable about these conventions when just starting and this is what all the professionals were doing. so that wasn't one i doubted. maybe it was because amtrol was making their bladder tanks that were like the kleenex of that industy sector right down the street at that point. regional preferences can be established that way.

Now maybe if everything was installed correctly from the pumping away perspective, I could run systems at lower pressure and still get reliable service. And maybe lower pressure has benefits on some equipment life just as modestly lower temperatures might.

So back to me immediate problem. The one instinctive argument against a pump on the return with the PONPC upstream on the return a short distance further from the boiler is that the boiler itself is a source of head. The temperature rise when the boiler is running increases head so the pump is working 'against' that hydraulic phenomenon. But with that increase dispersed around the system by circulation (less piping loss), I feel like this pump on the return option would be fine for my current job and conforms to options Seignthaler presented here in "Pumping away from what". (i had trouble signing onto pluming and mechanical mag to read this and when i finally did the diagrams are tiny and seem to have lost their links to larger versions but you can get the idea).

if there is concern about feedwater 'siphoning', is there any reason not to put the feed on the upstream side? it doesn't have to be at the air separator with the expansion tank. In fact the expansion tank won't be at the air separator in my proposed configuration. Maybe where all this went wrong in the first place was the idea of common tapping the air elimination device for those add ons.

And, bottom line, all the diagrams of the feed side logically place air elimination before the pump. That makes sense if my understanding that the heating and turbulence in the boiler can cause air to come out of solution and you are trying to prevent cavitation in the pump. But most hydronic systems were built using the hard piping off the boiler to support the pump[s]. So the pump was the first thing to come along, not the air elimination.

The availability of air separators that install in a vertical line help with this as i still prefer the close pump location for servicability. I'll take a nice vertically mounted pump accesible without a ladder (or milk crate) every time -- even where we're now using multiple zone valves and a single pump.

what about location of zone valves. I don't think that it looks hydraulically different where the zone valves are on the feed or return, but that is my low level scan of that question. Any sense that you'll get mildly longer life if they are on the returns?

brian

icesailor

You've overwhelmed me.

Hydropneumatic air tanks will absorb the air on the top of the tank. A reason they are not popular. They really don't add any air to the system because the system water doesn't circulate through the tank. If the air charge is lost, there is no place for expansion. Bladder tanks cant let system water come in contact with the air. Bladder tanks are better when properly sized. How many Hydro Tanks have you seen abandoned in place.

When turning on houses that were drained seasonally that had radiators, I always filled by hitting the fast fill and starting on the top floor. And worked my way down. Less walking and more pressure below. Once I had the system filled and the boiler firing, the system ran until the Fall when I would drain it again. No foolishness with going back to vent.

I believe from my heart of hearts that Watts replaced their iron 1156F valves with brass because the screens plugged up and didn't fill boilers. So they failed. I could only buy brass ones. I never had a plugged up brass Watts 1156F in all the time I used the brass ones. Lots of cast iron ones. A few every year. Brass ones would fail when someone used a black nipple to connect the brass valve to a brass/copper adapter into the heating system. The filter screen would become fouled with iron and stop passing water. Or make it so slow that it was hard to purge. But no one else ever had that problem.

If you need a Hydraulic mining pump on a Mod Con boiler like that Alpine boiler needs a 0014 to get enough flow through it, imagine the flow through a Buderus or a Weil-McLain WGO with that same pump.

hot_rod

Air control vs air elimination.

A plain steel tank is considered an air control system, while a diaphragm tank is an air elimination system.

With a plain steel tank you need to maintain that air bubble, and know that the system water will move in and out of the tank. As the water heats and cools some air can be entrained and circulated throughout the system. It's wise to use the correct air control valves with those plain steel tanks,like the B&G Airtrol fittings. You cannot vent the air out of the tank, or you lose the "expansion" mechanism.

Remember also a plain steel tank needs to be about 75% larger than a diaphragm tank, as there is no pre-charge in the tank to work with.

All things consider size, heat loss, maintaining the air bubble, potential air problems if not installed or maintained.. The diaphragm tank is a great improvement for closed loop heating, cooling, and solar systems.

With an air removal, diaphragm tank system you can, and should use a top quality micro-air bubble type of air eliminator. System performance and heat exchange is best when all air, bubbles, entrained, and dissolved air is removed. Only micro-bubble type of air purgers can provide that service.

If you have a chance get a copy of the Amtrol Engineering Handbook, printed in 1977, re-print in 2011. They have excellent info on expansion and tank comparisons. Plenty of math and theory to prove out the concepts

Be glad to send you a sample of the Caleffi Autofill, best, all brass autofill ever to hit the shelves. Set it and forget it.

Gordy

I guess the point is if you have a steel compression tank pumping on the return side into the ponpc, and you do not have issues why change anything. If you want to pump away from the ponpc, and keep a functioning steel compression tank then you have to move the pump to the supply side in order to keep the compression tank to boiler air control baffle link intact.

archibald tuttle

i'm baffled ;-).

this was a baffled tank setup before i got there. so i've learned something about the old air tanks but this is not an exercise in keeping one of those.

Since i'm opening the manifold area near the boiler, even though it has been 'working', i.e. heat runs, pumping toward the ponpc, my concept was best practices would be to have it pump away from ponpc.

while my first instinct is to equate that with pumping away from the boiler, it occurred to me after reading Seignenthalers "Pumping away from what" piece that i could effect the same thing by leaving the pump on the return and moving the expansion tank just upstream of it.

because i have limited space on the feed side to work with, this would leave space to install someone's microbubble separator.

on the fill side. hot rod, i'll PM you. i'm all over trying a caleffi fill valve. it does seem to me that brass is the way to go there. i don't have enough of the recent Taco's which I think are brass relabeled german(?) tech, in service to have a good concept on their longevity and reliability although i don't think it possible for them to be worse than the old onces. but i'd love to get a look at a caleffi, including the ergonomices of fill/purge function.

I've been so disgusted by fill valves, even when they are brand new, and i always found ball valves more convenient for purging anyway, so i always separate the backflow preventer and pressure reducing valve and tee off inbetween with a ball valve controlled fill for purging that hits the manifold somewhere that it can be isolated from the boiler, i.e. from the pressure relief. Not sure i'm ready to forgo that design component but maybe you'll make a believer of me and save me a few tees and valves and the opportunity cost in strategizing where to fit them.

lastly. (maybe i should have made this firstly if i wanted to get an answer but i wanted to reply to all the thoughtful comments so far) no one has taken the bait on zone valve location relative to boiler feed or return or relative to ponpc or relative to . . . ? Does it matter? if not , are cooler locations like the return, preferred.

hot_rod

I agree the circ could stay pumping into the boiler, but I would move the expansion connection tank to the inlet of the circ, as cloae as possible.

With ZVs I have always zoned return side to keep them in the lowest temperature area, and lowest delta P zone. In the end all electricial devices fail from some form of over-heating.

However with a single circ and multiple ZVs, the valves on the supply, downsteam of the circ can provide an additional benefit of preventing ghost flow thru non-active zones. If all the zones take off vertically from the header, you can experience some ghost flows with hot fluid rising up the center, cooler water dropping down the outer layers. A thermo-siphon of sorts.

With a quality zone valve, properly sized pumps, zone valve banging should not be a problem, when installed at the circ discharge.

We use a patented "lost motion" gear in our ZV drive train to disconnect the spring inertia from the drive when the valve closes. It's the spring tension that is wound in the gear train and motor that starts that bounce, that may lead to ZV water hammer.

With a slow motion video you can actually watch common spring return ZVs bounce 3 or 4 times before that shut and seal completely. When you have excessive velocity flowing you get water hammer induced by the close off "bounce".

Disconnecting the spring from the drive train as it closes eliminates any ZV banging issues.

Delta P circs are an excellent match with ZVs also. Banging is eliminated, power consumption cut in 1/2 and correct flow rate is assured to any and all zones when needed.

icesailor

Every modern boiler I have seen in my career has a tapping on the very top, next to the supply outlet for air elimination. To be used for a connection to an expansion tank. Or to be used for a float type device if an Extrol type tank is in place.

"Valve Closing Bounce"?

I never heard of such foolishness. I always used Taco 57* Series Zone Valves. The return spring eliminated any "Bounce" when the plunger closed. If you have so much pressure that the ball is bouncing, you must have a placer mining pump driving the water around the overly restrictive system.

Have any of you taken a close look at these new zone valves? They are wonders of modern technology. Have some of you forgotten about the Italian's Law, Bernoulli's Thingy about fluids traveling in a space at a certain speed, will accelerate while being forced through a restriction? While creating Negative a pressure behind the restriction. Which helps overcome the hold closed spring. Like a Mono-Flow Tee works? You buy a 1" CTS valve with a 3/8" hole in it for the water to go through.

Start using 3 speed circulators. Put them on mining speed. If there's a noise problem, drop them to #1 speed. If the problem goes away, the valve is being over pumped. The system might be another issue.

hot_rod

"Valve Closing Bounce"?

I never heard of such foolishness. I always used Taco 57* Series Zone Valves. The return spring eliminated any "Bounce" when the plunger closed. If you have so much pressure that the ball is bouncing, you must have a placer mining pump driving the water around the overly restrictive system.

Have any of you taken a close look at these new zone valves? They are wonders of modern technology. Have some of you forgotten about the Italian's Law, Bernoulli's Thingy about fluids traveling in a space at a certain speed, will accelerate while being forced through a restriction? While creating Negative a pressure behind the restriction. Which helps overcome the hold closed spring. Like a Mono-Flow Tee works? You buy a 1" CTS valve with a 3/8" hole in it for the water to go through.

So if the know it all Ice man hasn't heard of it, it must not exist??

Zone valve water hammer has been discussed many times on this site, in regards to fast closing flapper or ball style ZVs. The incorrect fix for the HW brand is to remove one of the springs.

The energy hog model you refer to is a thermoelectric valve with a slow open and slow close operation, I'm referring to fast acting ZVs.

Agreed the problem is related to excessive velocity, but ZVs are often used with high head circs and a means to shed excessive energy when you have a row of ZVs connected to one circ is important to understand. A PAB was invented for that purpose, or a delta p circ.

I am familiar with zone valve design being employed by a company that manufactures several million a year of the spring return, thermo-electric, and motorized ball valve styles, sold in 57 countries, so we have a good idea of installations and mis-applied installations. I know the engineers well that design and innovate hydronic components, including zone valves.

There is an important reason valves have different size openings or orifices. Our 3/4" Z-one zone valve is available with a 2.5, 3.5, 5, and 7.5 Cv all with different orifice sizes regardless of the pipe size of the body.

I'm an old dog also, willing and able to learn new tricks.

icesailor

Well then, you just agreed with my long held but longly denied that the cause of some of these problems comes from over-pumping in systems that don't have enough room for fluids to freely flow. I've been able to learn new tricks for years. The hard part was finding someone that knew the tricks and would share them. Like here on The Wall. Where anyone that comes here and doesn't learn something, didn't come here to learn. None of us are born knowing it.

Consider this. The Wright Bros were the first to fly. But FIRST, they had to learn how to fly the thing. They had to design a propeller to power the thing along. The propeller on the Wright Flyer of the 1900's is only slightly less efficient as the most modern aircraft propeller of today. All aircraft and birds fly on the same principle. Bending air. We're still bending air.

If I asked my Wholesale Supplier about different size orifice in your valves (which are excellent), I would have gotten another pile of crap and ridiculed after I left. Or more likely, I would have met you here and learned about the different orifice sizes. Then, gave him the model number of the pump I wanted and why. Then, he would start stocking the pumps I wanted so everyone else would gain from my research and experience.

I don't have to deal with THAT anymore.

Oh yeah. When the water is forced through the restriction in the valve and accelerates out the other end, it doesn't have the same velocity as it had going in. Restriction in feet of head pressure.

archibald tuttle

I love the fall colors here at heating help.

Thanks for the great thoughts on zone valve locations and

OK, so i'll bite.

I have solved the zone valve conundrum for years using circulators. I always hated those old TACO zone valves (not so much on the electric consumption side although there is that) because of the 3 terminal design. That it took them to the very end of the life of that design to finally give it up for an isolated end switch blows my mind. And I like those guys. But I never liked those valves so I didn't use zone valves. I know there were others, even before caleffi, but I had problems with 70s era honeywell eliptical ball designs on fan coil units freezing up 10 to 15 years in service with no practical servicability. So I was gunshy of zone valves and just stuck with pumps.

In all likelihood a great many of those systems are 'overpumped' as everything was an 007 in those days, but it all worked. (notice i didn't say perfectly, but well enough that systems i put in 35 years ago haven't been touched).

Hot Rod can probably tell me how much electricoty I could have saved with economical zone valves and a single pump - although delta P was just a twinkle in someone's eye at that point. But 007s cost about the same as zone valves and seemed to have similar service life and were easily replaceable. So you had $40 or $50 upfront savings (that's the old days of course but power was under a dime a KWH. ANd we were used to the old Red Barons so putting in 007s seemed like an economy measure.) (trust this doesn't violate the little moniker in every window about no discussing price. i'm not trying to parse to 2% difference what competitors are pricing or distributors are selling contemporary specific components for, pitting suppliers who support this site into some kind race to the bottom -- wait is low price the bottom or the top. And even with modern innovations I don't think it is possible to discuss the merits of innovative technologies like delta pumping and ECMs without generically comparing the scale of pricing across the technologies to generic pricing for older technologies. Dan, please cowrong me if i'm wrecked here.)

Just so i'm on the same page insofar as zone valve orifices, i assume you are relating them to desired flow rate for a zone relative to other zones? so they represent something like a fixed balancing valve? It sounds like you buy the valve body with a certain size. Are they changeable? How about an adjustable one?
The european habit of connecting components, inc. pumps and zone valves with unions starts to look handy if you could throw your selected orifice in the union. Easy to change . . .

Why is it that we only use those "G style" [??] unions for fill valves and backflow preventers? They allow 360 degree choice of angle for components (which we can get with swiveling flanges now available although you gotta retrofit). And I think there is probably less material involved in the component and receiver bodies so they should be cheaper than the flanged style?

I concede that flanges have been a pretty bombproof technology and i haven't seen a lot these unions in use on heavier components to see if you get more nuisances leaks or there is some other reason besides our hidebound nature not to convert.

brian

hot_rod

Here is the deal with zone valves. Notice as the Cv is lower the shut off pressure is higher. So basically the smaller the hole, or orfice in a valve, the higher pressure you can shut off.

So a low cv valve is often used on air handlers that may be used on a job with high delta P circs. Consider a large hotel building with hundreds of air coils throughout the building. Down in the mechanical room you may find a circ pump sized to pump the gpm and pressure to flow that entire building. That pump may be developing 50lbs delta P when it runs. A large cv, low shut off pressure, valve would not be able to close off that pressure and leak through.

Typically residential jobs want high flow, large cv valves like a 7.5 Cv = 7.5 gpm with a 1 psi drop. Yes you can flow more than 7.5 gpm thru a 7.5 cv valve, but you need to watch the pressure drop. Either use the graph supplied by the manufacturer, see below for a 3 CV chart, or a spreadsheet like this one below.

The limit to how much flow you can move through a valve, any valve really is the velocity. The guideline is 2-4 fps for hydronic use, some engineers are comfortable with 5 fps.

Above that flow rate you can get noise, corrosion erosion, and shortened service life. The hotter the water the more potential for corrosion erosion.

And of course the pipe size that you connect to the valves has flow limitations. 3/4 copper tube flowing 6.5 gpm will have a velocity of 4fps. So really no need for a 3/4 valve to have a cv larger than 7 or so, for hydronic applications.

DHW and potable water can be designed around 6-8 fps as it is not generally a 24/7 flow like hydronics will be at design conditions.

As for BSP or straight thread. Currently the US is the only country that still sticks to NPT. So most of the products built for the global market, or Euro market are BSP straight thread.

With straight thread the issue of bad threads and unknown torque is a non issue as gaskets or o-rings are used on the valves and devices. Loctite™ "floss" or hemp, or Loctite 575 are the main options for straight pipe threads.

Techman

hotrod, are the BSP straight threads the same as electrical conduit threads?

Ironman

Techman,
As an electrician with over forty years experience, I can tell you that electrical conduit threads are tapered just as plumbing threads are. The couplings that come on the rigid pipe are NOT tapered, but that's also true of the ones that come on black iron sticks.

icesailor

"" Here is the deal with zone valves. Notice as the Cv is lower the shut off pressure is higher. So basically the smaller the hole, or orfice in a valve, the higher pressure you can shut off. ""

That's true. Which way are you supposed to have the flow into the valve. So the flow pressure helps keep it closed? Or that the flow pressure helps it to stay open? I wasn't implying that the paddle/ball type zone valves aren't any good. I've installed them without any trouble. The second generation Taco are fine. I just never allowed myself to get burned with the first generation.

End Switches:

Taco 57* valves have individual end switched. Two actually. One to stop the power to the coil when the plunger reaches the end of its travel, the other NO, closes before the power switch opens. The problem I always found with them was that if there was any sweating or leakage that got on the steel plate that the plunger went through, and rust built up, the plunger couldn't always get back and although the valve was off, the end switch was still closed. If you can't pull the bypass lever all the way down, it was stuck. Properly remove the power head and spray the plunger, stuck in the hole with Kroil. Wait, and with a large pair of water pumps, squeeze the plunger down and release it. Operate it with the pliers as many times as it takes to loosen it up. Once loosened, slather it with Never Seize. Once the power head is back on, spray the lever and where it rides with Kroil of WD-40. You should be able to operate it with your finger and it not hurt your finger. If you find a nest of them, lube up all the levers. Not discussing price but, I always found it easier to repair them rather than replacing the whole valve. If I had a badly leaking plunger, it was always easier and cheaper for the customer to replace the whole plunger assembly and power head from a whole new valve. The valve body can take hours to replace what with not being able to get the trapped water out of the discharge. And if it was a nest of more than two, you going to change one to a new type and leave the orphaned ones?

I have a personal problem with zone valves that have shafts that seal with O-rings, that keep the water out as it revolves how many times in a lifetime? I have a 3-rd degree scar on my right wrist from a burn with a White Rogers 3 wire zone valves. They'd leak and the steam would foul the contacts that operated the motor. The 2-wire ones weren't any better.

Techman

ironman, are the couplings purchased from an electrical supply house tapered?

hot_rod

"" Here is the deal with zone valves. Notice as the Cv is lower the shut off pressure is higher. So basically the smaller the hole, or orfice in a valve, the higher pressure you can shut off. ""

That's true. Which way are you supposed to have the flow into the valve. So the flow pressure helps keep it closed? Or that the flow pressure helps it to stay open? I wasn't implying that the paddle/ball type zone valves aren't any good. I've installed them without any trouble. The second generation Taco are fine. I just never allowed myself to get burned with the first generation.


The flapper, paddle type spring return ZVs use the spring to pull the valve closed in a N.C. type of valve. So the spring needs to have enough tension to close the valve against the pressure provided by the flow.

Most ZVs use a coil type of spring to pull them closed, like a screen door type.

Springs actually have curve charts not unlike a pump curve.

When a screen door is wide open, lots of spring force trying to pull it close, as the door closes the tension lessens.

Caleffi uses a wound spring more like a garage door type spring. This allows a lot more metal and winds and also allows us to use a torque meter and dial in every valve to the same close off tension. So the spring has a very constant torque across it's range compared to a "screen door" type.

Now with more spring to work with we get higher close off, but need a better gear train to open.

Most ZVs use a sheetmetal stamped gear and a pinion on the motor. We use 4 1/4" thick gears and a 21-1 ratio. so our motors use all this gear "advantage to open against higher spring tension.

Here is an example of a caleffi design compared to another well know brand. Notice the gear train and spring differences.

After 30 plus years in the contracting business, the last 8 years working for a manufacturer has taught me a lot about the engineering involved in what seems like a simple valve.

You can build a simple, quick to manufacture pricepoint valve, or engineer it to perform perfectly and last long.

Many failures in components are related to water quality. If valves seize, chew up o-rings, loose switches and motors one of two issues, either poor price point design and materials, or fluid that gums them up over time.

You can engineer out many of the failure points but installation, maintenance, and the fluid inside takes out many valves or devices prematurely.

Ironman

Techman said:

ironman, are the couplings purchased from an electrical supply house tapered?

No, they're not tapered. They're the same as the ones that come on lengths of black iron, only they're galvanized.

archibald tuttle

Hot Rod

>With ZVs I have always zoned return side to keep them in the >lowest temperature area, and lowest delta P zone. In the end >all electricial devices fail from some form of over-heating.

when you say the lowest delta P zone, i assume you mean the lowest delta P area in the near boiler piping as there would be the least delta P across the valve at the apex of the loop -- sort of meaning the apex in height but also the apex in pipe friction terms.

at least that's my instinct. i'm going in there. wicked witch or no wicked with. i just want you to do one thing. talk me out of it.

it certainly is the location of the lowest absolute pressure give or take depending unless the boiler itself has high pressure loss but then i would assume you are running some kind of primary loop or manifold with its own circulation to handle the boiler anyway.

on the tangential question here of threads raised by my reference to "G" style unions -- don't know which electrical conduit threading is being discussed here. thickwall is just like plumbing pipe and has tapered threads to seal. but fittings like romex connectors, or offset nipples generally have pipe standard straight thread.

I forget where the thread conventions for the "G" style unions comes from and whether the threads are BSP straight or something i don't know. Let's just say it is isn't easy coming by the nuts when you need them. In the good old days you used to get one with every fill valve so you could save 'em up when you were doing a replacement but fuggehabod that now. Ditto riser nuts coming with faucets. that's a thing of the past.

last substantive question (I hope) -- having got authorization to leave the pump on the return and move the expansion tank, this leaves me wondering where to put the air elimination. normally -- as in the diagram supplied the air elimination (of course haven't seen a 'scoop' on any new system in about 20 years but I digress) goes before the pump. This would relate to the very idea of putting the point of no pressure change before the pump since the fill and expansion tank are often manifolded with or near the air elimination device.

This makes extra special sense when the pump is on the supply side of the boiler as my real or wives tale version of air coming out of solution is that this is catalyzed in the boiler. So now the question. If I leave the pump on the return and move the PONPC to just upstream of the pump, do I put air elimination just upstream of the pump to guard against cavitation, or just downstream of the boiler to catch the likely source or air, or both is better or put the mircobubble eliminator before the pump and stick with the boiler top tapping for air elimination or . . .

sincerely,

confused in exeter

icesailor

Again I ask. where does all this air come from a month after the system is put on line?

"Exeter"? New Hampshire? Is the earth different way up there as opposed to farther South?

I'm not an expert in this subject but marine propellers cavitate like crazy. Especially the closer you are to the surface with less pressure. Submarines can be tracked with Sonar by the cavitation signals from the spinning props. Nuclear Subs can go to much deeper depths than WW ll subs could. Going deeper and higher pressures cold stop the cavitation. Cavitatiion was worse at the same depth at the equator than it would under the ice at the North Pole. Cavitation is boiling water. Cavitatiion can be dangerous to a submarine in war time. You can be heard and located. BOOM. You're gone.

I noticed long ago that if I heard that "whooshing" noise inside a circulator pump, it would stop if I raised the system pressure.

With shallow well "Jet" water pumps, if they didn't shut off for a variety of reasons, the cavitation would cause friction. The air in the pump case would reduce the ability to continue to lift fresh cold water and the pump would seem to have "lost its prime". The pump case would get very hot to the touch. If you turn off the power to the pump and remove the top plug to add water to prime, it was already full of water. If you turned the power back on to the pump, and the plug was left out, the pump would start pumping water immediately. You could put your hand on the incoming suction pipe and feel it get cold. As long as the pump has cooler water to pump, it won't cavitate. If the flow slows down enough, the pump will cavitate. Just like in a heating system.

If the Sonar man on a Nuke Boat hears the sound of his own boat cavitating, they either slow down the prop, or go deeper for higher pressure to stop the cavitation.

They aren't like displacement water pumps like "1909" Meyers Piston Pumps that pumped 400 Gallons Per Hour regardless if the lift was zero or 27'. They just knocked. The higher the vacuum lift, the louder they knocked. Every back and forth passage of the leathers was two emptying of the cylinder. If the shaft seal was leaking, water would drip when the pump was off, it would suck air in when the pump ran. If the well screen was plugged, it still pumped 400 GPH if it could, and knocked so loud that you could hear it walking up to the pump.

Those zone valves mentioned are just another form of Globe Valve where the force of the fluid flow is supposed to clear the seat. Installed backwards, they just put pressure on the seat. Those ZV's with the rubber seats will have the rubber part worn out by getting hydraulic grooves worn in them while they are trying to close. Especially when closing against mining pumps. That's why systems need expensive ECM pumps that can vary the load.

I have no connection to Taco, but their newer "ESP" zone valves have ball valves in them. It doesn't take some giant power force to open or close them. I just wish they had a bigger port for better flow. Maybe they do have them with bigger ports. No one stocks them or understands why they are better.

And like that photo shown yesterday of someone reducing 1" down to 1/2" Copper and a zone valve or two, you can't stop Hackism by the no nothing Yabutts.

hot_rod

I have no connection to Taco, but their newer "ESP" zone valves have ball valves in them. It doesn't take some giant power force to open or close them. I just wish they had a bigger port for better flow. Maybe they do have them with bigger ports. No one stocks them or understands why they are better.

Ball valves close off flow by "shearing it off" so to speak. So ball type valves are prefered when high shut off pressures are required. Unless the building has a "mother of all pumps" as you have described in many posts I doubt that you ever need to have a 150 psi shutoff ZV in a typical hydronic system??

Good applications for ball style motorized valves would be main water shutoff, maybe a pump and dump geo system. Most residential hydronic circs develop less than 10- 15lbs delta P so a flapper, or disc style valve provides plenty of shut off force. Most flapper or paddle style ZVs have shut off pressures listed to 60lb, Caleffi to 75 Talking about delta P established by the pump, not static fill pressure, of course.

As for high Cv zone valves, what is the application for a Cv 11, 3/4" zone valve? (a typical full port 3/4 ball valve will have a Cv somewhere between 11-13, according to the Watts specs)

Flowing 6.5 GPM thru 3/4 copper tube develops 4fps velocity. Flowing much above that will cause noise, and accelerated erosion. Especially as temperatures are elevated, as in hydronics. Which is why we design around 4 fps max. flows in hydronics. So really the pipe and fittings connected to that valve will limit the accepted flow, as they will be the flow limitation.

There are some good advantages to a motorized ball valves if the operator can be modulated. Now you can do some flow adjusting, possibly temperature mixing. Usually you want a valve with a characterized ball so you don't flow against the sharp edge of a partially closed ball, if the valve is used to modulate flows. Once a typical ball valve closed down to 80% or more you have a not so desirable flow path. Look down a ball valve with the handle closed most of the way.

White Rogers has built the 1361 high flow, spool type ZV for 40 years or more. Some installers like them for indirect tanks where they can pump high flow rates, for short periods of time, not worrying about excessive velocity if the call is 30 minutes or less. If you can figure out the funky 5 terminal wiring on the darn things.

Keep in mind rotating type valves will be very sensitive to hard or crappy fluid conditions. The main failure in those old WR's were stripped or sheared off motor shafts. the motors had boatloads of torque, more that the valve stem could handle.

If I had a dollar for ever WR ZV I replaced with a stuck spool and broken drive Ball style ZVs will be prone to the same seizure if fluid is not maintained properly.

archibald tuttle

icesailor

>where does all the air come from

theory i guess. the point being made I thought was an effort at air elimination in baffled systems.

i agree again that cavitation can most often be cured by simply raising the system pressure.

done it a million times.

but i tend to associates its outbreak with a collection of entrained air at the pump. it isn't that i get cavitation everytime a system heats up.

i am speaking prohylactically here. My experience has also taught me that a good air eliminator limits cavitation and or airlocking from high trapped bubbles without interventions on operating pressure. I've never be one who shyed from running a system at higher than 'standard' pressure, e.g. the 12 psi precharge in the bladder tanks.

so the system is open, i'm going to refill and purge (i set up purge stations differently than most folks as well. i don't use the pressure reducing valve (PRV). I tee between the backflow preventer and the PRV and hit supply manifold with a main shutoff valve isolating the boiler (and, of course, the pressure relief valve) feed and return. then isolate the zone valves on the system side for service and put a bleeding tee in the return just upstream of that isolation.

This has given me pretty effective purging but then the water going in has some air and i you don't always purge the near boiler piping as forcefully or perfectly although you do pretty well, so i think air elimination is necessary so I'm just asking where it would be recommended by best practices in my proposed system design.

i tend to think putting two air eliminators on this system would be over kill but that there should be one so i'm just asking where would be the best spot. Thus I focused on the two areas i have modest knowledge of, managing cavitation at the pump and the tendency of the heating and flows in the boiler to release air which, if not eliminated, could accumulate high in the system causing air locking. -- (a really incredible phenomenon by the way which i first observed in a quick hookup of a baseboard system with clear pex maybe 20 years ago. I could actually watch the air bubbles ghost along as the circulator tried to circulate and then somehow it lost hyrdraulic traction and they slipped back. I don't know if this was simply an indication that in any airlocking circumstance there is some cavitation at the pump -- i can't remember all the noises involved. i only know that purging harder solved the problem and wet the floor as it was temporary hook up and i hadn't give myself isolation from the boiler so as the purge rose to 30 lbs i was testing my pressure relief.

thanks,

brian

PS - get all the discussion about flow rates, but hadn't thought of the contribution of high flow to errosive ciculation. ideally, it would probably really help the industry if a simpl [cost] effective flowmeter were available. all you caleffi and taco heads chime in here. i know i can probably read this back out of various sophisticated control setups, but it is such a basic to what's going on and there are probably zounds of systems out there that could benefit from a simple flowmeter.

of course this doesn't change flows from a single pump when multiple zones open and there is a strong proposition for a load sensitive pumping. i have not seen any figures that suggest to me that the electric savings alone make any sense whatsoever to just through load sensing pumping on, but if it really improves system longevity and can provide flow readouts for service simplicity, i would upsell it alot more.

to have an icesailor moement here though, what is all this about ECM pumps and zone valves.

I have to say, in years of just using 007s with flow checks and no zone valves and not calculating flow rates I've never had a significant internal corrosion problem (at least that has manifested itself in leakage or component failure. the pumps themselves want to be swapped every decade or so but that doesn't seem excessive.

So i keep getting tempted back to pumped loops without zone valves as the simplest most effective hydronic systems i know with modest appreciation for the multizone relays that have become popular for running these systems (although they never put what i want on them for features - including service switch that manually overrides thermostat or takes loop offline altogether, pump cycling with for two pathologies: 1 summer senescence 2 automatically timed runs during setback when outdoor temperature is extremely cold. more wiring space well i'll stop the wish list here but to my knowledge neither of the big competitors in this market has all or even most of those features. and i haven't even really begun my list. but i'd look forward to hearing it is all on the horizon.

I wonder which zone valves, ball, flap, wax motor etc. are going to prove to have the longest service life. although my first exposure to honeywell elipticals made me very skeptical.

finally - OMG i keep thinking of crap - icesailor. No #57 seris TACO zone valve that i have has a fully indendent end switch. they use three terminal for four wires and when we would go over a single transformer -- because of the VA requirements on those we had nothing but problems. and sometimes it caused a problem with a small number of zones where the boiler control had its own transformer that butted heads. nothing but headaches cause they wouldn't put a forth terminal. being local i bitched at them for years about that and now i see you can get them with 4 terminals although the wax motor design is a bit passe. I'm open to the churchillian idea, that its not perfect but better than all the rest. i just want a free 4 wire head to replace every 3 wire i come in contact with.


brian

archibald tuttle

lots of typos as usual in the last post.

but one other thing on overpumping, hijacking my own thread: i would think that would be really important on marginal condensing temps of operation where you have condensing boiler and could result in fuel savings more than the electric savings from the pump itself.

but the vast majority of systems i service simply don't have condensing emitters and even when controlled with outdoor reset don't get to condensing temps so i am in no rush to install condensing boilers (even though the imbecilic utility companies will give their ratepayers money as a bonus for doing it)

brian

hot_rod

You asked which type of valve will have the longest service. Really is has to do with the design and quality of the valve

A few years back a knock off ZV nAmed Sunnywell hit the market. We took one to the lab and put it on a cycle tester. After about 20,000 cycles the bearings and motors were crapping out

A quality valve can be built to last 20 years, millions of cycles. It's all about the quality of the components

Of course fluid quality has a major effect on hydronic components, perhaps the most overlooked piece of hydronics that shortens life cycles

4Johnpipe

Not sure of this was mentioned...An issue with moving EX tank is when zone valves close and the circulator stops. The stacking in the boiler may pop the relief valve. Due to flow checks in circulator. Guess how I know this...LOL

SWEI

Almost any emitter will exhibit condensing-friendly return temps for at least half the heating season. I've been pleasantly surprised at the real-world results we see from systems I would have doubted would really benefit if you had asked me just a few years ago.

icesailor

"" to have an icesailor moment here though, what is all this about ECM pumps and zone valves. ""

I had a home with 5 Taco 573 zone valves and 5 zones. It had a single Taco 007. There was never an issue of the ability to pump. But three of the downstairs zones were quite small. If only one zone called, the pump would be way oversized. As other valves opened, the pump would become more matched. The ECM type pump modulates and matches the load.

I could tell the difference immediately by the sound of the water in the system. I have acutely sensitive hearing.

icesailor

@Hot Rod:

You miss the difference between high flow and pressure through a small port and just flow pressure/turbulence. I'm only saying that I personally would be happier with a larger port on the zone valve. You say that they offer valves with larger ports. Bernoulli's laws are about flowing mediums flowing at some rate and meeting an obstruction. When it meets the obstruction, the medium increases in velocity but the flow stays the same. It's the expansion back to the original that I always wondered about. That's how Monoflow tees and carburetors work.

Even rivers flowing to the sea follow this rule. Water flowing in a river that meets a canyon/obstruction has the same amount of water flowing through the canyon as is flowing to the beginning and the end/outlet. If the canyon/obstruction develops an obstruction, the water backs up until it reaches equilibrium. Whatever the flow into the canyon/obstruction is in the beginning, becomes the same at the exit. Lots of air is added in the turbulence through the canyon/obstruction. Which is critical for the life forms living in the river that depend on dissolved oxygen in the water.