PRV blues.....

kcopp

I have been looking after a system for a couple years now that on and off had been giving me fits w/ leaking pressure relief valves.    12 yr. old System consists of weil GV boiler, Superstor 40, 1 zone HWBB, 2 zones of  Heatway onex. (I posted pictures a while back of the corrosion due to the poor O2 barrier.) I have replaced the 30# prv, turned off the water at the 1156, swapped out the #30 extrol 2 months ago it was fine....until monday. Now when the indirect calls the relief valve weeps. Pressure goes up to 30#....( no heat on in the house as the heating season is "over")

Any thoughts? I don't think its the coil but at this point....ugh!

Charlie from wmass

Leak in the indirect coil or

the 30 is just too small, or the boiler feed valve is passing just a little.

kcopp

the #30 size...

has been fine for 12 years. Even so w/ just the indirect calling there shouldn't be that much system expansion...should there?

Mark Eatherton

Round up the usual suspects.....

Are all pumps pumping away from the PONPC? If no, can the pressure reducing valve "see" the negative pressure being created by the circulator?



Can the DHW loop "see" the expansion tank when it is running (check valve that wasn't working before that suddenly started working)



Has the diaphragm become "stuck" (try firing the space heating system, smallest zone and see what the pressure does)



If it worked before, what's changed since then?



You'll figure it out....



ME

chapchap70

Can you isolate the indirect zone from the rest of the boiler?

I don't know what you mean by "closing at the 1156" so all I have written below may not mean much.



If you shut the valve upstream of the prv, shut the supply and return valves in the indirect zone, and run the heat zones, you may be able to determine if the indirect coil is leaking street pressure into the boiler water.



 If you do not have too much increased pressure when the heat zones are calling and the indirect isolated, the indirect would be the culprit if the increased pressure returns after opening the indirect valves again.

billtwocase

you know what I am going to say

as you would also say, pics please. Any IFC pumps in the mix?  Coil problem with the indirect will show whether it is heating or not. Sounds like the extrol is being isolated when making hot water only

kcopp

The ponoc...

may be a little off as the GV boiler has a circ of its own under the hood. The main has a spirovent which the extrol is attached to. 12" later the circs all come off the supply. they are ifc 15-58. They are all new as I has to replace them due to the O2 corrosion from the H-way Onyx tubing. I turned off the water to the boiler  and waited a day or so. went by yesterday and the pressure was 5 psi.... so that checks off the coil leak. The only circ that has not been replaced in the boiler one... starting to wonder if that is corroded to the extent of the others.

Mark Eatherton

The boiler pump could be your problem...

If it is corroded, AND the DHW coil has a significant pressure drop (most do) AND the pump is pumping towards the PONPC, it IS in a high head production mode, and IF the pressure reducing valve "sees" the low pressure the pump is generating because it is pumping towards the PONPC, it WILL allow additional water into the system every time that pump runs, and eventually hit the relief valves threshold setting (30 PSI).



Replacing the corroded boiler pump will probably help for the time being.



Buderus is not the only European company that regularly violates the PONPC condition. Their assumption is that the pressure drop through that circuit will never be high, therefore it is not an issue.....



ME

icesailor

PRV's & IFC's

ME,

You are describing a situation I have seen where today, I would blame the indiscriminate use of IFC's where they aren't needed, and the result is covered by "The Rule Of Unintended Consequences. That No good deed goes unpunished. If the PRV feeds up between the boiler with some kind of check valve, and a circulator with an IFC, you can get a hydraulic lock and cause the pressure to rise.

In olden times, just after the dark ages, we always used a B&G SA 1 1/4" flow check coming off the boiler We used the SA 1 1/4" flow check as a 90 degree turn at the top of a boiler and plugged the run end. Then, a 5" nipple and the air scoop with a #30 Extrol. Then, a series of Taco 572 zone valves. With the SA 1 1/4" left closed so you didn't get gravity flow when the circulator was off. However, the closed SA 1 1/4" isolated the #30 Extrol from the system and when it cooled down and the water contracted, the PRV would add water. And end up ruining the PRV. I know, we should have installed the PRV into the Extrol Tank. But then, when the system goes negative, it sucks air in through the air vents and you get an "airy" system. Opening the SA 1 1/4" and leaving it open solved the problem. Before anyone asks, having a SA 1 1/4" installed meant that if you had a bad power head that wouldn't open, and you didn't have one with you, you can open the bad zone valve with the by-pass lever and the other zones will heat the zone.

Did I mention that IMO IFC's suck? If you drain houses seasonally like I do and there are IFC's, how do you know they are there and how do you open them so they drain back? And not have broken pipes in the Spring? You can't,easily. They initiate Ghost Flow and add restriction that can be cavitation and air. They suck.

Unless the purging is set up so that you can blow air through the supply and back through the return, you are screwed and will have a problem in the Spring turn-on.

Mark Eatherton

I hear you Chris...

And I too am seeing more of this stuff in the field.



The use of IFC requires a lot more thought, and as you said, if done wrong, can create more problems that it would have avoided in the first place. They can NOT stop and forward gravity flow, which does suck. I have on rare occasions actually taken the PONPC, and split it in two in order to guarantee that numerous pumps could "see" the PONPC at their inlets. It is extremely tricky, and I had to use my plug nickel method to avoid significant unwanted flow between loops, but it was very effective.



Have you ever plugged a pipe leak with dinosaur dung? Oh, you're not THAT old ;-)



Ah yes, the good ol' days... exploding boilers, out of control coal fires, hauling coal, hauling ashes... All the modern conveniences of home...:-0



ME

furnacefigher15

Spirovent

This may be another case of a problem with the spirovent.



I remember a few weeks ago, someone posted about a relief valve mysteriously going off when the piping was more or less correct.



I'd remove the exp tank, and take a good look inside the connection at the spirovent.

icesailor

I don't make this stuff up:

Here us a place that a IFC would have helped out.

Installed in 2000 or 2002. Tennant always kept the windows open. Never mentioned why. I found it last month.

Charlie from wmass

may be some crud built up

you mentioned Onyx and a flag popped up in my head to check for sludge in the system.

kcopp

Charlie...

correct. I  posted some pix a month or so back that had the old 007 circs I pulled out ... all crudded up. I flushed the entire system w/ water, Rhomar and then added the Rhomar conditioner. I went by today and mover the relief valve to a neutral location. Lets see if that works.

kcopp

I think I got it......

After thinking about it for a few more days..... I thought  I should pull the Spirovent apart. It took a 24" pipe wrench but I did get it. The entire Stainless steel strainer was jammed full of crud. I removed it in pieces and then replaced it w/ some galvy screening. I reassembled it w/ Teflon and neversieze. So far so good after 3 days.

Jean-David Beyer

Spirovent crudded up?

Is the problem with Spirovents because the "screen" that collects the dissolved air and the microbubbles decomposing (it seems to be plastic), or is it that the screen traps foreign particle matter as it passes through the system and gets clogged up?



If it is the plastic that is decomposing, I have a Taco microbubble remover that uses stainless steel "pawl rings" instead that should be longer lasting.



http://www.taco-hvac.com/en/products/Air%20Separators/track_file.html?file_to_download_id=15268



See pages 2 & 4. I have a 49-125.

kcopp

not plastic...

copper/stainless screening attached to a 1/2" copper tube. that was blocking the entrance at the bottom of the 1/2" adapter where the #30 extrol was connected.

Mark Eatherton

HMmmmmm.....

Reminds me of the good ol' days of checking Entran 2 systems... I think the official name was "gunk". If memory serves me correctly, it was the polymers from the hose oxidizing and coming out of suspension.



I told you you'd find it. Persistence is a virtue.



ME

EddieG

Dirt Seperators

I was wondering why they made them! LOL I have been giving thought to making these a standard on installs. I have had issues similar to the ones described above. I liked the Caleffi idea of the magnet on the air remover (Hot Rod), which will take the metal out. But the gunk is a whole different story! Anybody using the dirt separator's? If so, brand, success, not worth it?

Charlie from wmass

Yep I was thinking that too Mark

That's why when it clicked he had Onyx it was time to check for "gunk".

hot_rod

always check the gunk with

a magnet. If any sticks, then possibly something is allowing the ferrous components to "shed" Non barrier tube would be a suspect Rubber, PB, Solaroll, etc. Even the EVOH barrier tube will not stop the O2 ingress 100%, especially at elevated operating temperatures..



We are starting to see more and more seized ECM type circs after a season or two. That type of circ has a permanent magnet style motor and causes any ferrous pieces to stick. If you dis-assemble one, scratch some deposit from the impeller and stick a magnet to it.



One wise Heatmeister in Colorado keeps a sample of boiler water and condensate water from every job he visits. Taking a magnet across all those Mason jars will tell you a bit about what is going on in the system.



A top quality dirt separator, with magnents may be a wise investment with ECM, or any pumped system really. It is best to find the cause and correct an iron problem. but if it is tube in a slab, the only solution is an on-going chemical romance, HX separation, or a separator and maintenance program.



It is possible for the metallic media in air and dirt separators to decompose if the fluid ph drops. Overheated, or un-checked glycol systems would be one example.



The composite type media used in some brands is not harmed by bad water chemistry.



hr

Mark Eatherton

You got my attention with magnets....

followed closely by the Heatmeister, and finally, what do you mean by "The composite type media used in some brands is not harmed by bad water chemistry."?



I was going to call your son this morning and if he was in Silverthorne, meet him for breakfast, but I got diverted (as usual...). I'm working on Hydronicahhh.



Greening 'er up as it were... Can't wait to take my first solar shower Friday :-) The Moon is to be full this weekend. It is also the closest the Moon will be near Earth in 2012. I stepped outside at 1:00 AM this morning and with only 3/4 Moon, it looked like daylight... Cinco De Mayo, and a FULL SUPER CLOSE Moon. Sounds like an opportunity to party to me :-)



ME

hot_rod

sharp edges

in an air removal device are what catch those small micro- bubbles. The more edges you present to the fluid stream the better you grab the small bubbles and allow them to form larger bubbles and rise to the vent.



By using a glass reinforced nylon (composite), for example, you can build the shape and present a lot of those edges for best air removal.



Some air separator brands use a wire core, like a large fitting brush. some use a mesh, and some rings.



It great to hear you have time to stop and smell the roses and watch the nightime sky, I'm envious.



Max traveled the territory with the Ecobee folks today. He was impressed with the product and the folks behind the product.



hr

icesailor

On The Edges:

HR,

There are some who might suggest that those "sharp edges" help form bubbles through cavitation and the bigger bubbles seen is in fact, the bubbles growing through the rough surfaces.

Those of us who have raced sailboats competitively, all know that the first third of the hull has laminar flow. Any roughness or foreign objects on the hull in this first third can and will cause separation and disturbed flow. On those mornings when you get up and find light frost on your car, remember, an aircraft with that same frost on the wings will stop laminar flow and make it disturbed flow. Disturbed enough that it may not be able to take off and fly. I fly to work every morning on Cessna 402C aircraft. They have vortex generators on the wing and tail surfaces. They cause the flow to stay attached farther back on the wing, lowering the stall speed from 87 Knots to 69 Knots.

Don't underestimate the affects of anything in the path of flowing water and what might happen.

Mark Eatherton

Gotcha...

I thought you were talking about tubing. Thanks for the clarification. Richard is testing his system washing machine on a problem child in SIlverthorne, a non O2 barrier system that had dissolved 2 sets of cast iron boilers (DUH!) before he got involved. (The Triplets). He said he was amazed at what was coming out of the system, and he'd already treated and flushed numerous times using Rhomar's products.



EcoBee, yes, Mr. Yates intro'd me to that concept a long time ago. Looks interesting for sure. I just have this fear of turning my thermostat up and seeing the neighbors garage door opening and closing in unison with my thermostat...;-)



ME

hot_rod

interesting info

on the hull and wings.



I have seen test results from both manufacturers and independent labs on air and dirt separation in hydronic, hot and chilled systems..



A lot of time an money has been spent on research and development. I believe all the manufacturers have proven the concept of their media. In our lab we test our products as well as the competitors, I suspect other competitors do also.



I will say our test show that all the brands of the "micro bubble" type of separators perform well and are very close in performance.



I have a few dozen clear displays working under different flow conditions with various glycol and water solutions, seeing is believing! Our displays use a medium size aquarium pump to constantly inject air into the display. Large and small bubbles go in one side, virtually clear fluid comes out the other side. Other manufacturers have similar displays, often seen at trade shows.



Further test have been done showing the effect of dirt and air in boilers and heat distribution, and the fuel cost associated with air and dirt in systems. After reading pages of data I feel all of the major manufacturers have done their homework and appropriate testing and certifications on the devices on the market.



I suspect the aviation and boating industry has done studies and testing related to their design concerns. I'm not sure how or if the two correlate?



hr

icesailor

Showers:

Funny you should mention that. I thought of this while in the shower a few hours ago (4:15 AM).

You are adding AIR into the system, when you do that demonstration. I've seen that on more than one occasion and was dubious of the claims. I guess it is the aquarium pump that bothered me.

Water is one part hydrogen and two parts oxygen. If you squirt water on a hot electrical fire, you can separate the hydrogen gas, volatile and explosive, and the Oxygen, which is an oxidizer. Which will help support combustion. There were a couple of firemen killed in Newton, MA a few years ago when they had a fire in a closet that had electrical equipment in it and the door wasn't marked as such. When the firepersons opened the door and sprayed water in the closet. the water exploded and killed two of them.

Air, on the other hand is about 20%+ Oxygen and 80%- Nitrogen. The Oxygen supports combustion and the Nitrogen retards combustion. If it weren't for atmospheric nitrogen, internal combustion engines would melt. Nitrogen provides cooling for the combustion processes.

Once you add the water to a heating system, and heat it up, we were once told that the dissolved solids settled out to the bottom, and the dissolved gasses boiled off and out the vents. There is nitrogen in our blood from breathing air. If you dive under the water and go to depths where the pressure is high, the nitrogen gas is compressed. Maybe to a liquid. If you rise too fast, the compressed bubbles expand with the potential of causing great harm. A farmer friend says that if you don not use Nitrogen in your daily functions, you ain't of this earth. There is nitrogen in sea water and pond and lake water. In small amounts. Phytoplankton use and make it. Ocean storms trap it into the water through wave action.

But air bubbles form from the resistance of an object passing through water. Water passing through a screen is the same as a hull or wing passing through a fluid or gas.

So is it the oxygen coming out of the liquid that forms the bubbles because there should be very little nitrogen gas in the heating fluid?  Or, is it allowing air, with nitrogen and oxygen into the system to mix with the fluid that causes the bubbles?

I started screwing down can vents tightly after purging heating systems and never have seen a sign of air in the systems. I also keep the pressure to 16# to 18#.

So, what is it? Inadvertently adding a gas to the system or is it already there. Once vented, it should not ever be there again unless added.

The Old Skeptic.

hot_rod

where's the boiling

taking place if the heating device is running at or below 180F, and generally under pressure. Radiant mod con boilers may run as low as 100- 120F.



I don't see how you can eliminate all the air when filling a system with 12 psi, or even a fill pump at 30psi. Those small air bubbles need to have a means to circulate and make it back to a device that can trap and eliminate them. The ramp style purgers do not catch the small and micro bubbles, as a mesh type separator does. If they are mis-placed in the pip;ing or see excessive velocity ramp or scoop type air eliminators are of little use.



We have tested the media or micro bubble separators to 10fps and they still do a great job.



It is possible for a large radiant job with thousands, maybe tens of thousand of feet of tube to take days or weeks to eliminate all the small air bubbles.



If you install an air removal device at the boiler or a float type vent at high points, and screw the cap down tight, why bother installing it in the first place? If you have a means to eliminate all the air with an initial purge, save your customer the cost of the purgers and vents. But my experience shows that 100% complete air removal at initial fill is not possible.



If there wasn't a need for micro bubble elimination and small micron dirt removal manufacturers would not be spending millions to engineer and test devices.



As for O2 ingress, head over to www.Mrpexsystems.com and read through some of Tomas Lenman work in "Water and Pipes" he explains how this is possible in PE tube.





It's the same with boats, airplanes, etc, engineers continue to built more efficient, faster, quieter, more reliable products.



Great reading in the latest issue of Popular Science about the future of aviation and the planes we will be flying in years to come. And some cool paper airplanes to cut out and build. www.popsci.com



hr

SWEI

System washing machine?

I'm intrigued...

icesailor

Boiling Over:

H Rod,

Cavitation is water boiling in the presence of negative pressure. The same negative pressure that happens when air flows over a wing. Or the negative pressure around the vanes of an impeller.

See if you can reverse engineer this.

In the old days of reciprocating piston well pumps, a piston moved back and forth in a cylinder with a cup leather on either side of the rod. Making it double acting. Take a Myers 1909 pump. It pumped 400 GPH, no matter what the lift was. If it was a 5' lift, it pumped 400 GPH. 25', 400 GPH. Because the cylinder displaced a given amount of incompressible water. Every time the rod went back and forth, it moved the same amount of water. What one side pushes out, the other side pulls in and fills the cylinder.Repeating itself. If the lift was high, or the screen was plugged, you would hear hydraulic knock. But no matter, it still pumped 400 GPH. With high vacuum from lift or plugged screens, you could get air into the system through a leaking shaft seal or the valve covers. If you had a "Airy Well", one that "developed air", it went into the hydro-pneumatic tank. If the air was too great, you could put an air eliminator on the tank. When "Jet" Ejector pumps came into play, the greater the lift, the less the output and pressure. The pump depended on a flow of water through the pump to keep the water and pump cool. If the pump couldn't get to the set pressure before shutting off, the friction of the impeller in the pump would cause the water to boil because of the negative pressures developed in the impeller and the nozzle/venturi (Jet) assembly. As the temperature continues to rise, the boiling gets worse and the pump appears to have lost its prime. If you shut the pump off, and you can close a valve between the pump and tank, and you take out the plug in the top and turn the pump on, it will immediately pump water to the ceiling, drenching you. Put the plug back in, drop the cut out pressure or clean the rust out of the nozzle and it is like new. Because you eliminated the cavitation. If I let the pump run up to pressure and it starts to cavitate but not get the set pressure, it sounds like a bunch of ball bearings and birds inside the pump. The same noise I hear on over pumped heating systems where a too high head is installed to overcome the resistance of a poorly designed system. The "Air" came from the water. Not, "The air came from the well".

The hydronic heating system in my home was installed in 2000. It has never been drained. It has no leaks and no air. I have had to replace numerous Taco #400 float vents because with the caps open, water works its way to the seats and boils or evaporates away leaving a powdery substance that promotes leaking. I would go to customers houses to turn water back on and find the 400's all leaking. I replaced so many of them that I expected to get blow-back from customers. I tighten the caps after filling and purging. I've never had a call back. I remember back years ago, having CI radiators get "air" and having to vent them. In retrospect, what I realized from here was that the system pressure was too low from defective of clogged PRV's. I don't disagree that you need to get the air out on the initial fill. Once filled, where's the air? I never see it and if I do, there is an underlying cause. The air gets absorbed, The oxygen and the nitrogen. I see air getting into systems where there are air handlers installed in attic spaces with float vents and not enough pressure. When the system goes off and contracts, air is sucked in through the open vents. Close the vents and raise the pressure. The problem goes away.

You guys here are the ones that pointed out higher system pressures. Something I hadn't thought that much about except when trying to fill a three story radiator system. I always fill from the top down, Well, it works well, and it pointed out to me what and how well pump mechanics are co-related with hydronic heating systems.

icesailor

Air elimination devices:

Try this. Take that same demonstration device you have with the aquarium pump providing the air. Turn off the air. Connect a big high head, high volume circulator like a Taco 0014. Circulate the water through the air elimination device with the screen. Let the water temperature rise because of the friction. Once the water in the loop warms up, I'll bet you get bubbles forming on the outlet side of the screen. If so, where did the "air" come from?

The water.

hot_rod

Perhaps

The hydronic heating system in my home was installed in 2000. It has never been drained. It has no leaks and no air. I have had to replace numerous Taco #400 float vents because with the caps open, water works its way to the seats and boils or evaporates away leaving a powdery substance that promotes leaking. I would go to customers houses to turn water back on and find the 400's all leaking. I replaced so many of them that I expected to get blow-back from customers. I tighten the caps after filling and purging. I've never had a call back. I remember back years ago, having CI radiators get "air" and having to vent them. In retrospect, what I realized from here was that the system pressure was too low from defective of clogged PRV's. I don't disagree that you need to get the air out on the initial fill. Once filled, where's the air? I never see it and if I do, there is an underlying cause. The air gets absorbed, The oxygen and the nitrogen. I see air getting into systems where there are air handlers installed in attic spaces with float vents and not enough pressure. When the system goes off and contracts, air is sucked in through the open vents. Close the vents and raise the pressure. The problem goes away.

You guys here are the ones that pointed out higher system pressures. Something I hadn't thought that much about except when trying to fill a three story radiator system. I always fill from the top down, Well, it works well, and it pointed out to me what and how well pump mechanics are co-related with hydronic heating systems.





If you are having that many vent failures, consider another brand That is a well know and quality brand of product it should perform well if all the conditions are proper. If that model can be disassembled open the leakers up and see what is under the seat causing them to leak. If it is a layer of crud, teflon tape, copper shaving, etc it probably didn't leave the factory like that.l



If they seal properly when you first install them, they are probably not defective. something in the system fluid is probably causing them to seep.



But it sounds like a system design or installation issue, maybe. This sounds like the sympton of an open, or un-pressurized system? Are the vents installed at the PONPC? Does the system have positive fill pressure? If so how is water or fluid "boiling" in the air vent? Install a pressure gauge and see if the pressure is dropping at the vent to allow the water to boil.



Dan's book "Pumping Away" does a great job of explaining the point of no pressure change, how it works, why it is important, and the issues it can present in a system when not observed.



OWF installers that pipe in un-pressurized outdoor boilers some times create sub atmospheric conditions in the system which can cause the fluid to boil at the upper levels, attached is a graphic and explanation of how this is possible and the math to calculate why it happens.



The vent should be shutting off before water is at the seat. Maybe some fine crud in the system is getting to the seat, allowing the leak, not vice versa? More often than not it is dirt or debris in the system that works it way to the air vent shut off valve and causes them to leak.



I know the vents need to be installed level, or plumb so the float can move freely, some brands of air vents have the float riding on a center pin to avoid the float from rubbing the side.



Another thing you could try is installing a hygroscopic cap on the air vent. it provides a second level of shut off protection should the internal float valve not seal completely.



I'd be glad to send you a vent with a pinned float hygroscopic cap to see if that solves the problems, but look deeper for a cause.



hr

SWEI

Water and Pipes

http://www.mrpexsystems.com/waterpipes.asp

Would you be so kind as to point us at the chapter with the O2 info?



--thanks

SWEI

positive displacement pumps

are still the most efficient way to move water.  Believe it or not, we still have pumps in the tradition of the Myers being made today.  I know several of these http://dankoff-pumps.com/dp/wp-content/uploads/2011/11/SolarForce-Spec-Updated7-20-10.pdf on remote PV systems that are still running after 15-20 years of continuous use (with maintenance, of course.)

icesailor

Vents:

H.Rod,

I guess you don't understand what I am talking about. Or, you have seen the same thing and not figured it out. These don't fail when I put them in, they fail after a year or two. And the reason that they fail is for the same reason that when you boil all the water out of a pan, there is a sesidue left in the bottom of the pan. And, in tghe process of probably venting a micro-bubble or two, or just having the hot water against the seat of the valve, it evaporates and leaves scuzz behind. The seep gets closer and closer to the tip over point and the valve starts to leak. I know that I could take them apart and possible clean them. But at what I charge per hour, and the cost of the #400, it would be stupid for me to run the risk of having a call back to fix a leak. Leaving the cap tight means it is OK for the next time. If it is leaking and it is a few years old, I might change it. Did I mention that I usually mark the date on the valve when I chaanged/installed it? \

It's the same leak cause that happens to those that use red rubber circilator gaskets in place of the manufacturer supplied black square cut O-ring gaskets.

Like these. Both are cranked down. The one scuzzed up I just left there. I unscrewed it and got a very slight amount of air. The other is new and is cranked down. The one on the top of the boiler is stained from the leaking. It was probably on the top of the scoop. If you would like more examples, I'll dig some out of the brass barrel tomorrow.

icesailor

Info:

SWEI,

Are you asking me that? I don't need to. Is it not true that atmospheric air is 20%+ Oxygen and 80%- Nitrogen? And is it not true that potable water is one part Hydrogen and two parts Oxygen?

You read the book. Does it not say that you need an Oxygen barrier on HEPEX tube to stop Oxygen from passing through the pipe? Even though there is Oxygen in the water.

Judgeing by how many Taco #400's my Wholesaler keeps in stock, and how often I see the bin down, I'm not the only one changing them. I crank trhem down and not hear a word from the customers about air rushing around the pipes. That's good enough for me.

SWEI

yes, asking you

because I have not read the book and wanted to know where to start.  I understand the physics but am always looking for writers who do a great job of explaining it (like Dan!)



thanks~



We work mostly on small-to-medium-sized commercial projects and do not use auto-fill valves - in fact I remove them from existing systems once the problems are remediated.  I wire a pressure sensor to the BAC system and alarm on low pressure, forcing a human to examine (or at least acknowledge) the problem before adding make-up water.  Caleffi ships air vents with their hydro separators, but we close off the valve once the system has de-aired itself and proven tight (and chemistry is checked.)

icesailor

System Fills:

There was a back and forth here a while back about leaving fill valves off. I'm told that some insurance companies want the valve OFF to prevent flooding. I'm conflicted. If I have a building with radiators in an attic, and it takes 16# to keep the water there, turning the valve off and having it drop to 10# may not keep circulation going and I could have a freeze up on my hands. Its happened to others before.

But what you describe is my experience. Once I have the system purged and running, it runs forever with the caps tight. Unless it gets a leak.

SWEI

(non) autofill

On a commercial system, the cost of the autofill plus a reduced-pressure zone backflow preventer is more than that of a pressure transducer with alarming.

hot_rod

I get it

I have heated water in a pan on the stove and watched the air bubbles.



I'm trying to understand you comment about water boiling in the air vents, or even evaporating from a sealed brass air vent?



All closed loop systems in my opinion should have a central air removal device, that is allowed to function. it needs to be able to release the air every start up that we both agree forms when the boiler warms.



If the cap is closed off the air cannot be released, small bubbles can form into large bubbles, causing noise and potentially the loss of flow. Some installers prefer a float type air vent on the high points to remove air that works it's way up. Notice quality radiant manifolds include float type air vents on them. Air handlers located in attics and high point radiators all benefit from a working air vent.



I feel the failure of the basic air vent is caused by the quality of the fluid inside the system. White deposits indicated probably hard fill water. Black sludge could be by products of manufacturing, flux, cutting oil pipe dope, etc. Or a system with non barrier tube allowing O2 ingress.



When the float drops down to vent any air, this "brackish" water gets onto the seat of the air elimination valve. That is my opinion of the failure. SOMETHING compromises the sealing ability of that small surface.



Certainly mis applying an air vent, or not selecting the correct vent for the application compounds problems. Mis applied high head circs can allow air into these vents also. which is why we sell check valve caps for air vents to help installers eliminate that potential until the cause can be corrected. often moving the expansion tank connection corrects the air sucking in. This concept is covered nicely in "Pumping Away" and also Modern Hydronics by Siggy.



If all systems were flushed and cleaned with a hydronnic cleaner and filled with de-mineralized water, vent failure would drop considerably.



Usually that same venting mechanism is used in central air eliminators. Discal, Spiro, Taco, B&G what ever brand you prefer. So the same problems occur in the more efficient micro bubble type eliminators as the basic float style that you show.



But a working vent needs to be somewhere in the system to eliminate the air you keep mentioning.



A catch 22 as you describe it. Vents need to be open to operate, Open vents are prone to scale or sludge which causes them to leak. This is why there is a large vent replacement market. It's not a perfect device, but it is as simple as a schrader valve on your tire stems of AC systems.



And isn't this the same issue with fill valves. With then isolated off you risk a no heat call when air vents out and the boiler pressure switch trips out, like on most all mod cons these days.



So every installer makes the choice air vent open, or screwed close? Fill valve open, or valved off. If you and your customers prefer a manual air venting every season, then closed is a good option, because we agree air "happens" If you leave themn open you run a good risk of them seeping someday.



Fill valves and auto fills fail from the deposits under the seats. My company manufacturers tens of thousands of these and we open and inspect returns. Ocassionally there is a manufacturing defect, bad seat or seal. 98% of the time they have debris on the sealing surfaces. Again it didn't leave the factory that way. Consider millions of air vents in operation. I doubt every one is replaces every two years. so there is a way to prolong their life expectancy.



Clean systems, best quality fill water, operating fill and vents is my idea of appropriate hydronics. But we all balance that against the COST of cleaning, flushing, running a cleaner, hauling or making DM water, and possibly adding hydronic chemicals that "condition" the fluid inside. These conditioners buffer ph, scavange O2 and provide a very thin film to protect the ferrous surfaces from corrosion. THIS procedure is the solution, I feel.



OR keep replacing air vents as a consumable component of the system. Like the oil filters on your engines We also sell a nice check valve for every vent to make that switch out quick and easy without loosing a drop of fluid. we understand installers want choices, we try to provide as many as possible, and you decide which are in your customers best interest.



hr

icesailor

Boils:

HR,

The bubbles you see in the water in a pot on the stove are more likely caused by the burner heating the water in the bottom of the pan, locally. And if it is cold tap water. it is more likely to bubble than hot tap water. If the water is under pressure, it is far less likely to make bubbles.If you manufacturer PRV's in RI, I haven't hardly had to change an 1156F since you went to the brass valves. Where I work, most do what  always do. Copper to a ball valve, 9-11 brass combo, brass nipple, an 1/2" IPS ball valve, and usually a brass nipple into the system. No steel directly connected to the PRV. The only "new" PRV's I've replaced were ones that someone used a black nipple on the outlet of the PRV. So you can change the PRV without draining the system.

If the heating pipes of my customers were gurgling, I would be getting calls. I don't.

I don't change float vents every two years. Only when they leak so badly when I am purging that water runs all over the top of the boiler or floor.

That #400 in the photo is 4 years old. I replaced it when I put the Wilo variable speed in. The cap has been screwed down tightly so it doesn't leak anymore. Notice all the white powder on the top.