moving the PONPC

Ron Schroeder

just what I expected.

CC.Rob

piping a PONPC relocation

I have a circ on the return by the boiler. PONPC is on the supply, and I've got air problems. Mark Eatherton said it's ok to move the PONPC to the suction side of the pump on the return, rather than moving the pump. The way it's piped presently, that is much easier to do.

What I would need to do is cut in a tee at the red box on the vertical portion of the return (see pic). There's not enough space between the indirect and the boiler to hang the expansion tank. It might fit over the back left of the boiler. Is it ok to crowd the draft hood or should it have a lot of free space around it?

Can I hang the expansion tank to the left of the indirect and run a ~3 ft horizontal piece of 3/4" pipe just above the indirect to connect the tank to the return? The feed valve would also move with the tank to the left side of the indirect. Basically unscrewing the feed and tank from the base of the spirovent, capping the spirovent base and moving the feed/tank assembly to the left of the indirect. (Alternatively, leave the feed valve where it is since it will not see any negative pressure.)

Thanks for insight.

Brad White_9

That will work...

You can install the ET remotely to where it fits better in the space, within reason. It is the connection point that is critical. Mine is about five feet away and at one time it was over ten feet away.

Mark's point about installing the PONPC on the suction side is the most critical thing. It does not matter if it is on the inlet or outlet of the boiler.

The reason it so often was on the outlet is, that is where the air separator is most effective (hot water releases more air). And that handy tapping just cried out louder than physics, demanding that you screw the tank in there....


I would leave the feed water connection where it is. You could move it but for no benefit that I can see. It will release most air right into the separator and what is missed will be picked up on the next pass..

Hope this helps.

Brad

CC.Rob

Thanks a million. Just edited above to ask if I can crowd the draft hood. Tank might fit over back left of boiler. That ok or a no-no.

Brad White_9

Personally, Rob

I would put the ET on the floor below the electrical panel out of the way. You can use a flexible braided washing machine hose as I do, to make for ease of moving it aside and routing it. Or hard-pipe it behind the boiler, your call, but out of the way is critical. When full of water it gets heavy and you do not want that kind of leverage without extra support.

My ET sits neatly in an old Wok ring on the floor by the way. Stable and easy.

I would not crowd the draft hood. No reason to.

Unknown

Rob

As others have stated, that is OK to do. We show this in some of our I&O manuals as well....in particular the V8 oil-fired that still comes with a return mounted pump. Here is a graphic from out of the manual. Hope this helps.

Glenn Stanton

Manager of Training

Burnham Hydronics

U.S. Boiler Co., Inc.

CC.Rob

Thanks Glenn!

subcooler

When all said and done

You are going to fine out that you have more of a velocity problem ( well lack there of ) than a PONPC issue. I can just about guess with the (what looks like 1 1/4" supply and 1" return) and a couple 3/4" zones you are not moving much water around the system. So the air does not what to come back, it just get stuck out in the system. Does that sound familar? The air vent on the crown of that boiler is all you should need for that system. The relief valve should also be mounted with the needle vertical. I would look at flow before you consider the other. If not you will re-visit this problem again. Sorry to be a bit down, but it's math. I will try and find the worst pipe job I have ever had the pleasure of working on and post it on you thread. It will probably help.

Brad White_9

I'm going to guess it is 1\"

You may be right but I am going with 1-inch copper being the larger lines. Rob?

A little "Eatherton Soap" to gather the air may help as well as isolating zones to increase velocity in the remainder. But you point is a fair one.

CC.Rob

Interesting perspective. I have given that possibility more than a fair bit of thought. Feedback to date suggests a PONPC issue. I'm but a mere HO armed with lots of math, some physics, Excel, and the kind contributors of The Wall. Other things that real experience might teach me are presently lacking.

FWIW supply and return are both 1". I hear you on the relief valve; I read "vertical" for its position in the boiler manual, too. One of the attempted fixes was the addition of an additional air vent in that spot. "I want to try this first because that's how I vent all my systems." No comment.

Some specs and what math I've done.... Calcs below assume 180F water, 3/4" copper pipe. For 3/4" copper, flow to entrain air should be 2-4 fps, i.e., 3.2-6.5 gpm.

Circ is a Taco 007.

1st floor zone TEL 267 ft.
2nd floor zone TEL 324 ft.
Prior to a recent addition, 2nd floor zone TEL was about 304 ft.

Here's the system resistance curves relative to the pump curve. For both existing zones and the old 2nd floor zone, flow is +/- 4 gpm. Should be ok, right?

Interesting data point is that the pre-addition system never, ever had an air problem. The ~20 ft TEL addition does have a fair number of elbows to get around things, but TEL is pretty much TEL, right?

Another data point: once I trusted that the system didn't have a leak or other issue, I began to pay attention to how the air noise starts manifesting itself, etc. Once I got the Holohan/Eatherton/White explanation of negative pressure due to PONPC, it really all fit together. (Thanks Dan for writing the book, and particularly Mark and Brad for contribs here.)

Now that we're coming out of heating season, the system spends a fair bit of time cold. And when it first gets going in the early AM after night setback, it is sometimes (not always) nearly air-silent during the first couple heat calls. But once it's been running for an hour or so, and we've had our morning DHW demand as well, there's air everywhere upstairs and cavitation down at the circ. That says to me this is a combination heat/pressure issue liberating compressed air. Of course, conceding no practical experience whatsoever, I could be totally wrong.

Thanks once again for all the insight and perspective. If I come across as somewhat exasperated, well, I am, and no disrespect intended. Is this a 1 hr PONPC move or a complete system overhaul, repipe with real supply/return manifolds, circs sized to each zone, etc. etc.??

thp_8

Since you know math and physics.

If you look at it long enough, you see that changing the tank position is not going to increase your flow. You have a flow issue.... That what makes your air issue happen. I did not what to quess, but I knew you where going to say that you had 250' runs. For the 300 footer, well your well past what that 007 on multiple zones will handle. You have to figure all zones open. Then calc. the circ. pressure and flow backwards.
With that kind of piping the best your going to see 1.5 gpm tops, per zone. If the domestic water heater is open, the heating zones will see zero to 1 gpm or less while in domestic operation till the zone closes. This is where the air part comes into play. That not an opinion it's math. PONPC is nice to get your static pressure set, but after that don't try to read into too far. For the multiple circ. set-up, I would not go that route. Get the correct circ., balance the system out and keep zone control. Plain and simple.

[Deleted User]

Sez who....

I'm still trying to figure out who you are and what you allegedly know... Based on your last post to Rob, YOU are missing the boat. PONPC has NOTHING to do with static fill pressure, and EVERYTHING to do with pumps making all positive pressure and keeping air in suspension and sweeping it back to the air removal device to be eliminated.

According to people with a LOT more knowledge than you and I combined, that 007 is capable of moving a LOT more water than 1-1/2 GPM per circuit. In fact, with the two heating branches set at 267' and 324' of 3/4"pipe, the ot7 is capable of moving a minimum of 3.68 GPM, and a maximum of 4.11 GPM, which by my calcs is pushing water thru the tubing at just over 3 to 3-1/2 foot per second which is MORE than adequate velocity to push air down hill.

I don't get why people like you want to ignore the simple truth that pumping away from the PONPC works, and works very well...

Rob, go for it. As far as blocking the air getting to your relief hood, it is not recommended that any surfaces be within 18" of the relief hood. Go with Brads recommendation that you mount the tank remotely.

Attached is a Siggy Graphic showing exactly what will happen with both heating loops on. The one thing that the heat police did say right is that when the DHW tank is on line, flow to the space heating loops will be robbed, and that occurs for how long?? And most manufacturers who promote DHW priority do what??

Some peoples kids...


ME

subcooler

So can I quote you on that ?

1. So your claiming that the circ. can't develop head pressure without a tank. Wow you should install multiple tanks and no pumps. 2. These a expansion tanks...... Their main use is to maintain an exceptable pressure from a cold start say 50*F to a hot run condition say 200*F. 12# to maybe 18# and not go nuclear. 3. For the flow thing you need to go back and find some-one who can help you read a pump curve and calc. piping flow. That little 007 is a good lttle circ., but it won't do that. That's math. 4. Impressive Mark, your little picture that is. By those calcs., is see you pipe everything in straight pipe, no fittings. That's gotta take a lot of time planning out those jobs. If you subtract all your fittings ( this includes more that your 2 pipe loops ) from the front of the circ., in and out the boiler, in and out valves, in and out zone valve, in and out gate or ball valves, 90*, tees, air elimination fittings, to your zones, back to return piping and then hit the return side of the circ., you'll be in the under 2 gpm per zone. Then that 007 doesn't seem so big anymore.

Rob_32

thp, I'm responding from a position of substantial ignorance, so it's probably pointless for me to try as I'll only get myself into trouble. Maybe others can weigh in here. But I was under the impression that with both zones open the system flow resistance is actually less than with one zone closed, so less pressure differential to move the water. How that translates into gpm per each zone, well, I've been dabbling in hydronics for a month or so and I guess I haven't read that chapter yet. And again, I could be totally wrong in which case correction is gratefully received.

I'm a guest here on The Wall. I appreciate all the insight. You guys have a great community and neat dialogues. As an HO, I've learned a lot about something I never really gave much thought other than when it's cold outside I like the fact that it's warm inside....

Thanks for the comments.

subcooler

D.P.

Look at it from the circs. point of view. It's job is to move water based on D.P. If one zone is open high D.P. on circ. and x amount of flow. If two zones open of different friction losses. What's going to happen. Water is going to favor the lower loss zone. The high loss zone will get less flow. Why because the circ. is not going give a higher D.P. on increased flow, if it could I think we would be talking about Cold Fusion making more from less. Now I know someone will have to say this is the perfect set-up for vari-able speed crap. Ooops. Marks other comment about Domestic Water heater I can't imagine where he was going with that, but the answer is not to aid in air elimination but to get full output of their waterheater.

[Deleted User]

You won't be quoting me...

You'd be quoting John Siegenthaler. I won't attempt to qualify the rest of your comments.

You're really something Tom...

ME

Rob_32

Just to be clear, the TEL figures I gave were done using standard values for elbows, ball, globe, zone valves, etc. on each circuit. I was interested, for example, to learn that a 3/4" 570 series valve has a TEL of 20 ft. Seems like a lot.

I'm going to guess that Mark's comment about DHW priority meant that during a priority call, flow to the heating zones stops, so there is no "robbing of flow" by the indirect. Although as I understand it, priority is more for BTU delivery to the indirect rather than flow, if flow stops to the heating zones, it stops.

You suggest that I need to figure out what circ to use, and balance the system. Do you have enough information based on what I've provided in this thread to make a suggestion? That would be really helpful. Thanks.

Rob_32

Just to be clear, the TEL values I gave were calculated using Crane Co TP 410 or manufacturer data for elbows, tees, ball, globe, zone valves, etc. on each circuit. I was interested, for example, to learn that a 3/4" 570 series zone valve has a TEL of 20 ft.

I'm going to guess that where Mark was headed with the priority comment was that during a priority call, flow to the heating zones stops (and/or that most manufacturers recommend putting the indirect on its own circ). As I understand it, priority is more for BTU delivery to the indirect than to alleviate "robbing of flow," but if flow stops, it stops.

You suggested previously that I need to have a proper circ and balance the system. Do you have enough information based on what I've provided in this thread to make a suggestion? That would be really helpful.
Thanks.

Ron Schroeder

thp,

You are missing the point (points).

Mark is stating that if the circ is after the PONPC then its pressure adds to the tanks pressure, he made no claim that the circ. can't develop head pressure without a tank.

Also, Rob quoted TEL (Total Equivilent Length) that by definition INCLUDES:

"all your fittings ( this includes more that your 2 pipe loops ) from the front of the circ., in and out the boiler, in and out valves, in and out zone valve, in and out gate or ball valves, 90*, tees, air elimination fittings, to your zones, back to return piping and then hit the return side of the circ"

so Marks figures using TEL are correct.

Rob, by the way, when you remote your expansion tank, just pitch the line up a little toward where it connects into the circulating part of the piping so any air in the new line can be eliminated too.

Ron

thp_8

Gee

Ron, Mark's claim "I'm still trying to figure out who you are and what you allegedly know... Based on your last post to Rob, YOU are missing the boat. PONPC has NOTHING to do with static fill pressure, and EVERYTHING to do with pumps making all positive pressure and keeping air in suspension and sweeping it back to the air removal device to be eliminated."

You know what would make this easier, if we banned the pressure and pumps from this conversation. Then if we substituted flow and circulators in their place.

The reason for saying that was, people need to get past thinking you need 10, 20, 30 power washer style pumps to get a hydronic job done. All we need is a little FLOW and zone control.

If you have your fill device before the PONPC you will obtain your fill static pressure easier that having it on the high side of the circ. as in Robs set up. I hope I don't need to explain why.

Mark answered his own question also when he said about sweeping it back to the air removal device. The reason we have a air problem, is because we have a flooooooooow problem. Not bring air bubbles back, low flooooooooow.

For the TEL, Incorrect information not on my part. Yes I ran the calcs., I know you did not. If you did or would, you would see that it is figured for straight pipe. I can't argue anymore on that one.

I hope I did not miss anything. Think flow problem. Or that person is a real piece of work.

Ron Schroeder

thp,

You still don't get it. TEL is the equivilent length of straight pipe that would have the same resistance as the actual length of pipe plus the resistance of the elbows, zone valves etc.

And yes, I did do the math. With both zones open, the flow rate is above 2fps in both the individual 3/4" loops and with the combined flow in the 1" common piping. My only assumption is assuming that Rob correctly calculated his TEL and from looking at his last post, he did his homework.


Yes, the fill point would be better if it was at the PONPC but if he doesn't move it when he moves the tank, the only thing that will happen is the fill will have to wait for both of the circs to be off to fill to the set pressure. Hopefully there are no leaks big enough for that to be any problem. ;-)

thp_8

Wow

Ron, the calc. that Mark used is for straight pipe. The program he plugged it into is calculating straight pipe resistance. It is not calculating a certain amount of pipe and fittings. But the program can if you use it that way. Say 325' of straight pipe .vs. 250' plus fittings big difference.

We are not disputing TEL, it's is how we are not calculating it correctly. And by we, I don't include myself.

Ron please lets look into this a little further.

Do you disagree that we have a flow issue.

S Ebels

I see two issues

Both of which have been covered/debated? here on the above threads.

The original question was asked about PONPC which is a valid question and a valid concern. In every system I've encountered that we moved the PONPC to its correct location, on the suction side of the circ, good things have happened. Static system pressure was more stable, and air was eliminated from the system easily, usually with no more effort that turning the system circ on and letting the air elimination device do its thing. In fact we just re-piped a system in a small bank building that had a replacement boiler installed about 1 1/2 years ago. The installer left the circ connected to the boiler as shipped, pumping at the boiler, which contained the built in "hump" for air collection/elimination, and the expansion tank/fill valve was located downstream. They had air noise in the system piping, 5-3/4" zones pumped by the standard Taco 007, since the boiler had been installed. Some zones would refuse to flow intermittently on a random basis. We re-piped to move the expansion tank upstream of the circ along with moving the fill valve to the same location. We also installed a decent air scoop/vent combo and deep sixed the bubble grabber on the boiler. That was the end of that. No other changes were made. No additional power purging or anything like that. It works as it should which is, of course, nice and quiet with everything flowing.

The other point, which I think Tom is driving at, is that you have to have sufficient circulating power to move the water/air around in the first place. That's so basic that it needs no further explantion. If your at the limits of a circ's capacity , it just becomes that much harder to move things around. Given your zone lengths, you might have some issues with having enough grunt to do the job. It's hard to calculate equivalent lengths and account for every single thing that shows up on a given loop. Been there, done that too. Hope this sheds more light than heat on the discussion.

Ron Schroeder

Yes, I dissagree that it is a flow issue. The flow is between the normal suggested flow of 2 to 4 fps even with both zones open (about 2.4fps in the longest equivilent zone). Rob's longest zone is less than 324' but with the elbows and valves etc. to have the same resistance as 324' of straight pipe. I don't know what it would be with the DHW open too but that DHW zone should be on priority. (actually it really doesn't have to be on priority, air would still be scavanged when ever the DHW zone wasn't on)

A shorter piece of pipe with the fittings and valves that makes it's resistance equal to 324' of straight pipe WILL flow the same as 324' of straight pipe. That's the definition of TEL.

thp_8

Zonk

Ron you don't agree that it's a flow issue, but at the same time you say we can't scavange the air back to the air elimination device. Am I reading this correct? For your logic to be true with proper flow in the system some of the following must take place.

1) Taking on gallons of water to provide fresh condensables, or

2) Flow moving so fast air elination can't catch it, or

3) Water quality issue, or

4) Rob is running like ah 5# fill pressure, or

5) Air is somehow entering the system from outside, or

6) Maybe Rob never ever got the air out because he's got ah flow issue.

CC.Rob

and the answer is...

We left the circulator on the return. We moved the expansion tank connection from the discharge side of the circulator to the inlet side.

One good purge later, this system is silent.

Thank you all, particularly Henry, Boyle, Carlson, Holohan, Eatherton, and White.

Having read and heard from folks here all about pumping away and how it changes the pressure characteristics of the system, it is really cool to see that play out in mine. Every symptom we've had has disappeared.

FWIW, the Taco 007 is one heck of a pump. The 2nd floor loop has a TEL of around 324 ft. In the grand experiment in hydronics that is my second floor, for at least a month this pump was also achieving sufficient flow rates to go through two (2) Taco venturi tees and a Beacon/Morris K42 kickspace heater on a 1/2" loop piped into the 324 ft TEL circuit. The additional head (2 venturi tees @ 28.9 ft TEL ea, plus the kickspace loop at ~2 ft head including piping and heater) should have put this pump at or close to shut-off head, if I did the numbers right. Yet it moved enough water to heat the zone just fine during the coldest part of the year (albeit rather noisily due to the negative pressure it was creating due to not pumping away). (The kickspace loop was cut out of the circuit some time ago, for design flow and real-world overradiating reasons.)

Thanks again.

Unknown

I'm a newbie to the wall

Hey guys, help me here... What's a PONPC ? Thanks...

Rob_32

Point Of No Pressure Change. aka the point where your expansion tank connects to the system. All very very clearly explained in Dan Holohan's book Pumping Away available on this site. Money well spent if you're at all curious about hydronics. (Independent opinion of homeowner now educated about a lot of this!)

Unknown

oh plz...

Plz tell me what TEL means....
Ray with the PhD*

Unknown

I seeeeee

I'm a wethead contractor myself, I finally figures (and still) learning to use the sidesick pager with website... I see the P0N0C, is a shorthanded verison, I been installing boilers and replacments with pumpings away system since 1990 after reading Dan's books and it took a 48 units, 4 stories condo to conviced my late father to change from pumping into to pumping away... Other story someday...

Brad White_53

Don't Ask, Don't TEL....

TEL is Total Equivalent Length, a short-hand way of expressing the resistance of a given run of piping. Each fitting of a given pipe size is assigned an equivalent length in feet. The sum of those plus the actual straight pipe is the TEL.

Say (making up the numbers here) a 90 degree elbow is worth 4 feet of straight pipe and flow through the branch of a tee is worth, say, 10 feet of pipe. And a ball valve at 2 feet equivalent.

Then suppose you had two such branch tees and 10 such elbows plus 50 feet of straight pipe and one ball valve. You would have:

2 x 10' (branch tees) = 20 Equivalent Feet

10 x 4' (elbows) = 40 Equivalent Feet

50 feet of straight pipe (self defining) = 50 Equivalent Feet

1 x 2 ' (Ball valve) = 2 Equivalent Feet

TEL= 112'

Same pressure drop and characteristics of 112 feet of straight pipe.

Unknown

thanks, Brad

Thanks for explaining the short handed terminology for TEL... You and others will be seeing my name more often on the wall in the future...