OKay all you non believers...(ME)

Gordy

I love this site and the Rpa site. As a homeowner with radiant heat I monitor these sites daily to learn and laugh, you guys are a blessing.
As for the pumping away, I have had three different profesionals do a yearly inspection on my system which is a ceiling radiant and floor radiant closed loop system. House built in 1952, it was my grandparents which built it so I know the history.
When I bought the house I did my research on the system being in the trades "wood tick" I'm very curious on how things function and like to learn and understand them.
I called the original installer to give me a walk through of the system first thing he said was the pump should have been on the supply side but granny did not want to spring the extra 700.00. I had already read up on these sites including pumping away from the B&G site.As he was telling me this I thought to myself, if that was how it is suppose to be than why did you not just figure it right in the bid instead of an option, also looking at the new copper installed on the supply side I could not comprehend 700.00 to mount the circulator on the supply side.
Second company I had out the following year after seeing a few things original installer did not do as I have read should be done,I asked him what he thought about the pump location he said it is not that big of a deal which side it went on and went on to critisize original installer for putting automatic air vents in system with steel compression tank,and no shut off valves on both sides of the circulator and on the supply side of boiler so the whole system would not have to be drained to change out pump or boiler, so I had him do this for me there is 4500' of copper tubing in my system. He was a nice guy eager to discuss any questions I had.
Third company I had out the following year because company 2 was no longer in buisness so I asked this gentleman what he thought about circulator location and he said return side always.
So I decided to test the theory myself I put a pressure gauge on the supply side after the boiler and mixing valve and one on the return side just before the circulator where automatic air vents were.Well at 12 psi I get about 6 psi on gauge just before the circulator so my pressure falls 5 psi from the point of no pressure change. So I say it can be a problem if my system pressure happens to fall below 12 I could suck air into system as I have read. I have no leaks. I bumped my pressure upto 15psi.which raises a question is it bad to have the pressure higher than the 12 psi I understand you don't want it so high as to pop the prv but in my situation until I get it resolved would it help to bump up the pressure to help keep the air entrained in the water? I run pump continuous which helps also among other benifits.
And yes I do have to burp air periodically from my returns because original installer never put a spiro vent in the system or even a airtrol fitting on the steel compression tank. Incidentally I asked the original installer if he had ever checked out this site or the RPA and told him the wealth of information and great discussions on these sites, and his reply was "I have been doing boilers since I was 14 with my Dad." I had to go get my sunglasses so he could not see me roll my eyes the rest of the time he was there. Sorry so long winded and would appreciate comments. And thanks for taking the time to answer questions and discuss topics,you can tell when people enjoy their work!

Gordy

I love this site and the Rpa site. As a homeowner with radiant heat I monitor these sites daily to learn and laugh, you guys are a blessing.

As for the pumping away, I have had three different profesionals do a yearly inspection on my system which is a ceiling radiant and floor radiant closed loop system. House built in 1952, it was my grandparents which built it so I know the history.

When I bought the house I did my research on the system being in the trades "wood tick" I'm very curious on how things function and like to learn and understand them.

I called the original installer to give me a walk through of the system first thing he said was the pump should have been on the supply side but granny did not want to spring the extra 700.00. I had already read up on these sites including pumping away from the B&G site.As he was telling me this I thought to myself, if that was how it is suppose to be than why did you not just figure it right in the bid instead of an option, also looking at the new copper installed on the supply side I could not comprehend 700.00 to mount the circulator on the supply side.

Second company I had out the following year after seeing a few things original installer did not do as I have read should be done,I asked him what he thought about the pump location he said it is not that big of a deal which side it went on and went on to critisize original installer for putting automatic air vents in system with steel compression tank,and no shut off valves on both sides of the circulator and on the supply side of boiler so the whole system would not have to be drained to change out pump or boiler, so I had him do this for me there is 4500' of copper tubing in my system. He was a nice guy eager to discuss any questions I had.
Third company I had out the following year because company 2 was no longer in buisness so I asked this gentleman what he thought about circulator location and he said return side always.
So I decided to test the theory myself I put a pressure gauge on the supply side after the boiler and mixing valve and one on the return side just before the circulator where automatic air vents were.Well at 12 psi I get about 6 psi on gauge just before the circulator so my pressure falls 5 psi from the point of no pressure change. So I say it can be a problem if my system pressure happens to fall below 12 I could suck air into system as I have read. I have no leaks. I bumped my pressure upto 15psi.which raises a question is it bad to have the pressure higher than the 12 psi I understand you don't want it so high as to pop the prv but in my situation until I get it resolved would it help to bump up the pressure to help keep the air entrained in the water? I run pump continuous which helps also among other benifits.
And yes I do have to burp air periodically from my returns because original installer never put a spiro vent in the system or even a airtrol fitting on the steel compression tank. Incidentally I asked the original installer if he had ever checked out this site or the RPA and told him the wealth of information and great discussions on these sites, and his reply was "I have been doing boilers since I was 14 with my Dad." I had to go get my sunglasses so he could not see me roll my eyes the rest of the time he was there. Sorry so long winded and would appreciate comments. And thanks for taking the time to answer questions and discuss topics,you can tell when people enjoy their work!

Gordy

I love this site and the Rpa site. As a homeowner with radiant heat I monitor these sites daily to learn and laugh, you guys are a blessing.

As for the pumping away, I have had three different profesionals do a yearly inspection on my system which is a ceiling radiant and floor radiant closed loop system. House built in 1952, it was my grandparents which built it so I know the history.

When I bought the house I did my research on the system being in the trades "wood tick" I'm very curious on how things function and like to learn and understand them.

I called the original installer to give me a walk through of the system first thing he said was the pump should have been on the supply side but granny did not want to spring the extra 700.00. I had already read up on these sites including pumping away from the B&G site.As he was telling me this I thought to myself, if that was how it is suppose to be than why did you not just figure it right in the bid instead of an option, also looking at the new copper installed on the supply side I could not comprehend 700.00 to mount the circulator on the supply side.

Second company I had out the following year after seeing a few things original installer did not do as I have read should be done,I asked him what he thought about the pump location he said it is not that big of a deal which side it went on and went on to critisize original installer for putting automatic air vents in system with steel compression tank,and no shut off valves on both sides of the circulator and on the supply side of boiler so the whole system would not have to be drained to change out pump or boiler, so I had him do this for me there is 4500' of copper tubing in my system. He was a nice guy eager to discuss any questions I had.

Third company I had out the following year because company 2 was no longer in buisness so I asked this gentleman what he thought about circulator location and he said return side always.

So I decided to test the theory myself I put a pressure gauge on the supply side after the boiler and mixing valve and one on the return side just before the circulator where automatic air vents were.Well at 12 psi I get about 6 psi on gauge just before the circulator so my pressure falls 5 psi from the point of no pressure change. So I say it can be a problem if my system pressure happens to fall below 12 I could suck air into system as I have read. I have no leaks. I bumped my pressure upto 15psi.which raises a question is it bad to have the pressure higher than the 12 psi I understand you don't want it so high as to pop the prv but in my situation until I get it resolved would it help to bump up the pressure to help keep the air entrained in the water? I run pump continuous which helps also among other benifits.
And yes I do have to burp air periodically from my returns because original installer never put a spiro vent in the system or even a airtrol fitting on the steel compression tank. Incidentally I asked the original installer if he had ever checked out this site or the RPA and told him the wealth of information and great discussions on these sites, and his reply was "I have been doing boilers since I was 14 with my Dad." I had to go get my sunglasses so he could not see me roll my eyes the rest of the time he was there. Sorry so long winded and would appreciate comments. And thanks for taking the time to answer questions and discuss topics,you can tell when people enjoy their work!

Gordy

I love this site and the Rpa site. As a homeowner with radiant heat I monitor these sites daily to learn and laugh, you guys are a blessing.

As for the pumping away, I have had three different profesionals do a yearly inspection on my system which is a ceiling radiant and floor radiant closed loop system. House built in 1952, it was my grandparents which built it so I know the history.

When I bought the house I did my research on the system being in the trades "wood tick" I'm very curious on how things function and like to learn and understand them.

I called the original installer to give me a walk through of the system first thing he said was the pump should have been on the supply side but granny did not want to spring the extra 700.00. I had already read up on these sites including pumping away from the B&G site.As he was telling me this I thought to myself, if that was how it is suppose to be than why did you not just figure it right in the bid instead of an option, also looking at the new copper installed on the supply side I could not comprehend 700.00 to mount the circulator on the supply side.

Second company I had out the following year after seeing a few things original installer did not do as I have read should be done,I asked him what he thought about the pump location he said it is not that big of a deal which side it went on and went on to critisize original installer for putting automatic air vents in system with steel compression tank,and no shut off valves on both sides of the circulator and on the supply side of boiler so the whole system would not have to be drained to change out pump or boiler, so I had him do this for me there is 4500' of copper tubing in my system. He was a nice guy eager to discuss any questions I had.

Third company I had out the following year because company 2 was no longer in buisness so I asked this gentleman what he thought about circulator location and he said return side always.

So I decided to test the theory myself I put a pressure gauge on the supply side after the boiler and mixing valve and one on the return side just before the circulator where automatic air vents were.Well at 12 psi I get about 6 psi on gauge just before the circulator so my pressure falls 5 psi from the point of no pressure change. So I say it can be a problem if my system pressure happens to fall below 12 I could suck air into system as I have read. I have no leaks. I bumped my pressure upto 15psi.which raises a question is it bad to have the pressure higher than the 12 psi I understand you don't want it so high as to pop the prv but in my situation until I get it resolved would it help to bump up the pressure to help keep the air entrained in the water? I run pump continuous which helps also among other benifits.
And yes I do have to burp air periodically from my returns because original installer never put a spiro vent in the system or even a airtrol fitting on the steel compression tank. Incidentally I asked the original installer if he had ever checked out this site or the RPA and told him the wealth of information and great discussions on these sites, and his reply was "I have been doing boilers since I was 14 with my Dad." I had to go get my sunglasses so he could not see me roll my eyes the rest of the time he was there. Sorry so long winded and would appreciate comments. And thanks for taking the time to answer questions and discuss topics,you can tell when people enjoy their work!

Tony Conner

Are You Sure...

...the pump didn't become air-bound as opposed to cavitated?

Mark J Strawcutter

pretty sure

I opened the TRVs wide and increased the cold static pressure from 12 to 20psi and it eliminated the noise and vibration.

But you're right - an air bubble could have the same symptoms.

Mark

Mark J Strawcutter

I agree

that changing to pumping away just for the sake of pumping away is pointless. Like we say at work, it would be "a solution looking for a problem".

Mark

Tony Conner

I'm Having...

...a tough time imaging these little low-head, closed loop pumps, in relatively low temp service cavitating. I can sure see them becoming air bound, though because of the lower pressure at the pump suction allowing dissolved air to pop out of solution. Any newer multi-story apartment or commercial building has the hot water heating plant in a penthouse. The main reason this is done is so that the boilers don't have a lot of pressure on them from several (or many) stories of water above them. (Having a lot of pressure on the boiler can drag the installation under some expensive code requirements.) The side benefit is that the pumps and air separators are located at the top of the system as well. If the layout has been installed as "pumping away", then this will be far and away the best location to have the air kick out of the system. There will be very little pressure on the pump suction in this arrangement. This kind of closed loop circ system has different pump considerations than say, a feedpump in an industrial steam plant having a deaerator under maybe 5 PSIG, a few feet above the pump suction, and pushing water into a boiler running at almost 300 PSIG. In cases like this, NPSH is critical.

Kal Row

what if the

primary loop is at 190 degrees and 5psi, due to an air leak in the secondary,

water's surface interaction with air due to it's molecular structure gives it interesting properties, like not freezing as it being compressed even when it's below 32, and boiling well below it's normal boing point if it's suddenly decompressed, 5psi water going into the eye of a pump at 190 is on the edge of cavitating - why chance it

Tony Conner

I Really...

...see air problems in closed loop hot water heating systems outnumbering cavitation problems by a factor of many. Somebody is actually going to have to show me a picture of cavitation damage on a residential closed-loop heating system circ impeller, because I believe that the situations that are being called cavitation are actually air problems. If the system has been designed and installed correctly, you'll have something like 12 PSI on the pump suction anyway. If you're down to 5 PSI at the suction, I think you're pumping right at the tank.

I'm not saying that you could never-ever cavitate a pump in a service like this, but I'd bet that long before you hit a true cavitation situation, you'll have a bunch of air related problems first.

Mark J Strawcutter

yup

Quite common on residential systems to have circ on boiler return right next to the boiler (where mfgr put it), expansion tank on supply right off boiler. So, yes, you're pumping right at the tank.

Mark

Unknown

As Noel stated

in a post above, we can also give you just about anything you want as far as brands of pumps and burners. They can be ordered with and without both as well. But part of the problem is that the didtributor is going to need more room to be able to have boilers with and without pumps and/or burners in stock. This is much of the reason that you see them with them. Many of our distributors stock packaged, knocked-down, and Semi-assembled boilers which gives you all sorts of options. But as I stated already, that all requires more space. Hope this helps.

Glenn

hr

Glenn, make it easy

on the distributors. Boilers come without pumps, period. Then they don't need to double stock!

Most distributors already stock circ pumps, at least the ones serious about hydronocs.

The other nice benefit is you don't end up with a boiler and a pump out of date code because it sits on the warehouse floor.

Lots of distributiors tell me they have to take a certain amount of "slow seller" boiler models with every order. Those can sit for years at the supply house.


It may even help you sell MORE boilers if the customer had a choice, other than black or green

hot rod

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hr

I agree, Tony

Small, low rpm, wet rotors tend to sieze up way before they destroy impellers or volutes from cavitation. Usually an air bubble issue.

Not a lot of difference between open system (dhw recirc)circs and closed, except for the volute material.

hot rod

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Mark J Strawcutter

So how do you tell

if it's cavitation or an air bubble?

Mark

Tony Conner

Cavitation...

...is the actual flashing of the liquid in the pump into it's vapour state, because the drop in pressure at the pump suction takes the liquid below it's boiling point, for that pressure. This can happen with any liquid. The vast majority of people on this board will be concerned with water.

When cavitation occurs in a pump handling water, little steam bubbles form in the eye of the impeller, where the pressure is the lowest. These bubbles move through the pump, carried by the water. When they hit the higher pressure areas of the pump, they suddenly collapse back into water. This leaves a vacuum, where the steam bubble previously existed. The inrush of water to fill the void is so fast, that actually takes a bite out of the impeller metal. The same thing can happen in steam system start-ups where you get steam and cold condensate rubbing up against each other in the same line. Steam bubbles trapped in condensate collapse instantly, and the water rushing in to fill the vacuum that's left can actual tear piping apart apart. This is on a much bigger scale however, than pump cavitation. If a pump is cavitating, it'll sound like it's pumping gravel. (That's the steam bubbles collapsing.) If it goes on long enough, you can see the metal loss on the impeller. Sometimes, there's a LOT of metal loss. We had a gasoline driven pump for pumping rainwater out steam manholes. (It would likely actually pump only 3 or 4 hours a week, on average.) We were always trying to get a suction lift (sometimes 10 or 12 feet from the manhole sump to the pump sitting on the road) on hot water. We knew that there was cavitation, but that was the nature of the beast - it was basically a consumable pump. Over a couple of years, it took longer and longer to pump the holes out. So we pulled the pump apart. I'm guessing that there was 1/3 of the impeller missing. It looked like it had been REALLY sandblasted. You won't see anything like that with air binding. Also with cavitation, it's unusual to have it so severe that the pump just totally stops pumping. It'll almost always keep moving water. It just sounds like it's pumping water with a lot of rocks in it. And every time you hear a "rock", that's another little bit of the impeller that's gone.

Mark J Strawcutter

I understand

what cavitation is and how it happens.

In my single experience with suspected cavitation, there was noise and vibration. Hardly any on cold start, more as temp increased. Opening TRVs and increasing pressure pretty much eliminated the problem.

So short of physically examining the impeller, what's the best way to tell if it's cavitation or air bubble?

Crack the pump flange bolts and see if any air "bleeds"?

Mark

Unknown

Hot Rod

Unfortunately it is not us that dictates this....it is the distributors choice and not ours. The other problem is making the other customers that are expecting the pump to be there, aware of why it isn't anymore. I tend to agree with you because I see one with 6 or 7 zone valves most of the time. As someone else in this thread stated, somehow the 007 has been labeled as the "Universal" pump. I think the most 571 Zone Valves I have seen on one pump was 12 and that job had a Taco 110 with a 1" supply and return main. I used to know a plumber in RI where I live that would save up all the 007's shipped with our boilers and use them together on on job so they all matched (painted black).

In black and white here on "The Wall", it appears to be a simple thing to stop shipping pumps with the boilers. But, in reality, it will require a huge effort to get the word out so that the contractor that called in a boiler and 3 pumps for a four zone job and is expecting the one with the boiler, doesn't get caught out in the middle of "East Overshoe" somewhere without that fourth pump. As Noel and I stated earlier, the distributor can order his boilers any way he wants them....we give them that option. Everyone has differing preferences in what they want to stock and we all pretty much let them make that choice.

I also will say that the selection of boilers that a distributor orders is his choice and that they are not necessarily required to order slow movers with each load. All they need to meet is weight so that the freight requirements are met. That may not so with other manufacturers though.

hr

Mark

I would start by looking for things that invite cavitation. Any restriction at the inlet of the circ, plugged strainers, closed valves, collapsed tube, etc.

Probably take a pretty trained ear to discern the difference in a small pump.

And actually why would it matter? In either case air, or cavitation, it needs to be fixed Usually in the course of the troubleshooting you'll determine what to call it. Like you did on your own system, with the flow restriction.

At the Grundfos traing lab they have demos panels with "means" of inducing cavitation into piping systems. Until you get up into the large pumps, it's pretty hard to pickup the noise. Certainly sounds a lot like air bubbles to me.

hot rod

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