Can't get basement zone circulation after replacing circulating pump

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  #1  
Old 10-16-13, 01:37 PM
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Can't get basement zone circulation after replacing circulating pump

I was hoping someone had some insight into this problem. I recently replaced the Taco circulator for the basement zone on our 3 zone hydronic boiler. With the old broken circulator, the first two baseboards on this zone would get super hot while the last baseboards were stone cold. The new circulator appears to be working and I can hear it whirl away when the zone is turned on.

Nevertheless, I am unable to get any water to flow through this zone. The circulator is located on the return to the boiler, between the boiler and the zone drain valve. When I open the drain valve, pressure from the boiler (10 psi) causes water to travel up the return through the circulator and out the drain. However, when I close the ball valve between the circulator and the boiler, all flow out of the drain valve stops. For the other two zones, I am able to get water to flow out of their drain valves with their ball valves closed, as pressurized water travels from the boiler through the supply lines to the zones and then returns to the drain valves. In fact, this is how I usually bleed air out of the other two zones.

Now the other two zones are located above the boiler which is in the basement. The basement baseboards are plumbed in series with pipes running between the baseboards at about the same elevation as the baseboards. The supply from the boiler runs at the top of the ceiling and then drops to the first baseboard. Similarly, the return from the last baseboard rises towards the ceiling before dropping down again to the drain valve/circulator/boiler.

There is a B&G flo control valve on the supply side. I gave this a few gentle taps with a rubber mallet just in case the valves were sticking.

Since the zone is basically plumbed as a "U" (piping dropping from ceiling to floor and then back to ceiling), could there be a problem with being unable to push any residual air out of the zone? That's what I'm starting to wonder.
 
  #2  
Old 10-16-13, 01:57 PM
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Purging air from a line located below the main can be extra difficult. Try jacking up the boiler pressure to, say, 25 psi. That will give you higher purge flow. The flo-control valve shouldn't be a problem unless you are trying to purge in the wrong direction.
 
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Old 10-16-13, 03:55 PM
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Your system is zoned with pumps I think? Pump for each zone? no zone valves?

pressure from the boiler (10 psi)
Why so low? How many stories is your home?

Agree with Gilmorrie, jack it up to bleed.

The flo-control valve shouldn't be a problem unless you are trying to purge in the wrong direction.
But purging at a very slow rate might not really be enough to lift the disc, presuming it's the weighted disc variety.

What make/model is the flo-check? Can you manually open it to bleed?

How is the water fed into your boiler? You have a 'pressure reducing valve' ? Does your pressure reducing valve have a 'fast fill' lever/handle on it?

If so, close the ball valve, hook hose to drain, open drain, lift 'fast fill' lever to push water through zone at higher pressure. 10 PSI won't be enough...
 
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Old 10-16-13, 04:39 PM
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OK, here's a back-up plan. Purge backwards from the boiler return, through the pump, and out the zone valve. The flo-check at the supply will block flow, and you will get a power purge through the leg between the drain and the boiler, which I seem to understand is where the air blockage is?

In either case, jacking up the boiler pressure will give a more powerful purge and compress any trapped air into a smaller volume. Increasing pressure from 10 psi to 25 psi will reduce the air volume by a factor of 2.5 based on the ideal gas law.
 
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Old 10-16-13, 05:21 PM
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Purge backwards from the boiler return, through the pump, and out the zone valve. The flo-check at the supply will block flow, and you will get a power purge through the leg between the drain and the boiler,
I don't comprehend... please explain a bit further.
 
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Old 10-16-13, 06:47 PM
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I may be confused here. It would seem that he has already been purging backwards through the pump if I understand the system configuration correctly. Jacking up the pressure ought to help, though.
 
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Old 10-16-13, 07:10 PM
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Maybe...

I think the whole procedure is correct with the exception of the low boiler pressure and not using a 'fast fill' to purge. If I'm visualizing it correctly that is...

Knowing where and how the water is entering the boiler will help.

As will PICTURES! GSM, please post some if you can so we can see what you are working with.
 
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Old 10-17-13, 08:47 AM
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Thanks for the replies!

Sorry I didn't post pics, but I'll try to soon.

FYI, there are no zone valves. Each zone has its own Taco circulating pump, not a common pump. Moreover, the water fill/make-up connects to the common return manifold for all the zones, immediately before the return back into the boiler.

The flo control valves are the original (late 1980s) B&G cast iron straight-angle types with dyna-disc assemblies. Honestly, I don't think I could manually open them if I tried - they are rusted up nicely. Plus, they are obsolete so I probably would have a hard time trying to find replacement packing/packing nuts, etc... in the event they failed upon turning. I have thought about trying to disassemble them for cleaning and do have the gaskets for reassembly. But that may be overkill at this point.

Also, it's a 2-storey house with basement. I get great flow through the 1st floor zone and adequate flow through the 2nd floor zone. So bumping up the pressure may not be a bad idea, to improve the 2nd floor heating.

There is a quick fill lever on the fill regulator pump. I'll give that a try to boost the purge pressure for the basement zone. The last time I used it, I went too far and got the 30psi pressure relief valve to open, emptying water all over the place. Unfortunately, there is no drain for the relief valve, so it was quite a mess.

I'm also wondering if it makes sense to install a drain valve in the basement zone after the last baseboard and before the return pipe elevates back towards the ceiling. In this case, I could use that drain valve to fully drain any water in the baseboards, leaving only air to purge in the future.
 

Last edited by GMS99; 10-17-13 at 09:04 AM.
  #9  
Old 10-17-13, 05:09 PM
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There is a quick fill lever on the fill regulator pump. I'll give that a try to boost the purge pressure for the basement zone. The last time I used it, I went too far and got the 30psi pressure relief valve to open,
Not only to boost the pressure initially before purging, but holding the fast fill lever open WHILE PURGING, keeping an eye on the pressure gauge while doing so. In order to move that air out of that zone you need to keep that water moving about 6 feet per second... any slower and the water will not 'pick up' the air and push it out of the piping.

I'm also wondering if it makes sense to install a drain valve in the basement zone after the last baseboard and before the return pipe elevates back towards the ceiling. In this case, I could use that drain valve to fully drain any water in the baseboards, leaving only air to purge in the future.
I don't understand the logic... you want to replace water with air... only to purge the air?

I don't think you will find it to be necessary to make any modifications once you purge properly by using the fast fill to 'power purge' the piping.

Also, it's a 2-storey house with basement. I get great flow through the 1st floor zone and adequate flow through the 2nd floor zone. So bumping up the pressure may not be a bad idea, to improve the 2nd floor heating.
Let's talk about physics...

In order to raise water in a pipe, you need 'static' pressure. It takes 0.432 PSI to raise water one foot.

Let's say your 2nd floor zone is maybe 20 feet above the boiler. In this case, you would need:

20 X 0.432 PSI or 8.64 PSI just to raise the water to the level of the highest rads. At this point, there is no 'static' pressure in the 2nd floor rads. That 8.64 PSI is only enough to get the water up there. In ADDITION to the 8.64 PSI we need to ADD about 4 PSI in order that the entire system is pressurized at all times. So the MINIMUM pressure when the system is cold can (should) not be less than say 13 PSI.

So you need to increase your COLD BOILER minimum operating pressure to at least that amount.

The pressure gauge on your boiler is probably not accurate. Read this:

http://www.doityourself.com/forum/bo...ure-gauge.html
 
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Old 10-21-13, 01:40 PM
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So increasing the purge pressure seemed to work

This weekend I carefully increased the purge pressure for the basement zone (roughly 15-20 psi) using the quick fill lever on the pressure reducer and was able to re-establish purge flow in that zone. There was a tremendous amount of air in that zone which is approx 80 linear feet. I also increased the boiler cold pressure to 12psi (now 25psi at full temp, roughly 180F). I figure my second floor baseboards are roughly 17 feet above the pressure regulator.

Nevertheless, I still only get modest flow through the basement zone when calling for heat, while the other two zones flow nicely. The new circulating pump seems to be working still and it was installed in the correct flow direction. Is this experience normal for a zone that has multiple "ups and downs" (floor to ceiling and vice versa) in the flow path?

For reference, I've attached a few photos of the boiler zone connections and configuration. The basement zone is far right while the first floor is far left.
 
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Old 10-21-13, 02:12 PM
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You've probably still got air in that zone... I'll look at the pics more closely and review your last post in an hour or two.
 
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Old 10-21-13, 05:34 PM
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OK, sorry, longer than I thought...

Not only to boost the pressure initially before purging, but holding the fast fill lever open WHILE PURGING, keeping an eye on the pressure gauge while doing so.
When you were purging the basement zone, did you do as above? Did you hold the fast fill OPEN while you were purging the zone? If not, do it again.

You need to 'force feed' the water through the zone.

Hook up drain hose to zone drain valve, close valve below circulator.

Make sure the boiler is OFF and temperature below 100F.

It's best if the end of the drain hose is underwater in a bucket so you can see when the bubbles stop coming.

OPEN the drain valve and OPERATE THE FAST FILL and flow AS MUCH WATER AS POSSIBLE through the zone without opening the relief valve. Do this by watching the pressure gauge. Try to hold the fast fill open in a position that maintains say 25 PSI on the gauge.

When no more bubbles, release the fast fill, and close the drain, in that order.

Remember that adding all that fresh water is also adding all the air that is dissolved in that fresh water. Once the boiler is heated, that air is going to come OUT of the water and form bubbles in the system again, so make sure that your air scoop and automatic air vents are working properly.

You may not have automatic air vents though... it depends on what type of EXPANSION TANK you have.

Is your expansion tank the type that looks like a gas grill fuel tank hanging from the pipes?

Or, is it the large steel tank in the floor joists above the boiler?

I ask this because you have 12 PSI cold, but 25 PSI HOT, and this may indicate that your expansion tank needs service, whichever type you have.

Why not stand back with the camera and give us a wide view of the entire system? It will help ...
 
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Old 10-22-13, 08:44 AM
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Yes, held fast fill open

Yes, I held the fast-fill open the entire time purging. I used a washing machine hose on drain valve, submerged the open end in a bucket, and the flow was rapid. About 20 gallons later, the water was running virtually bubble free. My guess is that at 80 linear feet of 3/4 inch copper tubing, the zone has a volume of about 2 gallons (the boiler itself has a 3+ gallon capacity).

The expansion tank is an old gray Amtrol bladder type tank (probably the original from 25 years ago). It is located on the supply manifold just below the B&G check valve for the basement zone (see bottom photo). Tapping on the tank's top and bottom indicates that the water (top) has not breached the bladder into the air portion (bottom). I have not measured the pressure in the air portion (factory charge was 12 psi) and it wouldn't surprise me that it needs to be recharged with air (on the to-do list).

Before I bumped up the system pressure, the pressure used to run between 10 psi (cold) and 20 psi (hot). Now the hot pressure seems to be slowly rising (nearly 30 psi last night before I vented off enough water to drop it back towards 20 psi). I'm sure the fast fill lever was pushed all the way back to automatic but there is no locking notch (it's another old part, 25 yr old Taco 329 regulator). The locking nut on the adjusting screw is tight. I hope the regulator hasn't failed after resetting the pressure and purging.

There is no air scoop on the tank; rather, there is an air scrubber on the top of the boiler itself (schraeder type valve, see top photo). I leave the cap on the schraeder valve loosely attached to allow the residual air to purge.

Sorry for the lack of additional photos. It a small boiler room with maybe 2-3 feet clearance around the boiler itself.
 

Last edited by GMS99; 10-22-13 at 09:30 AM.
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Old 10-22-13, 11:11 PM
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Do any of those circulators have built in IFC (flow check valves)? I've run into problems with the IFC equipped pumps on my heating system.
 
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Old 10-23-13, 07:54 AM
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No IFC on circulators

The the flo-checks are separate (B&G valves, the red valves in the photos).

I recharged the expansion tank last night to 12 psi. The pressure is now fluctuating between 12 psi (cold) and 19 psi (hot).
 
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Old 10-23-13, 10:05 AM
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I still only get modest flow through the basement zone when calling for heat, while the other two zones flow nicely.
Is this a 'perception' of modest flow? Or do you have some way of actually measuring the flow?

Are you basing your perception of flow on how much heat you feel coming from the baseboards/radiators?
 
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Old 10-23-13, 11:41 AM
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This may sound foolish but is the new pump going the right way. Check the arrow on the back.
 
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Old 10-25-13, 08:16 AM
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Perception of flow

I believe the basement zone is not getting proper circulation based upon baseboard performance. The baseboards are plumbed in series through the finished basement walls, with the upstream baseboards getting hot while the downstream baseboards are cold. The ambient temp is only 60F so dramatic heat loss can't be the reason. And the baseboards are located about 3 inches off the floor so it can't be heat loss into the ground.

I plan on replacing the expansion tank given its age and how cheap a new one is ($40). When I do that, I'll try purging the basement zone some more just to see if any further residual air is dislodged. I'm also going to repressurize the expansion tank on our water heater, which is about 10 years old (cold water pressure is 70psi at our house as measured by the water company earlier this year).

The circulating pump is installed in the correct direction (arrow pointing down, which is back toward the boiler in my installation where the pump is on the return side of the system).
 
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Old 10-25-13, 08:54 AM
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with the upstream baseboards getting hot while the downstream baseboards are cold.
How many feet of fin-tube element on this loop?

It does sound as if the flow is somewhat 'lazy', and sure, could still be air in there.

Looks like the air vent on top of the boiler is in poor condition also...
 
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Old 10-25-13, 10:29 AM
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When bleeding the basement zone are you closing off the other 2 zones to assure full pressure to that zone.
 
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Old 10-25-13, 10:46 AM
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As long as the ball valve below the basement pump is closed, the only way for the water to flow 'should' be through the basement zone, but I know that theory and reality sometimes differ.

So, yeah, to be absolutely certain that all the flow goes through the basement zone it's probably a good idea to close all three of the valves below the pumps.
 
 

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