No water flow in one zone

AlMiller

We have a 5 year old Lenox boiler with a TACO 007 F5 circulation pump. This year we are having difficulty getting heat from all 3 of our zones. The 2 zones that do heat are pretty straight forward.
The living, dining kitchen zone has minimal vertical rise, only about 3 feet and all registers are at floor level. This zone has the most heat.
The bedroom zone has a 11 foot rise, all registers on the same level and then back down 11 feet. This zone has slightly less heat but adequate.
The family room level is where we have trouble. It has about the same lineal feet of registers, but has 3 different 8 foot rises and 3 separate 8 foot drops before it joins the return line.
If all zones are open hot water flows through the first 2 zones, but does not flow through the family room zone. If I shut off the first 2 zones I can get flow, but it takes approx 15 minutes before the return lines feels warm (100 deg??) to the touch.

I think the circulation pump isn't moving enough water. I know in theory all the up land down of that zone shouldn't matter, but what else could it be?

Any input would be appreciated.
Al

rick in Alaska

Check to make sure the pressure in the boiler is at least 12 pounds. If it is, then make sure all the air in the system is out. If you can hear gurgling noises in the piping, you have air in the lines and they will have to be bled out. Those are the most common problems that slow down flow, but there is a possibility of it being the pump.
Rick

Gordy

What is the system pressure on the boiler gauge?

Could be an air issue, but if system pressure isn't correct there won't be enough pressure to get the water to the high point in the system. Should be 12-15 psi while the boiler is at ambient, not hot.

AlMiller

I bled all 3 zones and found no air.
Pressure gauge shows 30 psi.

Jamie Hall

30 psi is about twice as much as you need at any time. If nothing else is wrong, the expansion tank is either failed or waterlogged, or the pressure reducing valve feeding your system is failed or set wrong.

AlMiller

When the boiler was installed, the guys set it at the 30 psi and told me that was the proper setting.
Would lowering the pressure do anything for me?

AlMiller

I forgot to mention that the 30 psi is constant either hot or cold.

Gordy

Lowering the pressure will not help. Sounds air bound. Which means radiation needs bled.

30 psi will pop the relief valve the boilers relief valve is 30psi.

rick in Alaska

When you bleed air out, does it spray out pretty strongly? I am wondering if your gauge is accurate.
Rick

Gordy

In light of last post I question the accuracy of the psi gauge, or the PRV is in need of replacement. It should start opening at 30psi. You would see water on the floor.

Gordy

If this is a problem In relation to the new boiler installation. The installer should be called back to resolve this issue. Since trapped air sounds like the problem, and the air was part of draining the system to install the boiler.

However...... if he says that 30psi is normal system operating pressure. I'd question his abilities........

AlMiller

When I bled the system the end of the hose was under water. No big burps, but very small bubbles came to the surface from all 3 zones. Definitely not enough for an air block.

Gordy

Don't be so sure about that. Small micro bubbles will form big ones while system is idle collecting at the high points. Plus your system psi is very high which compresses those bubbles.

Should bleed until no air bubbles big or small are present.

Is there an air removal device at the near boiler piping area?

What type of expansion tank?

JUGHNE

I see a real concern about the 30 PSI and the relief valve not passing water.
Pictures of your boiler piping and especially the tag on the relief valve. They might all look the same but are not.

Gordy

One other thing look at the pressure relief valve, and tell us it's rating.

AlMiller

Had to go out for a couple hours, but back in the cold house.

I must apologize for my stupidity and 70+ year old eyes. When reading the pressure gauge I was looking at the Feet instead of PSI. Actual PSI is between 15 & 20.
Pressure relief valve is 30 psi.

As an experiment, I partially closed the ball valves (60 degrees) on the two zones that are putting out heat. I hope that that would force more water through the cold zone. So far no effect.

On the boiler I have set the hydrostat at 200 degrees. When the gauge reads 200 she shuts down, but the temp keeps rising up to about 220. I can hear the circulation pump continue to run. I would expect the water temp to start falling as soon as the boiler stops, but it doesn't, just the rise in temp for another 5 minutes or so. It than slowly drops to 180 and the cycle repeats.

Alan (California Radiant) Forbes

That rise in temperature is normal. Once the flame turns off, there's a lot of residual heat in the heat exchanger that increases the water temperature. And the increase in temperature is a function of how much water is flowing. More water will give you less of an increase in temperature.

Try completely closing the two ball valves on the zones that give you heat. That will divert all of the pump's pressure differential to the one errant zone and may be enough to remove the air.

AlMiller

I have tried that already and hot water does start flowing in the zone. Following the warmth from register to register it seemed to take a long time for the hot water to make a complete round trip back to the return.
I'm ready to pack it in and have the original installer back out for a "professional bleeding".

As we say here in Minnesota, 65 degrees in the house is actually good sleeping weather.

Thanks to all for your interest and suggestions. Time for a beer.

Alan (California Radiant) Forbes

Prosit!

Let us know how it goes.