flow valve passing

ray hickethier

I have a home that now and again has a problem with the 2nd floor loop getting gravity heat even though there is a flow valve and the t'stat is not calling, nor is the circulator running. I purge the loop and all is well for a time. I know I could put a spirovent on the loop but how is the air causing the loop to hold the flow valve open or pass it and gravity heat the space?

billtwocase

all you are doing

is somewhat flushing the flow check out. It needs to be replaced. If you want a better shot at flushing out whatever is stuck in it, run the circulator for that zone, and lightly tap the valve while the water is flowing thru it. This usually does the trick. Also make sure it is closed, meaning the threaded stem op top. Just a few good raps should dislodge what may be in there. Pics will also help here.

ray hickethier

flow valve passing

The flow valve was replaced shortly after the addition was put on within the past 10 years. It was again replaced two years ago. The problem is not the flow valve. I opened it and it is clear. There is something strange going on here that when the loop gets air in it it causes the flow valve to pass. The expansion tank is not full which could cause the expansion to occur in that loop if it were. ????

billtwocase

I would

like to see a diagram or better yet pics of what you have, and how it is piped. Was that zone added 10 years ago, or was  this valve replaced 10 years ago? 

ray hickethier

flow valve passing

The home has convectors with a mono-flow system on the 1st floor with its own circ. and flow valve. They raised the roof about ten years ago and added a standard baseboard loop with a Taco 007. The contractor replaced the flow valve within a year of the addition completion according to the homeowner because it was passing. It was replaced again two years ago. A month ago a tech purged the loop and it was ok until the other day. I purged it again, and got air out and it is now working as it should again.

I just don't understand how the air in the piping is causing the flow valve to pass. (I believe the air is coming from # 67 air vents on the 1st floor loop convectors) 

billtwocase

I don't see

air causing this. It would have the opposite effect. The air issue needs to be rectified, but that is not causing your ghost flow. It sounds like the piping configuration to me. Without pics, or a diagram, one can only guess at this. Where are the pumps and valves? The monoflow flow check definitely has to be on the supply, but where, and what size is the valve for the 2nd floor? Is it an iron or swetcheck? I would close the auto vents upstairs, and put one on the boiler

icesailor

Air Vents:

You may have air vents on the first floor. If you have auto air vents on the second floor, it is far more likely that the air is coming in through the second floor vents. The pressure in the system probably isn't high enough. If you have a thermal expansion tank and it needs to be recharged with air, that will cause problems. If you have an Extrol type tank, it may not be working properly.  You need to know that the system pressure is high enough. Don't trust the gauge on the boiler.

Carefully trace the newer added on pipe to the monoflow loop. You might have a connection in the wrong place. That's why i always use zone valves. They are motorized flow checks. They CAN'T leak by. Circulators with Internal Flow Checks $uck. They always suffer from Ghost Flow when you don't want or expect it.

lchmb

Do

you have an expansion tank or the old style steel tank?

ray hickethier

flow valve passing

It is a steel tank. I'm thinking perhaps the feeder isn't feeding correctly and it's causing the air in the upper loop but it still doesn't explain why the flow vave passes when this occurs. Many systems get airbound w/o getting gravity heat. BTW the flow valve is 1" on a 3/4 line. I have not had good luck with 3/4 so I beefed it up when I repaced it two years ago.

icesailor

Passing:

And you know for a fact that the pressure reading on the gauge is accurate? That if it reads 15" on the gauge, and you put another pressure gauge on the boiler or system, it would read 15#? Or will it read something lower?

You know for a fact that there is air in the tank and the air is under 15# pressure?

If not, very strange things can happen.

Ron Jr._3

Agree with Bill

I doubt gravity flow would happen if air is trapped in the flowcheck . Like he said , flow would actually stop if there's an air pocket trapped in the system like that . Do you ever hear rattling coming from the check ?  Are the circulators near the flow checks ?  Some manufacturers recommend a 2nd flowcheck for each zone . One on supply and one on the return . 



Probably not part of the problem , but you shouldn't have any means of auto air elimination when you have a standard compression expansion tank . Any air in the tank will eventually find it's way out through the vents .

lchmb

If

you have an old steel tank you do not want to add air elimination to the system. The idea is to divert the air to the tank itself not bleed the air out of the system. If you do want to add a spirovent, then you need to replace the steel tank with a bladder type tank...

Paul48

Lose

the vents on the convectors.Just a thought.....the air is compressible,the water is not.