Boiler pressure rising to 30psi when cold water feeder is on

klamb88

i have a natural gas single zone forced hot water base board system, just replaced the cold water feed reducer, PRV, expansion tank, and temp pressure gauge. boiler ran fine for a few hours at 20psi with the cold water feed on, but after about 4 hours the pressure rose to 30psi and the PRV began to drip. I shut off the cold water and release pressure down to 20psi and the boiler is working normal.

any idea why this is happening only when the cold water feed is on?

JUGHNE

How do you heat your domestic hot water for sinks etc?

Jamie Hall

If there's no domestic hot water involved -- no indirect, no tankless coil, etc. -- then either the PRV is leaking by or the shutoff valve on the water feed is.

unclejohn

Pressure reducing valves do not drip. Backflow preventers drip and so do relief valves. Post a picture of the work you have done.

unclejohn

After rereading your post I guess it is the relief valve that is dripping and not the reducing valve.  A few pictures would still help. It seems you have replaced every thing that would cause over pressure of the boiler. Is there a shut off valve between the expansion tank and the boiler. 

klamb88

JUGHNE

Did you check the air charge of the tank before installing?
You can do it now by isolating it with the ball valve and bleeding off water with the pressure relief valve right next to it....with the CW supply off of course.

Tank pressure isolated and drained should equal the fill valve adjusted pressure, usually 12 -15 PSI.

klamb88

Just bled the pressure down to 14psi and opened the cold water feed. Charged up to around 17psi after running for a few hours. Going to keep an eye on it, I think maybe the system was filled up to fast last time with the quick fill wide open

klamb88

same thing happened, after 4 hours with the cold water feed on it came back up to 30psi. i think the auto fill value must have been damaged when installing

EdTheHeaterMan

The Auto Feed Valve (Pressure Reducing Valve PRV) is adjustable. You can remove the fast-fill handle, then loosen the locking nut, then back off the pressure adjustment (you might need to remove the rod inside the adjusting screw). After you back off the pressure adjustment til there is no spring pressure (easily turns by hand) you can see if the pressure rises over time. If it does, then the valve is defective or there is something stuck in there not allowing the valve to close.

Let say it does stop allowing water to flow ... then the PRV is probably fine. Now you can adjust the valve slowly up to the needed pressure. turn clockwise until you feel the spring pressure on the adjustment screw. keep tightening until you heat some water flow thru the valve. I use a mechanics stethoscope but a plastic tube or a straw will also work. Once you hear the water flow allow the pressure to rise to 12 PSI in the boiler then slowly back off the adjustment until the flow stops. You are set.

Respectfully Submitted.
Mr.Ed

BTW PRV can also mean Pressure Release Valve. That is why I use Auto Feed for PRV and Relief Valve for the other PRV

HomerJSmith

My eyes aren't so good anymore. Can you tell me why a Watts pressure relief valve is connected to a Watts pressure fill valve? Ok I just magnified the picture and the Watts connected to the Ex Tank is a reducing valve set to 15 psi and an inlet pressure of 30 psi.? Why the redundancy?

EdTheHeaterMan

There was a time in days gone by that installed started with a bunch of parts and built a boiler in the basement. @HomerJSmith, There were many "time saving" devices made to get an edge on the competition. Like putting the relief valve and water feed in the same box, already put together. B&G did that for years with this product.

I remember upgrading old coal boilers with this device when we installed new oil burners in them.

That thing in the photo is the Watts version of it.

I would not have chosen that particular device for that boiler because that boiler already has a relief valve included from the manufacturer. I might have selected a combination Backflow preventer auto feed in this case.

Respectfully Submitted,
Mr.Ed

HomerJSmith

Yes, Ed a Watts 1450. I didn't see a drain on the relief valve to the floor, but it does look like drips on the EX tank. I was taught years ago that the relief valve had to be within 6" of the boiler HX.

I would say that the EX tank pressure may be too low or too high.
Too low and the tank will become water logged with little room for acceptance, too high and there won't be any water acceptance into the tank. The air charge should be set at 15 psi and as the boiler fills with water check the gauge for 15 psi. If you don't have a gauge put one with a 30-60 psi read on the boiler drain next to the white bucket and stop filling when the gauge reads 15 psi.

It has happened that sometimes a replaced part like the pressure regulation valve thought to be good can be bad, too. That pressure regulation valve can be adjusted.

The other possibility is flashing in the HX which I doubt.

https://s3.amazonaws.com/s3.supplyhouse.com/product_files/0388798-Install.pdf

JohnNY

You haven't shown the position of your pump. Stand back and take a picture of all the boiler piping.

woodrow

There should be a 9d backflow preventer not another relif valve .

woodrow

pump looks to be right above but feeder is at the expansion tank i would think low charge on expansion tank or something stuck in feed