Boiler psi help

[drunknpirate]

I just bought a building in March. During early spring when I had the heat on I had no problems with the boiler. Now that winter is kicking in and the heat is back on the pressure relief valve is pissing out water when the system is running. It is a gas fired hot water system. The psi is at 20 when at rest and reaches 35-40 psi while running. The vavle is rated at 30psi so I understand why its leaking but I don't know why the system is reaching this high of pressure. I never bothered to check the psi this past spring since there were no leaks.
I have drained the expansion tank which had no effect. The building is running cast iron heaters. I have the pipes running upstairs shut off because I had to remove the cast iron to sand the floors. They should be hooked back up sometime this week. Is the high pressure caused by half the system shut off? Is the higher then normall pressure causing any harm to the system? The upstairs has its own pump and thermostat.

 

[havasu]

Bump to top for anyone with boiler knowledge!

 

[buhrly]

I would check the expansion tank again.
Does it have air in the bladder?
Is the pressure less than the systems operating pressure of 20 psi?
Is it large enough for the system?
Jeremy

 

[drunknpirate]

The system as an old style expansion tank that hangs from the ceiling. I have replaced the regulator that takes the water main pressure down to 12 PSI and drained the expansion tank and refilled it as per info I found online. The Pressure relief valve is no longer leaking but the PSI is still getting up to 30. I'm guessing just low enough to not have the relief valve open. I would still like to get the system working correctly and not "just enough" to not have water leaking. Since the system is so old I don't mind updating some parts. I bought a new bladder style expansion tank and want to hook it up and get rid of the huge tank hanging from the ceiling.
I bought a Watts ETX-30 from home depot. I don't know if this tank is big enough. They also had a ETX-60 but I dont know if that is over kill. I know it depends on how many gallons are in your system but I have no clue on that one. The building has 4 big cast iron heats and 2 smaller cast iron heaters up stairs in the apartment. Down stairs in the two store fronts, there is newer copper base board heat that runs on its own zone (each floor is about 1200 sq ft) . Is the 30 tank I bought big enough? I'm hoping this tank will function better then the dinosaur I have and cut the pressure down a few psi.

 

[buhrly]

The systems pressure should not fluctuate like that which is what a properly functioning pressure tank will fix. The old style can easily become waterlogged and not function. The new bladder style must be checked on occasion for correct bladder pressure.
Here is a sizing chart for your use.
http://www.watts.com/pdf/ES-ETX-ETSX.pdf

 

[drunknpirate]

Thanks for the reply. One of the first things I did after buying the new tank was check out the watts website for instructions. I honestly have no idea as how many gallons of water my system holds so the calculator on their website doesnt do me any good. Can some one take a good guess as to how many gallons my system might hold?

 

[buhrly]

Try to estimate pipe length and size. Then use Pi R squared by length.Next change to this to gallons. Add in the amounts of gallons for the heaters, boiler, expansion tank, etc. This should get you in the ballpark.

 

[EinsteinHQ]

Quite intrigued, did you ever figure out how many gallons your system was and did you get the pressure regulator figured out?
Regards,
Jared
Moderator note: No links in the body of posts, please!

 

[frodo]

adjust the water pressure with the pump running at the PRV




IF, after you have set your pressure, and the pressure rises

replace the defective PRV


to adjust, hook a hose up to a drain, look at the gauge

if above the psi you desire, bleed the system down.

to below your desired psi. adjust prv to below the desired psi

turn on ppump, slowly incrementally bring pressure at prv up to desired psi
stop.
bleed system
let it fill, ck that it is correct at gauge

if you need to adjust. do so

stop, bleed down
let fill, looking at gauge

go to end of the system,,bleed any air

come back.
check system.
go outside, smoke a cigerete
go back and check

if pressure is creeping up
remove/replace prv