View Full Version : H/W Boiler High Pressure

10-21-2010, 11:42 AM
My boiler is running at 20psi cold. I'm concerned this is too high. I'm using a bladder type expansion tank and Taco autofill valve (boiler feed). The convectors are cast iron radiations. The house is a 2 story cape with the boiler located in the basement. The fill valve is before the expansion tank which is in the return side of the boiler. The pumps are located on the supply side, so pumping away.

I've been reading up on this subject and have some items to check. The air pressure in the expansion tank is the factory fill so will be checking that this weekend. The fill valve is brand new, replaced over the summer, and it too has the factory setting.

My only concern is I installed the fill valve vertically, due to space restrictions in the system. I just noticed the Taco documentation says to install horizontally. Do you think this would cause a high pressure problem? Should I relocate the fill valve to a horizontal position?

10-21-2010, 12:16 PM
Mine is installed in a horizontal line. Not sure how much difference it makes other than the override lever wanting default position. Most residential boilers run closer to 14-15# cold, but 20 could be okay. You need to check the setup manual for your boiler. As long as the pressure is within the min/max of the acceptable range, it should be okay. Keep in mind when checking the static pressure in the expansion tank, you have to remove the pressure from the system first, otherwise, you'll just be reading the system's water pressure, not the static air pressure. The fill valve is (I think) adjustable within a certain range. Also, your pressure gauge might not be all that accurate.

10-21-2010, 12:30 PM
Thanks Jim, I have the manual for the boiler, 20+ years old now, so will have to see if the list an acceptable range. The relief valve is 30psi so I worry that might pop one day but maybe I'm overreacting.

The lever is NOT in the fast fill position. With it's current orientation, the lever now moves left to right in a vertical position. It hasn't automatically flipped yet so I don't think that is an issue. My only concern is the spring loaded mechanism might not work properly if not horizontal. I took a quick look at the B&G fill valve and that one can be mounted vertically.

I will drain out the system before checking the tank.

I did see several posts about not trusting the boiler gauges. Last time I was at HD, I saw a pressure gauge in the sprinkler section, will go this weekend and see if I can find it again. Looks like I can screw it onto one of the boiler drains.

10-21-2010, 02:10 PM
Assuming you have an accurate air pressure gauge, once repressurized with water in the boiler, it will read the same as the water pressure. Being able to view it all the time and moderately accurately is good, though.

Since the house was down to 68, I decided to bite the bullet and start up mine. The autofill had it at 13# when cold, if that's anything.