American Standard boiler high pressure/expansion tank

Discussion in 'Boiler Forum' started by Amatuer repairman, Nov 16, 2020.

  1. Amatuer repairman

    Amatuer repairman New Member

    Joined:
    Nov 16, 2020
    Location:
    Indiana
    I can't get pressure to stabilize on this old boiler - pictures below. There are two zones: family room and 2 second floor bedrooms. The family room was built on a slab over 30 years ago and has two baseboards with radiant tubing in the floor and a heater box with a fan on the floor. Overkill yes but former owner added the room.

    I recently replaced the pressure reducing valve and the safety valve because it was leaking. Boiler is heating all the rooms quickly and pressure starts around 12 pounds and climbs to 18 to 21 and runs for 3-4 hours stable. Then it will go higher to mid to high 20's. The boiler is heating to about 100 degrees but the gauge may be off. I've tried running the boiler with the water supply valve open and closed and the same result. Pressure climbs eventually. Yesterday afternoon with water off the psi was high teens.

    Turned off the boiler last night before going to bed. This morning it ran fine but couple hours later pressure was over 40 and hot water temp was around 80 which I'm thinking is not good. I drained some water and pressure drops to 12. Been bleeding the baseboards but still hearing gurgling from the heater box which lasts for only 30 seconds. There is no bleeder valve on the box. The box is about 18" by 18".

    What is the purpose of the expansion tank? I thought it was to capture air in the system so did nothing with it other than to bleed air off the schrader valve. There is no valve on the bottom of the tank. There's been no water when I released pressure with schrader at the top of the tank. I just read the tank should be pressurized. Is that correct? What am I doing wrong?

    IMG_0473 - Copy-002.jpg
    IMG_1626-002.jpg
    IMG_2766-002.jpg
     
    Last edited: Nov 17, 2020
  2. fitter30

    fitter30 Well-Known Member

    Joined:
    Feb 2, 2020
    Occupation:
    Retired service tech
    Location:
    Peace valley missouri
    Can't see any pics. Expansion tank is not for air removal its for expansion of the water as it heats. 60* fill temp 180* heating temp water expands. With a cool boiler 100* water average house 12lbs pumps off. Tank pressure scharder valve 12 lbs if low fill with a tire pump. Fire boiler and pumps.
     
  3. Sponsor

    Sponsor Paid Advertisement

     
  4. Amatuer repairman

    Amatuer repairman New Member

    Joined:
    Nov 16, 2020
    Location:
    Indiana
    Thanks I'll check out expansion tank. Since there's no valve on the bottom of the tank, how can I tell if the tank is shot? I uploaded different picture files. Can you see the pics now?
     
  5. Reach4

    Reach4 Well-Known Member

    Joined:
    Sep 25, 2013
    Location:
    IL
    You start with cold water at pressure, let's say 15 psi. As the water heats, the water expands. If there is no thermal expansion tank and no pressure relief valve, the pressure could rise to well over 100 psi. If there is the relief valve, then the pressure will rise to the relief valve pressure, because the relief valve has to release water to limit the pressure.

    The expansion tank can absorb the expanded volume of water, and keep the pressure from ever reaching the relief valve pressure.

    If your Schrader valve is on the top, the tank could be almost full of water, and no water would come out of the Schrader valve. With air precharge, usually set to the cold design pressure, the air pressure will read the precharge value if the water pressure is less than the precharge pressure. If the water pressure is higher than the precharge pressure, the air pressure will pretty much match the water pressure (except for the difference due to altitude). There can also be differences in the calibration of your water pressure gauge and your air pressure gauge.

    When cold, the air precharge should be enough to force all of the water out of the expansion tank. Knocking on the tank will give a hollow sound.
     
  6. fitter30

    fitter30 Well-Known Member

    Joined:
    Feb 2, 2020
    Occupation:
    Retired service tech
    Location:
    Peace valley missouri
    Normally tanks hang from the piping. Your 40 lb water pressure is 10 lbs over design pressure. Relief valve should be dumping water big time. Does water come out the schrader valve? From boiler to highest heat emitter is your house?
     
  7. Amatuer repairman

    Amatuer repairman New Member

    Joined:
    Nov 16, 2020
    Location:
    Indiana
    IMG_3733-001.JPG IMG_3737_1-001.JPG IMG_3738-001.JPG IMG_3739-001.JPG

    I replaced the expansion tank and the PRV and turned off the auto water supply valve. My concern is that with the auto fill valve open the pressure climbs too high getting to about 20 psi. The system is working but the PRV must have released again. It sounds like there's air in the system when the circulator starts running. I can hear water in the family room. The family room was an add on by a previous owner and has two radiators and radiant in the floor. I have bled at least 10 times over past few months and never got air on the first floor but for some reason think there must be air in the radiant tubing. Here's pics of the expansion tank and the temp gauge when the boiler is operating and off.

    1. Should the pressure be dropping to below 10 psi when the boiler is off? Is it normal for the PSI to reach 18-20?
    2. Was the expansion tank installed incorrectly when the furnace was originally installed? All the pics in the forum have the tank positioned opposite to my install?
    3. There are two zones - one first floor family room and 2nd floor two rooms. With the auto fill off when I bleed the 2nd floor should I get water from the valves? I bled them today and got some air but no water. Then I turned on the auto fill and had water pressure on 2nd floor.
    4. Could air be causing the high pressure? I ran a lot of water from the valve to the right of the pump to bleed the system a few months ago but sounds like there's still air in it.
     
  8. fitter30

    fitter30 Well-Known Member

    Joined:
    Feb 2, 2020
    Occupation:
    Retired service tech
    Location:
    Peace valley missouri
    Take some pics of boiler, piping, ex tank and make up water. What water temp your running? Your 4 pics are posted but there to close to se how there run. Is that 1/2" pipe on the bottom of the pump? Minimun water temp is 140*.
     
    Last edited: Jan 5, 2021
  9. Amatuer repairman

    Amatuer repairman New Member

    Joined:
    Nov 16, 2020
    Location:
    Indiana
    You can't see the 4 pictures in the previous post? Does anyone know how to post pictures because I'm seeing the pictures in my posts but others apparently can't view them.
     
Similar Threads: American Standard
Forum Title Date
Boiler Forum American Standard boiler Oct 23, 2020
Boiler Forum American standard Ideal boiler Sep 3, 2020
Boiler Forum An American Standard Gas boiler Mar 13, 2017
Boiler Forum Diaphragm expansion tank location on American Standard ng boiler Jun 15, 2014
Boiler Forum American Standard Arcoliner - Control for Domestic Hot Water Aug 21, 2011

Share This Page