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  1. #14
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    Quote Originally Posted by icy78 View Post
    First thing to do is pull that expansion tank and check its condition. If water comes out of the Schrader it is shot. If water does not come out it's probably just leaked air through its membrane and you can recharge it. That is something that happens at a slow rate every year.
    I would change the fill valve while at tank is off and yes they do fill slowly. The tank pressure controls the system and that needs to be set up right first.
    If the pressure dropped to 4 PSI that is more than likely not enough pressure now to get to the top of the radiators on the second floor and maybe not on the first floor.

    Also the pump needs to be pumping away from the pressure tank /fill, and towards the rads.

    Sent from my SM-G950U using Tapatalk
    Good advice but replace them both while you are there along with the air vent. I assume the homeowner had heat last year. It is normal to lose app 1 lb of pressure or so/year. If this is 4-5 lbs psi then it is ready to go. It will be less expensive to do it together and the homeowner would only get upset after paying for a repair only to have another one possibly happen. The air vent was either closed or not working so that should be replaced too.

    To the OP forgot to ask if there was a backflow preventer installed already. Always good to mention it at least
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  2. #15
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    Thread Starter
    Quote Originally Posted by icy78 View Post
    First thing to do is pull that expansion tank and check its condition. If water comes out of the Schrader it is shot. If water does not come out it's probably just leaked air through its membrane and you can recharge it. That is something that happens at a slow rate every year.
    I would change the fill valve while at tank is off and yes they do fill slowly. The tank pressure controls the system and that needs to be set up right first.
    If the pressure dropped to 4 PSI that is more than likely not enough pressure now to get to the top of the radiators on the second floor and maybe not on the first floor.

    Also the pump needs to be pumping away from the pressure tank /fill, and towards the rads.

    Sent from my SM-G950U using Tapatalk
    Checked the tank and no water came out, only air. Found out the expansion tank only had 4 psi. Pumped it up to 12 and all is good again.

    Just don't understand how bleeding off a little air from the auto bleeder caused this whole issue.

    This is a 50 year old boiler (oldest I have see).
    Can someone please explain to me -
    Why is there never enough time to do it right the first time, but plenty of time to do it twice?


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  3. #16
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    I think what happened here is that your tank pressure, unbeknownst to you was only at 4 PSI. Your system pressure was 12 to 14 PSI. But that pressure included the air trapped in the system. Then when you let that trapped air out, the system pressure dropped to 4 PSI. If the fill valve is not filling the tank then it would stay at 4 PSI and probably not circulate properly to the high points. Then when the pressure had come back up, assuming now a good fill valve, the room for expansion in that system would have been very small , and there's a good chance the relief would have blown especially later on this year when that old boiler will likely be putting out 210 degree water .

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  4. #17
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    Quote Originally Posted by icy78 View Post
    I think what happened here is that your tank pressure, unbeknownst to you was only at 4 PSI. Your system pressure was 12 to 14 PSI. But that pressure included the air trapped in the system. Then when you let that trapped air out, the system pressure dropped to 4 PSI. If the fill valve is not filling the tank then it would stay at 4 PSI and probably not circulate properly to the high points. Then when the pressure had come back up, assuming now a good fill valve, the room for expansion in that system would have been very small , and there's a good chance the relief would have blown especially later on this year when that old boiler will likely be putting out 210 degree water .

    Sent from my SM-G950U using Tapatalk
    Thanks Icy. That makes sense.

    How ever I am still somewhat baffled to understand how only having 4 psi in the expansion tank would not all the fill valve to allow the boiler to fill to 12-14 psi. It seems counter-intuitive to me. I am still trying to get my head around this and how it san operate this way. It may have something to do with this old style fill valve (which does now seem to be operating correctly).
    Can someone please explain to me -
    Why is there never enough time to do it right the first time, but plenty of time to do it twice?


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  5. #18
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    Don't see a water regulating valve just a gate valve if thats what u have the gate valve is broke gate. Ex tank will not stop a fill valve from filling.

  6. #19
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    Quote Originally Posted by servicefitter View Post
    Don't see a water regulating valve just a gate valve if thats what u have the gate valve is broke gate. Ex tank will not stop a fill valve from filling.
    No it has one it is an Amtrol Filtrol.
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  7. #20
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    Don't see a water regulating valve just a gate valve if thats what u have the gate valve is broke gate. Ex tank will not stop a fill valve from filling.

  8. #21
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    Quote Originally Posted by servicefitter View Post
    Don't see a water regulating valve just a gate valve if thats what u have the gate valve is broke gate. Ex tank will not stop a fill valve from filling.
    "Fill-Trol combines a boiler system expansion tank with an automatic fill valve to control system pressure. This eliminates the need for a separate, automatic fill valve."

    https://www.amtrol.com/product/extrol-specialty-models/
    Signature removed Violated rule #15

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  10. #22
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    Quote Originally Posted by pageyjim View Post
    "Fill-Trol combines a boiler system expansion tank with an automatic fill valve to control system pressure. This eliminates the need for a separate, automatic fill valve."

    https://www.amtrol.com/product/extrol-specialty-models/
    Yup! That is exactly what I had on that job. As soon as I pumped up the expansion tank, I was able to get the boiler up to 12-15 psi.

    Job is done now and working properly thanks to all the help I got here- Thanks guys!
    Can someone please explain to me -
    Why is there never enough time to do it right the first time, but plenty of time to do it twice?


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  11. #23
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    From what I'm reading, you still have a non-functional auto fill. Also, you can't accurately read or fill the pressure in an expansion tank with (water) pressure on the system side.

    You bled air out, the pressure dropped and the auto fill didn't refill. You then made up for the pressure loss on the air side of the expansion tank.

  12. #24
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    And yes, prv's/auto fills go bad all the time.

  13. #25
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    Extank air pressure sets the system pressure by pressing up against the fill valve portion thats why when the tank was at 4 lbs it wouldn't take any water and raising it to 12lbs system filled to 12lbs. Look at post 21 for the web site.

  14. #26
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    Thread Starter
    Quote Originally Posted by servicefitter View Post
    Extank air pressure sets the system pressure by pressing up against the fill valve portion thats why when the tank was at 4 lbs it wouldn't take any water and raising it to 12lbs system filled to 12lbs. Look at post 21 for the web site.
    Thank!

    I never say that kind of fill valve before. I am used to the other kind. So it works sort of backwards and only allows the water pressure in the boiler to build to the pressure in the expansion tank.

    Now I think I got how it works.

    Great info for the future.
    Can someone please explain to me -
    Why is there never enough time to do it right the first time, but plenty of time to do it twice?


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