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Low boiler pressure

MReib Member Posts: 5
I have a brain teaser for somebody. :-) The pump motor went out several years ago and I had it replaced by a technician. When the pump wasn’t working the pipe coming out the top was were the heat left which I’m assuming is the supply line and I thought it through the radiators on the first floor. Several years later I’ve gotten serious about figuring this out. The pump is running and The supply line is about 30° cooler than the return line on the backside of the pump give or take a few degrees. The boiler is showing just under 180°. The pump motor itself is at 175. The return line is 140, 150. The supply line is right at 118°. The small line between the pump and the furnace is way over 200. My thought processes the flow is backwards. I have always tried to bleed the radiators upstairs while the boiler was running and it used to work fine. Now it seems they do more sucking in air than bleeding. I have not had heat upstairs for years. By the way my boiler pressure is always under 3 pounds. I changed the gauge on front this year hoping that was part of the issue but it’s not. I have a cash acme valve on the supply line and I have messed with the screw on top and opened up the bypass I never hear any water running nor is there ever a change in pressure in the boiler. Also this year I drained the expansion tank because it had never been drained and from what I was reading it may have been full of water which messed everything up. With boiler running it is staying at 74° so I’m assuming there’s no water in  it at all.  Could someone please tell me where I need to go from here. Am I on the right path?. Thanks in advance.


    EBEBRATT-Ed Member Posts: 13,770
    That old girl looks pretty tired. Looks like some flame roll out there. I need to see the RH side of the pump to see if it is backwards.

    You need to get water in the boiler. Use a garden hose from a sink and feed water in through a drain valve you need 12-15 psi for a 1-2 story house. Use a female-female hose connector or a washing machine hose to get water in there and get back riunning.

    Then replace you water feeder its probbly plugged up. you need to find out where the water is stopped

    I would start saving for a new boiler
  • MReib
    MReib Member Posts: 5
     I think the flame rollout was from that panel not being on those burners for a long time. I put it back on and they seem to be staying in there. :-) The only drain in the system is there on the bottom of the boiler. Nothing I can see you in line. I’m going to change that cash app me a soon as I can get one
  • mattmia2
    mattmia2 Member Posts: 8,381
    That cash-acme valve is just a pressure reducing valve and hopefully a check valve. Caleffi makes a nice one that automatically does fast fill without having to lift a lever and a built in pressure gauge.
  • hot_rod
    hot_rod Member Posts: 19,854
    Yikes, looking at that beast I would buy a CO detector as soon as you can, if you don't have one now.

    Looks like a water heater burner on the spare parts pile? If you have a tank water heater, does it show signs of flame roll out also.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • MReib
    MReib Member Posts: 5
    Thank you for the heads up on the Caleffi.  
  • MReib
    MReib Member Posts: 5
    The water heater is fine it’s fairly new and working great. The boiler looks bad because that one plate was not on there blocking the flame.
    JUGHNE Member Posts: 10,782
    Normally, the flames should not roll out even with the cover plate off.
    You may have passageways plugged in your boiler or bad chimney.

    IMO, you should have a pro in to look at your installation.
    When have you had anyone do a serious service/cleaning other than changing the pump?
  • retiredguy
    retiredguy Member Posts: 797
    edited January 2022
    My observation; from what you have said about the temperature of the pipes, supply and return, I have to assume that there is little to no flow of water through your boiler. I will address the pump first. Looking at the inlet piping to the pump you could have air trapped in that piping above the pump. That design makes it near impossible to remove the air from that section of pipe between the return and the pump. Next, just because the pump is new does not mean that it is pumping water. The impeller could be loose on the shaft, or plugged with some type of debris. The motor will get very hot when there is no water flow since the water flow cools the pump. The hot pipe below the pump and the cooler pipe above tells me that there is no flow through the pump.

    The PRV valve should be set to keep the cold fill pressure in the boiler at 12-15 lbs as @EBEBRATT-Ed stated. I would suspect that that PRV needs to be replaced and that the galvanized supply pipe may be plugged and should be replace with copper all the way to the boiler.

    I notice that the relief valve has a stop valve installed ahead of it. That valve can't be there. I once tried to take the guts out of a valve on a commercial job and the state and insurance inspectors both said "no".

    For the expansion tank, you need to know how to drain that tank completely. You need to get air into the top of the tank while the water is draining. Some of those old tanks had no way to get air into the tank to allow the water to drain. That is the main reason residential systems utilize pre-charged bladder tanks. You select the proper size tank, precharge the bladder side, and install the tank. Job done.

    You need to have your system serviced by a good service company to insure it's has a long life.

  • MReib
    MReib Member Posts: 5
    I want to thank each and everyone of you who commented and helped with this. It was low water. And I could not find it until I brought the pipes apart to change the valve. The boiler is working like a champ now and 8 pounds is reaching the second floor. Thanks again for all your help it was very much appreciated.