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Hot water heating system - troubleshooting baseboard radiators not enough heat

datank4 Member, Email Confirmation Posts: 1
I recently purchased a home that has a Peerless M1 Boiler feeding a single loop of hot water baseboard radiators on one floor (3 bdrm apt, ~1000 sq ft). After purchasing (inspections happened before winter hit), the tenant alerted me that the heat has never been sufficient for her. The thermostat does call for heat. Here's the steps I've taken thus far:

1) I thought the system may be airbound. There is only one air bleed along the radiator loop to release air, and it immediately released water when I opened it. Then I went to the boiler and followed the airbound system repair instructions provided by InspectApedia (https://inspectapedia.com/heat/Air_Bound_Heating_System.php) - flushing the whole system through a garden hose from the boiler. There was a lot of air bubbles and spurts of water.

2) Upon turning the heat system back on, the temperature increased from 50 F to 57 F, but topped out at 57 F. At this temperature, the pressure in the boiler did increase beyond 30 PSI, causing the pressure relief valve to release excess pressure (pressure relief valve may need to be replaced as it looks aged, but it seems to be functioning properly, it is not leaking when the pressure is lower). We adjusted the pressure back down below 30 PS and the system seemed to be operating properly.

The copper pipes at the radiators get very hot when there is a call for heat, but the radiators are not effectively heating the space, and never heats the space beyond 58 F.

I am unsure whether the issue is:
1) Fins and radiator covers need to be replaced
2) Pressure at the boiler (is it over pressurizing once you get to 58 F and therefore losing hot water heat efficiency?)
3) If there is possibly a leak in the system that is taking on air, creating an airbound system each time the heating system runs for a while (how would we diagnose this?)
4) Or if it issue with other equipment at the boiler (Aquastat, circulator pump, communication between thermostat and boiler)

Any recommendations of how to diagnose and prioritize our efforts from here would be greatly appreciated!



  • HomerJSmith
    HomerJSmith Member Posts: 2,511
    edited February 2020
    Heat energy travels on a conveyor belt called FLOW.

    There are several considerations here.

    1) The boiler isn't putting out enough heat energy.
    2) The FLOW of water from the boiler is inadequate.
    3) There is inadequate amount of heat emitters (baseboard) to put heat energy into the building.
    4) The heat loss from the building envelope is greater than the boiler or heat emitters can put into the building.

    (1) Check the temperature that the tridicator (boiler gauge) is reading. 180 degrees?
    (2) What is the model # of the pump. Is the pump too small? Small pump, small FLOW.
    (3) What is the temperature of the first baseboard and the last baseboard and what is the model of the baseboard?
    (4) How much insulation in the roof, walls, and floor? How many windows? Double pane windows?
    (5) Is the thermostat operating properly?

    Post pictures of the boiler and boiler piping, baseboard, and the problem rooms.

    Is the system using monoflo tees?

    The boiler pressure on a single floor sys should be about 12 psi,cold, and that is MORE than adequate. The expansion tank should be charged with air at the system pressure if it is a bladder tank. The pressure will increase several degrees as the boiler heats up. Pressure has very little to do with your problem but should be set appropriately.
  • Jamie Hall
    Jamie Hall Member Posts: 23,655
    @HomerJSmith pretty well covered the possibilities there -- but there is another, probably unrelated, problem.

    The pressure.

    There should be an expansion tank somewhere on the system -- hopefully near the inlet to the pump, but I wouldn't count on it. It's there to hold the operating pressure in the system more or less constant. In a single story home, it should be right around 12 to 15 pounds which the system is cold, and not more than 15 to 20 pounds when it is hot. If the pressure is rising as you mention, that expansion tank may have failed, or been improperly charged in the first place. Assuming it's there...

    If you have the right collection of valves, it's easy to check and recharge properly. If you don't, you can at least get a rough check: if it is the usual more modern type, it will have a Schrader valve on the end opposite the water connection -- a valve just like a tire. Using a tire gauge -- again just like a tire -- you can check the pressure. If it is low (12 to 15 pounds is wanted), you can pump it up and see if the situation improves. If water comes out when you try to check -- the tank needs to be replaced. If the situation improves for a bit, but then goes back, it probably also needs to be replaced.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England