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Lower apartment in radiator system hotter than upper apartment

I am new to this message board and new to my home with its high efficiency Utica UB90-200 condensing boiler in the basement. I have never owned a boiler heating system and am trying to learn as much as I can about it. The building is a multi-family apartment with 4 units. The two front units are on one zone with a 3 speed grundfos circulating pump (3 speed settings, currently on highest speed) and the two rear units are on another circulating pump which does not appear to have a speed adjustment on it. The first floor apartments have the thermostat for each zone.

I live in the upper rear unit and the other units are rented out to tenants. I have noticed that the upper unit I live in is always colder than the unit below me (both units same size, floor plan and number of radiators/location of radiators). I’ve bled all of the radiators in both units and they all do heat up. The average difference in temperature between the two units (upper is always colder) is probably in the range of about 5-10 degrees F. The upper unit is typically around 63-65 F while lower is in the 67-73 F range.

What is the best way to address this temperature discrepancy? It seems like my options are increase flow rate or increase temperature. Do the thermostats in the units only control the circulating pumps, or do the thermostats in the units also shut off the boiler itself? Or, does the boiler only shut itself on and off based on the water temperature as set and measured in the boiler?

I thought about increasing the water temperature in the boiler, but then I was thinking that the thermostat in the lower unit will still shut the (boiler? Circulating pump?) off once that unit reaches a comfortable temperature, then the upper one could still be cold. Or is the best bet to simply increase boiler cut in / cut out temperature? Since the circulating pump serving the rear two units does not appear to be adjustable, it is possible that it is undersized for the number of radiators in the circuit/height of the building (2 tall stories plus basement). Is there normally a separate pressure adjustment or is pressure really just dependent on temperature?

Sorry for all the basic questions, but really appreciate you taking me to school on this! I’m not that far off from a balanced system between the two apartments on this single zone, and hope that I can get the upper unit comfortably warm like the lower unit without too much invasive work.




  • nicholas bonham-carter
    Post some pictures of the boiler, and its piping. A hydronic specialist, rather than a plumber may be required to balance the system, and there are names here available for your area using the find a contractor button here.—NBC
    Erin Holohan Haskell
    JUGHNE Member Posts: 11,061
    One boiler, 2 T-stat's and 2 pumps....right?
    What kind of radiators.....cast iron.....or baseboard?