I have a 1200 square foot second floor apartment that is presently heated using a forced hot water radiator system. The system is called a Paloma "Paloma Pak" heating system. It is basically a tankless hot water heater that they used back in the 1980s to heat apartments. With today's technology, can I replace it with a standard tankless hot water heater for similar results? My biggest problem is I can't find anyone to service the unit. It has an 85% efficiency rating when I check, so I can get no assistance to pay for the replacement. I think the tankless hot water heater may be an option.

  • Where are you on this planet, and is this heating setup your responsibility or the landlord's?! Jan 12, 2019 at 0:18
  • Live in coastal Mass. And I own the home so it is on me. Jan 12, 2019 at 17:10

2 Answers 2


Just get a combi if you need both DHW and heating or just an 'only heating' boiler. Few brands names: Immergas, Baxi, Buderus, Bosch, Riello, Junkers.

If you get I condensing unit I suggest you to keep the flow below 55°C, to exploit the condensing capability of the unit.

DHW units usually aren't suitable for space heating because those units lack a feedback control on water temperature (they assume inlet is standard 'acquaduct' range: 5°-20°, so returning with hot water may cause serious issues bringing water to boil in the exchanger leading to steam production and eventual explosion)

  • Seconded that tankless HWHs aren't appropriate for space heat -- I would use a straight boiler with an indirect tank instead of a "combi" boiler/tankless unit, though. Jan 12, 2019 at 0:19
  • Combi are not a 'plain' DHW Water heaters, those have a 'primary' boiler circuit that heats water that can go directly to radiators or can be diverted to a 'plate heat exchanger' that heats DHW water as it flows trough it. Also exists 'heat-only' versions that lacks plate exchanger and 3-way valve, so are 'regular' wall mounted boilers that can be used to heat an external water tank as well radiator's water.
    – DDS
    Jan 12, 2019 at 13:31
  • Any names of wall mounted boilers as this is what the Paloma Pak does Jan 12, 2019 at 17:13

I do not think that a standard tankless water heater would work for space heating. A standard hot water heater does not have the feedback controls to keep a room at a specified temperature based on a thermostat.

A standard tankless water heater just delivers water at a temperature specified by its internal controls. It does have an internal feedback to deliver water of a certain temperature for a range of flow rates depending on demand, but I don't see how a room thermostat would control it.

A hydronic heating system pumps water around in a loop, but a standard tankless heater is designed for a single pass--it takes in cold water from the cold water supply and sends out hot water which goes to the drain after use.

There are tankless heaters whose output goes to a storage tank and presumably get recirculated water from the tank, but I don't think even this type is suitable for space heating. However, you should research this further.

See this: tankless water heater to heat home

  • 1
    I agree the other part of the problem most tankless units I have installed only heat to ~130f. It would probably cost much more in the long run, a boiler heats the water in the loop so it uses a much smaller heating element for electric, and the gas models ease a large amount of heat up the vent stack.
    – Ed Beal
    Jan 11, 2019 at 22:24

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