1 boiler vs 3 boilers

4 Replies

I have a 3 unit property in which there is only 1 thermostat across all 3 units.  It is an old hot water / cast iron radiator system.  I currently set the thermostat at 72 in the "coldest room" and pay about $3000/year in heat and hot water. Inevitably, someone always complains about being cold.

I have 2 options to update my heating system.


1)  Install 1 modcon boiler + indirect tank.  Plumb the supply and return (home runs) 1/2" pex tubing for the cast iron radiators. I would install BTU meters and charge each unit a fraction of their gas usage.  Each unit would have their own zone and thermostat.

Pros:  only 1 system to maintain. About 1/3 the cost ($30,000).  The total bill per tenant is probably cheaper due to modcon.

Cons: I have to deal with billing each tenant for their heat usage.

2) Install 3 hot water boilers.  Tenant would directly get billed for their gas/hot water usage.  Each unit would have their own thermostat.

First question: Why on earth would it cost $30k to install one boiler and some PEX if you are using the existing cast iron radiators? 

Second question: how much would it cost to do it right and separate the heat systems? Would you have to drop their rents to make up for the fact that each of them now has to spend ~$1000 on heat a year? Or would you be able to charge similar or even higher rents because lots of people prefer to be able to set the heat where they want it? (edit: I can't count)

Third question: Are you in a state where you are allowed to do RUBS to allocate the heat bills? 

All things being relatively equal, I would always rather have completely separate utilities and systems and have the tenants directly pay for all their utilities. But in older homes, the cost/benefit isn't always there. Really comes down to numbers and the intangibles of fewer headaches for you and higher tenant satisfaction for them.

I got quotes of $35,000, $40,000 and $35000.



Cut out and remove the existing cast iron hot water boiler, both hot water heaters.
Cut out and remove the existing 11/2"-21/2" supply and return heating mains that run from the mechanical room (back of the house) to the meter room (front of the house).

Install 2- 9 port manifold stations in the mechanical for supplying heat to the cast iron radiators.
Plumb the supply and return (home runs) 1/2" pex tubing for the cast iron radiators from the manifolds to the existing branch of risers in the basement ceiling.
Pressure test all piping.

Pipe new 11/4"x 50' gas piping from the meter room to the mechanical room.
Pressure test gas piping.

Install a HTP UFT 140 high efficient modulating condensing hot water boiler and a Turbomax 45 Reverse Indirect Tank (Buffer tank and Potable hot water) with near boiler piping and controls containing:
The supply and return header piping from the UFT 140 boiler to the Turbomax 45 will be piped in a 2 pipe buffer tank configuration.
Isolation drain and purge valves.
Air and dirt magnet separators.
High efficient ECM circulating pumps with isolation pump flanges.
Hydronic expansion tank with support bracket.
Back flow preventer and auto filer combo unit.
Inline sediment and De-minerlized filter.

Controls & Wiring:
Low Water Cut Off.
18- Manifold Actuators.
Zone Control Box's.
3-Thermostats with wireless sensors.
Outdoor Sensor.

Cold and Hot water potable water side:
Isolation valves.
Thermostatic mixing valve.
Thermal expansion tank with support bracket
Pipe 3" Polypropylene and PVC flue and air intake piping from the boiler to the outside along with a thin low profile termination kit.
Install a Condensate neutralizer pump and plumb the discharge tubing from the pump to the indirect stand pipe in the mechanical room.
Pressure test all piping.
Install and wire in all controls in the mechanical room.

Power flush the system and remove any debris that is in the radiators and piping.
Drain the water out of the entire system.
Re-fill the entire heating system with De-mineralized water and power purge all the air out of the entire system.
Set and adjust the flow meters on the manifolds as per radiators btu's output.
Perform a combustion analysis on the boiler and make any adjustments if needed.

Second question: how much would it cost to do it right and separate the heat systems? Would you have to drop their rents to make up for the fact that each of them now has to spend ~$1000 on heat a year? Or would you be able to charge similar or even higher rents because lots of people prefer to be able to set the heat where they want it? (edit: I can't count)

it would cost $10K more to have 3 separate boilers.  I would not drop rents. hopefully.  I don't see a scenario where rents go UP.