New HW baseboard in old cast iron radiator system

fatty

im no pro but it sounds like an additional pump would help regulate the flow

Alan_18

New HW baseboard in old cast iron radiator system

Hi,
I have an older house (1939) with an oil boiler/cast iron radiators (HW loop, as much as I understand it). We recently added an addition (2nd story, and expanded the first floor), and used 3/4" baseboard radiators. The contractor added two new loops, but all use the same circulator. The cast iron radiators (old side of the house) get hot, stay hot, but the new baseboard ones don't provide enough heat. He is attempting to fix this by throttling the return valve(s), mostly on the old side, but it still isn't balancing.
What is the generally accepted practice when adding to a old cast iron system? The house is about 1300sqft now (was about 900 sq before), the thermostat is centrally located (in a room with a new baseboard unit, but open to the living room (with an old radiator).

Thanks,
Alan

Matt_67

cast iron baseboard

did he use cast iron base board or copper finned ? i have found when adding base board to a cast iron system that you either have to use cast iron baseboard or make a seperate zone with a seperate thermostat if using copper finned.

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Big Ed

Hi Temp vs Low Temp


You need to seperate the two.

Cast iron radiation will run at a lower temperture then Fin tube convection.(120*-160*vs 180*-200*)

Cast iron radiation also produces two types of heat source , radiant and convection. Fin tube produces just convection.

The two should be seperated with there own pumps and the cast iron loop should be piped with a boiler bypass . This way you can set the boiler to the higher temperature for the convection heat and the boiler bypass will temper the cast iron radiation..

Sounds like you have flow or bypass problem ..But having it set up correctly will have all the problems fixed.

The base board thermostat should be no where near the cast iron radiation....


Heating is a trade all by its self...

tim smith

Sounds like copper or steel baseboard

I echo the idea that you need cast iron baseboard or separate zone. Even at separate zone you may have to run the boiler temp higher to get enough output out of fintube radiation to heat the room, I would vote to size cast baseboard to the sizing of the cast in rest of house so you can run same temp w/ may be substantialy lower. Tim