Mixing Cast Iron and Aluminum Baseboard Radiators

Rodney Summers

Thanks Bill.

The Aluminum is fin tube. Around the outside of the rooms.

I have been told that the Cast Iron ideally would be around 120 degrees. However the Aluminum needs 180 degress. That seems to be the main reason for the issue of how many circulator pumps/mixing valves.

Rodney Summers

Mixing Cast Iron and Aluminum Baseboard Radiators

First floor is cast iron. Second Floor is Aluminum.

I am working with two potential contractors for a new boiler.

One contractor has recommended using two circulator pumps. One for each floor.

Other contractaor has recommended a single circulator pump with a couple of mixing valves.

Any recommendations on best way for this to be done?

Bill Nye_2

When you

When you say baseboard aluminum radiators, do you mean fin tube ? or the 1" wide by 5" tall aluminum ones? Does it cover most of the outside walls?

I don't know if a mixing valve is needed, the same temperature should be ok for both floors. Seperate pumps, one for each floor would work. If you could do weather responsive water temperature reset and constant circulation it would quiet the aluminum down greatly. It does tend to expand and contract if operated on / off with high temperature water. Great comfort with constant circ. On a mild day my system may have water temp. as low as 110°F.

I have the aluminum in 6 rooms.I have operated it both on/off and with reset. The house is sooooooo comfortable I almost look forward to winter, but not the fuel bills. So far this year I have only had the heat on 2X.

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Bill Nye_2

180°

Well, it only "needs" to be 180° on the coldest day of the year. And 120° may not be "enough" on a real cold day. On long as the fin tube is on one zone and the cast iron is on another the temperature won't be a real issue. Hundreds of homes have this mix of radiation.

I guess a mixing valve could make it nicer but I am not sure if it would be worth the added expense. I could be wrong, but I would spend the money tightening up cracks and adding insulation. Or saving to buy $3 gallon fuel.

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