baseboard & radiators sharing a furnace?

Rebecca_2

We're planning to finish our attic, and have had hot water baseboard heating recommended for the ne attic bedrooms. The first two floors of the house are heated with radiators. I've had one contractor tell me we'd have to buy a new furnace for the baseboard system, because it needs to run at 220 degrees and radiator systems run at 140. Another contractor says it's no problem to run both from the same furnace if you set it at an intermediate temperature. Who should I believe?

Ken_8

Believe the one who says...

the existing boiler is fine for both loads.

BTW, it's a boiler, not a furnace. Furnaces are for hot (scorched) air with ducts - not rads. We knew what you meant anyhow. Happens all the time.

You may have a steam system? Radiators and baseboard heat can be either. Please advise of which you have. We're here for ya.

If you already have steam - have the heating guy use that system to add a few rads on the 3rd floor. The rads on the second floor by virtue of the reduced load to heat the current arrangement on it will be overheated slightly. You may want to switch a few rads around if they are the free standing type.

I urge you to use the "Find A Contractor" service noted in the pipework near the top left of thgis website. Plug in your zip code and talk to one of the wizards. Most of us could answer questions in this regard with eyes closed.

Good luck.

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Sue_2

Baseboards and radiators

For what it's worth, my house has radiators on the first floor and baseboards upstairs, and seems to work fine. I've got the boiler set for 185F, but that is more for pressure reasons. I never knew there were different settings for baseboards and radiators, which gives me something to think about.

-Sue

Uni R

220°? Oh man...

That's just wrong! I would get a third contractor that will try and size the baseboard for the temperature of your radiators. Baseboards all provide various ratings per foot at different temperatures. You'll need a lot more and you may not have enough perimeter space to do it but that's the first logical venue for me.


Don't worry about the furnace reference. Every dictionary would back you up and nearly every wethead will try and correct you. A boiler is a type of furnace with water passages.

Rebecca_2

Thank you!
Our current system uses hot water, not steam.
I'm not sure why our current contractor has not been talking about radiators as an option in the attic. I'll ask.
If we do use hot water baseboard heat in the attic, and therefore run the boiler at a higher temperature, does that make the system less energy efficient?

Uni R

baseboard & radiators sharing a furnace?

Baseboards are cheaper. You could use nice panels with TRVs. Tr

Joe_13

Price

Cast Iron Rads cost more then copper fin tube BB. Ask about Cast Iron BB. Those put out alot more BTU's per ft then copper fin tube. I hope you're looking into geting a seperate zone for the attic. Hot water boiler should go no higher then 200 degrees. 160-180 is more the norm for BB. Nice thing about having extra radiators/BB you can lower the water temp to save $$$. Only turn it up on those bitter cold days. This is known as outdoor reset, something else you might want to look into.

R. Kalia

partly true

It is true that for a given water temperature, baseboards don't give off as much heat as radiators. You can try to compensate by installing more baseboard, but you are limited by the perimeter of the room(s). We have a mixture of the two (cast iron baseboards, not copper!) and it works OK but the rooms with baseboard are very distinctly cooler.

It is ridiculous to buy two boilers to 'solve' this problem. If you can, put the baseboard rooms and radiator rooms on different zones controlled by separate thermostats, and that will do it. Or you can put thermostatic valves on all the radiators (assuming thermostat is in a room wih baseboard), and this has some additional advantages (individual temperature control in each room). The water temperature should be set for the baseboard, which means the radiators will have more than they need, but either the TRVs or the separate zone thermostat will prevent those rooms from overheating.

There is no rule that radiators must have water temperature x while baseboards have water temerature y. As mentioned in another post, outdoor reset varies the water temperature based on outdoor temperature, such that it is just enough to keep the house warm with water circulating 24 hrs/day. This is the best way to control hot water heat. With a mixture of baseboard and radiators, the outdoor reset curve (which determines what the water temperature will be for a given outdoor temperature) should be set for the baseboard. The radiators will get too hot and must be "held back" using TRVs or a separate zone thermostat.

Mark J Strawcutter

thermal inertia

Radiators have much more thermal inertia - slower to heat up and slower to cool down. So at a minimum you want the baseboard on a separate zone or else the baseboard rooms will experience wild temperature swings.

Mark