Mixing radiators and baseboard

Brad White_9

I am not sure of the context of what that quote from this site was, but on it's face, it is incorrect. It may have been later rebutted/corrected or simply misinformed. The preponderance of experience is that one does not mix radiation types on the same zone, with few exceptions.

Here is why:

Different types of radiation on the same zone will heat and cool at different rates. A house with cast iron in the room with the controlling thermostat would be satisfied (for it has control), while the lower mass fin-tube spaces would cool down almost immediately and lose the thermal barrier of warm air against their walls. You would feel cold rapidly while the cast iron-served room will continue to radiate for a period of time. Conversely, the CI will be slow to warm of course.

Reverse this and put the controlling thermostat in the fin-tube served room. The CI rooms would tend to overheat because the fin tube room needs more cycles of hot water.

An exception would be if the baseboard was cast iron and was mixed with standing cast iron (all sized to the heat losses of their rooms it is always assumed regardless).

Another exception, one that would allow mixing CI and fin-tube, is the use of continuous circulation with TRV's on each radiator. Of course, this would not be, could not be, a series loop. The radiators would need to be piped in parallel.

Glad you questioned what you read! Always do that.

Carl_19

Mixing radiators and baseboard

I have what this web site calls a "Loop hot water system". Where water goes from one baseboard to the next and then back to the boiler.

I just had a new boiler installed and the installer told me I should not have a hot water radiator (about 3 feet high by about 3 feet wide) and baseboard on the same system. He said I should either have all radiators or all baseboard.

According to some info that I read on this web site; the installer gave me false information.

Here is a copy/paste from this site:
Q: Does this mean I have to use baseboard radiation if I want to install a loop system?
A: Not at all. You can make a loop system with just about any type of radiation. All you have to do is pass the water from one radiator to the next in a series.


Well anyway, my question is this:
Is it acceptable to have a loop system with all baseboard and 1 old fashioned water radiator in the same loop?
Or do I need to replace that radiator with basebaord?

Thanks for the info

Carl

Robert O'Brien

Fin/Tube

and CI radiation don't mix well on the same zone but can certainly be on separate zones in the same house.

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Carl_19

Why is it that they don't mix well?

What does CI stand for?

Thanks for the info

Carl

Brad White_9

See above and

CI is short for Cast Iron (high mass). Fin tube tends to be low mass aluminum fins on copper tubing. Imagine how one holds heat when the water flow is stopped while the other cools rapidly.

EDIT: Sorry, Robert- that one was really for you. Sorry to step on your toes

Robert O'Brien

Cast Iron

Fin/Tube works by convection,when circ stops output stops,CI will continue to radiate.

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Robert O'Brien

Brad

You say it so much better than I do!

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Brad White_9

Thanks, Robert, but....

you said it first and with fewer words!

Carl_19

Thanks!!

Thanks to all!!

This is very useful information!!

So since I can mix my standing CI radiator with CI baseboard, I may look into doing cast iron baseboard and keeping my radiator.

Cast iron throws a really nice amount of heat (I love it)

D107

Replacing standard BB with CI

This thread leads me to ask--hopefully also for the benefit of Carl--how hard is it to replace existing Slantfin 5" 30 BB with 9"H CI BB? Can you do it without disconnecting alot of the supply piping? Old fins come off easy?

Thanks,

David

Ted_9

try zoning it.

If that cast iron rad is in a separate room, zone it. Or you could possibly pipe that one off mono flo tees and the put a thermostatic radiator valve on it so it doesn't over heat the space.

You have some options. It would be good to have someone with experience loop at the system and give you some options.

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Brad White_9

You would have to assess

your entry and exit point with your piping along with the output of the CI versus the fin tube you have now, David.

If the stars align, your piping would come up in about the right locations. Of course your baseboard detail and extentions of trim profile, if desired, would have to be taken into account.

If a true series loop is intended, all bets are off. Carl- if you do that, make sure that you compensate for cooler water at the end-of-run rooms by adding more radiation there. Best advice of all is to pipe each room in parallel or at least split the series loops to do half the floor rather than all of it. Keep the areas of deficiency to a minimum.

Carl_19

Actually a small system

The system will actually be a very small system.

I only use it to heat my first floor.

I plan to use two of those Hydroponic kick space heaters (One for kithcen and one for bathroom); they get mounted under the sinks. The rest of the floor is baseboard and 1 radiator.

I guess my options are the following:

1.) Keep radiator and get CI baseboard and also have the 2 kick space heaters (which throw out a really nice amount of heat when they get going).

2.) Get rid of radiator and install baseboard and keep 2 kick space heaters.

I don't really have much baseboard on the floor; there is one run that is about 25 feet and then another that is about 10 feet. If I removed the radiator, then I would add some in that room (assuming everything is the proper amount of BTUs for the heat loss of the room)

Thanks again for the info.