Hi,

My system is all baseboard, and I don't have enough of it to keep the house warm (long story). I am looking to add baseboard in a couple of spots, and was thinking about adding cast iron radiators instead of the usual copper and fins setup.

My first question is...........is it true that cast iron is more efficient and hold heat longer ?.

My second question is........how do I tie in a cast iron radiator into a copper line ?.

 

Cast will hold heat longer most of the time, but you have to think of the cost. Cast iron radiators are not cheap. You can also get cast iron baseboard, the same caveat. As far as tying cast to copper it should be no problem, they make transition fittings to go one to the other,[i.e. iron pipe to copper] I would suggest if you go this route to use a dielectric union between the two metals; they don't like each other. Lots of luck.

 

I don't suggest mixing cast iron radiators due to the large water volume of the radiators. If your baseboard is not heating well enough, you could replace the existing baseboard with high capacity baseboard.

 

I am sorry.......I meant cast iron baseboards.......not radiators.....

 

I would be reluctant to install cast iron baseboard in the same loop as fin tube baseboard due to the different heating rates. I could find not hing in the installation manual to back up this feeling but here is link to the installation manual. http://www.burnham.com/pdfs/CurrentPDFfiles/81441001R7(web).pdf
Cast iron baseboard heats & cools slower than does fin tube simply because of its mass. Before making any kind of commitment on the cast bsbd, I suggest you contact the manufacturer about mixing cast with fin tube.

 

Think of it this way. You asked if cast iron holds the heat longer. The answer is yes. Why do you want your baseboard to hold heat. Wouldn't you rather have that heat put into the room? Finned copper transfers the heat to the room almost instantly. You don't have to put heat into it for 5 minutes before it starts to give up some heat to the room. That is the reason not to mix cast iron and finned copper. The lead/lag of heat transfer will make part of the zone uncomfortable...guaranteed. I have seen people say, "It probably won't be too bad, I'll give it a try". and later admit that the area heated with finned copper is not as comfortable as the rest of the zone which had cast iron. If you move the thermostat to the area with the new baseboard, the rest of the zone will be uncomfortable. To answer your second question, the best way to connect copper tube to cast iron baseboard is with 3/4" copper to male angle unions. One end of the union screws into the baseboard and the other end can be soldered to the copper pipe. If you want to go cheap, you can use a copper to male adapter and just pipe it from there with copper.

Ken

 

Well.....here is the full story.......my kitchen is next to the unheated and attached garage. It is also built on top of a crawl space, so I get cold from the garage and from below the floor. To help the reader visualize the area....this used to be a 2 car garage, and half of it became the kitchen when the previous owner had an addition put in 30 years ago. Presently, there is one baseboard on the far end away (about 15 - 20 feet) from the kitchen cabinets, and some contraption under the kitchen sink cabinet that basically ties into the hot water loop, and has a temperature controlled blower that forces a small amount of hot air out around your feet if you are standing in front of the kitchen sink.

On cold days, the kitchen is freezing but the rest of the house is comfortable. The temperature difference is around 5 to 8 degrees on the worst days, so if the rest of the house is sitting at 68-70, the kitchen will be around 60-62.

I have one wall about halfway between the far wall and the kitchen sink where I can install additional baseboard to heat up the area. I thought
having baseboard that retained heat longer would be a good idea, as opposed to having the furnace fire all the time.

The other option (way more expensive) would be to tear out the kitchen (my wife wants new cabinets), and replace the whole thing with radiant heat, but I am not inclined to spend that much money.

I think at this point, I might consider one of those high capacity baseboards someone mentioned and be done with it.

 

You might want to consider making the kitchen a zone of it's own. Unless I miss my guess, the kitchen is at the end of the loop which means it is getting the coolest water.

 

Hmm.....hadn't thought of that one........certainly another (intriguing) option.

 

I have a gas furnace, electric baseboards and a geothermal heatpump in my house (never can have too many heat sources). Anyway, I am actually considering scrapping it all and going with radiant in floor heat. You just cant beat the comfort. Make the wife happy, it will pay off with lots of good food for you.

 

I think the point I was shooting for was missed. There is no more heat output from cast iron baseboard than there is from finned copper. As a matter of fact, I think cast iron puts out 10 btu/ft less than copper. So don't picture cast iron baseboard as a constant heat source. It will get hot later than all of the copper finned baseboard and will give you that heat back at the end of the run cycle. No bonuses just a different way of delivering the heat. It won't be more comfortable and won't save energy. The contraption under the cabinet is a toe space heater and probably puts out about 8000 btus. That should help the room out somewhat. Possibly they didn't insulate where they should have or there are other mistakes that may have been made when adding the heat to the addition. If you can make it a zone of its own, that would add the comfort you need and allow you to use the toespace heater.

Ken

 

You can not mix cast iron baseboard and copper baseboard! They dissipate heat at two different rates. You will cause all kind of temperature control problems in different rooms. Don't do it!

Pete

 

Thanks to everyone that has answered. Now, let me approach the same problem from a different angle:

The room (kitchen) we are talking about is 23 x 13 with 8 foot ceilings. The 23 foot wall faces the garage and has a door. It is insulated. The short walls both have windows, and one of those windows is a bay window. The other long wall connects to the dining room and living room. Both of those rooms aren't nearly as cold as the kitchen is on those bad days I mentioned way back.

I have one baseboard beneath the bay window, which is 9ft long, and then the toe space heater thingy on the other end where the cabinets are. There is some cold air leakage from one of 2 AC vents that is in the attic above the garage, but the door is pretty well sealed, although it is opened and closed once or twice per hour as people come and go, using the garage.

I can add a 5 ft. section of baseboard easily enough on a section of wall that is free, but I don't know if this will be worth the trouble BTU wise, so that is why I was asking about cast iron, etc. I once found a formula to calculate the linear feet of baseboard you need for a room, based on "stardard" heat loss. For the life of me, I can't find it again, so any help would be appreciated.

Thanks .

 

There may be something in here which will help: http://www.burnham.com/tools.cfm

 

I just did a quick heat loss calc for your room. I made some guesses as to insulation and window size, etc. So these are not fully accurate numbers.
I guessed around 30sq ft for windows/doors
R-13 walls and floor
R-19 ceiling
medium infiltration
It came up with around 9500 BTU on a 5 degree day.

A Slant/Fin kickspace heater will put out either 5640 or 7350 BTU (depending on model) at 180F water temperature.
9 ft. of baseboard will put out 5400 BTU at 180F.
A total of either 11040 or 12750 BTU.

Those numbers will drop quite a bit at lesser water temperatures. If it's at the end of the loop, it is probably seeing around 160F water.
The total ratings at that temp are either 9004 or 10234 BTU.

I think you probably have enough radiation in the room, however, you need to be able to control it better. Your best solution is to make the kitchen its own zone. Also, by being on its own zone, it will get hotter water straight from the boiler and be able to put a greater amount of heat into the room.

Michael

 

Thanks, Michael........


I think I have the smallest kickspace heater........the baseboard in this loop is the third one in the loop, and when the heat is on, it gets quite hot....also, I traced the entire loop, and it goes like this.....

boiler>bedroom bb( 8 feet)>living room bb (10 feet)>kitchen bb (9 feet)>dining room bb (8 feet)>kickspace>bathroom bb (3 feet) >den bb (6 feet), and back to boiler....... a total of about 45 feet of baseboard.....in the last room (the den) the baseboard still gets pretty hot.......

Just for grins.....the windows are: 6 x 4 feet for the bay window.....the other window is 2.5 x 3 feet , and the door is a standard 36" inch door with no glass....


Thanks again.......