Cast Iron Baseboard Radiators

Brad White_9

The water temperature setting is entirely dependent on your calculated heat loss (you do have one, don't you?) and the amount of radiation relative to that.

If you have a 50 MBH heat loss and say, 96 feet of Burnham Baseray, you would need 180 degree supply water (170 F average water if a 20 degree drop).

If you are blessed to have 200 feet of Baseray or better, half the heat loss, your water temperature could be 132 degrees. Such a deal.

As to the cast iron cracking, well, it is cast as molten metal at over 2200 degrees and you have water at less than 200....

Seriously, the coefficient of expansion is not as great as copper fin tube and provided your straight runs are reasonable and broken with copper elbow bends, the stresses should be managable. Especially if you are running reset water temperatures and from a ModCon.

Now, if you do have a loop system, any thoughts on splitting it into two zones? It is tough on itself when piped "in-series". Splitting is better than nothing but not as good as individually piping each room. Is that an option? Absent that, I am only hoping that the sizing is compensating for the series loop flow and that your last room is up-sized accordingly.

Derrick

Hi,

I have a loop system with Cast Iron baseboard radiators. I have recently put in a new boiler (the house had and old asbestos coated coke bioler when we moved in) the Trinity 150c. The question I have is what temperature should I set the water temperature to? I have heard it can not be as hot as copper-finbaseboards as it may crack. Is this true.

Thanks,
Derrick

Unknown

Loop C.I.

Every publication that I have read is "100% against" looping any kind of C.I. rad. It may be extremely tough coming up with an adequate water temp to satisfy every room on the loop. You have no way of "dampening-it", or restricting the flow, without affecting the others. I wish I had more for you, but I wish you luck!

Derrick

Well, looks like I have alot more reading to do on this. No idea what my calculated heat loss is. Is there a place to go to assist me with calculating it?

I am slightly over the 200 feet (210) and it looks like copper piping with copper elbows however there are very few straight runs. The line bends throughout the house from the second floor down to the basement where the previous owner put on a basement addition and attached copper fin baseboards on the same line. I already found out this is a no no since we get very little heat in that area.

My new boiler does reset water temperatures, I think, it has a sensor outside. This is the model T150c (http://www.nythermal.com/Products/boilers/gas/trinity.htm)

I have been searching for info on my setup but can't seem to find much on it.

Thanks for all the help!

Derrick

So do they recommend zones?

Brad White_9

I would think that

what they would suggest is that each room be fed in parallel to the hot water mains, not in series.

In parallel, each radiator will have the same incoming water temperature and be able to be balanced or have a TRV on each room's radiators.

When piped in series as yours seem to be, the first radiator gets first pick and all subsequent radiators get "leftovers". Thus if all radiators are sized for the same water temperature, the last radiators on the run will suffer with less output.

Brad White_9

Heat Loss

Derrick-

See the "Heat Loss Calcs" tab above on this site. Follow the instructions, take your time and do a good job with take-offs (measurements of windows, gross wall, doors, roofs, all surfaces which separate indoors from outdoors, heated from unheated areas.

All Hot Water Boilers are sized this way. You should NOT use the radiation to size a hot water boiler, nor replace the old boiler BTU for BTU. If you do that, you will not capture the efficiency of any improvements you have made to the envelope; insulation, new windows, sealing, etc.

From here the radiation you have will be compared and that will determine your high end water temperature setting.

I hope you enjoy the process.