Replacing Cast Iron Radiators

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  #1  
Old 02-22-18, 11:45 AM
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Replacing Cast Iron Radiators

I would like to replace 2 cast iron HW radiators in my living room. The room is approximately 17' x 19' with 9' ceilings. The radiators are 55" long with 22 fins that are 24" tall and 9" from front to back. The ceiling insulation has been nominal but is being increased to R-39. The room has also been very drafty but has since been sealed.

How much baseboard or BTUs of heat do I need to replace these radiators?

Thanks!
 
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Old 02-22-18, 01:17 PM
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You should run a simple heat-loss calculation for the room. There are computer programs listed on a sticky at the top of this forum. Why are you replacing the radiators?

Are you proposing to replace cast-iron radiators with fin-tube baseboards? Mixing cast-iron with fin-tube units on the same system is not ideal because their stored heat and thermal performance is different.
 
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Old 02-22-18, 01:46 PM
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b,
You mentioned radiators and then you said 22 fins. Do you have rads or cast iron baseboard. It make a difference in figuring the amount of BTU'S you have already.

Pics would be helpful.

As a side note I agree with Mike. If you're having trouble heating that room with cast iron you will have worse results with aluminum fin baseboard.

Hope this helps,
 
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Old 02-22-18, 03:56 PM
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We will need a picture of the radiators so we can see what style radiator you have. You gave the dimensions but you forgot the number of tubes in a section front to back.. Look over the radiators is there a name on the radiator Is the heating system hot water, 1 pipe or 2 pipe steam? If you are going to replace these radiators, you will have to use cast iron baseboard . If you insist on using finned tube baseboard radiation the system will have to be zoned since the finned tube yield a different heat than the cast iron radiators do. THese radiators are worth something. do not throw away, sell them.
 
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Old 02-23-18, 07:15 AM
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Picture of radiators to be replaced

Here is a picture of one of the radiators to be replaced.&lt;br /&gt;<br />
&lt;br /&gt;<br />
There are 3 tubes in each section or fin.&lt;br /&gt;<br />
&lt;br /&gt;<br />
I don't see a name on it.&lt;br /&gt;<br />
&lt;br /&gt;<br />
It is a hot water system with a supply and return on each radiator coming off a continuous loop.&lt;br /&gt;<br />
&lt;br /&gt;<br />
These radiators are on a separate zone, all other radiators in the house have already been replaced.
 
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Old 02-23-18, 07:56 AM
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What did you replace the old radiators with?
 
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Old 02-23-18, 08:26 AM
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They had been replace with Slant-Fin baseboard.
 
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Old 02-23-18, 09:39 AM
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b,
That rad is putting out about 11,220 btu's. of heat.

To replace that rad with enough baseboard depends on a couple of factors.

1) The water temp. in the boiler
2) The btu rating of the baseboard you use.

Whatever you decide to go with check what there BTU rating is per foot and divide that into 11,200 and that will tell you what you need.

For example Slant Fin #30 has 580 btu's a foot @ 180 deg. water. 11,200 div x 580 = 19.3 ft or 20 ft. of baseboard.

The important thing here is water temp. If you run your boiler at a lower water temp which seems to be what people are trying to do the less BTU'S the baseboard will put out so you must allow for that..

If your other rads are the same design ( 3 column) and the same height the formula to figure your rads btu rating is below.

1) Each section has a capacity of 3 sq. ft.
2) 1 sq. ft. = 170 btu's
3) ex. 3sq. ft. x 170 = 510 BTU'S per section. x number of sections (22). = 11,200 BTU'S for that rad.
4) Divide 11,200 x 510 = 19.3 or 20 ft. of baseboard, depending on what you use.

Just a note. There is no listing for a 24" column rad so I used 22". They listed 22" or 26".

If you use 26" height, BTU rating is 14,000. Instead of 3 sq. ft. use 3.75 sq. ft. per sec.

Btu rating would be 637.5 per sec instead of 510.

Divide 14,000 x 637.5 = 22 ft. of baseboard would be needed.

Hope this helps a little
 
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Old 02-23-18, 08:01 PM
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If you find I donít have 20 feet.... They make high output fin baseboards too, you may need to go to 9Ē... check in with you supply house specialist for sure.
 
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Old 02-25-18, 06:44 AM
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Thanks Spott! That is a big help.

The water temp for my boiler is 180 degrees.
 
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