Radiator plumbing

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  #1  
Old 03-26-18, 04:04 PM
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Radiator plumbing

Hi all!,
My wife and I purchased this awesome 200+ year old house and are little by little fixing it up. The previous owner had cut out all the baseboard heaters for whatever reason but did install a new gas boiler and installed baseboard heaters in two rooms. Now I got a bunch of very nice cast iron radiators I want to install in the rest of the house, my question is this: Is the best way to plumb them having two main lines (supply & return) and tee off to each individual radiator so I can install thermostatic valves and control the heat per room? Would using 1" main lines be enough and tee off with 3/4"? I would like to use PEX.
 
  #2  
Old 03-26-18, 04:52 PM
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I can not recommend PEX since I never used it or have any experience with it. As for the radiators, all radiators are not the same. Some radiators can be used with steam only and some can be used with either steam or hot water. I am assuming that you are installing a hot water heating system. In order to pipe the system correctly and to install the correct size radiators in each area you need to do a room by room heat loss of the property, determine the needed radiators size, choose the type of piping you prefer like mono-flo, reducing main, direct return or reverse return, calculate the size of the mains from the boiler to the end of that main, and size the pump for the flow needed. There a lot of guys that monitor this site and have a lot of experience with heating systems. I have been retired for over 10 years and may be a little old fashioned in my choice of installation practices. If you can post a picture of the radiators so we can see if they are hot water type radiators. Mentioning the area of the country where you live in may also help since some things change with location. How do you heat the house now? Give a better description of the house, it's construction, etc. Hope this helps.
 
  #3  
Old 03-26-18, 05:58 PM
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W,
First off as far as main pipe size goes it depends on the btu load of the rads. They have to be sized for btu ratings. Rads are figured differently than baseboard. There are different rad designs.
You could possibly get away with 1" zoning the rads but you should size the main as if all the rads were callng. 1" copper will carry 80,000 btu's

If you want to use thermostatic valves you are going to pipe them using a mono--flo or 2 pipe system so each rad works independently of each other.

Pex is fine and you only need 1/2" to feed the rads off the main.

As Steamboy mentioned the vent placement on the rads is important and must come off the top. If your vent position is 1/2 way up the rad that is for steam and cannot be used for hot water venting.

Hope this helps a little.
 

Last edited by spott; 03-26-18 at 06:16 PM.
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Old 03-27-18, 10:48 AM
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If they were originally plumbed with 1" pipe, how come 1/2" will do know? Also considering that PEX coupling further reduce the size to about 3/8", will that be enough?
 
  #5  
Old 03-27-18, 12:13 PM
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W,
I'm talking 1/2" for the branches to the rads. NOT the main. The main is sized by the BTU output of the rads. You can use 3/4" for the branches if you are concerned 1/2" is too small.

As far as the main goes you will need at least 1".
 
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Old 03-27-18, 02:17 PM
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Yes, that was my plan, using 1" for the mains and using 3/4" to tee off to the radiators considering that with the couplings it goes down to about 5/8"?
 
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Old 03-28-18, 10:34 AM
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@Steamboy,

Yes, I know there's a difference between steam and hot water radiator, they are easily converted from steam to hot water though. I will make sure that the supply and return will both go on the bottom and the air valve on top. I did a lot of research already.
Thsnk you for the replies!
 
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Old 03-28-18, 02:23 PM
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Actually, steam radiators can not be converted to hot water radiators. Steam only radiators are for steam only, and have no top connections. The other type is steam or hot water and if you are using hot water the preferred piping method is hot in at the top and cool out at the bottom. They can be piped in and out at the bottom but you will give up some heating efficiency.
 
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Old 04-03-18, 03:54 PM
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So, I know there's some kind of formula to calculate the BTU on a radiator, mine are 22" high (without the feet), 8" wide and 30" long (12 sections). Also, can someone explain to me why plumbing these with 1/2" pipe is sufficient even though they were originally plumbed with 1" pipe?

Thanks,
Bert
 
  #10  
Old 04-03-18, 04:16 PM
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Do you know if these radiators were used in the original heating system and were they used as steam, 1 pipe or 2 pipe , or hot water that was forced water (pump) or gravity flow? If the piping to the radiators was 1" on the inlet, what is the pipe size on the outlet? Also , what is the inlet and outlet pipe size, and location of each size. A picture of the radiators may help determining how they were used originally so advice can be given for changes if any need to be made. If there is a 1/8" pipe thread hole 1/2 way up the radiator on the last section the radiators were probably used with 1 pipe steam. Last question, are the sections of the radiators connected together at the top as they are at the bottom? A picture would help.
 
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Old 04-03-18, 04:28 PM
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The dimension of the radiators , the style , the number of sections, number of tubes/section, etc. all determine the btu output of cast iron radiators. Type in " cast iron radiators " in a search engine ( I use GOOGLE ) to get a lot of information on radiators. As I said in my previous post, a picture is worth a thousand words.
 
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Old 04-03-18, 04:41 PM
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Here's two pictures, hope this helps. Looks like they were already plumbed with 1'2" pipe.
 
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  #13  
Old 04-03-18, 05:32 PM
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Wow , they are nice cast iron radiators that can be used with hot water or steam. Remember; hot water in at the top and return (cool) out the bottom on the other side. Go to GOOGLE and type in "Aero cast iron radiators". You will get a lot of information . Click on any number of sites especially heating capacity guide-- Columbia heating supply. You can deliver about 15,000 BTU through a 1/2" pipe, 35,000 through a 3/4" and 75,000 through a 1" pipe Find out the BTU capacity of each rad, tag them, do a heat loss calculation for each room and select a radiator with the correct output or greater.
 
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Old 04-03-18, 05:37 PM
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Thank's for all the comments and answers Steamboy!
 
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Old 04-09-18, 04:37 PM
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Another question...

Right now I'm working in a 150+ year old house and completely remodeling it, this house has a oil burning boiler in it and 12 radiators throughout the house. So, I was looking at it today to see how they ran all the piping, there's a 1.5" pipe coming out of the boiler feeding into the Taco circulation pump (which has a 3/4" in and outlet), from there it goes through a short piece of 1.5" pipe and feeds into a 2.5" pipe which has several tees feeding 3/4" and 1" pipes to the individual radiators. So, 1.5 to 3/4 (pump), to 1.5, to 2.5 pipe to 1 and 3/4 again. My question is, if it's only a 3/4" pump why does it go to a 2.5" pipe, I guess it works because the house gets plenty warm. My boiler feeds out into a 1 1/4" pipe into two Taco pumps and out into two 3/4" pipes, one of these I will use for my acquired and to be installed radiators, Steamboy had mentioned before about feeding with a 1" pipe and teeing off with 1/2" pipes, there's still about 150' of 1 1/4" copper pipe running throughout my basement, can I just use that for my supply and return lines and tee off with 1/2" pipes to my radiators?
 
  #16  
Old 04-09-18, 04:53 PM
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You mention a lot of pipe sizes and your explanation gets a little confusing. I would not replace the 1-1/4" copper just to drop the size a little. The piping can be oversized but not undersized. By the way, you mentioned a 150 year old house, is this different from the original 200 year old house or just an addition. If it is a different house you need to start a different thread to end some of the confusion. So, where in the system is this 2.5" pipe and what material is it made of and is it a different material from the rest of the piping? I am not there so I can only guess. The 2.5" pipe again sounds like an old gravity system that has been partially re-piped. From your description of the house I would guess that you are in the eastern US and most probably in New England.
 
  #17  
Old 04-09-18, 05:07 PM
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Steamboy,

I should have been a little more specific, the 200+ year old house I started this tread with is my house, the 150+ year old house I'm talking about is were I'm working at as a contractor currently. The 1 1/4" copper pipe is in my house but needs to be all rerouted, right now it has many, many tee's on it with old gate valves for the original radiators which were all cut out flush with the floors. I'm planning on cutting everything out and just solder them with new couplings and tee's. I'm in PA.
 

Last edited by woopud; 04-09-18 at 05:53 PM.
  #18  
Old 04-11-18, 06:24 AM
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I sent you my e'mail address in the private e'mail I sent.
 
 

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