# Cast Iron Radiators with Wood Boiler



## hedgecutter (Feb 10, 2010)

I am helping a guy install a new Outside Wood Boiler in an old school house that has the old cast iron radiators which were originally used with steam. The the old two story school building is being used as a residence and is now being heated with four different propane fired forced air systems. We are planning on installing water to air plenum coils in the two forced are units for heating the first floor, but upstairs we want to use the old cast iron radiators (maybe 1900 vintage) by circulating hot water from the OWB up to a plate exchanger and then plumb two or three different closed loops using pumps and t-stats through the radiators. My question is how to plumb our lines into the cast iron radiators. Some of the rads have inlet/outlets on both the bottom and top on both ends and some on just the bottom. I was figuring the water temp to be around 170 to 180 F.

1. Would you plumb the hot water in the bottom and then out the top on opposite ends? In the bottom on one end then out the bottom on the opposite end? What is your opinion to maximize heat transfer?

2. What about pressure testing and flushing the rads? They have not been in service for decades and I assume there is some crust on the inside.

3. Any other advice or opinions on how to control or plumb this project. 

Thanks


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## ericjeeper (Feb 10, 2010)

I would take a trip over to www.heatinghelp.com and go to "the wall"
Great bunch of guys over there that will give you all the right answers.


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## leon (Feb 10, 2010)

*radiators*

As Eric has said you should visit heating help to learn more.


I would not waste any time with forced air heat when you can regulate the heat in every room with the radiator set for hot water!!!!


The radiators should be cleaned by a firm that does this as a part of thier business to be sure everything is ok with the radiators-clean, no sediment 
painted for you, tested for leaks etc.

Typically the converted radiator pumps from bottom to bottom through the castings to shed heat. 

FYI using the radiators will reduce the amount of dust you have in the home too.


leon


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## Clarkbug (Feb 10, 2010)

Was the steam system a one pipe or a two pipe? 

You will definitely need to flush them out before you use them, since there is probably scale and other badness inside. 

I think This Old House did a piece on the conversion from steam to hot water, you may be able to find it if you dig around online.


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## darnet (Feb 11, 2010)

This is exactly what I did last year. There is nothing better then the cast iron radiators imho. I converted 18 of them in my house. I had single pipe steam prior. I used some of the origanal inlets and took out the plugs on the bottom of the other side. Put a reducer and hooked pex to that for a return. I was able to go from a single zone to 5 zones. What is nice about the cast iron is it stays hotter longer than the baseboard heaters. Granted, they don't look as nice and they take up more room but they were already here.


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## darnet (Feb 11, 2010)

Also I forgot to sat you have to put a bleeder at the top outlet side. There is a plug there also. Mine had blow offs half way down on the outlet side. Just unscrew those and plug the hole and put the bleeder above that.


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## hedgecutter (Feb 12, 2010)

ericjeeper said:


> I would take a trip over to www.heatinghelp.com and go to "the wall"
> Great bunch of guys over there that will give you all the right answers.



Thank you Eric I will run it by them as well.


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## hedgecutter (Feb 12, 2010)

leon said:


> As Eric has said you should visit heating help to learn more.
> 
> 
> I would not waste any time with forced air heat when you can regulate the heat in every room with the radiator set for hot water!!!!
> ...



Thank you Leon. So pump the water in the bottom on one end and then out the bottom of the other end of the radiator. I was a little reluctant to try and use these old radiators with hot water as I knew they were originally used with steam and I have no experience with radiators. Sounds like a good way to heat.


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## hedgecutter (Feb 12, 2010)

*Two Pipe?*



Clarkbug said:


> Was the steam system a one pipe or a two pipe?
> 
> You will definitely need to flush them out before you use them, since there is probably scale and other badness inside.



I think these radiators were two pipe as they have a pipe attached on both ends at the bottom. One is larger which I assume was the steam supply and the other end has a smaller pipe which I assume was the water/condensate return back to the boiler. Does that sound right?


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## welder15725 (Feb 12, 2010)

You will wanna pipe the supply in the bottom and the return should be out the top on the other side. This will get all the air out of your radiator. A bleeder valve will be a great Idea also to help with air removal when filling the radiator with hot water. Don't pipe both supply and return in the bottom cause your radiator will only have a couple inches of water in it and probable won't put off that much heat.


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## welder15725 (Feb 12, 2010)

hedgecutter said:


> I think these radiators were two pipe as they have a pipe attached on both ends at the bottom. One is larger which I assume was the steam supply and the other end has a smaller pipe which I assume was the water/condensate return back to the boiler. Does that sound right?



Usually in steam radiators the steam will be in the top and condensate will be in the bottom.


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## hedgecutter (Feb 12, 2010)

*Sizing*



darnet said:


> This is exactly what I did last year. There is nothing better then the cast iron radiators imho. I converted 18 of them in my house. I had single pipe steam prior. I used some of the origanal inlets and took out the plugs on the bottom of the other side. Put a reducer and hooked pex to that for a return. I was able to go from a single zone to 5 zones.



Sounds like you are happy with the heat from your rads. So you plumbed yours in the bottom on one end then out the bottom on the opposite end. Do you know if there is any kind of sizing rule of thumb as far as wood boiler water capacity to how much water capacity you can have in your radiators?


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## welder15725 (Feb 12, 2010)

hedgecutter said:


> Sounds like you are happy with the heat from your rads. So you plumbed yours in the bottom on one end then out the bottom on the opposite end. Do you know if there is any kind of sizing rule of thumb as far as wood boiler water capacity to how much water capacity you can have in your radiators?



How does the radiator ge full of water when both are piped in the bottom??


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## hedgecutter (Feb 12, 2010)

welder15725 said:


> How does the radiator ge full of water when both are piped in the bottom??



As you and Darnet both posted above I will need a bleeder at the top of the outlet side of each radiator. Would that not bleed all of the air out when you fill the system?


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## welder15725 (Feb 12, 2010)

hedgecutter said:


> As you and Darnet both posted above I will need a bleeder at the top of the outlet side of each radiator. Would that not bleed all of the air out when you fill the system?



The bleed valve won't work properly if the supply and return are both piped in the bottom. The water would just come out one pipe and flow into the other. You need to put the supply in the bottom and return in the top. This would allow the ratiator to fill all the way up with hot water. Then the bleeder vale will need to be used to evacuate all the air in the radiator. If you don't bleed off all the air you can cause an air lock which will not let the water flow.


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## trax (Feb 12, 2010)

I have converted many steam systems to hot water, Darnet is correct plumb both supply and return into the bottom of the radiator and a bleeder in the top. If there isn't already a plugged 1/8" hole on top side of one of the end sections for the bleeder, there will be a small round flat spot where you can drill and tap it. Most time you can get away without having the radiators flushed to have some one do this is very costly. There are additives you can use that will help with the scale


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## darnet (Feb 12, 2010)

All my radiators are full of water. When you crack the bleader water will come out. This is how the plummer had me hook them up. If they were draining because the outlet is hooked up on the bottom they would get air bound all the time. So far I have had no problems with that. Just to let you know this is a closed system now. The pipes and radiators and header are full of water all the time.


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## welder15725 (Feb 12, 2010)

trax said:


> I have converted many steam systems to hot water, Darnet is correct plumb both supply and return into the bottom of the radiator and a bleeder in the top. If there isn't already a plugged 1/8" hole on top side of one of the end sections for the bleeder, there will be a small round flat spot where you can drill and tap it. Most time you can get away without having the radiators flushed to have some one do this is very costly. There are additives you can use that will help with the scale



Sorry for being a pain. How would the bleeder bleed the air when the air won't push through if they are both piped in the bottom?? How would the radiator get full of water to have max heat transfer??


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## welder15725 (Feb 12, 2010)

darnet said:


> All my radiators are full of water. When you crack the bleader water will come out. This is how the plummer had me hook them up. If they were draining because the outlet is hooked up on the bottom they would get air bound all the time. So far I have had no problems with that. Just to let you know this is a closed system now. The pipes and radiators and header are full of water all the time.



A plumber works on plumbing kinda things. Ask a pipefitter how to hook it up.


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## Clarkbug (Feb 12, 2010)

hedgecutter said:


> I think these radiators were two pipe as they have a pipe attached on both ends at the bottom. One is larger which I assume was the steam supply and the other end has a smaller pipe which I assume was the water/condensate return back to the boiler. Does that sound right?



You are right hedgecutter.

A one pipe system would have been for steam supply as well as condensate return. The pipes have to be sloped properly to work this way, and it went out of practice due to the restrictions on pipe runs. The two pipe system had the steam in and condensate out like you mentioned. Typically the condensate return line is a few inches above the bottom, so that any of the crud that would flake off or settle out of the steam would become trapped in the bottom of the radiator. That way it wouldnt plug up your condensate return line. 

Here is a page worth a read....

http://www.masterplumbers.com/plumbviews/2000/convertsteama.asp

And Another...

http://search.thisoldhouse.com/search.html?Ntt=radiator&bu=


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## darnet (Feb 12, 2010)

The radiators are connected with (for lack of a better term) a tube across the top and across the bottom. The water will work itself not only side to side but up and down. My radiators are hot from top to bottom telling me the hot water is traveling ok. I am not a expert at this, just letting you guys know how I hooked my system up.


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## Clarkbug (Feb 12, 2010)

welder15725 said:


> Sorry for being a pain. How would the bleeder bleed the air when the air won't push through if they are both piped in the bottom?? How would the radiator get full of water to have max heat transfer??



The radiator will fill up with water, once you can get the air out of it.

I see what you mean about the straight flow through it, and if this was an "open" system, you would be right. Open systems have something exposed to the atmosphere all the time, so the radiator would stay full of air and never get hot if this was the case. 

Since the water flows back to the boiler, is heated back up and then pumped, This is a "closed" system that shouldnt ever need water once its full (in theory). Since the piping and the associated water is under pressure, it will want to flow into the radiator and do whatever it can to get back to low pressure (outside the radiator). This will pressurize the air inside the radiator (just a little) to the point where if you open up the bleed valve, the air will come out. The water will then fill up the space in that radiator where the air used to be. 

You are also right in thinking that if your flow rate on your system is really high, the bulk of the hot water would want to shoot straight through the radiator. However, if its the right flow rate, the water will take a little more time to move through the radiator, and then it will give off a lot of its heat to the room.

Sorry if some of this was really basic, not trying to talk down to anyone at all.


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## darnet (Feb 12, 2010)

I called this guy a plummer but he is a heating and air conditioning guy.


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## welder15725 (Feb 12, 2010)

darnet said:


> The radiators are connected with (for lack of a better term) a tube across the top and across the bottom. The water will work itself not only side to side but up and down. My radiators are hot from top to bottom telling me the hot water is traveling ok. I am not a expert at this, just letting you guys know how I hooked my system up.



Right, the vertical peices are connected by "tubes." But if you connect just the bottom it will only fill the bottom. The heat must be transfering to the top on you system. If it is workin out for you, thats great. Just saying on heating hot water systems there is a rule of " in the bottom out the top." Now on your steam system it is backwards "in the top out the bottom." Sorry if I'm not making much sense. I do mostly Industial systems not residental.


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## hedgecutter (Feb 12, 2010)

*Just trying to learn something.*



Clarkbug said:


> Sorry if some of this was really basic, not trying to talk down to anyone at all.



I appreciate your simple explanation. You are not talking down to me. I am actually learning something here. I realize there is definitely more than one way to skin a cat. Please carry on.


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## mtfallsmikey (Feb 12, 2010)

welder15725 said:


> A plumber works on plumbing kinda things. Ask a pipefitter how to hook it up.




Hmmm...35 yrs. in the plumbing, HVAC trades....what am I?....look at my avatar!


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## darnet (Feb 12, 2010)

The vertical pieces are hollow also, so the water not only travels sideways but up and down. the water will constantly run through the radiator. By the time the call for heat is met I don't know how many gallons of hot water has gone through but the entire radiator is hot. Then what makes this system nice is the hot water is retained in the radiator witch is slowly used up in the room


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## mtfallsmikey (Feb 12, 2010)

ericjeeper said:


> I would take a trip over to www.heatinghelp.com and go to "the wall"
> Great bunch of guys over there that will give you all the right answers.




And for those of you who are doing a similar conversion, or have just found a pile of old radiators to use, EDR/BTU capacities of most all old radiators can be found in the specs listed there. 




Clarkbug said:


> You are right hedgecutter.
> 
> A one pipe system would have been for steam supply as well as condensate return. The pipes have to be sloped properly to work this way, and it went out of practice due to the restrictions on pipe runs. The two pipe system had the steam in and condensate out like you mentioned. Typically the condensate return line is a few inches above the bottom, so that any of the crud that would flake off or settle out of the steam would become trapped in the bottom of the radiator. That way it wouldnt plug up your condensate return line.
> 
> ...



Mostly true. at first, steam condensate lines were piped directly into the bottom of the boilers...then, they would go BOOM!....do a search on "The Hartford Loop"



TreeCo said:


> No, no and no! Damn.
> 
> I grew up with a radiator steam system that had been converted over to oil fired hot water. Both in and out pipes hook to the bottom of the radiator. Ours had a small valve and a special key for bleeding the air out of the top of each radiator. They only need bleeding every blue moon. The valve had a little outlet so you could bleed air until a small amount of water came out. An auto water fill system on the oil boiler in the basement kept the system at 8 psi. It worked flawlessly.




True. Unless you have a leaky old-school expansion tank. Placing the circs on the supply side of the boiler, using a good air separator have mostly eliminated these problems.


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## welder15725 (Feb 12, 2010)

Clarkbug said:


> Sorry if some of this was really basic, not trying to talk down to anyone at all.



I don't think so either. I have never seen it done with the cast iron radiators. I have takin hundreds out of some dorms at Purdue. They were all steam radiators. We replaced the with fin tube radiators and fan coil units. If it works like darnet said then go with that.


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## darnet (Feb 12, 2010)

Wish I would have known that last year. I ended up buying 3 more from a guy in vt. I added 1 in the bathroom and put 2 large ones in the basement. Nothing better than warm floors. You can't find them often and when you do people want to much money for them.


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## welder15725 (Feb 12, 2010)

darnet said:


> Wish I would have known that last year. I ended up buying 3 more from a guy in vt. I added 1 in the bathroom and put 2 large ones in the basement. Nothing better than warm floors. You can't find them often and when you do people want to much money for them.



They went to the scrap yard. Wish I knew someone would want them. Probably haul only 4 or 5 though. Those things are heavy.


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## darnet (Feb 12, 2010)

Ya tell me about it. We disconnected them and brought them outside and hosed them out. Then brought them back in, some up and down a flight of stairs.


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## welder15725 (Feb 12, 2010)

Working on an udated chilled water and heating system now. We may be tearing some more out. Not sure yet. Still workin in the mechanical room hookin up the pumps.


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## darnet (Feb 12, 2010)

I should take some pic of my system and see what you think.I have been meaning to do it but haven't got around to it. Just the header is 7ft long plus the water tank. I still have not did anything with the steam boiler. If you know of anybody that needs one it is a wel-mcclain 76. I think it is 350,000 btu


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## welder15725 (Feb 12, 2010)

Yeah, take a picture. That would be cool. Seems like everyone is getting away from steam. No one on the top of my head, but I'll keep that in mind.


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## darnet (Feb 12, 2010)

Here are some pics of my heating system. First time trying this so here goes.


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## darnet (Feb 12, 2010)

A few more


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## Clarkbug (Feb 12, 2010)

welder15725 said:


> A plumber works on plumbing kinda things. Ask a pipefitter how to hook it up.



I can tell you work on the commercial/industrial side of things 

I work on commercial design, and I started as a plumbing designer.

I had to learn quick that "plumbers" deal with water, sewer pipes, compressed air, and for some reason natural gas. The "pipefitters" (we also called them "steamfitters", which may be wrong) were the ones that used black iron for just about everything. That included all of the piping for hot and chilled water for heating, fuel oil and diesel piping for generators and boilers, and then all of the steam and condensate lines. 

In regards to the steam systems that put steam in the top and it comes out the bottom, those usually tend to be commercial steam coils or heat exchangers. They have the steam trap on them to regulate the flow of condensate that goes out, so they have to be located at the bottom of whatever equipment it is.


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## welder15725 (Feb 13, 2010)

Clarkbug said:


> I can tell you work on the commercial/industrial side of things
> 
> I work on commercial design, and I started as a plumbing designer.
> 
> ...



You are correct. Pipefitters are steamfitters. Seen a new guy call an old pipefitter a plumber...it wasn't pretty.


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## welder15725 (Feb 13, 2010)

Pics look good darnet. Ever think about insulating it?


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## darnet (Feb 13, 2010)

Insulating what the copper or the pex or both?


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## welder15725 (Feb 13, 2010)

darnet said:


> Insulating what the copper or the pex or both?




Everything that has hot water in it. You got some money in pump too. I looked at those for my OWB..they aren't cheap.


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## darnet (Feb 13, 2010)

I did start on some of the pex that comes into the house from the owb. I still have alot more to go. I do like the basement warm though so I don't know how much I will do.


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## welder15725 (Feb 13, 2010)

I still have alittle more to insulate on my hot water lines. My crawl space is nice and toasty. Plus I need to insulate my duct work.


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