# Cast Iron Radiators



## djblech (Aug 10, 2009)

I just got back from Duluth MN where I picked up 4 radiators for $65 each. They are in really nice shape. This is the cheapest I have seen used ones. Most of the prices have been $100-$125 and up. I plan on replacing some of my baseboard. I also have a radiant slab that is hard to heat. It was poured over 6" of sand over the radiant pipes. This is how it was being done 15 yrs ago. I can pump a lot of heat into the sand and I don't seem to get much out. I am thinking of abandoning it for a C.I. radiator or two. They sure are heavy.


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## Gooserider (Aug 10, 2009)

Sounds like a good idea...  If you haven't already done so, it might be worth doing a search on them, I know Eric has made some really good posts in the past about rebuilding and reconditioning cast iron rads.

Gooserider


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## Eric Johnson (Aug 10, 2009)

I love CI rads. Post some pics or tell us more about what you've got. They really are functional works of art, in my opinion.


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## tom in maine (Aug 10, 2009)

I redid our previous home over about 15 years ago. It had about 17 radiators with an old steam system.
The basement was a lot warmer than the upstairs, since there were 3 and 4" steam pipes throughout the basement.

We moved in in January and it was -10F. Once we got the steam boiler controls working properly (that first night it hung at about 52F--the kids flew out of the house to go to school that morning!), the upstairs overheated and the first floor was cold.

I installed thermostatic control valves on every radiator and was able to regulate the heat very nicely.

After a couple years, we had insulated most of the house (4250 sq. ft. built in 1855) to R-40 and removed the old steam behemoth with the 10" flue pipe and installed a tiny direct vented oil system WITH an outdoor reset control.

There was no thermostat in the house, constant circulation and the radiator valves would protect the rooms from overheating. One radiator was always on, in the biggest room so the circulator was not deadheading.
It never overheated since the outdoor reset took care of that.

I would not hesitate to to use either old CI radiators or new radiant panels with passive control thermostats. 

BTW, I would consider using the sand radiant as a heat sink for a (big)solar system, if that ever becomes a thought. Should work better than a tank, if it is well insulated.


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## Dune (Aug 10, 2009)

Tom in Maine said:
			
		

> I redid our previous home over about 15 years ago. It had about 17 radiators with an old steam system.
> The basement was a lot warmer than the upstairs, since there were 3 and 4" steam pipes throughout the basement.
> 
> We moved in in January and it was -10F. Once we got the steam boiler controls working properly (that first night it hung at about 52F--the kids flew out of the house to go to school that morning!), the upstairs overheated and the first floor was cold.
> ...



Back in the day, we used to talk about using stone for storage, How does sand work? I imagine you would need to run a grid of pipes through it, much more pipes than for a water tank I would think.


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## Dune (Aug 10, 2009)

djblech said:
			
		

> I just got back from Duluth MN where I picked up 4 radiators for $65 each. They are in really nice shape. This is the cheapest I have seen used ones. Most of the prices have been $100-$125 and up. I plan on replacing some of my baseboard. I also have a radiant slab that is hard to heat. It was poured over 6" of sand over the radiant pipes. This is how it was being done 15 yrs ago. I can pump a lot of heat into the sand and I don't seem to get much out. I am thinking of abandoning it for a C.I. radiator or two. They sure are heavy.



Before you pipe the C.I. rads, be sure to pressure test them. They often leak after having been bounced around. Been there done that.


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## tom in maine (Aug 11, 2009)

I think it was about 25 years ago, we did a really big radiant floor for a very large welding shop.
They worked on things like ferry boats and they knew that the slabs would crack. They also wanted to have the floors be warm since the gigantic
doors would be opened to get the big things in and all the warm air would just flow out of the building.
Since the welders were usually lying on the floor, the radiant floor was a great fit.

In that installation, we installed tubing in a layer of sand that was a foot deep. The sand protected the tubing and added thermal mass.
The biggest issue was keeping the tubing lying flat. We were using polybutylene, which was easier to work with than PEX. I think there is PEX hardware that would help assist installing this way.

The system worked with an outdoor reset and we ran an oil system to heat the floor. It took days to get up to temperature, but it worked well.

Sand is a poor conductor of heat, but if the floor system is well insulated, the system does work well.
We did another one, as a residence. It was gas fired. When the heating system went down, it was a week before the residents knew about it.

Insulation is the key, both for the slab and the house. This concept has legs for a wood system, but the details are important.
This type of system responds very slowly, so it is prudent to have tubing in the slab also (if it is a residence) or have some radiant panels for quick response.

Tom


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## djblech (Aug 11, 2009)

3 of the radiators are large, 38 " tall. 1 is 25" wide and 2 are 22.5"wide. The last one is smaller, 11" wide x 8" deep x 32" tall. This one will probably go in my mudroom (8x12). The largest one will go in my family room where the slab that sucks heat is. I have a VC Dutchwest woodstove in this room that I like, I just don't want to have to start a fire to watch TV. I have 5 zones in the house now, 2 radiant slabs (marginal), basement, main floor, and upstairs (bedrooms). These last 3 have baseboard that I would like to replace with C.I. rads. 
What was the temp control that was used with these? I thought I read that it was plumbed in line, if so does it stop flow? I think I saw one schematic where the rads where piggybacked on a main line so as to not disrupt flow. Does this make any sense?


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## Gooserider (Aug 11, 2009)

Essentially you can plumb C.I. rads just like you do any other heater - go back through the various threads with plumbing diagrams, and you can put your rads in in place of whatever other emitters might have been used...  You can plumb them in series, in which case they will essentially be controlled by the zone control for that zone, and all in that series string will come on and off at the same time - however note that each one will get slightly cooler water, and thus put out less heat than the one that came before it...  This is because all the water in the series passes through all the rads, and the water passing through the first rad will be cooled by the amount of heat it puts out.  That cooler water will go into the second rad, and get cooled some more, and so on.  Depending on the system layout this can cause issues of the first rads putting out to much heat, and the later ones not putting out enough.  It is sometimes possible to work around this by using smaller size rads in the first rads, and larger ones further down the line...

If you do some sort of parallel return, or other parallel configuration, then each rad can have it's own thermostatic radiator valve, which would control the flow to that one unit, in effect making each rad its own "mini-zone"

If I was designing the setup, I'd probably look at doing some sort of parallel configuration just because I think it gives better control and flexibility.  My initial inclination would be to do a "home run" type setup with small PEX lines from a radiant style manifold in the boiler room to each rad, w/ a Thermostatic Radiator Valve on each one.  This would give a lot of flexibility, and the smaller lines will probably be easier to run through the existing structure..

Gooserider


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## tom in maine (Aug 11, 2009)

To plumb radiators with thermostatic control valves, you need to install them in parallel or with monoflow tees.
This is pretty simple with PEX and I would suggest shutoffs in the basement for each radiator, in order to isolate them in case you need to move one or service it.

The radiator should have an air vent (aka coin vent) so it can be purged of all air. 

If they are in series, if you shut off one radiator, it will shutoff the entire loop.
Without the thermostatic valves, it will put you into the situation where the system can overshoot temperature wise, given all the mass the cast iron represents.


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## RobC (Aug 11, 2009)

I got a couple off Craigslist. First I cleaned out the old fittings, flushed tanks and did a pressure checked. I used a Schrader valve on the top 1/4" NPT fitting to be replaced by a coin vent at the install. I cleaned them up by wire brushing and pressure washing. Paying a little extra time to any ornamental areas where multiple old layers of paint had hidden the detailing. ( Sand blaster would have been nice ). I used a couple of coats of HI TEMP semi gloss black spray paint to finish. On a side note. One of the first times I did a air pressure check on a large item, I didn't allow for the expansion of the HOT compressed air in the filling for a pressure drop, COOLING, over the first couple of hours. For example, you fill to 45 PSI come back in a couple of hours and its at 38 ( not necessarily a leak) you need to come back in 5 or 6 hours and hopefully it will still be 38. Any comments on install pictures welcome.


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## Eric Johnson (Aug 11, 2009)

Nice.

I use regular rustoleum and it holds up well, even with pretty high temps. I do the Schrader valve thing for pressure testing as well. You can easily make one out of an old bicycle tube air valve and some standard fittings.

The thing to be careful about when buying cast iron radiators for hot water systems is that they have tubes (i.e., water flowing across the radiator) on both the top and bottom. Older steam radiators don't have a top tube, making them pretty difficult to bleed all the air out. It can be done, but it's not easy or convenient.


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## in hot water (Aug 11, 2009)

Tom in Maine said:
			
		

> I think it was about 25 years ago, we did a really big radiant floor for a very large welding shop.
> They worked on things like ferry boats and they knew that the slabs would crack. They also wanted to have the floors be warm since the gigantic
> doors would be opened to get the big things in and all the warm air would just flow out of the building.
> Since the welders were usually lying on the floor, the radiant floor was a great fit.
> ...



I'm not sure sand is a good choice under a concrete slab, especially a structural, heavily loaded one.  I've worked on a lot of heavy equipment shops and have never seen sand used for base.  Dry sand doesn't compact and has poor consolidation.  Google around for info on sand under concrete, and have a structural engineer sign off on any slabs you install over sand.

A slab is only as good as the base below it.  This is why compaction tests are required on all commercial slabs, radiant or not in many areas.

www.concretees.com/people/bruce/pubs/C99C023.pdf


As for high mass 12" thick sand bed radiant installs... keep in mind that flywheel works both ways.  When the weather warms, or the building heatload drops that large mass will still radiate energy.  Bob Ramlow is proponent of large sand bed radiant, generally solar powered all summer.  He instructs homeowners to open windows to control over heating.  doesn't sound like a practical or user friendly way to regulate comfort in your home or shop??

 hr


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## Highbeam (Aug 11, 2009)

Sand has great compressive strength IF it is confined. Well, most things do I suppose. It is frequently used in my area under slabs and in utility trenches for both bedding and for backfill.


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## Gooserider (Aug 11, 2009)

RobC said:
			
		

> I got a couple off Craigslist. First I cleaned out the old fittings, flushed tanks and did a pressure checked. I used a Schrader valve on the top 1/4" NPT fitting to be replaced by a coin vent at the install. I cleaned them up by wire brushing and pressure washing. Paying a little extra time to any ornamental areas where multiple old layers of paint had hidden the detailing. ( Sand blaster would have been nice ). I used a couple of coats of HI TEMP semi gloss black spray paint to finish. On a side note. One of the first times I did a air pressure check on a large item, I didn't allow for the expansion of the HOT compressed air in the filling for a pressure drop, COOLING, over the first couple of hours. For example, you fill to 45 PSI come back in a couple of hours and its at 38 ( not necessarily a leak) you need to come back in 5 or 6 hours and hopefully it will still be 38. Any comments on install pictures welcome.



As a bit of an aside and / or safety note, it is FAR safer to fill any device being pressure tested w/ water and then pressurize the water, the higher the test pressure the more benefit from doing so.  Air is compressible, and if you have a catastrophic failure of the device under test (DUT) it will instantly expand back to it's non-compressed volume, with potentially explosive damage, shrapnel, etc.  Essentially a bomb!  If you have the DUT full of essentially non-compressible water and the same failure occurs, then the water blows out and makes a mess, but the expanding air volume is limited to what's in the pressure hose, normally not very much of a problem...

Yes, filling w/ water and draining is messy, and if you have a leak it can be a bit harder to locate, but IMHO the safety benefits are worth it if you will be testing at close to design strength, or if the DUT has the potential for a shattering material failure, or a high internal volume.

Gooserider


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## Eric Johnson (Aug 11, 2009)

I agree with that. In my case, I use the air filler to test radiators "in the field" to determine whether they are worth hauling home. You don't need very much pressure to know whether a rad is water-tight. 5 or 10 psi with a bicycle pump is sufficient.

Minor leaks can be repaired with an automobile radiator repair kit, or, if you don't mind violating one of the basic tenets of plumbing/heating etiquette, use a bottle of Boiler Stop Leak in the system and the leak should disappear.


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## Gooserider (Aug 11, 2009)

Eric Johnson said:
			
		

> I agree with that. In my case, I use the air filler to test radiators "in the field" to determine whether they are worth hauling home. You don't need very much pressure to know whether a rad is water-tight. 5 or 10 psi with a bicycle pump is sufficient.
> 
> Minor leaks can be repaired with an automobile radiator repair kit, or, if you don't mind violating one of the basic tenets of plumbing/heating etiquette, use a bottle of Boiler Stop Leak in the system and the leak should disappear.



True, low pressure testing like you describe it doesn't really matter that much.  The DUT is rated for much higher pressures, so an explosive failure is unlikely, and even if it did happen the pressures involved are low enough to minimize the damage potential...  I'd start looking at using water pressure (hydrostatic) testing more if I was getting over 30-40 psi or so.  I will also say that my gut tendency is that somewhere along the way, I would want to bring everything I build up to it's maximum rated pressure, or whatever I can get out of my compressor, whichever is less...  I figure that sort of stress test verifies that all is as well as it can be, and that there aren't any marginal spots that might break down later once things are in service...

Gooserider


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## Eric Johnson (Aug 11, 2009)

If I have access to city water, I just fill it up from the bottom and bleed the air out the top. You're getting maybe 110 psi for a rad that will never see more than 30. Leave it for a couple of hours and see if you get any leaks.


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## pybyr (Aug 11, 2009)

Gooserider said:
			
		

> Eric Johnson said:
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...except stay well clear if trying such a test at any significant psi level --  sudden failures of vessels containing compressed air or any gas are nothing you'd want to be near


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## Gooserider (Aug 11, 2009)

pybyr said:
			
		

> Gooserider said:
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Just what I was saying - do a hydrostatic test, where the DUT is filled with water, and you just use a small volume of airspace to apply pressure.

Gooserider


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## Singed Eyebrows (Aug 12, 2009)

If you have leaks, boiler sealer works wonders,as mentioned. You can tie a rag to a boiler leg or section that is leaking & it will wick treated water into a container. With large radiators you can run some real low temps. I can heat with 110 degree water. Good luck, Randy


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## Eric Johnson (Aug 12, 2009)

There are so many good things about cast iron radiators. I think it's like having a little wood stove in every room. Nice place to warm your hands, butt, whatever.


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## WRVERMONT (Aug 13, 2009)

I love them.  It feels so good using something that was made a long time ago but remains perfectly "state of the art."  I'm busy getting a number of them ready for nieghbors system.


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## pybyr (Aug 13, 2009)

I dread to think of what new-manufactured cast iron radiators would cost !  It's fortunate that old units come available at somewhat reasonable prices.


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## heaterman (Aug 13, 2009)

Gooserider said:
			
		

> RobC said:
> 
> 
> 
> ...




Ditto on the hydrostatic vs compressed air testing. Fill with water,  test to relief valve pressure at a minimum, ASME specs are 1.5 times relief pressure IIRC.  If you do the same with air only you do indeed have a bomb on your hands. I know a guy who nearly lost his leg when a tire came off a rim at only 30PSI. He still walks with a limp 15 years later.


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## Jeff S (Aug 14, 2009)

Has anyone had any experience modifying these radiators,I just bought several of the same style and would like to add sections to some while making others smaller but I'm not sure how the sections are attached,best I can figure is that they are pressed together,if this the case not sure how delicate they would be to pry apart.Perhaps they are threaded with short pieces of pipe.Any suggestions would be helpful.


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## Eric Johnson (Aug 14, 2009)

Very, very old cast iron radiators are held together with threaded nipples. The vast majority of the radiators you'll find, however, are pressed together as you suspected. They're held together with "push nipples" which appear to be thin sections of pipe tapered down on both ends. In theory, you can make most ci rads bigger or smaller by adding and subtracting sections or columns. When they're originally built, the mfg puts in as many columns as desired, with special end-sections at each end. 

I think you can still buy push nipples for some radiators. I suggest going to heatinghelp.com and either posting on or searching The Wall, which is the message board over there. They have some really good threads describing all of this, including the best ways to take apart and re-assemble ci rads. It's not for the faint of heart, but it can be done.

Here's a couple of photos. You can see the push nipples in the disassembled rad. The black radiator is an old steam rad with no top pipe that I nonetheless figured out how to use in my hot water system. Works like a dream. No air in any of the columns.


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## Jeff S (Aug 14, 2009)

Eric,thanks for the quik responce I will check out the other web site,it does appear that you would need some decent equipment to pull apart and press back together these radiators,worst case senario is to use them as they are ,just may not be the most ideal but perhaps close enough.


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## Eric Johnson (Aug 14, 2009)

I think you can pull them apart with wooden wedges. Not sure about reassembly, but it could probably be done with careful hammering or with a hydraulic jack. Come to think of it, you could probably pull everything together with a come-along or a tie-down.


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## Jeff S (Sep 7, 2009)

Does anyone have an opinion on whether or not you can pipe these radiators in the bottom and out the top ?As much as I clean them there is always a chance of a chunk breaking loose and plugging a line if piped bottom to bottom or top to bottom.My theory is that the chunk would settle towards the bottom and therefor would be less likely to interrupt flow.Most of my radiators are 13" high with a few 18" ones so its not like there would be a huge difference in temp between top and bottom.


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## pybyr (Sep 7, 2009)

Eric-- can't help but be curious-- what was your technique to get air out of the upper parts of the radiator that was originally designed for steam?


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## Gooserider (Sep 7, 2009)

Jeff S said:
			
		

> Does anyone have an opinion on whether or not you can pipe these radiators in the bottom and out the top ?As much as I clean them there is always a chance of a chunk breaking loose and plugging a line if piped bottom to bottom or top to bottom.My theory is that the chunk would settle towards the bottom and therefor would be less likely to interrupt flow.Most of my radiators are 13" high with a few 18" ones so its not like there would be a huge difference in temp between top and bottom.



I would probably stick with the doing things the way previously reccomended, as I seriously doubt that you would actually get a chunk breaking loose that was big enough to be a problem, especially if you maintain proper water chemistry and all that...  

If feeling paranoid what I would probably do is put in a dirt separator, or at least a wye strainer downstream from the rads, and try to avoid having dirt sensitive plumbing like valves and circs or other stuff with tight passages between the rads and the dirt catcher.

If I was doing things the way that seems recomended these days and using a manifold / home run to each rad setup, I'd do something like; hot manifold > TRV > rad > return manifold > dirt separator > rest of system

Gooserider


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## Jeff S (Sep 7, 2009)

Gooserider,you are most likely right on all accounts,just curious if you think if the radiators would not preform efficiently the way I suggested ?


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## tom in maine (Sep 7, 2009)

There is not a problem plumbing in the bottom and out the top. 
There might be an issue if you have to open up old plugs. They do not always come out easily.

If these were water radiators originally, I agree with Gooserider, there is not much likelihood that an obstruction
will occur.

Flush them out with water and install them. Put some corrosion inhibitor in the system along with a dirt separator 
if it is really nasty.


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## Eric Johnson (Sep 8, 2009)

pybyr said:
			
		

> Eric-- can't help but be curious-- what was your technique to get air out of the upper parts of the radiator that was originally designed for steam?



OK, Trev. You asked for it.

Basically, I turned the radiator over, filled it with water, shut off the isolation valves that I plumbed in specially for that occasion, then turned the radiator back over, vented the zone up to the isolation valves, then opened the valves. This radiator is piped in series behind one other CI rad (which can be vented). Any air migrating up from the boiler gets trapped in the first radiator and can be vented out. The radiator is still going strong after two heating seasons. I thought originally that if I had to re-fill it once a year, no big deal. But that hasn't been necessary.

I have a picture around here somewhere of the vents and isolation valves (also unions for quick connect and disconnect). When I find it, I'll post it.


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## Gooserider (Sep 8, 2009)

Jeff S said:
			
		

> Gooserider,you are most likely right on all accounts,just curious if you think if the radiators would not preform efficiently the way I suggested ?



Probably wouldn't be a huge difference in performance, but in theory if you go in the top and out the bottom, or as I believe is more common, in the bottom on one end and out the bottom on the other, then convection currents will occur that will help ensure that the heat gets distributed evenly across the entire surface.

Seems to me like there MIGHT be a tendency for the hot water entering the bottom to convect up to the top as it goes past the first few risers, and then stay more at the top of the rad as it travels to the top exit on the other end, leaving a sort of triangular "dead zone" on the exit end bottom that wouldn't see as much circulation / heat exchange as the rest of the rad...  It might not be a noticeable factor, I'm really not sure.  I just figure the dead guys did it the traditional way for a reason...

Gooserider


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## Eric Johnson (Sep 8, 2009)

That seems to be a matter of personal/professional preference. I've always lived in houses where the rads were all piped bottom-to-bottom, and that's how I install them, too. Especially if they're piped in parallel, you want the coolest water possible emerging from that radiator. You won't get that if it exits from the top.


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