Cast Iron Radiator Project

[Eric Johnson]

I love old cast iron radiators. Can you think of another product that:

1.) Will last forever with a modicum of care;
2.) Is the best product of its kind;
3.) Is a work of art

Here's one that I refinished on Sunday and hauled into the greenhouse. I was delighted, upon cleaning and painting, to see the lion head cast into the design on the columns. This is male-oriented radiant heat.

You're not supposed to mix ci rads and copper finned baseboard on the same zone, but when the 24 feet of finned tube couldn't cut it, I reverted to the tried-and-true approach. When I bought the place, the greenhouse was heated with three small, ci rads which I appropriated for other uses. I thought the new baseboards would suffice. Eventually I'll probably paint the baseboards black, too; they're pretty worthless as heaters, but maybe they'll absorb some solar radiation in the summer that I can pump back into my system.

 

[Eric Johnson]

I painted it in the garage and wheeled it on a dolly down a step and into the greenhouse. Still needs to be connected, obviously.

 

[Eric Johnson]

Moving the iron.

 

[senorFrog]

Nice! I sent some of mine out to be sandblasted and powder coated. They came out real nice.

Just wanted to pass these links along in case you were interested. I have an addition w/new baseboards which are real ugly. I might get these at some point to dress it up a bit...

http://www.go-overboard.com/
http://www.radiantwraps.com/

 

[Nofossil]

So let me expose the depth and breadth of my ignorance here....

I've always assumed that most radiators are for steam heat - that steam would rise until it touched cooler metal - the radiator - then condense and flow back down the same pipe.

I also assumed that they're made up of two castings - an end section and a center section. Any radiator is made up of two ends and some number of center sections.

I don't understand how the style you have would work for hot water. Is there a blocking plate somewhere in the bottom manifold that forces water to travel up to the top in order to get from one end to the other, or would water just tend to pass through the bottom and heat the rest only via conduction and/or convection?

Is there a bleed valve port near the top to get air out of them?

I'm hoping to shamelessly take advantage of your experience with these.

 

[Eric Johnson]

Cast iron radiators work like you wouldn't believe with hot water. They work with steam, too, but it's tougher on the radiator because steam systems are open and thus they get a lot of rust, pet hair and other crap accumulating inside. Hot water radiators will last forever.

A hot water radiator consists of multiple sections held together, top and bottom, with pressure nipples. The sections are pressed together and then retained with steel rods running the length of the rad. This way, you can make a radiator as big or as small as you want. All you need are end sections and the appropriate number of middle pieces. You can even repair a damaged radiator by taking out the bad section and squeezing the remaining ones back together. Attached is a pic of what the sections look like when taken apart.

The physics is simple. You pipe hot water into the bottom of the rad and it rises up into the columns. The cooler water falls down and flows out the other side. When a ci rad is warmed up (which doesn't take very long at all with 160- or 180-degree water), the heat output is uniform across the length of the unit. On startup, you can feel the columns warm up in series, until the whole thing is hot. All hot water radiators have a top passage way (pipe) and an air vent at the top. Steam rads don't need a top tube, although most do have them, so that they can be used interchangeably in water systems. Steam rads have vents on the side, about halfway up one of the end columns. You need to vent hot water radiators when you fill them, and occasionally as needed, since rads in some locations on any system will tend to accumulate air at the tops, causing them not to work as well (no flow across the top). And the cast iron and water retains and radiates heat long after the pump has stopped. It's a generally accepted fact that there is no better radiant method, with the possible exception of in-floor, than hot water radiators. It's like having a bunch of little woodstoves around your house that you can warm your hands and butt on.

I actually have an old steam radiator with no top pipe heating our kitchen. Attached is a pic of it. If you can figure out how I filled it, I'll bring a sixpack of Old Smuttynose India Pale Ale when I pop in for a visit this winter or next spring.

 

[Nofossil]

I actually have an old steam radiator with no top pipe heating our kitchen. Attached is a pic of it. If you can figure out how I filled it, I'll bring a sixpack of Old Smuttynose India Pale Ale when I pop in for a visit this winter or next spring.

Great explanation - thanks. When you say 'filled', I assume that you mean that you got all the air out of it so that it's filled with water. I'll have to accept the challenge - old Smuttynose is too good to pass up.

How about this: install a valve on the both sides. Close the valves and connect a vacuum pump to one side, plumb to boiler on the other. Open the valve on the vacuum pump side. Pump it down to 99% vacuum. Close valve on vacuum pump side, gently open valve on boiler side. Radiator will fill to 99% with water. Disconnect vacuum pump, plumb to boiler return. Do I get Pale Ale?

Even if that wasn't how you did it, how do you keep air bubbles from accumulating in the radiator?

 

[Eric Johnson]

You and your high-tech approach to everything, nofossil.

I'll bring the beer because anyone who knows and appreciates Old Smuttynose has gotta be alright in my book.

But I took a decidedly low-tech approach involving muscle, which I seem to have in greater abundance than brainpower on occasion. Case in point: that shutoff valve doesn't have to be on its side like that, but I didn't realize that the bleeder works just as well in the vertical position (!).

Anyway, first thing you do on each side is pipe in a union and a self-bleeding shut-off valve, as shown in the photograph. You disconnect the unions, turn the radiator upside down and fill it by hand. Then you close the valves, turn the rad back over and reconnect the unions. Then you pressure it up and open the bleeders on the valves until they squirt water. Then you open the valves and you're in business.

It doesn't accumulate tramp air because there's a regular hot water radiator with a vent on it upstream of this one. Only two rads on the kitchen zone, so I piped them in series. The first radiator catches any air that might be traveling up through the piping. Actually, there isn't much of that. I installed this radiator 3 years ago, and it works just like it did at first. And whenever I've bled the other radiator, there's been little to no air in it. Both of these radiators are on the first floor. With all the water above them, first-floor radiators don't get much air buildup. Upstairs, for obvious reasons, it's a whole nother deal.

 

[Nofossil]

Old smuttynose in my future - one more thing to live for!

I have lots of air problems - whole nother thread, maybe. More than your clever low-tech/high-muscle approach to filling, I'm impressed that you got that union to not leak. I've had absolutely terrible luck with that style.

I'm thinking a whole new round of thinking on the CI radiator theme. Gotta find me some and play. Any idea how many BTU/section or BTU/ft those things put out when used with hot water? I'm cursed by lack of foresight in sizing HW baseboards. I only have 52' for the whole 3500 sq ft house.

 

[Eric Johnson]

I'll have to check again. There's a way to figure it out, but I've forgotten what it is. The water temp has a lot to do with it, of course.

As I recall, a big radiator will produce about 20,000 btu/hr. with 140-degree water. The one in my kitchen shown above is probably half that.

I knew what the formula was because I was trying to figure out how many ci rads I would need to transfer 200K btu into my tank, when I was thinking about using them as in-tank heat exchangers. What I didn't realize was that a cast iron rad immersed in water will transfer A LOT MORE HEAT than the same rad surrounded by air. Using to water-to-air calculation, you'd need more rads than tank.

I would really recommend cast iron, nofossil. You can even put TRV regulators on them and balance the heat output to your needs. Or, if you're like me, you just pump hot water through them when the room stat calls for heat.

I think this photo from our old house tells you all you need to know about cast iron radiators. Sold the house, but we still have the cat. That's a gravity-feed wood-fired hot water system, by the way. No pumps. Great for those multi-day Adirondack power outages in the dead of winter.

EDIT: Here's an online calculator. Let me know how to use it when you get it figured out. It's so complicated that it almost seems like some foreign language.

(broken link removed)

 

[Jags]

You hot water guys are sure an interesting bunch, I'll tell ya that.

 

[Nofossil]

You hot water guys are sure an interesting bunch, I'll tell ya that.

I sometimes justify (and evaluate) what I'm doing by considering what is technically known as the 'WAF', or 'Wife Approval Factor'. A boiler with hot water storage has a potentially high WAF for the following reasons:

1) No muss, no fuss, no firewood debris in the living space.
2) Hot water any time.
3) Want heat? Just turn up the thermostat.

Any time I can use technology behind the scenes to gain a high WAF is all good as far as I'm concerned.

Eric's cast iron radiators would provide a very nice butt/glove/boot warmer for even higher WAF. Now you know my motivations.

 

[Eric Johnson]

There was no rust in this one, enord. Just a fine, black film that smells like fish oil. They say black film (powder when it dries) is the sign of a healthy hydronic system.

The steam rad that I installed in the kitchen did have some rust and a bunch of crap in the trap at the bottom. I cleaned out what I could by hand and flushed the radiator out pretty good with a hose. I haven't lost a pump since doing that install 3 years ago, so I'm guessing we're still good.

I've found that you can get away with a lot of obsessing on your heating system (which is what I do) if your wife can do what nofossil's likes to do, which is have heat when she turns on the stat and unlimited, free DHW. And when the gas bill comes, it's payday from a domestic harmony point of view. Now if I had a car or a boat or another woman for a hobby, then the domestic dynamic starts to shift, I suspect. The only other thing I obsess on, other than gardening, is xc skiing. True, I have to leave the house to do that, but I'm generally ten miles back on some trail in the woods where it's pretty hard to get into trouble. Or let me put it this way: the trouble you can get into back there will be offset by a nice life insurance settlement.

 

[Nofossil]

EDIT: Here's an online calculator. Let me know how to use it when you get it figured out. It's so complicated that it almost seems like some foreign language.

(broken link removed)

Cute. Fortunately, there are many tools on the web for doing translations. I'm sure that the translation below will make the use of the tool abundantly clear:

Technical specifications

Approximately to stipulate how many sections (lamellen) be able heat a space you necessary have to can the calculator use.
By cubic meter space you must embarrass approximately 60 up to 70 Watt.
And the desired model fills in the number of sections, and bekijk how much Watt is generated at by you wished room temperature.
The water temperature in the radiators is 90/70°
Other data such as length, heating are oppervlak, water contents and find weight of the sections on the calculator.

Much better, yes?

My 1966 reprint of the 1933 'Handbook of Applied Mathematics' has a section on cast iron radiator calculations. For a modest consideration (IPA), I'll pass along the contents. Teaser: 150 BTU/hr/sq ft. They've got tables that give you an estimate of squate feet based on the design and dimensions.

 

[Mmaul]

I have an old Sear home that uses this type of heat I have read about it but I'm glad to see that there are people here to answer any questions that might come up in the future it is one of the best heats in my experience. Is anyone else's seem not very efficient.

 

[Eric Johnson]

Well, tell us what you've got, MM. Is it an oil or gas boiler or wood?

As to efficiency, there may be ways to make your system more efficient than it is now, depending on how it's set up. You can overall boiler efficiencies of 90% and higher with a modern oil or gas boiler. The older ones like I have (a 1958 Weil-McLain gas boiler) are about 80% efficient, which isn't bad considering the technology of the day. My new wood gasifier claims 91% efficiency, but I bet that's a best-case scenario under optimum conditions.

Beyond the thing heating the water, you can have all sorts of inefficiencies in your house construction and insulation, and the way your heating system is designed, constructed and piped.

I can't comment on hydronic heat vs. some of the alternatives, such as electric or forced air, from an efficiency point of view, because I don't know. I do know that hot water heat is some of the most comfortable, controllable heat you can have, regardless of efficiency.

 

[hkobus]

EDIT: Here's an online calculator. Let me know how to use it when you get it figured out. It's so complicated that it almost seems like some foreign language.

(broken link removed)

Cute. Fortunately, there are many tools on the web for doing translations. I'm sure that the translation below will make the use of the tool abundantly clear:

Technical specifications

Approximately to stipulate how many sections (lamellen) be able heat a space you necessary have to can the calculator use.
By cubic meter space you must embarrass approximately 60 up to 70 Watt.
And the desired model fills in the number of sections, and look up (bekijk) how much Watt is generated at the by you required (wished) room temperature.
The water temperature in the radiators is 90/70°
Other data such as length, heating are surface (oppervlak), water contents and find weight of the sections on the calculator.

Much better, yes?

My 1966 reprint of the 1933 'Handbook of Applied Mathematics' has a section on cast iron radiator calculations. For a modest consideration (IPA), I'll pass along the contents. Teaser: 150 BTU/hr/sq ft. They've got tables that give you an estimate of squate feet based on the design and dimensions.

That's funny, I never tied the translate tools. It just seemed to look right to me as it was, just fixed a few odd left overs..
I love those old cast relics, in our house it does come with a high WAF ;-)
I'm still looking for some to put in some upstairs rooms, no luck yet.

 

[Eric Johnson]

Here's the big bastid that heats my office at home. Needs a coat of paint. Note that this one is so big that it has a set of feet in the center for support. I think when they put hydronic heating systems in these old houses (I'm sure this was an early 20th Century retrofit to coal central heat), they did a rough heat loss calc for each room and then ordered the appropriate sized radiators for each room. Custom made, in a sense.

Of course, those calcs all go out the window as the house gets some insulation, etc. As a result, most houses with the original radiators are way over-engineered, at least from a heating viewpoint. You can compensate for that quite nicely with modern technology like automatic mixing valves, zone valves, pumps and other thermostatic and hydronic controls. It gets a bit more challenging when trying to run the system on wood, but it's worth the effort, IMO.

 

[Mmaul]

I have a weil maclane as well I dont know about the year but it is newer model. When I get home tonight I will look and maybe even snap a few pic to show the boiler it is how ever gas, but I have a wood insert to suppliment the heat. I will take a few pics of the radiators they still say Sears Chicago on them. I do have a question, I didnt think they were supposed to be painted, mine have quite a few coats of paint I'm sure.

 

[Eric Johnson]

I've always painted mine with plain old Rustoleum. Nothing fancy. And the paint lasts a good long time, even when you're pumping very hot (200-degree) water through them. The best approach is to do what SenorFrog did, which is to take them out, sandblast them and then put a power coating on. That must be beautiful and very durable. But plain spraypaint (any color you like) does a fine job, IMO, and you don't have to move anything. One tip: best done in warm weather, because you get a pretty good cloud of paint in the room. You have to cover everything and have some decent ventilation. I should probably learn how to put an electrical charge on the radiator to get the paint attracted to the metal, like the pros do.

 

[Mmaul]

That's good to know a few of my radiators are starting to crack and peel off and with two small children in a old house I'm worried about lead.

 

[senorFrog]

It was surpringly inexpensive to have them sandblasted & powdercoated, like $100 per radiator.

 

[Eric Johnson]

Lead is a good thing to be concerned about. I'd wait until the kids aren't around and then scrape all the loose paint off. Then clean the rads and paint them. If you're careful and do a good job, they will look fantastic.

The hardest part is probably the cleaning. It's important to get all of the dust out from between the columns. If you don't, it will catch the paint and look pretty tacky. A windshield snow brush (narrow) is a good tool to use. The narrow attachment that comes with some vacuum cleaners is also useful. A round brush on a wire would work pretty well, too. You can hang a sheet behind the radiator to cover up the wall and the baseboard. If it's possible to slightly lift the radiators at all (it usually is), slide pieces of paper under the feet to protect the floor. If you can't do that, masking tape on paper works pretty well.

It's not important to paint the back of the rad, because nobody will ever see it, but I always try to do a complete job whenever possible. If you're really ambitious, you can sand down the area around the chips for a smoother looking job. One thing I've always considered, but never actually tried, would be to go after the chipped areas with some Zip Strip soaked in medium steel wool. That should smooth them out with less effort and no lead-laden paint dust.

You can also paint the piping and valves. Remove the wooden handles if you can and either refinish or paint them black (my preference). If you use Rustoleum spray paint, you can buy a small can of the same color brush-paint for touchup and for painting the pipes and valves. Some of the fittings on old rads are nickle-plated brass. They look pretty snazzy if you remove the old paint and polish them up. Same thing with the bleeders. Might as well bleed the radiators while you're at it. That time of the year.

It takes about two standard cans of paint to put a good coat on a big radiator. Might as well put on more than one while you're at it. Watch for drips! If you have a lot of bare metal, consider using some primer. It may not be necessary with modern paint, but I figure it's worth the extra effort.

If you do it and you're happy with the results, post some pics.

 

[Eric Johnson]

It was surpringly inexpensive to have them sandblasted & powdercoated, like $100 per radiator.

I'm assuming that's if you take them out and haul them to the place, right?

That's a heck of a deal. But I'm reserving judgement until I see the results. Got any pics to post, sF?

 

[Mmaul]

I really need to post some pic tomorrow my radiator's look a bit different then the ones posted. They arent as open as these I will try to find pic's on the web. They look to like they are going to be really hard to clean inbetween the fins.