Another \"keep the steam?\" post

BC

For all the info and input, guys. I'm going to have to do some thinking and try to figure a way to keep the steam without pumping the middle east dry. Time to do some insulating!

BC

Please bear with my long post, I'm just trying to think things through out loud...

I have an 1850’s Victorian house with beautiful marble-topped one-pipe steam radiators. The system is reliable and comfortable for the most part, especially in cold weather. As an engineer I appreciate the simplicity of it and enjoy tinkering with the vents etc to get everything balanced as well as possible.

My problem is that I am currently burning about 2000 gallons of oil per year, heating only the 1st floor. Now that will improve as I renovate the house and insulate (R-19 walls, R-30 roof, new low-e windows, etc), but my heat loss calcs show an ultimate heat loss of about 65,000 btu on a 0deg day, which still translates to about 1200 gallons of oil per year (80%afue). The boiler is ancient and huge, but it is downfired about as low as it can go due to not running half the rads and the tech measured the efficency while it is running at 75% or so. It definitely needs replacing for safety and reliability reasons, but I’m not expecting to see a huge efficiency gain with the new boiler. The contractor quoted $8500 for new boiler, oil tanks, and chimney liner (he knows his steam, and he put in the current setup with his Dad many years ago).

Natural gas is not an option in my area, propane is still more expensive than oil, and the wife is less than enthusiastic about burning coal in a stoker boiler, which would be my first choice. So, to save a significant amount of money, the only option seems to be a geothermal system. As I am gutting the whole house, I can put in radiant floor/ceiling designed for very low water temps to maximize the heat pump efficiency. Geothermal also appeals to me as an engineer since it is about the most efficient and eco-friendly way you can heat. At current oil prices and electric rates I calculate the savings at nearly $3000 per year, so even though the up-front cost is high, the payback is not that bad.

I’ve convinced myself that the geo system is the logical way to go, but I just hate the thought of losing my steam rads! I don’t think I can convert them easily to hot water since they are individual columns that are not connected at the top. I thought about drilling and tapping each column and linking them with pex (which would be hidden by the marble top), but I’m also worried about running them at hydronic pressures. Assuming the radiator would hold together, would this work?

I’d like to find some way to keep a few of the steam rads around for use as supplemental heat at least, but the only way I can think of is with a new boiler, tanks, liner, etc. The geo only works out costwise if I can save the money on the replacement oil boiler. Since I'd only keep 4-6 radiators, I could use a smaller boiler, but I don't think this would save much since most of the cost is in labor to pipe it etc.

Steamhead (in transit)

Much of your efficiency loss

comes from running that huge old boiler which has been downfired. That's a lot of metal and water to heat up. A new boiler will do much better.

You'll never get those old rads to work right on hot water, and the increased pressure may cause them to leak. So forget that idea.

Since I don't know where you live I don't know if the heating season is much longer than the cooling season, or if the cooling load is a lot smaller than the heating loas as it would be in the North. But if cooling is much less than heating in your area and you really like geothermal, look into sizing it for the cooling season and the mild portion of the heating season, and run the steam system during the real cold weather. Put TRVs on the rads you won't normally be using so you can keep them off without problems, and turn them up if you need to use that space.

Richard_4

KEEP THE RADS

get rid of the old boiler, you should see aprox. 20% to 30% fuel savings. insulate all exposed steam and condensate piping. you will miss the steam when its gone.

Mike T., Swampeast MO

As Steamhead mentioned, much of your current inefficiency is coming from a downfired boiler driving only a small portion of the intended load.

It's also possible that your system has some problems that have not been addressed. Do you own Dan's book, "The Lost Art of Steam Heating"? If not, buy it NOW, put it in your preferred reading room and study, study, study. One-pipe steam does have an elegant simplicity, but elegance is not always simple to achieve...

You're correct that a steam system will NEVER rival the efficiency of a ground-source heat pump. I'd also venture to say that one-pipe steam system will never rival the comfort of a low-temp, large (floor/ceiling) radiant panel system.

You will pay LOTS of $$$ for such a conversion and you're almost certain to need HEAVY conduction plates or a product like Warmboard to work with temps available in a GSHP. If your floors are typically thick for the period, even heavy conduction plates may not suffice. Ceiling panels have a nice allure, but unless you embed copper in true plaster, or do a complete custom job with heavy conduction plates/structural aluminum "panels" intended for floors with very good back insulation you may not meet your heat loss with very low supply temps.

Victorian homes often have an extremely irregular footprint. Such significantly increases heat loss. Unless you're going the Constantin way with Icynene or similar insulation, your heat loss per square foot of heated panel may exceed the ability of a GSHP.

Crunch your numbers with EXTREME attention to detail. You may well find that a one-pipe steam system in top-notch shape WITH TRVs on the radiators will be the most cost-effective solution BY FAR. It may not be the most efficient, but I venture to say that it can be better than the majority of hot water systems NOT using a condensing/modulating boiler.

BC

Thanks for the responses - good input so far. Just to clarify, the steam system is currently working fine - comfortable, quiet, and reliable. I got Dan's books before I moved in, and the first thing I did was add main vents (they had been removed long ago), replace all the radiator vents, and add a vaporstat. If oil was still at $1.25 like it was when I moved in, I wouldn't even consider a different system.

The dilemma comes in since I really need to replace the boiler - it has not let me down yet, but it is 40+ years old and held together with boiler cement and metal strapping. The returns and the hartford loop are all very corroded and have been patched here and there. The chimney is unlined and in poor shape (plenty of draft, though), and the oil tanks are pretty rusty. In short, I really need a new boiler, tanks, chimney liner, and some piping repair. Add in the time and money to remove, sandblast, and paint each radiator, replace the radiator valves (nearly all are shot) and I'm looking at 8-10k to really get the system upgraded.

It comes down to fuel choice - If I want steam, I need to use either propane or oil, both of which are expensive and subject to big price swings. If I go to radiant, I can use a ground source heat pump, which at current rates is a 60-70% savings on a $/btu basis.

I like the idea of using a slightly smaller geo system with a few steamers for auxilliary heat for the really cold weather. After all, only about half the rads are really nice old ones, the rest are just newer ugly things. Unfortuately, even if I cut the size of the steam system in half, I don't think it will save much. I'd still need a new oil tank, chimney, piping, etc. Are there any steam boilers out there that would work well with just ~150-200 sq ft of radiation? Any that could be direct vented?

Steamhead (in transit)

You can get

steam boilers in almost any size these days, and in direct-vent models too. Or a powervent can be fitted to a standard boiler. Or, if you get the right liner in your chimney, it can handle any fuel not just oil or gas. This may pay off down the road if electricity becomes unreliable (think Enron).

When you say the rad valves are shot, do you mean they're leaking? If so, and the leaks are around the valve stems, just repack them. You can have them sandblasted at a later time if money is tight.

Mark_35

Relative cost of GSHP and fossil

Up here in Niagara Mohawk territory, a GSHP doesn't really beat fossil in heating mode by much. Granted it is one of the most $$ electric utilities in the country, but check your COP assumptions in heating mode. Remember the source water does not stay at 50 degrees year round (unless your field is way oversized) and the COP drops as the source temp drops.

Also agree that radiant under wood floor is limited in terms of output by the high R value of the wood. We have been called in to evaluate heating problems in high ceiling rooms with radiant under wood to settle contractor disputes. (The designer goofed, not the contractor). I guess that is all in the tables, but be careful.

BC

Some of the valves are rebuildable (and I've done a few), but a lot of them have been badly buggered up over the years by some gorilla with a pipe wrench and will need replacing. Not a big expense, but they do add up. I think I'll look into keeping at least some of the steam system going. It seems a shame to get rid of it.

BC

I'm designing to a 95-100f fluid temp on a design day. This is difficult in a house such as mine as people have mentioned, but with radiant ceiling using plates it seems possible. I'm insulating with polyurethane spray foam as I renovate, so it will be about as tight as an old house can be (heat loss currently figured at 65kbtu, 3400sqft, so about 20btu/sqft). Anyway, with 100F hydronic temp and 32F loop temp, most GSHP manufaturers quote a COP of around 3. For most of the season the hydronic temp will be lower and the loop temp will be higher, so COPs of 4 or higher should be possible much of the year. I haven't modeled it precisely yet, but a seasonal COP of 3.5 seems very reasonable. I'm not far from NiMo territory, NYSEG charges me $.12/kwh. I'm locked in at 2.45 for oil this year. So, 3412btu/kwh*3.5/.12=99500btu per dollar for the geo, while oil is 138500*.85/2.45=48000 btu per $. When I factor in oil burner maintenance, oil is well over twice the price. If I wasn't locked in on the oil price, I think it would be over 2.70 now.

I realize that electric rates can and will go up as the cost of oil does, but electricity prices are usually much less volatile (except in CA!). Much of the power in our region comes from coal, which should be cheaper for a while at least. I don't know which sie of the oil debate to believe. Some say that once production catches up to current demand it will go back to the $30-40/bbl range, some say it can only continue to climb. I wasted about a whole day reading arguements on both sides of the "peak oil" debate, and I'm none the wiser. At the end of the day it's a gamble.

BC

Incidentally, here's a picture of one of the radiators - hopefully you can see why I'm reluctant to ditch them!

Mike T., Swampeast MO

You said you prefered to fuel with coal.

Rebuild as a solid-fueled vapor system and those radiators will truly shine.

Dave Stroman

What a shame to ditch these old beauties. You really can not beat the comfort of cast iron. How many rads do you have? You could get some others that would work with hot water.

Dave in Denver

Steamhead (in transit)

Looks like either a Reed or a Bundy

The Reed was made by H.B. Smith Co. and the Bundy by A.A. Griffing Ironworks. You have a heating museum there, why close it down? Once in a while you'll find rads of this type for sale, you could outfit the whole house with them.

BC

It must be a Bundy

It is made by the Griffing Ironworks. Do you know if Dan's radiation chart book has these listed? I've been thinking about buying it, it would be nice to know in advance if these are in there.

BC

Now there's an interesting idea

What is required to turn one-pipe steam into vapor? I don't have Dan's book here at work, or I'd look it up myself!

Mike T., Swampeast MO

The steam experts can help you with that. I know of a few who would love to do such a thing, but the chances of them being in your area are probably slim... May be difficult to get all the components--particularly the automatic draft regulator used for solid-fueled systems.

Steamhead (in transit)

Dan's \"E.D.R.\" has some similar ones

but the real thing is in the Library. Make sure you have the Adobe Reader (formerly Acrobat Reader) then go here:

http://www.heatinghelp.com/pdfs/92.pdf

Steamhead (in transit)

Vapor

refers to the way the pipes were sized, allowing the system to run at a few ounces pressure. Most of these systems were two-pipe, using traps, orifices, water seals etc. to keep steam out of the dry return. But I know of at least one one-pipe Vapor system- it was marketed by Gorton, makers of the air vents we like so well.

I've seen one system that was almost certainly one-pipe when first installed, but had returns added which made it Vapor since the steam mains didn't have to handle the condensate and therefore had more capacity. It worked pretty well.

Mike T., Swampeast MO

The R. M. Starbuck books I've studied say that vapor was about MUCH more than just pipe sizing to allow very low steam pressure. To him, it was about keeping the system under a relative vacuum with steam being produced WAY below 212 degrees. Seem to recall him saying that this could occur in the 80s with a very tight system... The key to the entire system was modulation of the fire.

Steamhead (in transit)

He was describing \"Vapor-Vacuum\"

as found on systems like Richardson, O-E, Trane, Morgan, Dunham, Hoffman, Webster etc. These systems were designed to hold vacuum as the coal fire burned down, which produced steam at lower temps.

Other systems like Broomell, Vapor Regulator Co, VECO, Mouat and others were not designed to hold vacuum. These were simply Vapor systems, running at very low pressures.

Mike T., Swampeast MO

Sorry Frank.

Guess I'm still stuck on the idea of "vapor" being steam produced at lower than atmospheric pressure...

Know of three Trane vapor systems in my town (nearly identical side-by-side houses built for three daughters). All converted to natural gas (thus no vacuum any more) but [think] all the components were still hanging around and looked like they would last forever.

Is it still possible to build such a system with a solid fuel boiler?

Steamhead (in transit)

You would need

some way of keeping the steam from leaving the dry return in case of a leaky trap, and a way of holding the vacuum. Both would need some serious capacity which rules out Hoffman's #76 vents. I'd use a standard steam trap discharging to atmosphere thru a check valve.

Then you'd need a way to regulate the fire.........

Bob W._3

solid fuel

regulating the fire - probably a tailor made application for a pellet or biomass boiler?