Coverting Steam Distribution to Hot Water

skretz · June 2011

I am looking at converting steam to hot water using existing cabinet heater throughout a building. The reduction in heat output is typically 50% that of steam. What (if any) measures can be taken to compensate for the loss of heat output rather than adding additional radiation.

Mark Eatherton · June 2011

Add...

INSULATION.

No way to force more heat out of a given convector, short of adding a blower to the mix, which is going to make it noisy, dusty, ongoing maintenance intense and a parasitic consumer of electricity.

Maybe you should consider leaving it steam, and making it greener. Go to the book store here and look at the Greening Steam book that Dan recently produced.

There is a lot more to converting from steam to hot water than meets the eye, and done wrong, will cause more hate and discontent than heat and comfort...

ME

Greg Maxwell · June 2011

Steam Conversion

I couldnt agree more with Mark. Being a wholesaler in our market, I have a lot of experience in jobsite evaluations. In most cases, its steam to steam boiler swaps. I have though, been involved in quite a few steam to water conversions, and you had better dot your I's, and cross your T's. The only saving grace is that in most cases, the terminal units are grossly oversized to begin with. But, without doing a room by room heat loss, and identifying the convectors, you wont know that for sure, and if you have to increase the water temp to 200 degrees for more BTU output, you may negate the savings you thought you were going to get. You are better off to look at changing out your boiler, getting better burner / boiler efficiency, and changing things like main vents, or if its 2 pipe, radiator traps. Then, if your system allows, adding things like thermostatic air vents, or radiator valves, will offer creater control and comfort. Also, dont forget to check things like water quality, (you make steam much easier in clean water than dirty water), flushing returns, and boiler pressure. Keep that pressure low. People pay way too much attention to burner efficiencies, thinking that the "up to 95 percent" means that that will always be the case, and way too little in the way of distribution efficiency. Steam, by its very nature, is an awesome vehicle for heat distribution.

Patrick_North · June 2011

Apples to Oranges

Just a homeowner here, but...

The tantalizing boost in potential AFUE for a mod con relies on being able to run at lower temps. If you were dealing with grossly oversized rads this might well be possible. But if your radiation is (presumably) adequate with steam but undersized under hw conditions, then such a switch could increase your fuel bills.

And that's if nothing else goes wrong with the conversion.

I've been following these boards for years and don't recall many instances where simply updating and improving the existing steam system wasn't deemed (by pros!) the way to go.

Good luck,

Patrick

Steamhead · June 2011

What Mark, Pat and Greg said............

I'll add that since steam usually runs on ounces and hot-water might need up to 20 pounds, you really run the risk of leaks if you try to convert steam to hot-water.

And if those convector elements have orifices built into them, they will create a lot of noise on hot-water.

Keep the steam.

Henry · June 2011

It all depends

If the building has a one pipe steam system, your screwed. Since you mentioned convectors and not radiators, I assume it is a 1950s or 60s steam heating system. We have doen a number of transformations from steam to hot water in downtown Montréal where it is very cold and VERY humid in the winter. The radiators are all over sized! We usualy ad a reflective blanket in the cabinet (they are subsidised!). We also usualy keep the steam mains with some modifications. We ALWAYS go mod-con.

Payback can be as little as 3 years on some conversions and up to 5 years on others. I just quoted a $3.4 million conversion where the labour cost alone will payback the job in less than 5 years, nevermind the maintenance costs of steam. It will put 6 stationnary Eng out! Plus, the natural gas bill will come down some 30 to 40%!

Steamhead · June 2011

Henry, we've heard this before

so we'll ask the same question: What condition are the steam systems in now?

If, as I suspect, they are not in the best of shape, this is not a fair comparison and never will be.

A while back, we kept hearing about some savings figures that sounded too good to be true. Turns out they were- after doing some digging we found that the steam systems were so badly neglected they had almost completely failed. I'll bet those shiny new mod-cons are just limping along now, since they've likely suffered the same neglect- but we'll never hear about that, will we?

skretz · June 2011

Thanks

Thanks for the info. We tested the risers and distribution everything is in good shape. I will update on progress and results when the project is completed.

Steamhead · June 2011

So

which way are you planning to go?

Coverting Steam Distribution to Hot Water

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