Best New Steam boiler

carole

My son told me when I replaced my boiler, which has been going since 1935, to get a Viessman, not realizing that I had steam heat in my house, and that Viessman doesn't make a boiler for steam heat. Can anyone out there recommend a steam boiler that's as efficient as a Viessman?

thanks everyone.

Carole

Brad White_3

There is no comparison

in efficiency between a condensing hot water boiler and a steam boiler, Carole.

Condensing boilers (of which Viessmann is about the best in my opinion) operate most efficiently where the water they produce is lowest in temperature, generally 140F and down.

The key to condensing boilers is to have the return water -and if possible the supply water- temperatures below the dewpoint of the flue gas. By "collapsing" the volume of flue gas, more heat is extracted for your living space.

Steam as you know has to be 212F and higher for pressure. "Condensing Steam Boiler" is a contradiction in terms.

I am sure there will be other opinions on this site, but a good place to start is Burnham, a personal favorite of mine. Glenn Stanton of Burnham is a wealth of information and may well contribute to this thread. Weil-McLain is also a worthy competitor. There are others.

Key to application is to size the boiler for the radiation you have connected to it. Do not size for heat loss. If undersized, your boiler may run dry before the system is warmed up, in short.

If you stick with steam, modern controls, Danfoss valves on radiators, pipe insulation all enhance the experience.

Might this be a time to consider hot water? Nothing wrong with steam mind you, but due diligence leads me to ask.

Downside of replacing a steam boiler with another steam boiler is that if you spent money recently to improve your house envelope, replaced windows with Low E, insulated the walls and attic, you cannot readily "capture" the benefit of your energy improvements.

For example, say your older uninsulated house had a heat loss of 125,000 Btu's per hour (BTUH) and you had maybe 525 square feet of radiation. You insulate, replace windows and so-forth and get this down to 75,000 BTUH or about 315 SF of radiation.

Unless you reduce the radiation (tough to do unit by unit; you often cut some out entirely), you have to put in a boiler capable of serving 525 SF of radiation. Oversized boilers cycle and waste fuel in the process. To begin with in this example you would be about 40% oversized and that is on the coldest day of the year and it gets less efficient as the outdoor temperature rises. Great for fast warm-up but then it sits and cools with little direct benefit.

(Regardless of system, you want to size a boiler to run 100% on a design cold day, theoretically. Because most boilers commercially come in increments, you have to be at least big enough but most often default to the larger size. As a result, in coldest weather it may cycle a bit but as it warms up to the 20's, 30's and 40's, it cycles a lot more.)

Sorry for the dissertation! Just some things to think about.

p.s. A ca. 1935 boiler? Got your money's worth out of that, Carole. I would assume asbestos is in there which you probably know. Once abated, re-insulate the pipes with fiberglass made for the purpose.

carole

thanks, Brad

Brad-
thanks for such a considered response. one question: how difficult is it to switch to a hot water system? does this mean repiping or can you use the pipes currently used for steam?
Thanks again!

Brad White_3

Going to hot water, Carole

can be an adventure. Generally speaking, if the piping is as old as the house (1935 at least) I would re-pipe in copper and possibly with PEX. Definitely re-pipe.

You probably have one-pipe steam, most common on house steam systems. One pipe per radiator, correct?

The copper piping is a standard and the latter, PEX, famous for radiant heat, has applications in retrofit hot water. That plastic pipe can be threaded through spaces and when connected to a manifold gives excellent room by room control.

I would not plan on re-using the radiators without a detailed heat loss analysis. This will capture the benefit of any insulation/envelope improvements I mentioned earlier. Only in this way can you asses room by room what the heat loss is and compare that to what your radiators can do with hot water in them. (From 215F steam to 180F hot water, the capacities are reduced by 37.5 percent; if this matches your heat loss, great.)

Even if the radiators have adequate capacity, getting them re-piped is often a chancey thing. May go smoothly or some may crack. A heating professional can advise you on-site.

In decending order of simple to complex this is what I see as your options:

1. Stick with steam and do the best things in terms of controls. Make the best of it and you will be fine, just may not save as much operating cost over time.

2. Replace with standard 180F range hot water. Keep the radiators if possible. Re-pipe with copper. Add radiators to compensate for capacity deficits if any. (Use only cast iron to match what you have on a given zone -do not mix copper tube fin-tube on a cast iron zone.)

2A. Do the above but add Thermostatic Responsive Valves (TRV's)at all radiators for individual control. Add outdoor reset to lower the water temperature as outdoor temperatures rise. If a cast iron boiler, consider boiler protection circulator (Primary-Secondary). Burnham has this on their commercial line at least, maybe on the residential too.

2B. The above but buy new radiators if the old ones are not workable for any reason. Range from Fin-Tube to panels, cast iron baseboard, whatever you like. (I like Runtal but there are other brands. Burnham has a line of panel radiators, kickspace heaters, convectors and cast iron of all types to check out from one source.)

3. Do any of the above but use PEX. Connect to a manifold in the basement for individual control. Control valves can be placed on each zone at the manifold and thermostats in the rooms. This in lieu of TRV's at radiators. This last one may be easier to install.

Any of the above can be fitted with controls such as Tekmar for overall efficient performance. You can make domestic hot water off of your boiler too. Lots of choices.

4. New tack: Condensing boiler (remember this one? :^)> )

Size all radiators of whatever type for low water temperatures, say the 120-140F supply temperature range. This costs more initially but saves in the long term. This assumes you have gas. (If oil there is one choice of condensing and I am not that familiar with it. )

Pipe up in any way above, copper or PEX.

In a nutshell (Big Nut, I must say) you have lots of options, assuming the boiler is not now in pieces and can make it through the early part of the coming season.

Steamhead

Carole, there are pitfalls when converting

from steam to hot-water. One of the biggest is that a hot-water system runs at least twelve times the pressure of a steam system. If there any weak spots in your old piping, this will probably cause them to leak. Sure you could repipe, but that's a big job.

Another pitfall is that the radiators may not be able to work with hot-water. Or, they might work with hot-water but be too small to heat the house with hot-water. Or, they might leak under the increased pressure.

And if you have a one-pipe steam system, with only one pipe connected to each radiator, you must run another set of pipes to use hot-water.

Also, if you have a power failure that lasts several days, a hot-water system can be severly damaged by freezing. But a steam system holds no water, except for a couple of pipes in the basement and the boiler itself.

If the boilers and heat transmitters are similar, and the piping systems in good shape and well insulated, a steam system is just about as efficient as a hot-water system. And if the air is properly vented from a steam system, it gets heat to the radiators at least as fast as hot-water.

Since hot-water at the usual temperatures does not give off a much heat per square foot of radiation as steam does, if you try to convert you must get the system very hot to heat the house. So a "condensing" hot-water boiler won't run in its condensing range very much, and its efficiency will suffer.

I don't see any reason to convert from steam to hot-water. It's much easier and more cost-effective to install a new steam boiler and fix whatever problems may exist out in the system.

Any of the major boiler brands- Burnham, Columbia, Dunkirk, Peerless, Utica, Weil-McLain, among others- will give good service if properly selected and installed. For this, you need a good steam man. Go to the Find a Professional page of this site to locate one near you. If you're in the Baltimore area, e-mail me!

carole

Mr. Steamhead, I thank

you as well. I guess I'm a little bit confused. You think that steam boilers can operate at similar efficiency as a very efficient hot water boiler? That's my ultimate goal, fuel efficiency (and it is in fact oil).
I don't live in the Baltimore area, but as it turns out I have a friend who just moved into an old house down there and I definitely will give her your name

thanks again.

Unknown

I have to agree with Mr Head.

Your radiators don't need to heat every section to heat the rooms. In fact, the thermostat satisfies after just the right amount of sections get hot, and cool gradually. It's a built in outdoor reset equivilent.

With water, you would heat every gallon of water in every bit of the zones running to get to the same point. Run time comes into the equation, as well as combustion efficiency.

The newer steam boilers hold only 5 or 10 gallons of water, which quickly heats and delivers heat to the sections of radiators that need it. The room thermostat senses enough heat long before the last sections get hot, and stops the burner from heating that small amount of water.

This is the way that a steam system approachesthe efficiency of a converted to water system, and sometimes surpasses it.

Yanking everything out, replacing everything, and repairing the structure afterwards can cost a lot. Then you have a low temperature heating system. No hot radiators anymore.

Oh, what a feeling.

I'm all tingly.

Noel

Steamhead

Another thing to think about

is staying with oil or changing to gas.

Since the first energy crunch in the 1970s, switching to gas has been fashionable. However, this is not always the best way to go.

Most boiler manufacturers make boilers for either fuel. And the efficiency of either a new oil- or gas-fired boiler has advanced quite a bit since those days.

Oil-fired equipment can now burn with zero smoke and soot if set up properly. So there's nothing to smell, or to clean up.

Gas-fired equipment is usually sold with electric ignotion nowadays, so there's no problem with the pilot light going out.

So the choice comes down to which fuel is cheaper per BTU. Right now, oil costs less than gas, and this is likely to hold true for a while. And if the balance tilts the other way, you can have a conversion gas burner installed in an oil-fired boiler. Unfortunately, you can't convert a gas-fired boiler to oil.

If I was doing this job, I'd install a new oil-fired steam boiler.

And thanks for the referral. Have your friend call me at the office, (410) 821-3997, or at home (410) 466-8116.

Christian Egli

How to keep warm

Dear Mrs. Carole

To understand correctly what you are up to, it seems you have a steam system that was new in 1935 and still works fine to this day after nearly 70 years. You don't say anything is broken, so, to me, that is quite a testimony to how good steam heat is.

But you would like to change your boiler.

It seems also that you would like to get more efficiency out of your home as far as heating costs are concerned. The boiler is only one part. Granted, brochures show steam boilers with lower efficiencies compared to condensing boilers but for the whole system, steam heat is similar to hot water in efficiency. Sometimes better, sometimes worse, it depends on how the system is used, controlled and maintained.

With a thorough cleaning job and a system tune-up, you could possibly run at peak efficiency again. Changing the boiler, although it is a nice thing to do, may or may not yield an economic gain for you. And, converting an entire system that isn't broken will be an expensive and disruptive job that will take long time to pay off.

To make your home heat efficient, more insulation will pay off immediately. What will also be very rewarding is to have someone that knows, understands and is committed to steam to take a look at what you have. That would take good care of you.

You also have your son. Does he own a Viessman? Is he happy with it? As you see, there are many, mostly US made steam boilers that are all fine. It is more important to find the good installer. Have you enjoyed your steam heat so far? Does it keep you nice and warm?

Don't you think Steamhead and Noel make a lot of sense. Brad also came up with the good idea to install thermostatic valves (or thermostatic vents, either way); that would allow for less heating in the parts of the house you don't use, thus making your system more efficient and there is little cost to doing that.

Good luck and stay warm.