Drawbacks of running baseboard hot water zone off steam boiler

Kevin Esler

I have recently bought a house that has a 50 year old oil-burning steam boiler. The original parts of the house use steam-heated convectors to supply heat. Two additions, a large bedroom and a large kitchen, are heated by baseboard hot water off the same boiler. The same boiler supplies hot water for bathing.

I'm looking to upgrade this for the following reasons:

(a) the hot water is very slow to start and I suspect will be inadequate for the number of people that will soon be living in the house.

(b) I suspect the boiler is quite inefficient. No proof yet as I don't have a years worth of oil bills to examine. But it does seem to be burning oil at surprising times, like in the middle of a fairly warm day, with no-one using hot water.

(c) One of the hot water zones, the kitchen, is nearly always too warm, and the other one, the bedroom, is too cool when the weather is cold.

I don't know much about HVAC and would like advice about the best way to proceed. Broadly, the options seem to be:

1. get a more efficient steam boiler and continue the hybrid steam and water setup, OR

2. convert the steam to baseboard heat.

As for tht hot water supply, I've been advised that indirect-fired heaters are very efficient, if initially costly to buy.

Specific questions I have are:
- What at the disadvantages of staying with a hybrid steam/water system ?
- Can an indirect-fired water heater be made to run of a steam boiler ?
- How expensive is it going to be to replace the steam convectors with baseboard water equipment ? There are 5 rooms involved with 6 convectors (one room has two).

Paul Mitchell

Steam and hot water

To run hot water baseboard(hwbb) off of a steam system can be done but it has to be piped a specific way. This a qualified heating contractor can help you with. Possibly your existing sytem is not piped corrctly. Replacing a boiler is expensive but pays off in the long run. Based on your description of the system I would probably lean you towards converting to hwbb. Other people may have a differant twist but either way you have a significant investment to make. In most cases I like to keep steam and hot water seperate whenever possible.

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Steamhead

Kevin, I'll bet

that boiler maintains temperature all the time so hot water is available whenever someone opens a faucet. As you suspect, this is quite inefficient.

I think if I had your house, I'd remove the addition zones from the steam boiler and install a small hot-water boiler to run the baseboards and an indirect, firing only when the baseboards or indirect need heat. Then I'd set up the steam boiler to only run when there's a call for steam. This way would also give you some redundancy, since if one boiler quits the other one will still run.

You say your system has convectors- are they hooked up with one pipe or two? If the latter, I'll bet you have a Vapor system. This was the Cadillac of heating in its day, and is still one of the best out there now. We recently added to a system like this to heat a small addition and it worked perfectly.

There's no need to tear out an old steam or Vapor system- it's much less expensive and intrusive to maintain it!

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Kevin Esler

Steam and hot water

Steamhead, thanks for the idea. I hadn't though of that. So you'd recommend keeping the existing steam setup. What about the 50 year old boiler that is heating the steam. Would it be reasonable to suspect it to be fairly inefficient ? Worth replacing ?

Kevin Esler

Steam and hot water

...I forgot to answer that the convectors have a single pipe to them.

Steamhead

The steam boiler

could either be upgraded with a newer burner (if not already done) or replaced. But taking the baseboards and hot faucet water off of it will make it run less, and the burner could be re-tuned so it only provides enough heat for your one-pipe convectors.

It might make sense to re-tune it now, and replace it later when it's convenient.

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Joe_13

while expensive

replacing the 50 year old steam boiler just to heat the original steam riser will get you back some floor space for the 2nd HW boiler and indirect DHW tank. That monster probably weights over 800 lbs. Are you on gas or oil?

Kevin Esler

Steam and hot water

The 50 year old boiler burns oil. It does appear to be quite hefty.

It seems extravagant or redundant to have two boilers down there, but I see the sense in the proposal. I'd guess the controls and piping might be simpler if the steam and hot water are run separately. And as SteamHead helpfully pointed out, the old oil burner could be replaced later.

Anyone know someone capable of tuning a steam system in the greater Boston area ?

Kevin Esler

Steam and hot water

The 50 year old boiler burns oil. It does appear to be quite hefty.

It seems extravagant or redundant to have two boilers down there, but I see the sense in the proposal. I'd guess the controls and piping might be simpler (and therefore ultimately requiring less maintenance) if the steam and hot water are run separately. And as SteamHead helpfully pointed out, the old oil burner could be replaced later, if I can offload the water zones and have it tuned for the new load now.

Anyone know someone capable of tuning a steam system in the greater Boston area ? For that matter, I'd welcome suggestions for contractors to do the whole upgrade, or offers from contractors to submit a bid.