replacing working low pressure steam system

(Note: I did read WHO's response to Steam or Hot Air thread)

I currently have a Peerless G 660 ws 200,000BTU low pressure steam boiler. An 1800 sf house built in 1933. Replacement windows. The boiler is about 30 years old and when I moved into the house in the 70's I replaced air vents with good ones. Haven't replaced them since. The boiler seems to work fine. I use setback thermostat - bring the heat up to 68 at 5pm and down to 58 at 10pm, also up at 5am and down at 6am. The 68 actually takes the heat up to about 70 by the time the boiler shuts off at 68. A little spikky temp fluct, but we have learned to live with it.

Since the boiler is over 30 years old, I am wondering about replacing it - mostly efficiency wise. Seems like most of what I read says 85% is still best efficiency for steam or hot water boilers - so I am wondering if I would gain that much from replacement. Still have pilot light on this one.

I also have the option of either switching over to hot water heat (I have a 1 pipe steam system - so I would have to run new lines) - or even radiant heat. Hot water would be easier - but would I have to replace all steam radiators ? . For radiant I would probably go with 1 1/2" gypcrete over exisiting floors + 3/4" engineered wood floor or tile.

I know with radiant I can get a 98/99% efficient furnace - but I also know the redoing of all the floors ain't cheap even if I do it myself.

So my question is

1. what is the most efficient % low pressure steam or hot water heat system can I expect to get ? (Who responded - modulating condensing boiler with 95% efficiency - is there a recommended mfg and model ???? I am guessing that is a steam system)

2. Would it be worth swithcing to hot water/radiant heat over low pressure steam from an efficiency basis?

3. How do I calculate the size of base board I would need to replace exisiting steam radiators ? Is there a size conversion (like I have 3' x 3' steam radiator's right now - and some are wider or thicker than others - is there a way to convert btu replacement for baseboards ?).


Any suggestions or guidance on how to proceed in the decision making would be appreciated.

Thanks

 

As far as I know there are no 90+ efficient steamers.
Some radiators are made specificly for steam where others can be used for either steam or hot water.
The most important thing you need to do before buying a new boiler is to do a Manual J heat loss calculation.

 

Replacing a one-pipe steam system with a hot-water system would be extremely disruptive and expensive. If you are satified with the manner in which your heating system now works I would suggest that you not consider changing to a hot-water system.

The economics in changing to either hot-water convector baseboards, hot-water radiators or radiant floors is such that it would probably take several decades to recover the capital expense. Of course the rising price of the input energy (gas or oil) would have a bearing on the payback.

 

If you are happy with the way the system heats the house (and please know that the overshoot problem could be corrected with either a new thermostat or an adjustment to the existing one...) don't scrap everything and start over. You can't improve much so the pain isn't worth the gain. Steam heat has a lot of character, is one of the least mechanically complicated systems (once it's initially designed and installed) and provides a high level of comfort without many of the problems other heating systems suffer from (although radiant floors are very good too).

Replacing the boiler with a new much more efficient one should provide fast return on the investment. Just remember, steam systems were meticulously designed as a whole. Changing the capacity of any component will effect the design of all the other components. I agree that the house has changed a lot since 1933 and that a manual J would be of great benefit, but the radiators were sized for the boiler you have. If you change to a smaller boiler, the rads may have to be resized too.

Have a reputable company, that specializes in steam heating, swap out the old boiler. This also provides a good opportunity to tune the whole system. Make sure all the air vents are working properly, the pipes are still pitched correctly, the rads are level AND the thermostat is adjusted to properly anticipate it's setting (or replaced with one that can be). Then sit back and enjoy the warmth.

Doug M.

 

Thanks to all. I appreciate the comments. While Dougm says "Replacing the boiler with a new much more efficient one... " - my only thought is that I really haven't seen where a new one is that much more efficient than the one I have from 30 years ago.

 

Since you mentioned a pilot light I assume this is a gas-fired boiler with a constantly burning pilot light.

A newer boiler with either a hot-surface or direct-spark ignitor will save you some gas. A new boiler with a "power" burner (either forced draft or induced draft) will have a bit higher combustion efficiency and decreased losses when the burner is not operating.

The new windows (I assume new since the present boiler was installed) along with any upgrades in insulation and air exchange reduction may mean that your heating requirements have been lessened. You may be able to get along just fine with a smaller BTU rating boiler. You would need to do a heat loss calculation to determine this.

Bottom line is that yes, a new boiler could save you money in operational costs but that saving must be balanced against the initial capital cost of the new boiler.

 

If you are interested, I can put you in touch with someone in the Denver area who deals with your kind of issues, or could refer you to a couple people if he's too booked up. He is outstanding. PM me if you wish.