Reasons for not selecting the highest efficiency steam boiler?

Typically

The best steam boilers such as Burnham Megasteam (oil-fired only) the MPO and others fall into the mid-high 80's (85-87%) AFUE for what that is worth. Naturally this depends on how well the boiler is matched to the radiation and how well the radiation is matched to the heat loss.

Of course the aspects of proper venting, insulation of piping, how well your house itself is insulated, how low a pressure you can run and how well you control it, use of TRV vent valves if on one-pipe steam, all play significant roles, especially together.

Installing the best and most efficient steam boiler in a poor match-up will defeat the best number on that yellow energy efficiency tag...

If you burn oil, to me that is the best use of it because you will not be in a condensing mode anyway; you will be running above flue gas dewpoint.

If you are burning gas, so be it. Your efficiencies will tend to be a point or two less than oil.

The rationale of using a less efficient boiler is a matter of your first cost savings amortized over the life cycle cost of the boiler, just like that. You may find that a so-called lower efficiency boiler may be a "better fit" to the system to which it is connected so you may in the end get a better efficiency than a poorly applied 87% AFUE boiler. One has to take all things into consideration.

My $0.02

Brad

AFUE

Most gas steam boilers will not qualify for a rebate. Most will not break the 83% AFUE and will not be "Energy Star" rated. Look close at the ratings, some of the boilers have a dual AFUE rating one for steam and one for hot water. Make sure you are looking at the right one. The smaller the boiler the better the AFUE rating is.

If you find a gas fired steam boiler that does make the "Energy Star" rating let me know, I have been looking long and hard.

That being the case, would it be worthwhile to switch from natural gas to oil, in order to get a Burnham Megasteam?

Standing pilot boiler

For my home (WM EG-35) I went with a standing pilot instead of an electronic ignition system. Even though the SP reduces efficiency, it tends to keep the boiler slightly warm and dry during the off season. Since the boiler is in the basement, where humidity is up, the drying effect of the SP is helpful. BTW, this was a recommendation by the steam expert I had install the boiler at which time he disclosed the reduced efficiency tradoff. So...here was one reason for selecting a lower efficiency boiler.

Mike

As of 07-28-06 The only steam boilers that qualify are as follows. Peerless EC/ECT-04 1.25 GPH, PeerlessEC/ECT-03 .75 GPH PeerlessEC/ECT-05 1.75 GPH . I'm sure more were added but I haven't got the updated list yet. Hope this helps ED

Oh what a model of efficiency the tax code is

Dirty little secrets about combustion temperatures tell us not much at all happens beyond the universal 80% efficiency. Bang. Play with dampers and pilot lights for true savings - yes - but I find them a hard swallow as they are added onto efficiency numbers. Oh well, labels are not worth the glue they come with. Is there anyone here who actually believes the EPA estimated gas mileage on the sticky stickers they glue inside our new cars? Not me, not for one second.

Playing with these numbers is a gooey subject and I have no advice to offer on what taxable issues are involved in NY and I wish the government did not push us into twisted decisions based on tax code language. Aren't we all glad we got big promises out of the telephone back tax refund? The next big one will be the HDTV rabbit ear conversion refund. You mean you didn't save the receipt for your 35 year old TV set? Oh dear. Meanwhile, I still hope you'll meet the qualifications for getting your very own $500.00 back.

What's up with creepy numbers on steam boilers, hot water boilers and warm air furnaces?

First off, condensing features are routinely achieved in hot water boilers and even more so in warm air furnaces. While these low temperature machines yield exactly not much in increased appliance efficiency they do deliver some amount of extra bonus heat that gets squeezed from the smoke coming off our gas fires. It's real money, it's nothing to spit at but it isn't either a whopping return on your gas purchases.

Only the natural gas fired appliances get to fog up enough humidity to make condensing a worthwhile effort. LPG numbers are not so impressive and oil is rarely a fruitful candidate for the bonus percentages that come from low temperature flue gas condensation. Plus, system wide now, when you go low temperature you loose lots of thermal efficiency which affects your home heating operation in many weird ways. (I am hinting here of course at why warm air furnaces don't operate with the thermal efficiency of a steam radiator system; hot water systems fall in between)

To go off a physics tangent, when we play with 1 kWh of power in either fuel, we are playing with, in the case of oil, 0.10 liters of water in the form of humidity in the flue gasses. Play with LPG, and the available water goes up to 0.12 liter. For natural gas, we allow ourselves a whole shot of 0.16 liter. It is not ever possible to de-evaporate all that moisture. Practical sales brochure tout natural gas condensation but usually not that of oil burners and so we can guess that under most optimal conditions we'll be able to render about 0.05 liters of condensed water for every 1 kWh of fire consumed.

In numbers, that's about 110 BTU for the rendered condensate off of 3414 BTU for the 1 kWh, a bonus return on your utility money of about 3% when all is condensable. If we guess that we burned about $2,000.00 worth of gas to survive the winter, the bonus kick back condensation yields (at 3%) $60.00. It's real money but it is not necessarily significant.

I don't mind eating $60.00 worth of doughnuts though. How else can we improve all this? Well, the damper, the pilot, the increased system wide thermal efficiency, and of course, the lowering of the indoor thermostat. This last action leads to a treasure trove of doughnuts.

Back to boilers and furnaces.

In warm air furnaces the condensing feature does a nice job - if not a vital job - of recouping the lost thermal efficiency of the generally low temperature warm air floating through the ductwork. Hot water boilers achieve less of the condensing bonus, but they also operate with less to loose on the system wide efficiency. If not a wash, at best a small return on your heating dollars. In both cases there is value in recuperating the heat of condensation.

Hotter steam comes with a higher system wide thermal efficiency and so there has always been less of an urge to scrape the condensation bonus. That's why it does not significantly matter to steam boilers to be of the flue gas condensing type, plus, it's not a natural thing for steam boilers to be condensing in the first place... However, big power plants do all that sort of thing and it's (just) a matter of scale to get residential steam in the same boat. Thank you Burnham for the new Megasteam.

Back to cashing in on the tax credit and getting more work done.

Maybe there is some qualifying equipment you can buy to produce your domestic hot water independently from the boiler - steam boilers don't exactly shine at this task during all of the summer. Work the job all together to get cost efficient and energy efficient.

Perhaps also considering installing a new combined AC and heat pump will do very nicely for shoulder season and redundancy. Keep the winter steam for effective heat. Again, I've stretched out the job a bit more than what the $500 would cover, but there are always lots of opportunities to work on.