high efficiency gas boiler

Matt_21

designed to run at temperatures below 140* then your boiler won't condense and you won't get the higher efficiency out of it. if you try to run your supply water temp at 140* you won't get the full output of your radiators and will not make setpoint temperature in your house this winter. your system was probably designed to run at 180* with a return temp of 160*. you could look at a viessmann vitola 200 which i believe gets 85% efficency at the higher water temps.

david byrns

high efficiency gas boiler

We have a 1920's hot water gravity system. We own a 1987 Burnham V18 boiler that was converted from oil to gas. We have a 3100 square foot house with 13 radiators. I can't phantom how our 1987 converted boiler can be very efficient.

We would like to replace our boiler with a high efficiency model. Our local natural gas company says that natural gas will be 50% higher in our area this coming winter. We spent $3000 last year so it looks like a $4500 heating season coming up. Sounds easy to justify a boiler replacement.....

I'm looking for recommendations on a replacement system? Is a condensing boiler like a wall hung MZ condensing boiler even an option for us?

Should we be looking at TRV's as well?

Any suggestions would be appreciated.

David Byrns
Webster Groves, MO

don_156

It depends

David.If your heatloss is great,no matter what type boiler
you put in and with the rising gas cost,you're properly still have the same comsuption and, even a higher gas bill.

Why not take a look at your thermal envelope and see if its
possible to make upgrade to it first...then you might be
surpise that you can go with a lesser btu boiler.

More return on your investment if you will.

Tony_23

funny

I've seen Ultras run condensate out the drain with return temps of 150+. Their listed efficiency minimum is 92 %.

Besides, design is for max days. That's LESS than 5 % of the year.

I'm going to keep on installing high efficiency condensing boilers on all kinds of emitter systems and saving people money. By the time some guys figure out that it DOES work, I'll already be the more experienced expert

Jim M

boiler replacement

Your thinking is right on track. A condensing boiler with a 5 to 1 turndown would be a great system. I would reccomend the following:

1. Pipe it primary secondary with the with the closly spaced T's the same size as the the primary (example 1 1/4" primary, 1 1/4" secondary with 1 1/4" T)

2. Use outdoor reset on boiler and constant circ on the pumps, warm weather shut down on everything.

3. Use trv's at each radiator and a pressure bypass on the secondary after the pump to the retun.

4.If you have a tankless coil replace it with a water maker.

5.Adding insulation, new windows or storms, and sealing are always good ideas.

By the way Ultras are great boilers, Last year we did a replacemnt using an Ultra 310 connected to fan coils (designed at 180 supply). With reset this condenses all the time. Customer reported best benefit employees are no longer complaining, followed by better than 30% reduction in utility bills.

hope this helps

Jim

Guy_6

efficiency

As much as I hate NOT to sell something...
I would have your fuel supplier perform an efficiency test on your boiler. Having actual numbers to work with will help with your decision.

GW

Steamhead

David, you need to start

with a heat-loss calculation of your home. There's a very good chance that V-18 is oversized. This series of boilers offered AFUE percentage ratings in the low to mid 80s, which at the time was pretty good. I must admit to some partiality toward the V1 series since I have a V-14 which still runs great. But if yours is oversized, it will start and stop a lot which is quite wasteful.

Once you know how much heat the house needs, you know how big your boiler needs to be. While doing the heat-loss you may find places in your house that need more insulation, weatherstripping etc. When corrected, these may put you into a smaller boiler, justifying the outlay.

Then you can look at different boiler brands. If your contractor has one that he or she likes, that's as good a recommendation as any.

Mike T., Swampeast MO

You've been given good advice. Conduct a heat loss calculation--not difficult to do yourself and then you can really begin with the homework. HVAC-Calc offers a one-time use program at a reasonable price. There's also a free heat loss calculator available here, but it's not as compresensive as HVAC-Calc.

Your heating cost does sound extreme for your area--about what mine would have been before weatherization, insulation, TRVs, and a Vitodens. Am rather confident in suggesting that your current boiler is extremely oversized.

After conducting your heat loss, you need to assess your radiation ability. Quite likely again that you have an abundance and that it will be able to operate at quite low temperature--even in extremely cold weather. Once you know the EDR of each radiator and loss in each space you can reasonably estimate the required supply temperature. If you need some help, you can write me privately.

Insulation/weatherization will definitely help, but your ability to insulate may be somewhat limited--particuarly if you have a solid brick home. The downside to insulation/weatherization when a boiler is already oversized is that it becomes even more inefficient--particularly in moderate weather. You really don't receive the full benefit of the work as long as the old, oversized boiler remains.

When used properly, TRVs are wonderful--both for comfort and for fuel savings. When used on oversized standing iron radiators I daresay that you get the finest heating system ever made with comfort rivaling radiant panels and response rivaling forced air.

If any of your radiators are covered, UNCOVER THEM! Covered radiators loose most of their ability to radiate and are forced to heat via convection. Your heat zooms to the ceiling and drafts are pulled across the floor. While it is possible to design a radiator cover that actually increases output (by greatly enhancing convection) it's my experience that most are built by carpenters who have zero understanding of heating. The manufactured metal "cages" are no better as they reduce radiation without enhancing convection.

The MZ certainly seems to be a fine and reliable condensing boiler. IMHO however, you should use a condensing AND modulating boiler if you install TRVs. While the Vitodens is expensive, it can also be the easiest to install on a TRVd system as the built-in circulator can frequently handle the load by itself and the only major component that must be added is a differential pressure bypass valve. Other condensing/modulating boilers (and the Vitodens if head loss is too high) will require some form of primary-secondary piping with at least two circulators. This can add significantly to installation cost.