Condensing vs non-condensing boilers

Guy_6

It seems like a few well placed 100 watt bulbs may do the trick!! All kidding aside, consider what you are going to do for domestic hot water. Although the heat load will be minimal (understatement), the hot water load may become an issue. A modulating boiler with an indirect will work efficiently, as well as cover any engineering glitches in the load calcs.

Art M.

Condensing vs non-condensing boilers

I had a heat loss calculation done which showed a 12,600 BTU loss. My heating contractor wants to put in a condensing boiler such as a Baxi HT330 or a Trinity. I question whether the condensing boiler will run long enough to condense. Am I totally off base? Is my contractor correct?

Thanks in advance.

Bob Forand

Baxi

This is not a good application for the HT330. If you read the literature it's lowest setting is in the neighborhood of 35,000 BTU. This low BTU is very difficult to get a boiler for. The Lochinvar Knight gets down top 16,000 BTU. Good luck...

Joe Brix

With such a small load

does a boiler even make sense? Maybe an electric HW tank.
Is their another system you can throw a HX on, like another WH?

Constantin

How big is the space?

There is the remote possibility that the heat loss is off, so if you don't mind, how about sharing some of the specifics for the space, location, etc?

As for very low loads like yours (if correct), I have seen luminaries like hot rod resort to electric water heaters with upgraded elements/controls do a great job of delivering heat. Even a T50 Munchkin would only start to operate on a design day...

Another alternative (please feel free to laugh) is to consider a truck heater like a Webasto or Espar/Ebersp

singh

small boilers

Try www.thermolec.com/boilers.htm
If the heat loss is correct, electric not a bad idea.
How big is this space, wall construction ,windows etc..
Where part of the country are you located in,that you have such a small loss.
What type of heat do you have now?

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Art M.

Condensing vs non-condensing boilers

Thanks guys for your response. The house is being built in Northern Maine where the degree days is 9500. It's a two story with 2700 SF. The exterior walls are 12" thick built with an inner load bearing and a non-bearing outer wall. The insulation is a blown in fiberglass product called Optima which will yield an R-50 along with 3" of Roxul RXL80 on the outside which will give me a total R-value of R-62 in the outer wall. Attic space will be about the same R-value. Windows are all casement with triple glazing, 2 Low-E coatings and argon filled.

I'm concerned with the heat loss calc also. The engineer stated that the low heat load is based on having R-10 insulation on the basement walls on the inside. Without the basement insulation the heat loss was 39,400 BTU. There is also an HRV that will be installed.

Thanks again.

singh

sounds like

your building a pretty tight house.
Have you thought about geothermal?

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Unknown

thats what i was about to suggest

sounds like no matter what you choose, utility bills will be light but with geo they will be peanuts.

chapchap70_2

Is there such a thing as too tight?

I've heard of people being concerned about not enough infiltration of air and that it may become "stale" and unhealthy. Does anyone want to comment on this?

I would think that it would be best for any boiler you might choose to get its combustion air from outside, preferably sealed combustion. I also think that heated domestic water off the boiler could be a problem because of the vastly different loads required. I don't think that an oil heated appliance would have such a low BTU per hour rating.

You might want to check this wall hung boiler out. I do not know much about gas heated appliances. It seems by what this brochures states that this boiler varies the gas input according to the load required!? The rating for this appliance is 19,000 to 175,000 BTU's per hour with LP.

http://energykinetics.com/pdf/EKpak.pdf

Carl

singh

AFUE

What is the effciency rating on the EKpak, I noticed it is non-condensing?

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Joe Brix

The EKPak

Looks suspiciously like a Takagi tankless unit.

Constantin

Except...

... you also have to consider ground conditions. Much of maine is granite with a thin layer of soil on top. Drilling the wells for a GSHP under those circumstances would be a very unhappy undertaking. Plus, there isn't much need for AC in ME. Never gets that warm...

On the other hand, if there is a large body of water nearby that you can tie into, GSHPs make more sense.

I would stick to a small boiler. The efficiency of the heating plant matters less because the home is so well insulated. If the boiler is non-electric, I'd consider a buffer tank to allow the boiler to operate better across the shoulder seasons. I would also use an indirect water heater. If the budget allows it, I'd spring for a low-mass, modulating, condensing boiler to minimize operational costs. Around here, you can buy a lot of LP for one GHSP well...

chapchap70_2

Efficiency Rating

There is no AFUE listing on the EK-Pak. The rating is 85% Energy Factor for LP. From what I understand, Energy Factor is a rating commonly used for water heaters which takes into account off cycle heat losses where the AFUE does not take this into account. This boiler purges the heat out of it every time it runs so the off cycle losses would stand to be very low. My guess is that the AFUE would be somewhere around 87%.

It seems from what I've been reading about gas units is that most of the manufacturers are not leery about condensing because of the corrosive condensate issue. Is there a corrosive factor that should be weighed; ie In a low heating load house, does a 6% efficiency gain overcome the possible costs of maintaining or replacing equipment earlier? Again, I don't know much about gas.