High Efficiency Boiler vs Standard

Old 12-08-09, 03:44 PM
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High Efficiency Boiler vs Standard

I am entering the market for a new gas hydronic boiler. I recently received an estimate and the installer told me he highly recommends getting a boiler that is approx 85% efficient as the high efficiency boilers that are eligible for the tax credit must be AFUE>90. He said that the high efficiency boilers require new plastic piping and upgrades that far exceeds the cost savings from the tax credits and the increased efficiency.

Can anyone verify if this information is correct? He gave me a ballpark figure of $6,000 for 85% and $9,000 for 90% boiler due to the necessary upgrades. My current boiler is approx. 40 years old and my average winter gas bill is $200 a month.

Thank you for the feedback!

Last edited by Lv2trav; 12-08-09 at 04:08 PM.
Old 12-08-09, 04:25 PM
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You need to start with a heat loss to determine the proper size of the boiler. Do not put in the same size as you have now unless a heat loss determines it is the right size. Also do not size the boiler off the existing connected radiation as many want to do.
As far as which type boiler is an opinion everyone here has. I do suggest whatever boiler you go with include outdoor reset. This will improve the system efficiency along with the newer boiler efficiency and improve home comfort. I feel the decision is more related to the heat loss and amount of radiation and/or type of radiation.
For heat loss FAQ see this link
Old 12-08-09, 04:52 PM
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To follow with what rbeck has said, consider what changes have been made or will be made to the efficiency of the home since that boiler was installed. Back then the practice of over sizing was common. Now the home should be requiring less heat and there are probably more improvements to make. PLUS even today the calculators and definitely the HVAC quotes you got will CYA with a unit bigger than they think you will need.

If you do your own heat loss and understand what they are looking at, you could end up with a boiler less than half the size of what you have. I'm shooting in the dark, but we can get specific if you want. There are homes being upgraded today that are having trouble finding boilers small enough to meet their needs.

As for brands, they are tied to the service and you need a good service co. I'm not an HVAC guy, so can't suggest one brand over another. I have recently looked at an on demand hot water boiler 100k btu that was the size of a microwave and hung on the wall. It was $3,000 and direct vent and 93% efficient. So your quotes, at least to me, look high.


Last edited by Bud9051; 12-08-09 at 04:54 PM. Reason: spelling
Old 12-08-09, 05:26 PM
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As far as the quotes, I think they are good. My boiler alone was in the neighborhood of $3000.

Anyhow, on to what you were actually asking about. The 93% AFUE boiler is a condensing boiler. You won't see that high of efficiency unless it condenses. Low water temperatures are what you need for it to condense. Your water temperature will depend mainly on how much radiation your have. The more the better. That's where the heat loss will come in handy. You can figure out what temperature your water will need to be to heat the house. If it is below 130 degrees for a large part of the heating season, then a condensing boiler will make a lot of sense.

The other thing about condensing boilers, they don't withstand neglect like a conventional boiler will. So you need to make sure that it is maintained properly every year. They also aren't expected to have lifespans as long as a conventional boiler.

It's those reasons that I choose a conventional boiler over a mod/con. I had a Burnham ES2 installed in September in my house. It's only 85% AFUE so it doesn't qualify for the federal tax credit. You need at least 90%.

You will definitely need new near boiler piping if you go with a condensing boiler. It is very important to have that done properly. As far as the venting, I know quite a few of the boilers can use pvc pipe for venting. I don't see how that would be very expensive to install unless you had a long run to make.
Old 12-12-09, 01:13 PM
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I just had a weil mclain utra 80 installed in my house. The reason I went with the high efficiency boiler is after the 1500 from the irs and the 1000 from the gas comp the boiler cost me 500 plus the install. You can not buy a standard boiler for 500. and your going to have to pay for the install anyway, plus it will save on gas. it seemed like a win win to me.
Old 12-12-09, 01:38 PM
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The topic of AFUE got me to think about what rating my boiler is? I have posted before about my Hytech model HT-14NE wall mounted gas boiler. Thanks to those that have replied. I am always looking for more info on this boiler. So far not too much. The boiler is an on demand unit that cycles on and off. It is a natural draft into the chimney in the garage. I am thinking around 80% AFUE maybe 85%..
Old 12-12-09, 05:10 PM
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Several installers told me that it would cost substantially more for a mod/con even with the the tax rebate, which was not accurate. I think a lot of installers out there just don't understand how a mod/con and outdoor reset work, so they try to steer people away from them. With the $1500 tax credit and a $600 rebate from my gas company, the mod/con ended up being a little cheaper than a conventional boiler would have been.
Old 12-31-09, 05:18 PM
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Originally Posted by jmpowie View Post
I just had a weil mclain utra 80 installed in my house. The reason I went with the high efficiency boiler is after the 1500 from the irs and the 1000 from the gas comp the boiler cost me 500 plus the install. You can not buy a standard boiler for 500. and your going to have to pay for the install anyway, plus it will save on gas. it seemed like a win win to me.
I'm also in this situation. I am in MA and have up to $1k from the gas company as a rebate for a high-efficiency unit plus the $1500 from the feds as a tax credit. However, the costs of the install seem to be very high from the one quote I've gotten so far -- $13-$14k for install on units that cost $3-4k.

But this doesn't seem to be the thing you want to install yourself, correct?
Old 12-31-09, 06:45 PM
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Convential vs. High Efficiency boilers

I had the same decision that you did. I went with the Viessmann WB1A 95% efficient unt. There are pros and cons each way. The high efficiency models are more expensive than convential units, but the installation costs weren't that much more. Most of the companes I obtained quotes from have not installed that many high efficiency units, so I think the higher price was to cover the unknowns. Condensing boilers are far more popular in Europe than the US. For example, just go to internet heating supply company based in the UK and try to find a convential boiler.

I decided on a convential hot water heater. The high cost of the indirect heaters and the complexity of the priority circuit did not seem worth it.

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