Boiler replacement Help and info

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Old 02-10-08, 02:38 PM
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Boiler replacement Help and info

I am looking to have my existing natural gas fired boiler replaced, it is for hot water base board heat. The one we have now is a Dunkirk and is probably 20 years old and I am sure is not that efficient. Please bare with me I know nothing about HVAC. I am a garage door guy. A few questions,
(1)How many BTU for a two story 2 zone 1200 square foot house
(2)what manufacture do you recommend and what one's to stay away from
(3)What is a good efficiency rating, 90%?
(4) what would I expect to pay for a new one and is the installation usually included in the price? (that's how we do it with garage doors)
(5) what do you think of a Utica boiler with a cast aluminum heat exchanger
Thanks for any help you may have
 
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Old 02-10-08, 03:37 PM
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First do a heat loss. There is no way we can tell you what size you need. Bear in mind, boiler sizing has nothing to do with the amount of or type of radiation.
The more efficient the boiler the more it cost's, which are all up front costs. If condensing it will save money every time it can run under 130f. Also, buying a 90%+ efficient boiler does not mean you will get 90%. It depends on the system, near boiler piping, ratio of radiation to heat loss and type of fuel used. Remember the high efficiency means annual maintenance, more expensive parts and less boiler life. The fuel savings between condensing and non condensing with proper sizing, piping and control strategy is not that much different.
 
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Old 02-10-08, 03:52 PM
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Thanks for the reply, I get most of what you are saying, like most things, there is not cut and dry answer.
I do not under stand what you mean by "condensing and non condensing" What is that?
 
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Old 02-10-08, 04:26 PM
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You can download a good heat loss program over at:

www.slantfin.com

look for Hydronic Explorer II ... run the heat loss program to determine the size boiler you need. Don't be surprised if the program tells you that you need one half the size of your existing boiler.
 

Last edited by NJT; 02-10-08 at 04:26 PM. Reason: forgot to mention, it's free ...
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Old 02-10-08, 05:07 PM
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Old 02-10-08, 05:15 PM
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rbeck, I don't quite get why you would say this.

Remember the high efficiency means annual maintenance, more expensive parts and less boiler life.
Shouldn't all boilers be maintained at least annually? What are these expensive parts? If its the controls, they benefit non-condensing boilers just as much and are a normal part of any good quality install.


The fuel savings between condensing and non condensing with proper sizing, piping and control strategy is not that much different.
I wasn't aware of a single proper study that had been done on this confirming anything one way or the other and I've looked. A proper condensing boiler system might have flue temps in the range of 100 - 125 whereas a proper non-condensing system should have flue temps of somewhere around 300. The difference in flue temps to me means that there are a lot more BTUs going out the exhaust. Between that and the additional recovery of latent heat in the fuel I fail to see how the fuel savings wouldn't be different. What am I missing?
 
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