Stronger Boiler Better?


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Old 09-17-02, 08:32 PM
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Stronger Boiler Better?

I'm about to have my boiler replaced(Oil to Gas). Am I better off getting a "Stronger" Unit? The plumber says that a stronger unit is not necessary for my size house & that I'll just end up spending more to run it. In my ignorance I would think that a stronger unit would not have to work as hard or run at or near its maximum capacity and thus not eat up as much gas. On the other hand a weaker unit that "is adequate" for my size house would have to run more often near its maximum capacity thus burning more gas. Can someone help "educate" me on this matter? Thanks.
 
  #2  
Old 09-17-02, 09:56 PM
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The thing to remember is what we learned in high school and that is, "We can neither create or destroy energy, all we can do is transform it". Let's assume that your home should have a size boiler that produces 80,000 btu's/hr., the size of the rooms, baseboards and/or radiators are sized to accomodate that much heat per hour. You decide to put in a larger unit, let's say 100,00 btu's/hr. The question is, where does the 20,000 btu's go, if the house and your system can only accomodate 80,000 btu's/hr.? The answer is, it goes back to your boiler. This is cumulative throughout the day and the season as the system meets demand for the home. This is because all boiler systems are closed systems, even steam 1-pipe systems are closed.

Though it is somewhat more complicated than this, this is what causes a oversized system to cycle frequently. It is the frequent cycling that will affect not only your energy bill, but also maintenance and your comfort in this home. Remember, the manufacturer of boilers makes the assumption that the unit is properly sized when they designed the boiler, which was based on ASHREA's calculations for heat loads.
 
  #3  
Old 09-19-02, 07:53 AM
TheZman
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Hello Bvgas,

I would agree with your plumber. You should properly size the boiler to the house taking into consideration the usual stuff like square footage, insulation values, windows, etc.

Boilers operate most efficiently when they are operated within a certain range of duty cycles. Maintenence is minimized and the lifetime of the boiler is maximized when the boiler is correctly sized for the house.

An undersized boiler is on longer than necessary and wastes fuel. The boiler is run hotter than it should be and will probably have a shorter lifetime.

An oversized boiler is cycled more frequently and mechanical parts like relays and valves are subject to more wear and tear. More moisture is retained in the flue and chimney, since the furnace does not always get hot enough to drive it out. Moisture will damage masonry over time.

Regards TheZman
 

Last edited by TheZman; 09-19-02 at 10:52 AM.
  #4  
Old 09-19-02, 08:58 AM
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Thanks for the info guys.

It was helpful.
 
 

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