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Efficiency of over-sized boiler

Posted by ooopie (My Page) on
Fri, Oct 12, 12 at 11:41

I'm starting to question the efficiency of my heating system...

For my decently insulated 1500 sq/ft home in CT, currently I have a 175,000 btu boiler that does both heat and hot water.

I'm wondering if I can gain significant efficiency by:

1. getting a new boiler that is sized smaller


2. getting a separate hot water cylinder

Contractors have had conflicting opinions, and are of course trying to sell me something. What do you all think?

Follow-Up Postings:

RE: Efficiency of over-sized boiler

What type of fuel does the boiler use? How old is this boiler?

RE: Efficiency of over-sized boiler

The current boiler is only around 5 years old. Burns oil.

I'm already looking to convert it to a gas burner, but now I'm wondering if it makes more sense to replace the whole unit...

On one hand it seems wasteful to replace a newish boiler, but I'm wondering if it would make sense if I could gain some efficiency with a new heat/hot water system.


RE: Efficiency of over-sized boiler

You could convert it to gas, but you would be giving up efficiency. There are not a lot of contractors who specialize in conversions. I am not sure this is a good strategy.

Switching to gas will save a lot of money and you can also size the boiler properly. The pay back period at current prices could be in 5-7 years, maybe less.

RE: Efficiency of over-sized boiler

I wouldn't necessarily go to a smaller boiler. I believe you can gain efficiency by replacing even your 5-year old oil boiler with an 'Energy Star' 90+% efficient combination modulating condensing gas boiler/instantaneous domestic hot water heater with outdoor reset control.

Some questions first.

What is the efficiency of your oil boiler?
How much oil do you consume annually?
How much does an average gallon of oil cost?
Is natural gas available, if so at what cost?
What will it cost to install a gas line if gas is available?
What incentives are available for conversion?
What type of rads do you have?
What is the water temperature required for these rads?
How are the rads connected, series or parallel?
Is your system zoned?
Do you have hot and cold spots in your home, if so where in relation to your boiler?

I'll guess that based on your square footage that it's not zoned. Modern hydronic heating systems are not your parents' heating system. A LOT can be done to increase efficiency and comfort. It will cost money to save money and you need someone that KNOWS what they're doing beyond just swapping one boiler for another!


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