# Thread: power vent water heater and HVAC impact

1. Originally Posted by BadgerBoiler MN
I believe the question was of combustion efficiency and the confusion was over CA. I find great use for the CA nearly every day. Though thermal efficiency can't be measured in the field it pays to know you stack temperatures (one aspect of the CA test). Suffice to say, atmospheric water heaters, including power vents are not efficient. We use a lot of condensing water heaters.
Thermal efficiency would be almost impossible to measure on a water heater. But on boilers and furnaces it is easy to measure, in fact it is the only efficiency that is possible to accurately measure.

2. Originally Posted by gravity
I would stick with ol' fashion water heater.

If something were to break on the power vented one, it cost about as much as a new water heater.

keep it simple.
X2,

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3. Originally Posted by chuckcrj
Thermal efficiency would be almost impossible to measure on a water heater. But on boilers and furnaces it is easy to measure, in fact it is the only efficiency that is possible to accurately measure.
Is it easily explainable? I'm very interested in learning all aspects of this subject.

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4. Originally Posted by Joehvac25
Is it easily explainable? I'm very interested in learning all aspects of this subject.

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To get an accurate thermal efficiency on a boiler you need to have know the GPM through the boiler. Then measure delta T. BTUH = GPM x Delta T x 500. Then clock the meter.

If you clock the meter at 100,000 BTUH and measure 75,000 BTUH leaving the boiler, you know that your thermal efficiency is 75%.

On a furnace you need to measure CFM and temp rise. CFM x Temp rise x 1.08 will give you the output.

If you want a little more detail just PM me.

5. Originally Posted by chuckcrj
To get an accurate thermal efficiency on a boiler you need to have know the GPM through the boiler. Then measure delta T. BTUH = GPM x Delta T x 500. Then clock the meter.

If you clock the meter at 100,000 BTUH and measure 75,000 BTUH leaving the boiler, you know that your thermal efficiency is 75%.

On a furnace you need to measure CFM and temp rise. CFM x Temp rise x 1.08 will give you the output.

If you want a little more detail just PM me.
Thanks that's a good start, I can't PM, can't figure out how to change settings. I may have to try on a computer or something

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