Gas and Oil Home Heating Furnaces - Furnace Replacement
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ttonnis
10-28-09, 07:20 PM
Hello,
I was hoping I could get comments from the members of this forum. We are beginning the process of getting quotes to replace a 17 yr old propane fule furnace, that's beginning to show signs of age. Being in the Northeast we are trying to be proactive instead of reactive on a 0 degree winter day. Here are a few questions I hope I can get comments on.
1. Any comments or thoughts about replacing with York equipment? I didn't recognize this as one of the common names such as Lennox, Trane etc. But would be interested in any comments whether good or bad. We are also considering Trane and Lennox but there appears to be a premium for their products.
2. We currently have a standard 80% furnace. That uses B vent for both my propane 40,000 BTU water heater and furnace. This then exhausts to the roof. We are considering a 95% efficient furnace replacement. Here is the concern with that change. We are getting different opinions if having only the water heater exahust through this vent will create CO problems. The feedback we are getting from contractors is there may not be enough draft to properly exhaust the water heater if we remove the furnace. One has gone as far as saying flat out they will not do this. If we make the change on the furnace we would need to covert the water heater to power vent or tankless. With the water heater being only 2 yrs old it's a tough expense to justify. I also don't know if our building inspector would even allow this based on code.
We really would like the benefits and cost savings of a high efficiency furnace. But I don't know if we are creating possible problems with our "standard vent" water heater.
Any thoughts or comments would be most appreciated.
Thank you
I was hoping I could get comments from the members of this forum. We are beginning the process of getting quotes to replace a 17 yr old propane fule furnace, that's beginning to show signs of age. Being in the Northeast we are trying to be proactive instead of reactive on a 0 degree winter day. Here are a few questions I hope I can get comments on.
1. Any comments or thoughts about replacing with York equipment? I didn't recognize this as one of the common names such as Lennox, Trane etc. But would be interested in any comments whether good or bad. We are also considering Trane and Lennox but there appears to be a premium for their products.
2. We currently have a standard 80% furnace. That uses B vent for both my propane 40,000 BTU water heater and furnace. This then exhausts to the roof. We are considering a 95% efficient furnace replacement. Here is the concern with that change. We are getting different opinions if having only the water heater exahust through this vent will create CO problems. The feedback we are getting from contractors is there may not be enough draft to properly exhaust the water heater if we remove the furnace. One has gone as far as saying flat out they will not do this. If we make the change on the furnace we would need to covert the water heater to power vent or tankless. With the water heater being only 2 yrs old it's a tough expense to justify. I also don't know if our building inspector would even allow this based on code.
We really would like the benefits and cost savings of a high efficiency furnace. But I don't know if we are creating possible problems with our "standard vent" water heater.
Any thoughts or comments would be most appreciated.
Thank you
SeattlePioneer
10-28-09, 08:47 PM
<<Here is the concern with that change. We are getting different opinions if having only the water heater exahust through this vent will create CO problems. The feedback we are getting from contractors is there may not be enough draft to properly exhaust the water heater if we remove the furnace. One has gone as far as saying flat out they will not do this. If we make the change on the furnace we would need to covert the water heater to power vent or tankless. With the water heater being only 2 yrs old it's a tough expense to justify. I also don't know if our building inspector would even allow this based on code.>>
There are two issues---- if the vent is too large for the equipment using it, it may not reliably create a "stack effect" to carry the combustion gasses out of the house, and second, if combustion gasses cool off too much in a big vent, the water vapor produced by burning the gas can condense ab run down onto the water heater and doing various kinds of moisture damage. So problems with water from the combustion gasses of the water heater condensing in an oversized vent could be real.
There is a lot of water vapor produced when propane burns --- that's why a condensing furnace can save you money.
However, the water heater is not designed for condensing the water vapor it produces. Those combustion gasses need to remain hot in order to create a draft to carry them up the vent and prevent them from cooling off and condensing in the vent pipe.
I'm presuming you have a metal chimney pipe rather than a masonry chimney. What is the diameter of the vent pipe? I'm guessing 6" diameter --- that would be pretty heavily oversized for just the water heater. Offhand, I'd suppose 4" vent pipe would be OK, although still oversized.
Most 50 gallon style water heaters can be vented with 3" vent pipe. You might ask if 3" "B" or "C" vent can be inserted up through the existing metal vent pipe ---- that might be quite possible if it' 6" vent. Alternatively, it might be possible to run new 3" vent pipe up through the roof.
I don't know of any code that would prevent inserting vent pipe into a larger vent pipe, but there might be one.
Seattle Pioneer
There are two issues---- if the vent is too large for the equipment using it, it may not reliably create a "stack effect" to carry the combustion gasses out of the house, and second, if combustion gasses cool off too much in a big vent, the water vapor produced by burning the gas can condense ab run down onto the water heater and doing various kinds of moisture damage. So problems with water from the combustion gasses of the water heater condensing in an oversized vent could be real.
There is a lot of water vapor produced when propane burns --- that's why a condensing furnace can save you money.
However, the water heater is not designed for condensing the water vapor it produces. Those combustion gasses need to remain hot in order to create a draft to carry them up the vent and prevent them from cooling off and condensing in the vent pipe.
I'm presuming you have a metal chimney pipe rather than a masonry chimney. What is the diameter of the vent pipe? I'm guessing 6" diameter --- that would be pretty heavily oversized for just the water heater. Offhand, I'd suppose 4" vent pipe would be OK, although still oversized.
Most 50 gallon style water heaters can be vented with 3" vent pipe. You might ask if 3" "B" or "C" vent can be inserted up through the existing metal vent pipe ---- that might be quite possible if it' 6" vent. Alternatively, it might be possible to run new 3" vent pipe up through the roof.
I don't know of any code that would prevent inserting vent pipe into a larger vent pipe, but there might be one.
Seattle Pioneer