Question
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Sep 16, 2005, 04:16 PM
| | New Member  | | Join Date: Sep 2005
Posts: 4
| | | Preheat Hot Water?
Here is my situation.
I am about to install a new electric hot water heater and am wondering if it would make sense for me to feed the new heater from our oil furnaces hot water jacket output, or simply hook it up to the cold water street feed.
We typicaly run our oil furnace about 6 months a year so we need the electric heater but with the drop in the temperature of our water feed in the winter it seems like it might make sense (financilay) to at least raise the input temp into the heater by running it through the furnace first.
Does this make sense or would I just be running a lot of unnecesary pipes?
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Answers
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Sep 16, 2005, 07:42 PM
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#2
| | Full Member
Join Date: Mar 2005
Posts: 427
| Quote: |
Originally Posted by nomad943 Here is my situation.
I am about to install a new electric hot water heater and am wondering if it would make sense for me to feed the new heater from our oil furnaces hot water jacket output, or simply hook it up to the cold water street feed.
We typicaly run our oil furnace about 6 months a year so we need the electric heater but with the drop in the temperature of our water feed in the winter it seems like it might make sense (financilay) to at least raise the input temp into the heater by running it through the furnace first.
Does this make sense or would I just be running a lot of unnecesary pipes? | i dont how much oil/electric/ gas cost in your area......... but here are some information...... 1kw will raise 10gal of water 41F..... 1 gal of #2 oil will raise 100gal of water 120F.... 1 ft3(therm) gas will raise 100gal of water 96F........ |
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Sep 17, 2005, 07:12 AM
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#3
| | | Senior Plumbing Expert
Join Date: Jan 2003 Location: Sarasota, Fl.
Posts: 19,004
Pay to call speedball1 for advice ($.95/min) | Quote: |
Originally Posted by nomad943 Here is my situation.
I am about to install a new electric hot water heater and am wondering if it would make sense for me to feed the new heater from our oil furnaces hot water jacket output, or simply hook it up to the cold water street feed.
We typicaly run our oil furnace about 6 months a year so we need the electric heater but with the drop in the temperature of our water feed in the winter it seems like it might make sense (financilay) to at least raise the input temp into the heater by running it through the furnace first.
Does this make sense or would I just be running a lot of unnecesary pipes? | Hey Nimad,
Sure makes sense to me. You'll not only save the cost of the energy needed to heat the water but will also save on wear and tear on the elements in the heater. A win-win situation all the way around.
1kw will raise 10gal of water 41F..... 1 gal of #2 oil will raise 100gal of water 120F.... 1 ft3(therm) gas will raise 100gal of water 96F........
Great breakdown on energy cost cuibuadday. Tom | |
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Sep 17, 2005, 07:40 AM
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#4
| | New Member
Join Date: Sep 2005
Posts: 4
| From my perception of how the system will work, the furnace would be running anyhow and if I dont use that energy to preheat the water it will just get sent on up the chimney. Lots of good BTUs there, but I am uncertain if it will increase the load on the furnace causing it to run more frequently. Here our electric rates have been fairly stable but oil price has doubled.
I am also looking into using the exhaust stack gasses to heat the cellar by sending through a type of pass through unit I have seen around. | |
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Sep 17, 2005, 08:01 AM
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#5
| | | Senior Plumbing Expert
Join Date: Jan 2003 Location: Sarasota, Fl.
Posts: 19,004
Pay to call speedball1 for advice ($.95/min) | Quote: |
Originally Posted by nomad943 From my perception of how the system will work, the furnace would be running anyhow and if I dont use that energy to preheat the water it will just get sent on up the chimney. Lots of good BTUs there, but I am uncertain if it will increase the load on the furnace causing it to run more frequently. Here our electric rates have been fairly stable but oil price has doubled.
I am also looking into using the exhaust stack gasses to heat the cellar by sending through a type of pass through unit I have seen around. |
Back in the 40's when I was learning the trade up in Wisconsin all of our coal and oil burning had a "furnace coil" installed to augment heating the water.
This will put no additional strain on your furnace if that's your concern.
Great idea to boost the basement heat using the heat that would normally go up the chimney. Regards, tom | |
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Sep 17, 2005, 03:49 PM
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#6
| | Über Member
Join Date: Feb 2003 Location: Northern US
Posts: 10,646
| I hope you are not planing on mixing your hot water service with the water recirculated in the furnace. Also, if the furnace is relatively new, You may not recover much heat from the stack gas, but could cause a condensation problem in the vent. Look very carefully at everything. | |
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Sep 17, 2005, 04:56 PM
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#7
| | | Senior Plumbing Expert
Join Date: Jan 2003 Location: Sarasota, Fl.
Posts: 19,004
Pay to call speedball1 for advice ($.95/min) | Quote: |
Originally Posted by labman I hope you are not planing on mixing your hot water service with the water recirculated in the furnace. Also, if the furnace is relatively new, You may not recover much heat from the stack gas, but could cause a condensation problem in the vent. Look very carefully at everything. |
Labman,
This is a black iron or copper coil that inserts itself in the furnace pot
and connects back to the water heater. It heats the water by passive convection. You're referring to a hot water heating system and I don't think Nomad ment to mix his bath water in with the water in a radiator. You didn't did you Nomad?? | |
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Sep 17, 2005, 06:07 PM
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#8
| | New Member
Join Date: Sep 2005
Posts: 4
| Our furnace has an entirely separate coil for domestic hot water which isnt connected to the hot water heating system that is plumbed through the main jacket. The two water systems are entirely seperate.
As for the exhaust gas idea, let me explain. As our furnace is now, the exhaust vents into a pipe which then rises several feet and attaches into the chimney. I have seen devices , about a one foot cube, which are constructed of a type of iron, which has numerous tubes through which air is forced by a fan. The passing exhaust gas comes in contact with these tubes, heating them and the forced air which is being blown through.
You just cut the current exhaust pipe about halfway up to where it connects to the chimney and attach this device, connecting the top back up to the chimney. The exhaust gas passes straight through the device, roughly the same path it originaly had. I dont see how condensation can become a problem.
Any thoughts? | |
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Sep 18, 2005, 06:28 AM
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#9
| | Senior Plumbing Expert
Join Date: Jan 2003 Location: Sarasota, Fl.
Posts: 19,004
Pay to call speedball1 for advice ($.95/min) | Quote: |
Originally Posted by nomad943 Our furnace has an entirely separate coil for domestic hot water which isnt connected to the hot water heating system that is plumbed through the main jacket. The two water systems are entirely seperate.
As for the exhaust gas idea, let me explain. As our furnace is now, the exhaust vents into a pipe which then rises several feet and attaches into the chimney. I have seen devices , about a one foot cube, which are constructed of a type of iron, which has numerous tubes through which air is forced by a fan. The passing exhaust gas comes in contact with these tubes, heating them and the forced air which is being blown through.
You just cut the current exhaust pipe about halfway up to where it connects to the chimney and attach this device, connecting the top back up to the chimney. The exhaust gas passes straight through the device, roughly the same path it originaly had. I dont see how condensation can become a problem.
Any thoughts? | Hey Nomad,
The tubes act as baffles trapping the heat and radiating it as the fan picks it up up and blows it out in the basement. Right? If you had no condensation problem before I fail to see how adding this "heat exchanger" would cause one. | |
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Sep 18, 2005, 08:08 AM
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#10
| | New Member
Join Date: Sep 2005
Posts: 4
| I have only seen these things used in a few homes and they really are remarkable in their simplicity ... Like sometimes the most obvious ideas are the ones that get overlooked. The only drawback I know of is the tiny amount of electricity it takes to drive the fan and in return you get a heated basement instead of a heated backyard  | |
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