Consumer Homes.

Question:

This may fall more under an efficiency group however, I’m on the tail end of installing my solar hotwater heating system and am having brain storms  f#rts).  Does anyone have any experience pro or con with running hot water from gas hot water heater through coil in solar storage tank as an added heat source when shower, washer or dishes are being done?  How about wrapping gas hot water heater exhaust pipe with copper tubing and running water from storage tank through the copper when gas is heating household water?  I figure since most of the hot water the family uses goes down the drain anyway why not try to be more effective with its use? I use hot air from the gas exhaust now to help warm fooor space, why not let it help heat more water? Ray

Response:

A lot of people have wanted to extract the last drop of heat from their gas water heater or furnace. However there is a problem with it. The water heater or furnace uses the heat to draw the exhaust fumes up the chimney. Without this heat the fumes would stay in the house and poison the air you breath. You will notice there is a space between the water heater or furnace and the chimney pipe, this is to prevent the chimney from drawing too much creating a suction pulling too much heat from the appliance, allowing room air to be drawn if the chimney sucks too much. In other words, the appliance is engineered to allow only enough heat to go up the chimney that is needed and no more. Your device would upset this balance, possibly causing carbon monoxide to enter the house —– you don’t want that. – Hide quoted text — Show quoted text – >This may fall more under an efficiency group however, I’m on the tail end of >installing my solar hotwater heating system and am having brain storms > f#rts). > Does anyone have any experience pro or con with running hot water from gas >hot water heater through coil in solar storage tank as an added heat source >when shower, washer or dishes are being done? > How about wrapping gas hot water heater exhaust pipe with copper tubing and >running water from storage tank through the copper when gas is heating >household water? > I figure since most of the hot water the family uses goes down the drain >anyway why not try to be more effective with its use? I use hot air from the >gas exhaust now to help warm fooor space, why not let it help heat more >water? >Ray

Response:

 Hi Eric,  Your point is very well taken and when I first installed the duct around the exhaust flu I kept a very close eye on exhaust heat and leakage. I have also installed a couple of detecters.  I’m not actually cooling the flu pipe or the exhaust. I’m letting the hot exhaust heat the air in the chamber created by the duct wrapped around it. I detect the temperature of the duct and replace the hot air in the chamber with room temerature air that would be there anyway. The far end of the exhaust pipe gets just as hot as it ever did.  The water pipe will use the same principle. 4 runs of 1/2" copper tubing inserted into the chamber created by the ducting. A thermister on the exit end of the pipe will turn on a pump according to the setting through an opamp circuit. The cooler water going into the chamber will be room temerature also as the storage tank sits right next to the gas water heater.  Your concern is very well taken. I will be keeping a very close eye on the water idea also. Any sign of trouble of exhaust cooling  or an alarm sounding and the unit will be yanked and the idea scrapped.  I had a bad experience with exhaust fumes a couple of years ago. I had installed an attic fan. On a fall day my eight year old had opened a window and turned on the fan. A couple of hours later my 16yr old simply closed the window. Guess where the air came in from. I wired a light to the fan circuit that can’t be missed. So far no more trouble.  Thanks again Ray

– Hide quoted text — Show quoted text -> A lot of people have wanted to extract the last drop of heat from their gas > water heater or furnace. However there is a problem with it. The water > heater or furnace uses the heat to draw the exhaust fumes up the chimney. > Without this heat the fumes would stay in the house and poison the air you > breath. > You will notice there is a space between the water heater or furnace and the > chimney pipe, this is to prevent the chimney from drawing too much creating > a suction pulling too much heat from the appliance, allowing room air to be > drawn if the chimney sucks too much. In other words, the appliance is > engineered to allow only enough heat to go up the chimney that is needed and > no more. Your device would upset this balance, possibly causing carbon > monoxide to enter the house —– you don’t want that. >This may fall more under an efficiency group however, I’m on the tail end > of >installing my solar hotwater heating system and am having brain storms > f#rts). > Does anyone have any experience pro or con with running hot water from gas >hot water heater through coil in solar storage tank as an added heat source >when shower, washer or dishes are being done? > How about wrapping gas hot water heater exhaust pipe with copper tubing > and >running water from storage tank through the copper when gas is heating >household water? > I figure since most of the hot water the family uses goes down the drain >anyway why not try to be more effective with its use? I use hot air from > the >gas exhaust now to help warm fooor space, why not let it help heat more >water? >Ray

Response:

> A lot of people have wanted to extract the last drop of heat from their gas > water heater or furnace. However there is a problem with it. The water > heater or furnace uses the heat to draw the exhaust fumes up the chimney. > Without this heat the fumes would stay in the house and poison the air you > breath.

Some condensing boilers are so efficient at extracting the heat from combustion products they only require plastic drain pipe for the flue – the Keston.  Another efficient boiler is the Sogno no-flame that also uses plastic flue pipe.  It burns gas at a temp lower than what supports a flame, making it 95% efficient at all heat loads of the boiler.

Response:

 I’ve installed several 95 – 98% efficient furnaces and they all force the cool gas out PVC. I’ve not detracted from the exhaust temerature yet anyway. I’m trapping the air that the exhaust flu heats. I can install a cyclone flu cap or a fan for the exhaust if necessary. Ray

– Hide quoted text — Show quoted text -> A lot of people have wanted to extract the last drop of heat from their > gas > water heater or furnace. However there is a problem with it. The water > heater or furnace uses the heat to draw the exhaust fumes up the chimney. > Without this heat the fumes would stay in the house and poison the air you > breath. > Some condensing boilers are so efficient at extracting the heat from > combustion products they only require plastic drain pipe for the flue – the > Keston.  Another efficient boiler is the Sogno no-flame that also uses > plastic flue pipe.  It burns gas at a temp lower than what supports a flame, > making it 95% efficient at all heat loads of the boiler.

Response:

another point…if it does work and you keep it running watch out…heat, moisturefumes,gavanized metal and copper all in one place will eventually lead to a lot of corrosion…any where two dissimilar metals touch is a place where they may eat thru eachother…even if the pipe is steel and you use silver solder you may have long term problems   it may take years but all that means is that your co2 detector has had a longer time to run it’s battery dry.

– Hide quoted text — Show quoted text -> Hi Eric, >  Your point is very well taken and when I first installed the duct around > the exhaust flu I kept a very close eye on exhaust heat and leakage. I have > also installed a couple of detecters. >  I’m not actually cooling the flu pipe or the exhaust. I’m letting the hot > exhaust heat the air in the chamber created by the duct wrapped around it. I > detect the temperature of the duct and replace the hot air in the chamber > with room temerature air that would be there anyway. The far end of the > exhaust pipe gets just as hot as it ever did. >  The water pipe will use the same principle. 4 runs of 1/2" copper tubing > inserted into the chamber created by the ducting. A thermister on the exit > end of the pipe will turn on a pump according to the setting through an > opamp circuit. The cooler water going into the chamber will be room > temerature also as the storage tank sits right next to the gas water heater. >  Your concern is very well taken. I will be keeping a very close eye on the > water idea also. Any sign of trouble of exhaust cooling  or an alarm > sounding and the unit will be yanked and the idea scrapped. >  I had a bad experience with exhaust fumes a couple of years ago. I had > installed an attic fan. On a fall day my eight year old had opened a window > and turned on the fan. A couple of hours later my 16yr old simply closed the > window. Guess where the air came in from. I wired a light to the fan circuit > that can’t be missed. So far no more trouble. >  Thanks again > Ray > A lot of people have wanted to extract the last drop of heat from their > gas > water heater or furnace. However there is a problem with it. The water > heater or furnace uses the heat to draw the exhaust fumes up the chimney. > Without this heat the fumes would stay in the house and poison the air you > breath. > You will notice there is a space between the water heater or furnace and > the > chimney pipe, this is to prevent the chimney from drawing too much > creating > a suction pulling too much heat from the appliance, allowing room air to > be > drawn if the chimney sucks too much. In other words, the appliance is > engineered to allow only enough heat to go up the chimney that is needed > and > no more. Your device would upset this balance, possibly causing carbon > monoxide to enter the house —– you don’t want that. > >This may fall more under an efficiency group however, I’m on the tail end > of > >installing my solar hotwater heating system and am having brain storms > > f#rts). > > Does anyone have any experience pro or con with running hot water from > gas > >hot water heater through coil in solar storage tank as an added heat > source > >when shower, washer or dishes are being done? > > How about wrapping gas hot water heater exhaust pipe with copper tubing > and > >running water from storage tank through the copper when gas is heating > >household water? > > I figure since most of the hot water the family uses goes down the drain > >anyway why not try to be more effective with its use? I use hot air from > the > >gas exhaust now to help warm fooor space, why not let it help heat more > >water? > >Ray

Response: