Question:

Actually, this is close to how our furnace works.  We have a Wiessmann millivolt gas furnace, with a 83% AFUE rating.  It uses a pilot light system combined with a very sensitive connection to a millivolt digital thermostat.  As such, there is no connection to Hydro-Quebec except for our pumps which push the hot water throughout the house. In case of power failures, we simply bypass the pumps using a shunt, while our thermostat flips over to batteries.  Naturally such a system is less efficient during a loss of power, but at least we have heat when all else has failed. We were planning to do this anyway, but the ice storm of 1998 forced our hand. I can’t think of any modern heating system, other than a wood stove or something, that is capable of operating with no electricity however. — Robert Hancock      Saskatoon, SK, Canada Home Page: http://members.home.net/hancockr

– Tim Lapin     Desktop Consultant     Concordia University TEL:    (514) 848-7639         FAX:    (514) 848-7622 web:          http://alcor.concordia.ca/~timl

Response:

I am about to move from oil to natural gas (central heating with hot water). I am looking for a 85000 BTU furnace able to run without electricity. My neighbor had one recently installed but is not happy with the way the exterior air intake was fixed. When speaking with the utility gas tech he told me that not all the furnaces need an fresh air intake from the outside and that the very high efficient furnaces also don’t need a liner in the chimney, pvc pipe is enough. Does anybody have any suggestion on brand and/or model? (no intake from the outside, pvc pipe for exhaust) Other question about hot water: I also was told that some furnaces are able to produce domestic hot water through a separate circuit inside the body of the boiler. What are the advantages/drawbacks of such a system. Plumbers seem to prefer install a gas furnace AND a gas water heater instead of the combo stuff. I guess they get more money by installing 2 systems but is it the only reason? Thanks for any tip. Pierre

Response:

If you want to vent with a PVC pipe then it will have to be a 90% or higher efficiency model, and I believe all of those use an air intake from outside. An 80% class midefficiency model will vent through the regular chimney, but a liner will probably be required if it’s a real masonry chimney (not a metal B-vent). Typically 80% models don’t use outside combustion air. I can’t think of any modern heating system, other than a wood stove or something, that is capable of operating with no electricity however. — Robert Hancock      Saskatoon, SK, Canada Home Page: http://members.home.net/hancockr

– Hide quoted text — Show quoted text – I am about to move from oil to natural gas (central heating with hot water). I am looking for a 85000 BTU furnace able to run without electricity. My neighbor had one recently installed but is not happy with the way the exterior air intake was fixed. When speaking with the utility gas tech he told me that not all the furnaces need an fresh air intake from the outside and that the very high efficient furnaces also don’t need a liner in the chimney, pvc pipe is enough. Does anybody have any suggestion on brand and/or model? (no intake from the outside, pvc pipe for exhaust) Other question about hot water: I also was told that some furnaces are able to produce domestic hot water through a separate circuit inside the body of the boiler. What are the advantages/drawbacks of such a system. Plumbers seem to prefer install a gas furnace AND a gas water heater instead of the combo stuff. I guess they get more money by installing 2 systems but is it the only reason? Thanks for any tip. Pierre

Response:

External air — not necessarily. I have a 92% furnace from Goodman that doesn’t require an external air intake although they sell a model that looks virtually identical that does use one. PVC does work nicely for the venting on this one and it gets barely warm to the touch in operation. It does condense out a LOT of water during operation though. One thing for sure, all of these super-efficient furnaces need something to force the draft and since they aren’t using a big temperature differential they can’t be using waste heat to manage it  – that means that some sort of a blower is required. — John McGaw Knoxville, Tennessee, USA —– —– This is not your average boring web site! This is MY average boring web site: http://www.public.usit.net/jmcgaw – Hide quoted text — Show quoted text – If you want to vent with a PVC pipe then it will have to be a 90% or higher efficiency model, and I believe all of those use an air intake from outside. An 80% class midefficiency model will vent through the regular chimney, but a liner will probably be required if it’s a real masonry chimney (not a metal B-vent). Typically 80% models don’t use outside combustion air. I can’t think of any modern heating system, other than a wood stove or something, that is capable of operating with no electricity however. — Robert Hancock      Saskatoon, SK, Canada Home Page: http://members.home.net/hancockr I am about to move from oil to natural gas (central heating with hot water). I am looking for a 85000 BTU furnace able to run without electricity. My neighbor had one recently installed but is not happy with the way the exterior air intake was fixed. When speaking with the utility gas tech he told me that not all the furnaces need an fresh air intake from the outside and that the very high efficient furnaces also don’t need a liner in the chimney, pvc pipe is enough. Does anybody have any suggestion on brand and/or model? (no intake from the outside, pvc pipe for exhaust) Other question about hot water: I also was told that some furnaces are able to produce domestic hot water through a separate circuit inside the body of the boiler. What are the advantages/drawbacks of such a system. Plumbers seem to prefer install a gas furnace AND a gas water heater instead of the combo stuff. I guess they get more money by installing 2 systems but is it the only reason? Thanks for any tip. Pierre

Response: