Over the years I have supplied systems to new owners of modular or
mobile homes, each of which comes with a forced air furnace unless
special ordered without one. I would caution the homeowner against using
the furnace as a primary heat source for the reasons already given.
However, keeping the installed furnace operational only as a
fast-responding means of bringing the temperature up until the woodstove
kicks in was a popular approach, as long as it's not a substantial
phantom load. I had one client who left the breaker off, but who could
fire it up occasionally when needed. All of this is from years back when
modules were $$$/watt, systems were smaller and efficiency was king. The
principles still apply.
Allan
On 8/24/2018 2:51 PM, Drake wrote:
A wood stove heats the house, and will be the primary source of heat.
An un-vented propane wall heater is installed and can heat the small,
earth bermed, well insulated structure. A furnace will be a nice
supplement, and will quickly pay for itself in insurance savings.
During even a moderately cloudy day, it will be fine, but will not be
used much on batteries. Still, I'd like as efficient a model as possible.
If I can find a unit with a 400 W draw, like the one in our on grid
house, that would be adequate. The specifications I've found on the
blower motors are sketchy. I will likely need to order it on line (or
take a trip to a neighboring city), so reading the nameplates might
not be so easy.
Does anyone know how to get accurate data on furnace blower motors?
Thanks,
Drake
I always try to talk the client into hydronic heating with ECM drive
circulation pumps. They do make ECM drive blower motors that can be
retrofitted in some furnace systems. Overall, its just a bad
combination off grid: the worse the weather is the less PV production
you have, and this corresponds to the same time that the furnace is
operating 12 hours/ night. They are either running the generator a
bunch, or waking up in the morning to a cold house with the power
off, and dead batteries. If its an AC coupled system, they won't
even have any PV production the next morning either. This is another
reason AC coupled is not a great idea, or at least you need to always
have some DC coupled PV as well, but I digress......
Ray Walters
Remote Solar
303 505-8760
On 8/23/18 5:43 PM, Dana wrote:
Drake,
All the conventional units I have amp clamped over the years are
pushing 900-900+ watts per hour. I do not recommend them ever & to
date I have never found a lower wattage blower. I would assume that
a permanent magnet motor would fit this suggestion, but I have not
found one.
For off grid I recommend: Radiant floor heat first and hot water
base board second long before hot air. Air is a better insulator
than a heat transfer agent.
The new ECM (electronically commutated motors) pump motors are
basically at DC permanent magnet motor power draws [Taco &
Grundfoss] these days.
Best of luck with this one.
Dana
*From:* RE-wrenches <[email protected]>
<mailto:[email protected]> *On Behalf Of *Drake
*Sent:* Thursday, August 23, 2018 2:37 PM
*To:* RE-wrenches <[email protected]>
<mailto:[email protected]>
*Subject:* [RE-wrenches] Forced air Furnace Hello Wrenches,
What is the best choice for a propane, forced air furnace for an
off grid house? We would prefer one that doesn't have a phantom
load, although the transformer for the thermostat may not be
avoidable. Low blower current would be preferable. The furnace
AC will be powered by a Magnum 4448 PAE.
Thank you,
Drake
--
*Allan Sindelar*
[email protected] <mailto:[email protected]>
NABCEP Certified PV Installation Professional
New Mexico EE98J Journeyman Electrician
Founder (Retired), Positive Energy, Inc.
*505 780-2738 cell*
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