[RE-wrenches] Forced air Furnace

[Sindelar Solar]

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 <re-wrenches-bounces at lists.re-wrenches.org> 
>>> <mailto:re-wrenches-bounces at lists.re-wrenches.org> *On Behalf Of *Drake
>>> *Sent:* Thursday, August 23, 2018 2:37 PM
>>> *To:* RE-wrenches <re-wrenches at lists.re-wrenches.org> 
>>> <mailto:re-wrenches at lists.re-wrenches.org>
>>> *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*
allan at sindelarsolar.com <mailto:allan at sindelarsolar.com>
NABCEP Certified PV Installation Professional
New Mexico EE98J Journeyman Electrician
Founder (Retired), Positive Energy, Inc.
*505 780-2738 cell*

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