[RE-wrenches] Gen preheat in cold climates

[Larry]

About the carb heat idea...LP is a liquid at -44°F. The liquid does not 
combust, it must be vaporized. As the ambient temperature drops closer 
to the LP liquid temperature, there would be a reduction in how fast 
liquid is vaporizing and therefor a reduction in volume. What you need 
in cold weather is enough volume to maintain at least 11" wc while 
cranking or running the engine. You can test the vapor pressure with a 
manometer while cranking to verify if this is the problem.

If this is the reason the engine does not run, my thoughts are that 
heating the LP regulator would be much more economical from an energy 
standpoint, than heating the whole engine block. Perhaps an insulated 
enclosure with silicone heaters appropriately attached would work. They 
are available in many DC or AC and at various voltages.

Larry Crutcher
Starlight Solar Power Systems

On 4/2/15 10:34 PM, Allan Sindelar wrote:
> Gary,
> Mac's approach is intelligent and will work well, as an automated 
> system with the right hardware. We took a quite different approach on 
> a somewhat similar scenario in 2009.
>
> This was a Kohler 8.5REZ, with the electric carb heater and AC charter 
> for the starting battery. No block heater, but that could have been 
> handled the same way. The inverter was a Magnum MS4024PAE, but that 
> doesn't matter here. When we ran the bundle of gennie output 
> conductors, we added a separate load circuit conductor, on its own 
> breaker in the system E-Panel. Here's an excerpt from the original 
> proposal description about our approach:
>
>     The unit uses an electronic generator controller with modest
>     (estimated at 200-700 mA, depending on state of operation) draw on
>     the starting battery. This controller drops to minimal “sleep”
>     draw automatically after 48 hours of non-operation. This generator
>     does not have a starting battery charging coil, but rather uses a
>     separate AC battery trickle charger to maintain the battery. I
>     will install a 20W PV module and small charge controller on the
>     generator to keep the starting battery charged. I will also
>     install the AC charger to operate whenever the generator is
>     running. While this combined setup has worked successfully for
>     other installers with whom I have spoken, if this proves
>     insufficient I can later add a switch and relay to allow the
>     charger to also operate off of inverter AC if ever needed.
>
>     The unit also requires a built-in carburetor heater to operate
>     during cold weather. This heater is normally controlled by a
>     thermostat to conservatively come on at or below 40°F, which would
>     mean that it would operate nearly continuously during Taos’ winter
>     months, draining the PV system. My solution is to put the
>     carburetor heater on a manual mechanical one-hour time switch
>     located at the generator; you will activate the heater through
>     this switch 15-30 minutes before starting the generator.
>
> This may not work for you. This is a modern doublewide serving as a 
> seasonal family meeting place, rather than a full time residence. With 
> our usual sunny winters, we figure that if nobody is there, loads are 
> minimal, and we don't want automatic (unattended) generator operation. 
> I think we used a DG WP box inside the generator enclosure, with a 
> mechanical timer (maybe one-hour) controlling a GFCI receptacle, with 
> carb heater and battery charger plugged in.
>
> I hope that gives you some ideas you can use.
>
> *Allan Sindelar*
> allan at sindelarsolar.com <mailto:allan at sindelarsolar.com>
> NABCEP Certified PV Installation Professional
> NABCEP Certified Technical Sales Professional
> New Mexico EE98J Journeyman Electrician
> Founder (Retired), Positive Energy, Inc.
> *505 780-2738 cell*
>
> **
>
>

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