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*
[email protected] <mailto:[email protected]>
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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