Re: [RE-wrenches] Gen preheat in cold climates

[Allan Sindelar]

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 al...@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   On 4/2/2015 9:10 PM, Mac Lewis wrote: Hi Gary, We have implemented a preheat strategy that has really worked well at a site using dual sunny islands.  They have a load shed function built in with the control relays.  We are using that function to add the block heater load.  When a generator start is likely (~50% SOC) it triggers a relay that energized the block heater.  The generator start is then programmed at a lower SOC (~30% SOC).  It takes some guesswork to know how many watt hours its going to take to get the block heated up, but we conservatively chose and have fiddled with it.  I imagine this can be done with either the Radian or the XW, and you could trigger with voltage instead of SOC, but SOC is a superior way to do it. Another way is to use a propane block heater.  This will work well, but they use quite a bit of propane, and are very expensive (~$1500). Good luck On Thu, Apr 2, 2015 at 8:47 PM, Gary Higbee <g...@windstreamsolar.com> wrote: Wrenches, I'm curious what strategies you use to preheat a propane gen in cold climates. This is a large off-grid design in a sub-zero winter climate and ideal would be to turn on a block heater an hour or two in advance, then run the gen cycle. We plan to use either a Schneider XW or Outback Radian configuration (still very interested in which you'd use and why). We could set up a logic/relay system to first send the gen request to the heater for a while and then turn off and initiate a gen cycle but that would eliminate the ability for autostart on short notice. I've read of heat lamps on a thermostat, just wondering if you have seen other solutions. Thanks! Gary

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