Generac expert needed

14 years ago

We have a 25kW Generac (Elite 5324) feeding two 200-amp automatic transfer switches. It is mounted inside a very large mechanical room (several feet of clearance on the nearest side). The room has a large (3x3) motorized intake vent and an equally large exhaust fan setup. The area of these vents is calculated at approximately twice the area required to supply adequate ventilation while the generator runs, and they are aligned with the generator to provide good constant airflow directly across the unit. The generator actually runs noticeably cooler inside this room than it did in open air. I did quite a bit of research on how generators are installed indoors before the room was designed.

Right now we use the generator on manual start so that I can flip a switch to open the vents and start the exhaust fan. I have wired these to both a switch and a relay. I had hoped to pull 12V from the generator engine as a trigger so the vents would open and the fan would run during the exercise and cooldown cycles, as well as during actual power generation (and eventually I'll also wire a discreet indicator light inside the house for when the generator is running). I do have a zener diode in there, too, to prevent an induction spike when the relay opens.

However, I can't find a good +12V source when the engine is running. The alternator fluctuates too much, pulling from the coil wire interfered with ignition, and the only other wired item was the oil pressure sensor which is a very low signal voltage. I suspect I could pull a signal from the electronics side of the generator, but I don't know enough to go poking around in there. That's where my request comes in:

Can someone advise me as to how I might accomplish tripping that relay? It doesn't have to be 12V... if I can get some other voltage, I'll just buy a different relay (although I'd prefer 12V since I've already spent $30 on this one, and it's already wired up).

Again, I want a trigger ANY time the engine runs, not just when it generates power (otherwise I look for a way to run 110 on the house side of the transfer panel).

Generac refuses to discuss it since this is not within their installation guidelines, and I can't blame them, even though it's frustrating. Incidentally, the genset is out of warranty, so that isn't a concern.

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Comments (9)

christophersprks
14 years ago
Looks like you have a expensive set-up. You really should call an expert in your area.
bus_driver
14 years ago
Ignition? So this is not a Diesel?
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wayne440
14 years ago
Try asking your question here.
http://zillerelectric.com/forums/index.php

Here is a link that might be useful: Generac BBS
wayne440
14 years ago
Or just put an airvane microswitch in the blast from the radiator fan. The set starts up, fan blows, vents open.
mcguirev10
Original Author
14 years ago
Christophersprks, the Generac experts in my area won't touch it because Generac doesn't like it: the only way I can reach them is through the electrical contracting company they work for, and by then it's "official" and too late.

To clarify, the rest of the system is set up and working. If I put 12V across the trigger side of the relay (for example, wire it directly to the battery), the vent opens, the fan runs, etc. ... The 120V side of the relay actually powers two outlets, and the vent and fan is plugged into those. It's just this last connection to the 12V trigger source that I need.

From the Generac schematics (which are a little confusing since they cover multiple models) I suspect I could pull this trigger from the voltage regulator, and it looks like it might even have a run indicator inside, but I'm only comfortable messing around on the engine side of things.

bus_driver, it is an LP fueled generator.

wayne, I'll check out those links, thanks. I've never heard of an airvane switch, that's a cool idea, I'll look into it.
mcguirev10
Original Author
14 years ago
Wayne, that link did the trick! Thanks!

Somebody else wanted to wire a 12V hour-meter:

"Find the two wires that go to the fuel solenoid on top of the fuel regulator (behind battery) you'll find wire #14 & #0 here also....#14 has +12V when the unit is running. This is consistent across the entire Generac / Guardian product line."
fix_it
14 years ago
Why not just tee in another oil pressure switch. A normally open switch commonly used on automobiles would work. Then you could feed 12 volts to one side of the switch and the relay to the other.

For the pressure switch, try a 1987 Chevy S-10 with a 4 cyl. This switch actualy is two switches in one. There are three terminals. The middle one is NC and grounded to the body of the switch when the engine is off. The two outside terminals are NO and care connected together when the engine is on.
wirenut1110
14 years ago
If tapping in to the inlet fuel solenoid doesn't work for you, you should have a terminal strip with wire # 15 or 15A. One of these , I think it's 15A and 0 will give you 12 volts when running.
wirenut1110
14 years ago
If I may add, the oil pressure switch only makes or breaks ground.