Generac expert needed

mcguirev10December 26, 2009

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.

Thank you for reporting this comment. Undo

Looks like you have a expensive set-up. You really should call an expert in your area.

    Bookmark   December 26, 2009 at 5:55PM
Thank you for reporting this comment. Undo

Ignition? So this is not a Diesel?

    Bookmark   December 26, 2009 at 5:57PM
Thank you for reporting this comment. Undo

Try asking your question here.

Here is a link that might be useful: Generac BBS

    Bookmark   December 26, 2009 at 6:40PM
Thank you for reporting this comment. Undo

Or just put an airvane microswitch in the blast from the radiator fan. The set starts up, fan blows, vents open.

    Bookmark   December 26, 2009 at 6:43PM
Thank you for reporting this comment. Undo

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.

    Bookmark   December 27, 2009 at 11:48AM
Thank you for reporting this comment. Undo

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."

    Bookmark   December 27, 2009 at 12:01PM
Thank you for reporting this comment. Undo

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.

    Bookmark   January 1, 2010 at 3:10AM
Thank you for reporting this comment. Undo

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.

    Bookmark   January 3, 2010 at 8:15AM
Thank you for reporting this comment. Undo

If I may add, the oil pressure switch only makes or breaks ground.

    Bookmark   January 3, 2010 at 9:36AM
Sign Up to comment
More Discussions
Reuse electrical panel
I replaced a 24 circuit Square D panel with a new 40...
Replacing fan speed dial back to standard toggle?
I am removing a ceiling fan and replacing it with a...
Spa Capacitor question
My spa is wired for 220v. The pump motor is rated for...
Does a refrigerator need to be on a separate circuit?
Does a refrigerator need to be on a separate circuit?...
Replacing dimmer switch: different wire colors on new switch
My DR lights, which are controlled from two switches,...
People viewed this after searching for:
© 2015 Houzz Inc. Houzz® The new way to design your home™