Over the past two days I've been digging, cutting and gluing conduit, and now I started framing out my generator hut:







The hut is for this generator, which is nothing short of "big" with it's 992 cc engine and it's 240V @ 62A output.



I haven't used the generator in an emergency situation yet but playing with it, I have to say it's barely louder than my 10 y/o 4500W Coleman with a 9 or 11 HP Briggs (I forget which). The Generac 4852 produces 15.something KW and has a peak of 22.something KW for starting big motors. The muffler is huge and enclosed with a chrome "grate" to keep it from burning your pant leg if you stand too close, and has a very nice "low" tone to it.

The one feature I really like is the oiling system - filter, pump, and external oil cooler, and already-installed adaption to remote draining rather than the usual stupidity if making it impossible to get something underneath the drain port without lifting the generator off the ground.

Anyway, I thought I'd share since I'm sure others might find this useful or at least, entertaining.

And when you run your wire, always use THWN or UW-rated wire (both are for wet in case the conduit leaks down the road).

 

Some more pics:

 

looks great

 

Thank you!

As it turned out, I tested things this morning for 30 minutes with the doors closed and locked, and the noise wasn't bad at all, even though I hadn't insulted the interior walls as of yet.

Unfortunately, the test failed because the in-hut temperatures started to climb to the point where the air coming out the pair of nutone bathroom fans was very hot to my bare hand. Nowhere near as hot as the exhaust outlet mind you, but hot enough that holding my hand there was unpleasant. I opened the doors to shut the generator down, and wow, it felt like the middle of summer.

I think the pair of bathroom fans do not have anywhere near enough flow. Looking at them closely, I see why - the fan has such a large gap around the blades I'm surprised they exhausted what heat they did.

I will be removing them, the PVC and the wiring and plugging the holes where the outlets were, and installing a 1200 cfm roof fan come morning. If a 1200 cfm roof fan can't exhaust heat out of a 3'x6'x4' space, I don't know what will

 

try an inexpensive smoke ejector

 

I already bought this though... I was debating adding more bathroom fans until I started reading the boxes and saw what I installed was rated 50 cfm. Reminded me of a good lesson - read the darn box before buying lol.

Anyway, I already bought one of these and cut the hole so tomorrow I'll wire it up and repeat the 30 minute temperature test.



I'm just glad I tested it now rather than tested it in use in an emergency - it would have sucked to do this work in a snowstorm or hurricane under pressure.

It's very scary though cutting a 18" diameter hole through a brand new roof I just installed though lol.

I can't imagine this fan isn't big enough... but I guess I'll find out tomorrow !

 

Its a real nice setup for sure!

Where is the air intake? It doesn't look you have any venting into the enclosure, just the exhaust fans. If no fresh cool air can get in, it won't matter how big a fan you use to suck out. If you haven't already blocked them off, maybe you can use the spots where the smaller fans were.

 

Yes! That may have been part of the problem, because you're right, there is no intake vent(s). Duh!

Since the bathroom fans vent out at the bottom, I'll open that area up a little and put grills over the holes as an intake.

 

Also the engine requires oxygen to run. If in a sealed chamber it will burn all the oxygen and shut down.

 

The original vent holes for exhaust are now squared out to 8"x9.5" and covered with two grilles, and being at the bottom of the structure they're drawing in air below the generator.

The 1200cfm roof fan was installed and the roofing I damaged trying to install it was replaced, and today's 30 minute test was splendid - the fan has enough draw to keep things nice and cool inside. Unfortunately, it has enough suction that leaves on the ground near the shed got sucked up against the grilles but that's easy to solve by waving a rake through there once in a while.

I was annoyed by the fan's thermostat which seemingly wouldn't close no matter how hot it got inside the hut, so I ripped open the box and bypassed it entirely. I don't see any issue with the fan going all the time as this ensures heat is removed and fresh air is drawn in. That should make for a happy generator.

Now all I have to do is put the latch hardware back on, and finish painting it.

 

try running a rheostat on the fan to cut back the flow to around 800 cfm, and it may not suck in the leaves.

 

Keep in mind that running with no load is a lot different than load.

A 15KW Generator head should have a ~28-30HP engine driving it.

30HP is about 23,000 Watts of mechanical energy. An air cooled gas engine like that is probably about 25% efficient. So at full load, the engine will be generating about 69,000 Watts of waste heat. Assume half goes out the exhaust, you're still dealing with 34,500 Watts of heat from the cooling system. 34.5 KW of heat is over 117,000 BTU of heat dumping into that shed. HVAC guys recommend about 400 CFM per 12,000 BTU.

You'll be needing something closer to 4000 CFM to keep that shed cool if you ever plan to fully load that generator up. 2000 CFM would probably be enough to cover as much load as you'll ever put on it during an emergency though.

 

Duct fans, available is several sizes, are quiet and move masses of air. They are good pushing or pulling.

I put a 10" duct fan on my 9 x 13 bathroom and it pulled so much air it would pull the door shut. Went down to an 8". Still strong but doesn't make your ears pop.

 

I would recommend installing air vents near the 1st 6 inches of the floor in the walls...........flammable vapors can accumulate and cause some real fire-related issues.

 

I didn't post pictures yet but I replaced the bathroom fan ductwork and outside vents with two 10" square vents as an air intake. The fan on top sucks air through them, across the generator's engine and genhead, and out the top.

I ran it yesterday with the subpanel fully loaded as it would be during a power failure - to big UPS systems that power my server farm, the fridge, the coffee making in "brew now" mode, the furnace, and the sump pumps. I got one of the sump pumps to "work" by putting a hose in the sump well, and the furnace I got to stay on for the hour long test by setting the thermostat to 99 degrees.

The air coming out of the fan on top was somewhat warm, but not as warm as I would have expected. Of course it was 35 degrees outside and that certainly helped, but as a first test things were good. It's supposed to be upper 50's later this week so I'll repeat the test and see what happens.

I installed a fire extinguisher today, I figured that was a good idea, "just in case".