bob md

Running a generator in a shed?

Hi,

I'll be building a small shed for my generator, probably be 5x3', 7' high. If I make this well ventilated, can I run a generator in here? I'd rather keep the generator somewhat enclosed for noise & security reasons and there's no issue with any carbon monoxide getting into the house.

Thanks!
Bob

chandler

Bob, Yes, as long as it is separate from living quarters and is not to be used for any other purpose. I have mine in a shorter version for weather protection, etc.

bob md

Thanks Larry! I just remembered, I have an unused attic fan around somewhere, I could always mount that.

chandler

I don't think I'd jump off the bridge just yet. Maybe a nice roof vent would suffice to move the heat and exhaust out. I have doors on mine that I open when I operate it to let exhaust go out and the heat dissipate.

bob md

I was just looking at a roof vent:

6 in. Black Galvanized Flush Roof Cap with Removable Screen, Backdraft Damper & 6 in. Collar-EX-RCGC 06 at The Home Depot

ray2047

Why not extend the exhaust through the wall?

bob md

I've decided that the shed is going to be much smaller than I was originally thinking, I have a perfect spot for it - it will have a footprint of 3'x5', probably 7' tall (still thinking about height). Anyhow my attic fan will be much too large for the shed so I think venting will be passive. Current thinking (changes by the minute) is to have a couple of simple wall vents and one on the roof. Thoughts?

XSleeper

Why not extend the exhaust through the wall?

My thoughts exactly.

bob md

Doh, now I understand what Ray & XSleeper are saying, it was too early for my brain to function. Great idea - what would I use to extend the exhaust - galvanized metal or something?

XSleeper

I'd go to an exhaust shop and tell them what you're doing, and what you need. Use a double wall water heater style duct to isolate your exhaust pipe from wood members when running it through the wall or roof.

Don't build the shed too small, you'll need room for you and it in order to hook the thing up inside after the shed is built!

ray2047

Actually would suggest an insulating thimble through the wall such as used for gas heaters and wood stoves. May take a bit of creativity to center the exhaust in the center. Maybe three springs equally spaced around the exhaust pipe holding it centered.

chandler

Agree with Ray and Brant. I have three doors on mine. I can access any part of the controls, exhaust, repair areas as needed. Don't forget make up combustion air, as you will need to put in a vent for that on the intake side as well, opposite the exhaust.

bob md

Awesome - i like the idea of 3 doors! Looks like you might have it connected to a natural gas supply line, right?

Northern Mike

The only issue with extending the exhaust out the wall would be the raise of noise levels and potentially create a home for small cridders.
Otherwise, it would solve heat and exhaust fume issues. Still need the shed to be vented or you'll have gas fumes and potentially sufficate the air intake.

ray2047

Can't you put a larger muffler outside and put a flapper on the exhaust pipe?

chandler

Ray, I would suggest doing like the large diesel trucks and extend it up through the roof and put one of those counterweighted flappers on it.

Bob, yeah, when Ivan came through several years ago, I was ahead of the game and tested it to make sure it would run. It ran, although with old gas I knew I would have to replace it and keep fueling it every two hours. Royal PITA. I opened the right door and a hose fell out......hmmm.....hey it was a propane hose!! Hooked it to my propane tank which was less than 5' away and it ran for 3 days without refueling, only used a fraction of fuel I thought it would and ran muuuuccchhh smoother than on gasoline.

With the doors and only a "pallet" floor, I find that I have to keep rat poison in the confines, since they love to have their parties in there I am thinking of pouring a solid concrete floor this fall to help alleviate their migration.

ray2047

Now this is just me but to keep water out I'd prefer through the wall then a ninety degree straight up.

XSleeper

Only reason I was suggesting the double walled pipe to go through the roof (as used for water heaters) was because they already have rain/animal proof caps made for that sized pipe.

ray2047

Seen that method used on commercial buildings to run power to roof mounted equipment. Forgot about that.

bob md

As the OP, I went back and forth with this idea for awhile and finally did it a month or so ago. Here's the first picture - a lean-to against the side of the house. As it turns out I had a drainage pipe running up against the house and I wanted to dig a bit of a foundation so the lean-to isn't really one, it is about 5" from the house.



This second picture shows what I did to run exhaust from the generator (7,500 watt). The generator's exhaust pipe is about 3/4" so what I did was get a 1" galvanized pipe (with a 60% extension to point it down). Next I lined everything up so when I put the generator against the side of the shed, the exhaust with the extension would protrude. I then took two 1' square ceramic tiles and drilled a 1 1/4" hole through both. Next I cut away about 11" square of the wood sheathing, used plenty of Durock and made a tile sandwich - one on the outside and one on the inside with the pipe extruding. On the inside of the shed the extension pipe covers the exhaust pipe about 1" deep or so. Then (not shown) I used chimney caulk to cement the pipe in the slightly larger tile hole.

Also note - I put a powered foundation vent on the same side as the exhaust. The plan was this would help draw air from the vent on the other side (see picture 1) and help keep things cooler in the shed. It is always plugged into the generator so as soon as I fire it up, air is moving.



Next I fired up the unit and ran it for about an hour with a thermometer in the shed. It was a 45 degree day, the temp in the shed rose to about 110 degrees. That has me a bit worried, not too hot to burn anything but it might decrease the life of the generator. Any thoughts? One thing I found out is the foundation vent, while nicely packaged to fit in the wall, isn't really all that powerful. I might look for something that can move more air.

We lost power for about a week this past summer when the temp rose to nearly 100 degrees. I'm not sure I want to run the generator in the shed when it is that warm outside so I built a concrete platform on the side of the shed. Then I put up a 2x4 horizontal support to hold a removable roof over the generator when I run it outside.



So that's the setup. This week I got a transfer switch, I've installed a power inlet box and will finish up the transfer switch wiring shortly. Of course now that I have this setup I probably won't lose power, but in case I'm ready! (that is until I get a conversion kit to run the unit off of natural gas).

chandler

Looks good!! I thought I posted a pic of mine, but it must have been on another thread. Similar construction. I have 3 doors, one front, one on either side. I let the exhaust go out one door while bringing in cooler air from the other one. Guess I could do as you and extend the exhaust, but it works. BTW, what is the black figure above the exhaust? Two way mirror ?

I don't know if you would benefit by a roof vent or not, but it may help keep the hot air at bay while it is running.

ray2047

Very nice. Maybe a simpler but more effective ventilation. Install a louvered steel grill about 18"X18". Inside mount a 18" box fan against the grill. Their cheap, speed is adjustable thus airflow is adjustable and they move a lot of air.

Hardwarenutz

My Generator Shed

I built a generator shed using information from many others.

Pilot Dane

Bob MD; the first thing I notice is you have one large and one small air vent in the side of your shed and I don't really consider either large enough. Don't forget that you have a decent sized gasoline powered heater in a small box. A good half of the gasoline's energy is being turned into heat from cooling the engine and generator.

I would look at a mushroom attic ventilation fan mounted as high as possible. Even a small 1/6 hp model will give you about 1'500 cfm which is about ten times more than the foundation vent. You could start with the existing hole for your foundation vent and work up from there. Then install a much larger or several more intake grills on the opposite side of the shed and get them as low as possible.

DMCman

I have a PAD generator that was designed to run in it's small case. It has a lot of vents but does not use any fan to move the air. I can post some photoes if you like. Would be interesting to check the temp inside the case when it's running.

Pilot Dane

If you could build shrouds/ducts to direct the engine's hot cooling air directly outside you could really cut down on the ventilation needed. Then you'd just need enough for the generator and whatever heat comes off the engine's case.

rentprop1

sound

can you tell us how much of a sound difference there is now that its enclosed

do you have a plan to extend the exhaust any further maybe have it end in a bucket of water or anything to reduce the noise any further, I have seen videos where folks tried this before running exhaust through water to quiet, but the actual noise of the gen set was tough to overcome, but theirs were not enclosed ??

Pilot Dane

Putting the exhaust is not a good idea and it will not help much with the engine noise except to add the sound of water splashing. Water exhausts are commonly used in marine applications but include some special plumbing & anti siphon valves to prevent water from being sukced back into the engine. If you wish to quiet the exhaust further I'd add an automotive style muffler to the tail pipe instead. They are cheap, don't require maintenance like adding water to a bucket and you don't risk killing your engine.

rentprop1

yea, the water isn't like next to the gen set, it has a pipe that extends about 4-6 feet then a muffler that terminates under water, the amount of bubbles wasn't a tsunami or anything, but definitely larger that a fish tank, noise from water splashing...lol...it was a lot of bubbles thats all......the added length was to prevent any water from being sucked up and I doubt the engine could pull water back up through a muffler and then 4 feet of pipe

there are several videos on youtube where people added auto mufflers and it didn't help much , my question was more about the water and noise

exhaust for marine application also have one above and one below the water line

Hardwarenutz

Well ventilated generator shed - Inside View

Works well even in 95 degree weather. Runs cooler with doors closed due to cross ventilation. Quiet due to adding sound insulation.