Running Generator Inside Shed

f150skidoo · Oct 3, 2013

So i finished building a little shed attached to our shop so we can run it inside. The reason behind this idea is if my father and I are away at the cottage snowmobiling and the power goes out my mother can use the generator with out trying to dig it out of storage which she would'nt be strong enough to do. So were having a issue with heat, i originally had a 4" dryer vent for the exhaust but the exhaust melted it so i got a 6" All metal range hood vent which helped but the shed still gets really hot even after 15 min of running what would you recommend to help with heat. I'm going to add a couple of vents of the door and high on the siding but if you guys can think of anything that would help. I don't really want to tear everything apart to add a soffit.

Heres what it looks like

Steven67fr · Oct 3, 2013

I'd recommend building up routing for the exhaust to vent directly outside, that way the HOT exhaust is not building up in the shed but going straignt outside instead. I'd also recommend a fan to exacuate the hot ambient air from inside the shed since that's an air-cooled unit you'll want to make sure there's a supply of cool air coming in to ensure the longevity of the unit.

Nice little shed ad-on!

rlitman · Oct 3, 2013

You're not even close on airflow. You need well over a THOUSAND CFM to get it there, or else you're going to rapidly destroy that nice air cooled generator.

I would open up all four of the panels in that door, and replace them with louvers. They make a fixed louver panel of molded plastic that's real cheap.

Then open up a big hole in the side wall where that silly little dryer vent is, and put in an attic gable vent van. That can be covered with a closing louver vent.
Disconnect any thermostat that comes with the fan, and just power it directly plugged into the generator.

I would use EMT conduit to extend the exhaust out through the wall if possible, with space around the conduit so the hot metal does not touch something combustible.

Rookie2 · Oct 3, 2013

too late to be asking about heat. i think you should start over or you'll end up chopping up that nice built cabinet.

432bullet · Oct 3, 2013

Put a all metal exhaust, with plenty of clearance Thur the wall and then put a hook on the door so that you can leave it open when you run the unit. you will have way to much heat in that wooden structure as it is with out the door open.

Thumper68 · Oct 3, 2013

During the winter I have my genny in the shed and I leave the doors wide open while it's running.

theoldwizard1 · Oct 3, 2013

Steven67fr said:
I'd recommend building up routing for the exhaust to vent directly outside, that way the HOT exhaust is not building up in the shed but going straight outside instead.

I'll go one step further.

Remove the existing muffler. Use the exhaust gasket as a pattern ans make a manifold out of heavy steel. Clamp on flexible stainless exhaust tubing and run it out side pointing it down toward the ground. Wrap the entire length of tube in high temp exhaust wrap, probably 2 layers.

You will still need a powered vent.

AirJunky · Oct 3, 2013

I did something similar for my air compressor. Used a bathroom fan to vent the heat out. For a while I put a thermometer inside it to see how warm it got. Never saw it more than about 7 or 8 degrees warmer than the outside air temp.

mds5951 · Oct 3, 2013

Why not just leave the door open?

theoldwizard1 · Oct 3, 2013

AirJunky said:
I did something similar for my air compressor. Used a bathroom fan to vent the heat out. For a while I put a thermometer inside it to see how warm it got. Never saw it more than about 7 or 8 degrees warmer than the outside air temp.

An air compressor does not run continuously.

dbabicky · Oct 3, 2013

mds5951 said:
Why not just leave the door open?

Exactly!

ZRX1040 · Oct 3, 2013

Just a thought. My buddy has a generator in his shed at camp. The exhaust is ran through a flex hose through the wall and underground about 15 ft before it comes back up. Can barely hear the thing run.

install a latch to hold the door open when running

G_P · Oct 3, 2013

My neighbor has a smaller type of setup.

On theirs the front wall drops flat on the ground and the roof hinges up and latches to the side of the house. This way while running the genny has plenty of air too stay cool and the exhaust is still stock.

Their shed is only 3' tall though. Just big enough to house the genny. In bad rain they keep the roof down
to keep it dry.

No matter what you do you need a ton of air to keep the heat down.
Sent via carrier pigeon.

MadMechMaster · Oct 3, 2013

Put the Generator on a slide out platform. This will get it out to open air and done right, should be easy enough for your mother to do.

Keep that window closed!

DanarchyCustoms · Oct 3, 2013

Even with the exhaust routed outside, the generator will still produce heat obviously. Let the heat work for you and put a vent with a fan as high as you can in the shed to expel the heat to the outside. If the door is closed just make sure you have a vent on the bottom to let in cool air. Its all simple physics.

f150skidoo · Oct 3, 2013

Thanks for all the advice guys, running with the door open doesn't do enough to keep the temps down. This evening i ran it for 25 mins with the door open the ambient air temp out side was 60 F and in side the shed the thermometer went off the scale @120 F and the all metal 6" range hood exhaust vent was to hot to touch. I going to take some of your guys ideas like exhaust fan and vents in the door.

nit2wn · Oct 4, 2013

This is just a suggestion at best and not sure how much it would help. What about adding some louvered metal at the top and maybe the bottom especially on the side with the dryer vent. Maybe find a shroud off an older ac unit that covers the coils and repurpose it. Otherwise your just about going to have to fix a tray for it to sit on and let it slide out of the window when running.

rlitman · Oct 4, 2013

nit2wn said:
This is just a suggestion at best and not sure how much it would help. What about adding some louvered metal at the top and maybe the bottom especially on the side with the dryer vent. Maybe find a shroud off an older ac unit that covers the coils and repurpose it. Otherwise your just about going to have to fix a tray for it to sit on and let it slide out of the window when running.

Passive airflow is not going to be nearly enough.

HoosierMark · Oct 4, 2013

why not put a temp controlled fan in a wall or ceiling of the shed and wiring it to the generator. When the genny runs so does the fan exhausting air out. Could also put a fan in that pushes air over the unit. I know it takes power but it also solves the problem and mom does not need to open, pull, push or do anything else. It only runs when the genny is running and the temp is up.

DangerousDan55 · Oct 4, 2013

Be Very carfull with the exhaust. Every year people die!
It looks like your shed is built onto your home. That concerns me. Are your soffets vented on the house. Thinking of CO getting into the attic.
Remembr, CO is a silent killer.
Your priorities should be:
Personal safety 1st
Equipment operation 2nd

f150skidoo · Oct 4, 2013

DangerousDan55 said:
Be Very carfull with the exhaust. Every year people die!
It looks like your shed is built onto your home. That concerns me. Are your soffets vented on the house. Thinking of CO getting into the attic.
Remembr, CO is a silent killer.
Your priorities should be:
Personal safety 1st
Equipment operation 2nd

The genny shed is beside the shop which is 75 feet from the house.

72Anthony · Oct 4, 2013

No offense, but it looks like a good way to burn your shop down!

If that generator catches fire the shed will become involved because it is built of combustible material. The burning shed will create a big enough fire to spread into your attic because of the over hanging roof. It also looks like there is a window to the left of the enclosure in the photo.

An unenclosed generator located that close to the building may or may not create a big enough fire to ignite the house siding and spread into the building.

Permenantly installed, natural gas standby generators are required to be 3 to 5 feet from buildings to provide adequate air flow and reduce the chance of a burning generator spreading to the building.

I would rethink this setup. Can you build a detached shed? If you leave it in place I would line the interior with two layers of 5/8 type X drywall and install a fixed temperature heat detector inside (they have models for high ambient temperature environments).

Regards,
Anthony

John in OH · Oct 4, 2013

rlitman said:
Passive airflow is not going to be nearly enough.

+1 You are going to need a ton of fresh air to keep this thing cool! You have to provide enough cooling air and heat dissipation for three components: the air-cooled engine; the air cooled generator; the exhaust piping and muffler.

Probably the best suggestion offered so far is the attic exhaust fan. These may not be too common in Canada, but are used in nearly all houses in southern US. Typically, they are 18"-24" in diameter (or more), have automatic louvers (weighted or electric), and a temperature switch. They exhaust outward so you also need a big inlet vent to provide the replacement air.

Fab up a custom exhaust pipe & muffler to discharge the engine exhaust directly out of the shed. Install the exhaust fan and auto louver on one side of the shed and the air inlet vent on the opposite side. Don't skimp on sizing the inlet!!

theoldwizard1 · Oct 4, 2013

John in OH said:
+1 You are going to need a ton of fresh air to keep this thing cool! You have to provide enough cooling air and heat dissipation for three components: the air-cooled engine; the air cooled generator; the exhaust piping and muffler.

Probably the best suggestion offered so far is the attic exhaust fan. These may not be too common in Canada, but are used in nearly all houses in southern US. Typically, they are 18"-24" in diameter (or more), have automatic louvers (weighted or electric), and a temperature switch. They exhaust outward so you also need a big inlet vent to provide the replacement air.

Fab up a custom exhaust pipe & muffler to discharge the engine exhaust directly out of the shed. Install the exhaust fan and auto louver on one side of the shed and the air inlet vent on the opposite side. Don't skimp on sizing the inlet!!

It has to be insulated with header wrap, preferably 2 layers !

mpraddict · Oct 5, 2013

72Anthony said:
No offense, but it looks like a good way to burn your shop down!

If that generator catches fire the shed will become involved because it is built of combustible material. The burning shed will create a big enough fire to spread into your attic because of the over hanging roof. It also looks like there is a window to the left of the enclosure in the photo.

An unenclosed generator located that close to the building may or may not create a big enough fire to ignite the house siding and spread into the building.

Permenantly installed, natural gas standby generators are required to be 3 to 5 feet from buildings to provide adequate air flow and reduce the chance of a burning generator spreading to the building.

I would rethink this setup. Can you build a detached shed? If you leave it in place I would line the interior with two layers of 5/8 type X drywall and install a fixed temperature heat detector inside (they have models for high ambient temperature environments).

Regards,
Anthony

Very good advice

Sureshot · Oct 5, 2013

Slide it out to run it. Get a big set, double up, or fab drawer slides that make it easy to get in and out.

Pure silicone heater hose will also last a long time on the exhaust to vent it away depending on the load and size of the gen.

mikester · Oct 5, 2013

72Anthony said:
No offense, but it looks like a good way to burn your shop down!

If that generator catches fire the shed will become involved because it is built of combustible material. The burning shed will create a big enough fire to spread into your attic because of the over hanging roof. It also looks like there is a window to the left of the enclosure in the photo.

An unenclosed generator located that close to the building may or may not create a big enough fire to ignite the house siding and spread into the building.

Permenantly installed, natural gas standby generators are required to be 3 to 5 feet from buildings to provide adequate air flow and reduce the chance of a burning generator spreading to the building.

I would rethink this setup. Can you build a detached shed? If you leave it in place I would line the interior with two layers of 5/8 type X drywall and install a fixed temperature heat detector inside (they have models for high ambient temperature environments).

Regards,
Anthony

I would give the same advice. Plus in my area that would never pass an inspection by the building department. If that burns down your house the insurance might not even cover the damages.

nehog · Oct 6, 2013

72Anthony said:
No offense, but it looks like a good way to burn your shop down!

If that generator catches fire the shed will become involved because it is built of combustible material. The burning shed will create a big enough fire to spread into your attic because of the over hanging roof. It also looks like there is a window to the left of the enclosure in the photo.

An unenclosed generator located that close to the building may or may not create a big enough fire to ignite the house siding and spread into the building.

Permanently installed, natural gas standby generators are required to be 3 to 5 feet from buildings to provide adequate air flow and reduce the chance of a burning generator spreading to the building.

I would rethink this setup. Can you build a detached shed? If you leave it in place I would line the interior with two layers of 5/8 type X drywall and install a fixed temperature heat detector inside (they have models for high ambient temperature environments).

Regards,
Anthony

As others are saying, this is my advice too. There is no way, IMHO, to make this a safe installation. The combustable surfaces, the air-cooled motor, a gas vs. diesel engine, etc., all are working against you.

I'd re-think the plan, and use that area for storage and make a standalone building/shed for the generator.

HavATampa · Oct 6, 2013

Using wood for the gen shed is not a good idea IMO. There are kits out there for this purpose. I installed a small metal shed and used this kit http://www.nooutage.com/powershelterkitii.htm . It consist of a 16"x24" motorized louvered intake shutter and a 16" square louvered exhaust with an attached 1600cfm fan that ***** hot air of the shed. Both devices turn on when the generator is running. I lined the shed with sound absorbing, non-flammable material and built an exhaust system that consist of a motorcycle muffler that exists out the shed wall through a high temp silicone sealed port. The kit also included a temperature cutout sensor that installs on the generator and turns the gen off if the temp get too hot.
I built my shed by the back wall of my garage. Not real happy about it being so close to the house, but my options were limited. I have it connected to main breaker box with a 6 circuit transfer panel.

This same site also sells metal gen enclosures with fans that may work better for you parents setup:
http://www.nooutage.com/powershelteriii.htm

theoldwizard1 · Oct 6, 2013

HavATampa - Nice kit and nice install ! Is there a fire rating on those walls ?

If I were to build one on my own, I would put 2 layers of plasterboard on all of the inside surfaces !

f150skidoo · Oct 6, 2013

So i solved the problem with the heat. The door and side wall is all vents and i also installed a 24" 3,000 cfm exhaust fan. I ran the generator for 2 hours and inside the shed is running 5-10F above outside air temp. The exhaust vent is running steady around 200F. To prevent the risk of the wood scorching or even burning i left a 3/4" air space around the 6" exhaust vent and i also wrapped the wood with aluminum. I measured the temp where i wrapped the aluminum around the wood and it was around 100F.

rlitman · Oct 6, 2013

Nice. Yeah that should deal with the heat very well.

Now if you line the inside (without blocking the vents) with cement board, you can reduce the fire risk and noise.

HavATampa · Oct 6, 2013

The material I used is Prodex Reflective Insulation. It's advertised with a Class A/Class 1 Fire Rating. I mainly used it for sound insulation though. I lined my garage doors with it too and it made huge difference in blocking street noise and radiant heat.

theoldwizard1 said:
HavATampa - Nice kit and nice install ! Is there a fire rating on those walls ?

If I were to build one on my own, I would put 2 layers of plasterboard on all of the inside surfaces !

Running Generator Inside Shed

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