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Trying a new idea for the exhaust on my 802a

Summerpaws

Summerpaws

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Someone mentioned my lack of an exhaust system on my last post. It was a valid point. Carbon monoxide is nothing to joke about. I had plumbed an 1 1/4 black iron pipe from the generator, out the side of my enclosure. I removed the pipe when I took off the covers for my testing. I did not have a flexible pipe in it and I was going to fit one. Being an engineer, and one that thinks outside the box, I wondered if there was a better way. What if I could construct a system that didn't need a flexible pipe? In the power plant where I worked, we had many gas fired boilers and other equipment. The big ones had a hard ducted exhaust but the smaller ones used a venturi system. I even had one for my motorhome's generator for when we were parked near other campers and had to run the generator. The principal is simple. Hot gasses introduced into a larger diameter vertical pipe will cause low pressure to draw cool ambient air in thus cooling the pipe and accelerate the flow. I decided to try it. My whole system is made from 4 inch duct from Home Depot. I bought a dryer vent for the termination and a venturi hat for a gas water heater for the intake. I used the 1 1/4 coupling and an 8 inch nipple screwed to the generators muffler. I suspended the ducting to the rafters. The pipe from the generator does not touch the ducting. I ran the generator under load for 1/2 an hour and, although hot, I was still able to rest my hand on the ducting. There was no exhaust smell in the enclosure. I did not have a way to test the airflow with smoke, but using a long stemmed lighter I noticed the air being drawn into the intake side of the duct from almost 6 inches away. Total cost was under $50. I am planning on doing a multi hour run in the next week or so and I will monitor the duct temps where the termination is screwed to the fence. I can easily fabricate an air gap there if needed but I don't think it will get anywhere close to the combustion temp of the wood. (Anywhere for 300 degrees F to 600 degrees).
 

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2Pbfeet

Well-known member
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Summerpaws said:
Someone mentioned my lack of an exhaust system on my last post. It was a valid point. Carbon monoxide is nothing to joke about. I had plumbed an 1 1/4 black iron pipe from the generator, out the side of my enclosure. I removed the pipe when I took off the covers for my testing. I did not have a flexible pipe in it and I was going to fit one. Being an engineer, and one that thinks outside the box, I wondered if there was a better way. What if I could construct a system that didn't need a flexible pipe? In the power plant where I worked, we had many gas fired boilers and other equipment. The big ones had a hard ducted exhaust but the smaller ones used a venturi system. I even had one for my motorhome's generator for when we were parked near other campers and had to run the generator. The principal is simple. Hot gasses introduced into a larger diameter vertical pipe will cause low pressure to draw cool ambient air in thus cooling the pipe and accelerate the flow. I decided to try it. My whole system is made from 4 inch duct from Home Depot. I bought a dryer vent for the termination and a venturi hat for a gas water heater for the intake. I used the 1 1/4 coupling and an 8 inch nipple screwed to the generators muffler. I suspended the ducting to the rafters. The pipe from the generator does not touch the ducting. I ran the generator under load for 1/2 an hour and, although hot, I was still able to rest my hand on the ducting. There was no exhaust smell in the enclosure. I did not have a way to test the airflow with smoke, but using a long stemmed lighter I noticed the air being drawn into the intake side of the duct from almost 6 inches away. Total cost was under $50. I am planning on doing a multi hour run in the next week or so and I will monitor the duct temps where the termination is screwed to the fence. I can easily fabricate an air gap there if needed but I don't think it will get anywhere close to the combustion temp of the wood. (Anywhere for 300 degrees F to 600 degrees).
Click to expand...
Nice job on the custom Venturi exhaust!

If it were me, I would think about an air gap at the fence, since the fence is connected to the house via the rafters. (It's fire season out here, so we tend to see fire risks. Hammer/nail issue.) It might never happen, but I tend toward the view that during a grid outage, there may be other things going on that might distract me from the generator at times.

All the best, 2PbFeet
 
Summerpaws

Summerpaws

Active member
Steel Soldiers Supporter
97
207
33
Location
Hampton, NH
2Pbfeet said:
Nice job on the custom Venturi exhaust!

If it were me, I would think about an air gap at the fence, since the fence is connected to the house via the rafters. (It's fire season out here, so we tend to see fire risks. Hammer/nail issue.) It might never happen, but I tend toward the view that during a grid outage, there may be other things going on that might distract me from the generator at times.

All the best, 2PbFeet
Click to expand...
Probably not a bad idea. I do have some 12 gauge aluminum sheet. The enclosure is not connected to the house, by the way. I like everything modular. I made it so I can move it if I ever find the need. I have enough cable and if I ever got real ambitious, I've thought about putting it in my side yard about 25 feet from my house.
 
C

Coug

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Even with the top opening, and what I assume is the shed area possibly being open at one end, additional air movement isn't a bad idea to have, even something as simple as a box fan to move new air into the enclosed area.

I've seen the end results of multiple generators being run with insufficient ventilation, and it can get expensive. It isn't just the exhaust gasses, but the waste heat generated by the engine that causes issues.

Plastic components become brittle, wiring insulation breaks down, capacitors fail, and other heat related issues.

One Honda engine had the camshaft gear (plastic) fail from heat buildup and caused catastrophic engine failure, as well as capacitors that leaked. (installed into a shed with battery inverter system, ran with the door opened and exhaust ported outside, but nothing to force the hot air out of the building)

Generac home standby generators tend to warp the crap out of the controller plastic before anything else has any issues. (people keep thinking they can make them quieter by running them inside of a box enclosure with no ventilation.)

One Kohler home standby has the entire polymer housing become brittle and was breaking apart any time someone used even a little bit of force on it. Was outside, in an inside corner so there was only about a foot of space on the intake end, and then they parked a trailer a foot from the exhaust end. Even with the front and top open, it just recirculated the heat until the plastic baked to death.
 
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