MEP-802A - can this thing function with a 60' exhaust run?

[Smithsonite]

Great site here. I searched this topic but I seem to be the only one with this crazy idea ...

So, my newly acquired unit is going to be in a barn, set up with an automatic transfer switch for whole house power. I want to run the exhaust out back, just to keep future bad actors guessing as to where the unit actually is (And hopefully pass on by if I can hide lighting well enough). Added bonus is there are no houses behind me, so the noise won't be directed at neighbors. To do this is going to take all of 60' straight back, plus several feet going up from the unit, then up to match the ceiling height of the attached building in back. Probably will be closer to 70' -75' now that I think about that.

I might just get lazy and take the easy way, straight up through the roof. But, what do you guys think about such a long run? I'm wondering what that would do to engine performance, especially at full bore.

Another bonus, the last foot will probably be at ambient temperature, so there won't be a need for double-walled insulation going through the wall.

 

[SCSG-G4]

The larger diameter of the pipe will reduce back pressure, so, if I were doing it about every 8 to 10 feet the pipe diameter would be increased by 1/2 to 3/4 of an inch, starting right at the generator. Probably want to go up first. You will still have to deal with wet stacking on a long run - pipe has to get hot to keep the 'smoke' moving and not sticking to the inside of the pipe.

 

[WWRD99]

There might be some engineering info out there on this since in buildings basements in cities have them ...probably some vacuum fans to pull the exhaust out with a certain cfm per foot of run...after so far a pvc pipe could be used since temp would be low...possibly grab a fan off a furnace that you could switch on when the genset is on. The exhaust fans on those are not expensive and designed to be in exhaust.

Sent from my SM-S906U using Tapatalk

 

[Triple Jim]

40 foot long school busses and motor homes often have the exhaust going all the way to the rear. If you choose a pipe diameter like 2" or 2-1/2", I don't think you'd have a problem. As the gasses cool, they take up less volume anyway. But going out the roof and aiming the pipe the way you want sounds like a better idea.

 

[Digger556]

The length of tubing is only restricted by the backpressure it creates on the engine. The factory Lister engine service manual likely lists the allowed backpressure. (You need to include the muffler too)

Cheap digital manometers are available on Amazon.

Like others have said, the bigger the tube diameter, the less restriction.

 

[Chainbreaker]

Also consider using "Exhaust/Header Wrap" as far as you can (at least up to roof penetration). An exhaust pipe that long is going to absorb a lot of "ambient cold" from air temp when genset is not running & then wick away heat from the exhaust gasses.

You want to keep the exhaust pipe hot/warm as far as possible when genset is running or you might possibly end up with genset manifold wet stacking especially if not under constant heavy load when running (less than ~50% load).

 

[DieselAddict]

Its a balance between velocity/temperature and back-pressure.

A couple of items not mentioned here is you want the exhaust line to slope AWAY from the generator. You will want well insulate the piping to keep condensation to a minimum.

If you go through the roof, you will want to set a TEE in the vertical line with a drip leg on the low side.

 

[Smithsonite]

EXCELLENT info everyone! Much appreciated! Still on the fence, but I'm leaning towards going through the roof just for simplicity, even though I'll have to climb up there & flash the projection at the shingles. Should be within the next couple weeks, whatever I decide - I'll post back when I get it figured out.
Thanks everyone!!

 

[2Pbfeet]

Personally, I would move the generator, and run wires for the distance. It is cheaper and less likely to cause issues with your house/outbuilding.

If the goal is to hide it, I would hide it out back, and go from there. If you need ideas, look at moonshiners' tricks.

All the best,

2Pbfeet

 

[Ray70]

Diesel Addict , Chain Breaker and the others all hit it on the head.... you won't have a problem with regards to back pressure, but that long run is going to cause the exhaust to condense in the pipe causing acidic liquid to want to run downhill, so you'll need to either slope the pipe away and/or install a drip leg where the water can drain away from the engine. Also keep in mind that the acidity of the liquid will corrode everything other than stainless steel. you WILL have carbon building up in the pipe no matter what you do, and that WILL cause smoke from the pipe, so don't be surprised and don't get alarmed thinking the engine has developed a problem when you see the smoke start.

 

[Smithsonite]

Great point, Ray. I appreciate that. I think what I'm going to do instead is run the pipe out the side of my barn, opposite my house. Much shorter run (15'-20' tops), and much simpler (And cheaper - that's a win for me). Will be visible from the road, but we're pretty rural here, thankfully.

 

[Smithsonite]

Diesel Addict , Chain Breaker and the others all hit it on the head.... you won't have a problem with regards to back pressure, but that long run is going to cause the exhaust to condense in the pipe causing acidic liquid to want to run downhill, so you'll need to either slope the pipe away and/or install a drip leg where the water can drain away from the engine. Also keep in mind that the acidity of the liquid will corrode everything other than stainless steel. you WILL have carbon building up in the pipe no matter what you do, and that WILL cause smoke from the pipe, so don't be surprised and don't get alarmed thinking the engine has developed a problem when you see the smoke start.

Yeah, in hindsight I think it would've been better to move the unit outside, behind the barn, but I've already ordered 55' of cable, so now it's going to stay where it's at (Center of my barn). I would need at least 110' to get behind the barn out of sight. Ends up cheaper wire-wise, at least. Plus the direction I've decided to go with the iron pipe will save me at least $120 in materials, too. That works for me.

It's the former auto / small engine mechanic in me that wants to keep everything with an engine inside, out of the weather, even if it was designed for it. Things just last longer, and stay looking better that way. Less work for me in the long run, too.

 

[Tinstar]

Don’t forget to mouse-proof your generator.
Mice love barns and can cause serious damage to wiring, etc
Lots of threads on how to keep them out.

 

[Ray70]

Being that you have an auto repair background, I assume you already know to put a flex pipe of other flexible connection between your muffler and exhaust pipe... Universal flex pipes for cars work good and are only about $25.

 

[Smithsonite]

Great points. Definitely flex for a least a couple feet up.

The previous owner installed some screens around the unit. I think there's just one area he didn't do, that I'll have to mouseproof. We've got plenty of them around here. My cats usually grab at least one a day from the basement of the house, never mind the barn.

 

[Smithsonite]

Found a nice flex pipe on Zoro. Wasn't cheap, but it'll get the job done.

I had ordered pipe I had planned to weld together from some company in NYC - 4 days later I'm looking at the email they sent. No shipping! What a waste that was. They refunded my card at least. Back to the drawing board on that. Might see if I can get 10' lengths of automotive exhaust cheaper than black iron. I can't believe the price of that stuff these days! Used to be so cheap! Not anymore ...

 

[Light in the Dark]

Find a local plumbing supply shop, should be good to price compare black iron. Lowes over in Ware has 1.25" x 10ft in stock at $50.xx per length.

I used to buy a fair amount of BI from R.A. Manley in Palmer.

 

[Light in the Dark]

Thinking outside the box, not sure its the greatest idea but you could always find a conduit coupler with a spread clamp on one side (to go onto BI already on the machine) and use EMT instead on the way up? Lighter for certain.

 

[Tinstar]

I'm sure you did already, but recommend using quality anti-seize on the pipe threads.
Months/Years of engine exhaust heat and then sitting idle in a barn will make that a bear to remove at a later date.

 

[Ray70]

Just go to your local auto parts store and buy 10' lengths of exhaust tube. Any 1/2-way decent store can order it quickly.
O'riley's here in RI has in in their warehouse and can get it same day.
You can also order it on line from places like Summit Racing and Jegs performance.
Can get aluminized pipe or even stainless if you prefer.
Black iron is way thicker , heavier and more expensive than you need.