# Exhaust Heat



## Bluwolf (Nov 8, 2020)

Something that's been nagging at me. Below is a picture of my exhaust running out the back of my gen shed. I feel like a lot of the heat in the shed might be generated by the exhaust (or not, that's the first question. Is it or isn't it?

Second question, what can I do to reduce that heat? Would silicone hose do it? Isolate it with a bigger piece of ducting that would fit that exhaust vent flange?

If it makes any difference I will be moving the shed to a better spot, closer to the inlet and farther from windows. I'll be able to shorten my cord too. Point being I'll have access to the back if that helps with the exhaust modification.


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## OrlyP (Oct 19, 2021)

All that heat from the combustion has to go somewhere so yes, most of the heat is generated by the engine.... I'd say 80-90% of it. The power head windings also produce a good deal of heat, especially when they're loaded. Not as much as the engine but significant enough that it has its own blower.

As long as the exhaust ducting and pipe work doesn't touch anything combustible, you should be fine. Where did you install the shed inlet vents and the exhaust fan?


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## Bluwolf (Nov 8, 2020)

OrlyP said:


> All that heat from the combustion has to go somewhere so yes, most of the heat is generated by the engine.... I'd say 80-90% of it. The power head windings also produce a good deal of heat, especially when they're loaded. Not as much as the engine but significant enough that it has its own blower.
> 
> As long as the exhaust ducting and pipe work doesn't touch anything combustible, you should be fine. Where did you install the shed inlet vents and the exhaust fan?


Thanks OrlyP. I understand that it all makes heat. But I was specifically asking about the exhaust ducting. I have an intake vent on the left and an exhaust fan on the right. The exhaust goes out the back. When in use, the gas cans and shelf come out. Then the propane tanks are spread apart to expose the intake vent. See picture below.

My thought was, if I shorten the exhaust ducting that would reduce an X amount of heat. Less surface area to be radiating heat. There is cement board on the back of the shed, and the hole that passes through the shed is much larger than the exhaust duct. In other words, the heat passing through the shed back wall is not an issue. But, would wrapping the exhaust ducting with a silicone hose or exhaust header wrap reduce the heat build up in the shed. Or am I over-thinking all this?


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## OrlyP (Oct 19, 2021)

You are overthinking it a little bit. The fan should be able to provide enough airflow to prevent any heat soaking. But as a precaution, you may want to put a remote thermometer that will notify you in case the temperature goes past a certain threshold (ie. in the event that the fan fails).

But if you want to insulate the pipe so there's less heat that can escape within the shed, however negligible in the grand scheme of things, I'd probably choose the header wrap.

I wouldn't want to move the generator closer to the back of the shed as that will restrict airflow on that side of the generator.


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## Bluwolf (Nov 8, 2020)

OrlyP said:


> You are overthinking it a little bit. The fan should be able to provide enough airflow to prevent any heat soaking. But as a precaution, you may want to put a remote thermometer that will notify you in case the temperature goes past a certain threshold (ie. in the event that the fan fails).
> 
> But if you want to insulate the pipe so there's less heat that can escape within the shed, however negligible in the grand scheme of things, I'd probably choose the header wrap.
> 
> I wouldn't want to move the generator closer to the back of the shed as that will restrict airflow on that side of the generator.


Good point about restricting air flow on that back side. I have a remote thermometer in there when it's running. Sometimes it's just a bit warmer than I would like. The manual says keep it under 120 degrees. I've been close to that in the summer here in SW Florida. I just figured as long as I would be moving the shed I would have to empty it, and that would be the time to make modifications.


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## OrlyP (Oct 19, 2021)

I think they mean to say that the generator shouldn't operate in >120°F ambient temperature. Does it get anywhere near that temp inside the shed?


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## Bluwolf (Nov 8, 2020)

OrlyP said:


> I think they mean to say that the generator shouldn't operate in >120°F ambient temperature. Does it get anywhere near that temp inside the shed?


Yes, it does in the summer. Well, okay, I'm in SW Florida. So it's over 90 degrees 8 months a year. And the shed is on the side of the house that's in the sun ALL DAY LONG. So it's 90 degrees before it even gets fired up. I've even bought one of those EZ Up canopies to put over it. But I haven't tested to see how much that would help to keep it out of the sun. I was thinking along the lines of, say, a fridge sitting in the sun running and how hard it would have to work to keep food cold. The exhaust fan is supposedly 1320 CFM. And it's a good size intake vent on the other side. But I've seen the temp get up to 115+ in there, and that was only after an hour. 

I just run with the doors open but the lid closed to try to keep the sun off it. When I left the lid open, to try to let the heat rise, it got hotter. So I've been trying to think of ways to try to bring the temp down in there. Hence why I've been looking at small details like the exhaust ducting.


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## iowagold (Jan 22, 2020)

if you are on gasoline the heat can be a BIG issue.
the fuel boils thing.

and yes on the silicone hose it does help for sure.
if you force air along side of the vent tube like a triple wall pipe setup that helps on the heat to the shed heat.
some setups use the same style they use on the hot water heaters where the cold air intake is on the outside pipe.
and the exhaust is in the center pipe.

for winter cold that helps pre heat the air for a better run.
for me i would run another muffin fan for the outer jacket to cool the outside pipe on a triple wall and vent it all out for summer hot or south climates


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## ronskal (Feb 18, 2021)

I like what I see in your Gen Shed. Beast of a Gen too, must put out the heat.
Worth a try on the exhaust wrap. Anecdotally, when I replaced the steel/painted exhaust headers in my old muscle car with ceramic coated headers- big difference in the engine bay temps. Point is the exhaust is worth a try, especially with what effort you already have in the shed.


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## Bluwolf (Nov 8, 2020)

iowagold said:


> if you are on gasoline the heat can be a BIG issue.
> the fuel boils thing.
> 
> and yes on the silicone hose it does help for sure.
> ...


Nope, no gasoline. Only propane. Any good links for the silicone hose?

As for your second paragraph, it all went over my head.

Being in SW Florida the closest we get to winter might be a couple of odd days in the mid 40s.


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## Bluwolf (Nov 8, 2020)

ronskal said:


> I like what I see in your Gen Shed. Beast of a Gen too, must put out the heat.
> Worth a try on the exhaust wrap. Anecdotally, when I replaced the steel/painted exhaust headers in my old muscle car with ceramic coated headers- big difference in the engine bay temps. Point is the exhaust is worth a try, especially with what effort you already have in the shed.


Thank you. I tried to put some effort into it. I bought it bigger because I knew I only wanted to run on propane. If you look at the picture, in small green print, it says the running watts with propane is only 6750. I also bought a little bigger so I wasn't running so close to the max running watts. Hopefully it's adding a little life to the generator. And it doesn't make a fuss when I start the water heater.

I also have a small 2000W dual fuel inverter so I can give the big one a break and not eat so much propane. The little one can run run a window A/C unit at night and be much quieter, and again, way less propane.


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## Bluwolf (Nov 8, 2020)

ronskal said:


> I like what I see in your Gen Shed. Beast of a Gen too, must put out the heat.
> Worth a try on the exhaust wrap. Anecdotally, when I replaced the steel/painted exhaust headers in my old muscle car with ceramic coated headers- big difference in the engine bay temps. Point is the exhaust is worth a try, especially with what effort you already have in the shed.


Forgot to mention, you're right about the ceramic headers. We used to wrap the headers on the race cars with the exhaust wrap for just that reason. But we found the the wrap also accelerated rust on the headers. Then we switched to ceramic coated and that did work very well.


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## OrlyP (Oct 19, 2021)

Bluwolf said:


> Forgot to mention, you're right about the ceramic headers. We used to wrap the headers on the race cars with the exhaust wrap for just that reason. But we found the the wrap also accelerated rust on the headers. Then we switched to ceramic coated and that did work very well.


Quite true on the negative effects of using header wraps. However, we need to put things into context. You're not going to wrap the generator's header. You're applying the wrap on the exhaust pipe extension.... which doesn't get anywhere near as hot as the header.

Another option is to wrap it in hi-temp mineral wool like Rockwool, etc.


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## drmerdp (Apr 10, 2018)

You have a nice enclosure, but there are improvements that you can make.

I had a similar CFM exhaust fan on my old enclosure for a champion 7000watt generator 439cc like yours. But it was paired with another 1000cfm fan on the intake side. It worked for me up in the northeast. But for your climate and the size of the generator the fan and inlet are grossly undersized for closed door operation. You need 3-4 times as much for summer in south Florida. My current setup is is rated at about 4000cfm which is perfect for my dual generators except maybe for 90+ degree days. I have more testing to do on that front. I’m my own situation Im currently venting engine exhaust directly into the enclosure. Adding silicone hose to vent exhaust gasses outside the enclosure would be my next move if needed. 

Lining the interior of the enclose with materials that won’t heat soak will help, cement board, fiberboard, foil faced foam will reduce some noise and keep temps more neutral.

As for the exhaust, wrapping any exposed pipe will definitely reduce heat into the enclosure. Header wrap is good but foil faced fiberglass is even better. Silicone hose if fiberglass lined and also works very well.


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## OrlyP (Oct 19, 2021)

Good call.

I'd start with how Zombiebox design their ventilation as baseline:

Fan:1200 CFM
Net free or total enclosure intake vent opening: 600sq.in. (or about 4 sq.ft)


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## iowagold (Jan 22, 2020)

Bluwolf said:


> Forgot to mention, you're right about the ceramic headers. We used to wrap the headers on the race cars with the exhaust wrap for just that reason. But we found the the wrap also accelerated rust on the headers. Then we switched to ceramic coated and that did work very well.


and over heats the pipe on road race cars...
they melt the pipe on the inside...
at least on the super thin wall stuff.

on the triple wall duravent is the brand name
*click here for one reseller listing for them*
*some of the tru value stores also had that brand.
we found some that were 4 inch id and worked well for a couple of projects.*

i will pm the other links


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## Bluwolf (Nov 8, 2020)

OrlyP said:


> Quite true on the negative effects of using header wraps. However, we need to put things into context. You're not going to wrap the generator's header. You're applying the wrap on the exhaust pipe extension.... which doesn't get anywhere near as hot as the header.
> 
> Another option is to wrap it in hi-temp mineral wool like Rockwool, etc.


I wondered if I could wrap the pipe in that rockwool. But I didn't know what the effect would be on the Rockwool having constant direct contact with the pipe.


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## Bluwolf (Nov 8, 2020)

drmerdp said:


> You have a nice enclosure, but there are improvements that you can make.
> 
> I had a similar CFM exhaust fan on my old enclosure for a champion 7000watt generator 439cc like yours. But it was paired with another 1000cfm fan on the intake side. It worked for me up in the northeast. But for your climate and the size of the generator the fan and inlet are grossly undersized for closed door operation. You need 3-4 times as much for summer in south Florida. My current setup is is rated at about 4000cfm which is perfect for my dual generators except maybe for 90+ degree days. I have more testing to do on that front. I’m my own situation Im currently venting engine exhaust directly into the enclosure. Adding silicone hose to vent exhaust gasses outside the enclosure would be my next move if needed.
> 
> ...


I was going to try the Rockwool on the walls. Mostly for the sound deadening. Even though I have 4 openings where noise gets out. I started with the intake and exhaust openings. Then added 2 openings, one each in the doors up high to try to bleed off more heat.

I had also considered an intake fan. I'm not sure if my 1320 CFM fan is really putting out 1320. I was thinking I would use the one I have for the intake and getting a bigger one for the exhaust side.

Will the foil faced fiberglass hold up in direct contact with the exhaust ducting? And what kind of CFM do you thing would be sufficient for the exhaust side?


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## Bluwolf (Nov 8, 2020)

iowagold said:


> and over heats the pipe on road race cars...
> they melt the pipe on the inside...
> at least on the super thin wall stuff.
> 
> ...


I had actually considered one of those multi walled stove pipes. But holy crap! Those things are not cheap!


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## Bluwolf (Nov 8, 2020)

OrlyP said:


> Good call.
> 
> I'd start with how Zombiebox design their ventilation as baseline:
> 
> ...


Well, I'm (supposedly) at 1320 CFM now. But as I mentioned, I have my doubts. I got it at Home Depot. I'm going to look into those ILiving fans. They seem to be pretty popular. Unless there are others that you guys like.


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## Browse Deweb (Jan 16, 2021)

Is the enclosure approach a safety or noise thing? The reason I went with a Honda inverter was so that I wouldn't need to worry about noise. In fact, I can hear my two neighbors whole house Generacs over mine and they are over 300' away while mine sits just outside my den sliding doors. I keep the generator in the garage until it is needed, then I move it to the backyard and connect it to the natural gas line and the input box. If the weather is bad, I clip on a homemade canopy to keep the rain off. This setup pretty much removes any heat concern issues. I can chain up the generator if I need to try to prevent someone from taking it. I have read that the Honda's can be sensitive to running on very hot days, but we don't have that issue in NY. I don't see how an enclosure would help me, but we don't lose power very often.


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## drmerdp (Apr 10, 2018)

Bluwolf said:


> I was going to try the Rockwool on the walls. Mostly for the sound deadening. Even though I have 4 openings where noise gets out. I started with the intake and exhaust openings. Then added 2 openings, one each in the doors up high to try to bleed off more heat.
> 
> I had also considered an intake fan. I'm not sure if my 1320 CFM fan is really putting out 1320. I was thinking I would use the one I have for the intake and getting a bigger one for the exhaust side.
> 
> Will the foil faced fiberglass hold up in direct contact with the exhaust ducting? And what kind of CFM do you thing would be sufficient for the exhaust side?


Technically fiberglass insulation has a melting point of 1000 degrees Fahrenheit. So it can withstand the temps of engine exhaust which hovers around 600 degrees at its peak. A header wrap in conjunction with foil faced fiberglass can provide piece of mind and have substantial heat control.

I think you need a 20” exhaust fan minimum. CFM will vary a bit from brand of fan and it’s rated horsepower. I looked back at my invoice from 2020 when I bought my 20” exhaust fan and motorized intake. Prices have literally DOUBLED. Wow.

Here’s what I used. 








DURAFAN® 20" Select Speed Shutter Fan


This 20 inch Durafan Select Speed exhaust fan is economical and versatile. The totally enclosed motor comes complete with built in speed switches and a 9' cord.




www.qcsupply.com


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## Bluwolf (Nov 8, 2020)

Browse Deweb said:


> Is the enclosure approach a safety or noise thing? The reason I went with a Honda inverter was so that I wouldn't need to worry about noise. In fact, I can hear my two neighbors whole house Generacs over mine and they are over 300' away while mine sits just outside my den sliding doors. I keep the generator in the garage until it is needed, then I move it to the backyard and connect it to the natural gas line and the input box. If the weather is bad, I clip on a homemade canopy to keep the rain off. This setup pretty much removes any heat concern issues. I can chain up the generator if I need to try to prevent someone from taking it. I have read that the Honda's can be sensitive to running on very hot days, but we don't have that issue in NY. I don't see how an enclosure would help me, but we don't lose power very often.


Can't I have my cake and eat too? And at half the price while we're at it?  Safety and reliability is the most important. Noise reduction would be a nice bonus. Its also because I have no room in the garage for storage. I've never even had cars in the garage. It's filled with tools and machines. But the generator being pretty much ready to go, so that even my wife could do it in a pinch is a bonus.

We lost power 3 weeks after I finished the shed. In less than 10 minutes the house was lit up like a Christmas tree. The look on my wife's face was worth all the time and every penny I spent doing it. And we've been having more frequent power outages. Now I'm just trying to make the set up better. Security-wise the shed is behind a 6 foot privacy fence with a very large dog who prefers to be outside and doesn't like people in his yard. He still barks at the pool guy from inside the house after 8 years. If he knows you you're golden, if not, I really don't want to have to clean up the mess.


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## Bluwolf (Nov 8, 2020)

drmerdp said:


> Technically fiberglass insulation has a melting point of 1000 degrees Fahrenheit. So it can withstand the temps of engine exhaust which hovers around 600 degrees at its peak. A header wrap in conjunction with foil faced fiberglass can provide piece of mind and have substantial heat control.
> 
> I think you need a 20” exhaust fan minimum. CFM will vary a bit from brand of fan and it’s rated horsepower. I looked back at my invoice from 2020 when I bought my 20” exhaust fan and motorized intake. Prices have literally DOUBLED. Wow.
> 
> ...


Wow is right. Those fans aren't cheap. Maybe I could get by with a 16" fan if I put my fan on the intake side? And I will look into the fiberglass wrap.


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## drmerdp (Apr 10, 2018)

Bluwolf said:


> Wow is right. Those fans aren't cheap. Maybe I could get by with a 16" fan if I put my fan on the intake side? And I will look into the fiberglass wrap.


What do you have for an intake louvre? Maybe a fan on the intake as well as the exhaust. If ambient tamps get to high you can always just open the doors at least. Wireless thermometers to monitor things is a good idea.

On my old champion I installed a normally open temperature switch parallel with the low oil shutoff just incase enclosure temps got too high.


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## Bluwolf (Nov 8, 2020)

drmerdp said:


> What do you have for an intake louvre? Maybe a fan on the intake as well as the exhaust. If ambient tamps get to high you can always just open the doors at least. Wireless thermometers to monitor things is a good idea.
> 
> On my old champion I installed a normally open temperature switch parallel with the low oil shutoff just incase enclosure temps got too high.


I've got one of those indoor type vent covers. It has a custom screen to keep out critters and insects behind it. That's what I was thinking. I could take the (supposedly) 1320 CFM exhaust fan I have now and turn it around for the intake. Then get a better one for the exhaust side. I have critter screening in front of the exhaust fan also. As I've been driving myself nuts with this, I've been thinking I've been losing some air flow velocity with the screening too. But I don't really know if that's true. Pictures below of current set up.


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## drmerdp (Apr 10, 2018)

I did the same thing on my previous enclosure for the champion generator. It did boost airflow by adding a push fan to the intake. That may work for you, but I can’t say for sure it would be enough for your climate.


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## Bluwolf (Nov 8, 2020)

drmerdp said:


> I did the same thing on my previous enclosure for the champion generator. It did boost airflow by adding a push fan to the intake. That may work for you, but I can’t say for sure it would be enough for your climate.


I guess all I can do is try. But it certainly can't hurt.


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## iowagold (Jan 22, 2020)

Bluwolf said:


> I had actually considered one of those multi walled stove pipes. But holy crap! Those things are not cheap!


yea they are pricey in stainless..
you can build you own if you have a good cheap salvage yard close.
metal right now is up there and in high demand for the good stuff


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