ReplyAre you talking about the combustion exhaust (smoke) or heat exhaust (from the radiator)
The combustion exhaust should not have any fans. It should be a sealed, insulated piping system the goes straight to the outdoors.
Regular Guest
Exhaust fan capacity for generator
Hi all,
I work in dubai as HVAC designer. Can anyone please help me in sizing an exhaust fan for a generator with an exhuast of 118 m3/min. However the exhaust gas will have its own velocity to carry itself through the duct, but to avoid any back drop I have decided to provide a fan which wil boost up the flow.
Exhaust outlet of generator is of 200mm dia, & it shall be connected to a duct of 300mm dia as we proposed.
But my query is, how much shall be the capacity of exhaust fan?
I believe it shall not be equal to the exhaust flow (which is too high) but much lesser than it as the fan is just to assist in the gas flow out of the room.
I have roughly selected a fan of 470m3/hr.
Please help me know the flow & esp the fan shall have?
Professional Member
Are you talking about the combustion exhaust (smoke) or heat exhaust (from the radiator)
The combustion exhaust should not have any fans. It should be a sealed, insulated piping system the goes straight to the outdoors.
Regular Guest
Thanx a lot mr.craig for your valuable time and response.Originally Posted by craig1
You caught it ryt. Its combustion exhaust. As i am from construction field and so doesnt have much knowledge about this subject.
Can you please give me some details about what shall be done. And how it has to be carried out. I mean, is the duct/pipe size that was selected is ok to carry away the air.
And we will be running a straight duct of GI sheet above false ceiling through which the droplets will be connected to the outlet of the generator.
Turbo exhaust temp of generator is specified to be 550C. Do we have to use a fire rated duct for the process or the temp will fall down more until it reach outlet?
Should i remove the fan and just directly run the duct outside the room into the atmosphere?
Please help as this issue shall be resolved soon.
Thanx for your concern again !!
Professional Member*
Sounds dangerous.
Is this generator room or attic space anyway joined with occupied areas?
The sheer temp is way higher than we deal with typically. Ive seen exhaust glow red before. And you mention its turbo diesel?
Professional Member*
A fan wont live lng in that app.
Abandon that idea.
Although you will need some serious air moving to keep coolant from overheat no???
Regular Guest
The temperature mentioned is actually the turbo exhaust temp of diesel generator.
So i believe that temp might be within the generator during its operation. But the exhaust smoke coming out may not be so hot (my assumption)
Its just a normal training room with a generator where its operation will be shown to the trainees.
Professional Member*
I would start with the gen mfr for all the exhaust venting and let them spec it out. They deal with it, puts you out of the loop.If its just venting the room the gen is in they should be able to help out there also. If this is a new job I would write the spec,s into the job, that all this is covered by them,if they want to sell you a gen.
Regular Guest
I was desiring that i can do this on my own with the help of folks on this page.
And if sent to mnfrer it wil take longer time to get a feedback.
This was not present during tender stage of project. The project is almost finished and during handing over the client requested for this. So, u may understand the rest..!
Regular Guest
I wish mr.craig come up with a solution for my query !!
Professional Member*
+1 anytime I've seen this done its vented outdoors directly. Unless its a really long run, you should be able to size a flexible ss pipe designed for this application.
This can basically be treated the same add a oil boiler....except ours a positive displacement pump so you need a heavier duct/pipe. A diesel vs. tolerate some backpressure. Its common to use those small flappers on to of the stacks to keep rain out.
Sent from my DROID RAZR using Tapatalk 2
Regular Guest
Ya its not a long run. Maximum 13m of run. So do you think the fan is not necessary to be installed?
What about the selection of duct material etc?
Professional Member*
The mfg should have all this info in the install doc,s or be able to provide on short notice.There is a lot of knowledge on this site but asking to design a fix for this problem,this late in the job, should be on the people who sold and installed said gen. Or maybe do not buy the same brand again.
Professional Member*
Hmmm...
About 13 meters (around 40 ft US) is a fair run for a flue (what we call an exhaust pipe from a stationary fuel burning appliance). Flue engineering is VERY complicated... more going on than meets the common thought process.
I would definitely contact the manufacturer on this... and while you are at it; do you have enough MUA; that is 'make up air'? MUA is the air which MUST come in to displace the exhaust going out. This is a zero sum game, if you do not have enough air coming in... well your diesel generator will choke and quit. Another thing to verify with the manufacturer is BTU's of heat you need to exhaust to cool the engine.
I am not being difficult; just trying to get you to realize you are asking for trouble if you do not think out these things and find solutions that work.
Good luck!
GA-HVAC-Tech
Your comfort, Your way, Everyday!
GA's basic rules of home heating and AC upgrades:
*Installation is more important than the brand of equipment
*The duct system keeps the house comfortable; the equipment only heats and cools (and dehumidifies)
*The value of comfort, over the long term; leave economic choices behind!
Choose your contractor wisely!
Professional Member
Sorry, I don't really know anything about the construction of exhaust systems. My original comments were just based on what I've seen installed over the years.I wish mr.craig come up with a solution for my query !!
Professional Member
I do not know how big your engine is but here is a 855 cummins on a 300kw Onan genset. Think it is 6" off the turbo and bumps up to an 8". Don't think you can run with these measurement I don't know what you have. Talk to manufacturer or dealer. The muffler is mounted on the ceiling and exits out the side of building. It is all heavily fiberglass insulated. Since this generator is on an exterior wall you can see the fresh air intake and radiator are right there close. Sometimes fresh air must be piped to the intake and sometimes radiators are mounted remotely outside. Sizing of the exhust is important so you do not harm your engine. Ring those phones and read those books!
Regular Guest
Thanx heaps for this helpful response.
I do not know how big your engine is but here is a 855 cummins on a 300kw Onan genset. Think it is 6" off the turbo and bumps up to an 8". Don't think you can run with these measurement I don't know what you have. Talk to manufacturer or dealer. The muffler is mounted on the ceiling and exits out the side of building. It is all heavily fiberglass insulated. Since this generator is on an exterior wall you can see the fresh air intake and radiator are right there close. Sometimes fresh air must be piped to the intake and sometimes radiators are mounted remotely outside. Sizing of the exhust is important so you do not harm your engine. Ring those phones and read those books!
The outlet size of gen is 8" and we will use 12" pipe connected to it. And the pipe will directly run outside the room above false ceiling to discharge the exhaust air to atmosphere.
Tha gen is perhaps 500kw. I just want to confirm if we need any fan to pull exhaust or the exhaust will itself carry out. As the exhaust is 118cu.m/min which is high and pipe size being small, the velocity will be enough to clear 13m distance.
Please comment.
Professional Member
What engine? I am assuming it is turbocharged. Make sure to have vibration isolation like in the picture. Well insulated pipe will help the exhaust scavenge also. You need to make some calls about the exhaust sizing. Also the mufflers used for this if you are using one are not something like on a tractor.
Professional Member
What if pictured is probably 40' worth of pipe and the turbocharger on this one does well enough to push the exhaust. You need to talk to your dealer or the engines tech support. DO NOT TAKE MY WORD for it. I am just trying to show you how typically the exhaust is ran. That is a high dollar machine and the plumbing is not cheap either. Do it right the first time so you don't royally screw up.
Regular Guest
Thanx again. Yeah i will however try consulting the technical person from the perkins team.
Its actually a perkins diesel generator.
Can you just say about the pipe material and specs to be considered as per your assumtion and experience. Just for an idea. (will however confirm with the mnfrer.)
Professional Member
I am not the guy to size it for you. I do not have enough experience in that department. I turn wrenches on big diesels as a hobby. Just trying to help you out since the facility I was at had a typical indoor setup that I could take pictures of. I would like to also learn about this and further assist you. Any more info on your generator you could give me would be helpful for me to help you. I honestly have never heard of an additional fan in this application. Proper sizing and the turbo should blow it right out I would think.
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