Indoor Generator Question.

[horrorsix]

I have a big commercial client that wants a 3Ph generator for their IT room installed inside the building. On top of the electrical room. Physically there is room. My distributor says that's not recommended for obvious reasons.

Is there a generator manufacture that makes a generator designed for indoor use or a special exhaust system and additional CO2 systems required or is this just not done?

 

[iwire]

I have installed many inside and see inside generators often.

About the only difference I can think of is having a exhaust duct work fabricated from outdoors to the radiator and a supply air vent of equal size allowing air into the room. Typically these vents will have motorized dampers that need to be tied into the generator so they open anytime the generator is running. You may need to make a generator room to contain the cold air (and noise) that is brought in when the generator runs ... if you have fire sprinklers in that space you may need a dry system.

Also you will need an exhaust thimble which is just a device that allows running the hot exhaust pipe out through the roof without burning the building down.

 

[hbiss]

It could be that the generator you have chosen is not suitable for indoor installation. As iwire says, it's done all the time. I would recommend that you have an engineer provide the design. There are many details that have to be considered. Ventilation, make up air, noise and vibration, fire suppression, is the floor capable of handling the weight, fuel storage etc. Other trades will have to be involved obviously.

-Hal

 

[iwire]

I would recommend that you have an engineer provide the design. There are many details that have to be considered.

Best advice.

 

[just the cowboy]

Propane or natural gas

Propane or natural gas

Any of the ones inside that I have seen are LP or natural gas. Most are larger size with a 4 or 6 cyclinder car type engine and the exhaust run outside.

 

[fmtjfw]

Any of the ones inside that I have seen are LP or natural gas. Most are larger size with a 4 or 6 cyclinder car type engine and the exhaust run outside.

Also lots of really big Diesel-fueled ones

 

[ron]

Also lots of really big Diesel-fueled ones

Gens of many sizes are perfectly fine to be installed indoors, if done properly. I have personally been involved with (6) 3250kW's down to (1) 200kW

 

[zbang]

If the generator will supply a UPS, existing or new, check with both UPS and generator suppliers for compatibility. For instance, you may need a crystal-sync governor or you may need to oversize the generator. It depends.

Definitely something that should be properly engineered although the generator company may be able to do this for you.

 

[hbiss]

Very good point. I have heard of instances where UPSs don't play nice with generators.

-Hal

 

[qcroanoke]

Very good point. I have heard of instances where UPSs don't play nice with generators.

-Hal

Not only have I heard of it I've seen it.
We have had to add resistive loads to the ups to make the generator like it and be very aware that many UPS mfgrs. require a much larger genset than required. I've heard of 1 and a half times larger than required.
You really should get engineering involved in this.

 

[horrorsix]

Thank you. I will advise an engineer.

 

[Jraef]

By the way, it's not just the exhaust...

I visited one site with an LP generator where they ran exhaust pipes outside through the roof and had the radiator mounted outside, because they didn't want to have to deal with bringing in outside air to the clean building (a data center). When they tested the generator, everyone got trapped in the building because the combustion air intake to the generator pulled a vacuum in the building and after about 5 minutes, the doors wouldn't open. Oops...

 

[zbang]

Not only have I heard of it I've seen it.

It was kind of fun to watch the throttle whacking back and forth between full open and full closed, but only fun for maybe 10 seconds.

 

[qcroanoke]

It was kind of fun to watch the throttle whacking back and forth between full open and full closed, but only fun for maybe 10 seconds.

Yeah, especially when everyone was looking at me and saying why is it doing that??

 

[ceb58]

Not only have I heard of it I've seen it.
We have had to add resistive loads to the ups to make the generator like it and be very aware that many UPS mfgrs. require a much larger genset than required. I've heard of 1 and a half times larger than required.
You really should get engineering involved in this.

The 1 1/2 larger is the rule of thumb. We run, for the most part, 40 Kw generators with 18Kw UPS's. Just be aware that if the UPS doesn't play nice with the generator, the generator people will blame the UPS. The UPS people will blame the generator. Just have to weed out the possibilities.

 

[JoeStillman]

You must not rely on your generator sales team to help with this. It's outside of their expertise, even though all of them supply indoor generators.

For indoor installations, you need mechanical engineering. The exhaust is important, yes, but you also have to have adequate air flow over the radiator. Its also a good idea to have an exhaust fan on a thermostat that runs to cool the engine down after shutdown. Its all about the heat transfer.

Wire the intake and exhaust dampers so they open on power failure. That way, the engine fan won't cause too much pressure for the dampers to operate on startup.

For the engine exhaust, you will need to know the maximum back-pressure the engine can tolerate. You will also have to take care of the fire-stopping around the exhaust pipe. It gets really really hot.

 

[qcroanoke]

Wire the intake and exhaust dampers so they open on power failure. That way, the engine fan won't cause too much pressure for the dampers to operate on startup.

Absolutely! Most exhaust Louvers are no match for a generators fan.

 

[topgone]

Absolutely! Most exhaust Louvers are no match for a generators fan.

On bigger units, it is a built-in control logic to keep the engine running (even when the breakers are off) to allow for the engine block to cool down to desired temperature. Natural circulation of the cooling water will then take over after engine stop.