Generator on roof? What kind of base?

[electricblue]

I have to put a small 22kw gen on a roof. I've never done this. What kind of base do I need?

 

[John120/240]

One that will carry the load. What do the generator instructions say about roof mounting ? Any input from your architect or structural engineer ?

 

[mgookin]

I have to put a small 22kw gen on a roof. I've never done this. What kind of base do I need?

On first view it seems you need a PE but let's see what we can do for you and your client first. Please describe the building and the roof structurally. And how high is this?

You're pretty much doing what a HVAC contractor does with a package unit or chiller, and he needs an engineer.

 

[GoldDigger]

On first view it seems you need a PE but let's see what we can do for you and your client first. Please describe the building and the roof structurally. And how high is this?

You're pretty much doing what a HVAC contractor does with a package unit or chiller, and he needs an engineer.

In addition to loading, I would thoroughly check out vibration isolation. Most generators are designed to be mounted on concrete floors or separate pads, and putting one on a roof might well require additional vibration isolators, not just a flexible raceway section.
Chillers and air handlers which are routinely mounted on roof surfaces will have engineered vibration isolation either as a standard feature or as an option.

 

[rav555]

Base isn't your only consideration.

Base isn't your only consideration.

I have to put a small 22kw gen on a roof. I've never done this. What kind of base do I need?

You should also design containment for when you develop a fuel, lube oil or coolant leak. It would not do to cover your structure in flammable petroleum products or anti-freeze. Vibration is also going to be a huge issue but someone else already covered that.

I did install a generator in the second floor of a commercial building but that was on a concrete floor and it also had containment curbs cast in place as well as a means to drain any spilled liquids to an appropriate reservoir outside of the structure. Stored flammable liquids on your roof may also be an issue. You may want to consider a fuel pump from the ground level.

 

[n1ist]

Careful with fuel pumps at ground level; there was a lot of problems during Sandy with damaged or flooded fuel pumps making it very difficult to refuel rooftop tanks.

/mike

 

[John120/240]

For roof mounted units I would choose a natural gas supply one. Who wants to carry a five gallon can of diesel or gasoline through their building ?

 

[petersonra]

such a simple question that led to so many less simple issues.

 

[WENTY]

generator on roof? what kind of base?

generator on roof? what kind of base?

You may also want to consider fire separation distances from combustibles

 

[SmithBuilt]

I called a structural engineer to look at the ceiling support. He drew up plans to support the extra weight. It required welding extra supports to the bar joists. Four posts that would go thru the roofing to a frame to fit the gen base. My welder had made up the frame and the project got canceled.

I wondered how much noise and vibration there would have been.

 

[GoldDigger]

I called a structural engineer to look at the ceiling support. He drew up plans to support the extra weight. It required welding extra supports to the bar joists. Four posts that would go thru the roofing to a frame to fit the gen base. My welder had made up the frame and the project got canceled.

I wondered how much noise and vibration there would have been.

IMHO, without adding vibration isolators to the standard generator assembly it would have been pretty bad. But that may vary from manufacturer to manufacturer and model to model.

 

[iwire]

We put them on roofs, in basements, on the second floor pretty much everywhere.

On roofs in almost all cases there will be structural steel added by others for us to place the generators onto.

I do not recall ever seeing any additional vibration mountings. The ones we locate inside on upper levels can be heard through the floor. These are usually 6" cement decks with steel deck pans.