Generators - In electrical estimates, your take-off for generators should list the following:

1) KW size of generator, type of housing, indoor, outdoor, sound attenuated.

2) Seismic anchorage, isolation spring mounts.

3) Accessory items that require additional material and labor to connect. For example: muffler, battery charger, engine block heater or load bank.

4) Exhaust pipe, rain cap and exhaust pipe hangers. These may be furnished and installed by Pipe Fitter or by Electrical Contractor. You should verify this.

5) Load output circuit breakers and control panel. These items are usually factory mounted but will require field wire terminations.

6) Remote annunciators. These will require material and labor to mount and connect.

7) Fuel tanks and fuel for testing and fuel to fill the tank when testing is complete. Usually the Electrical Contractor is required to furnish the fuel necessary for testing.

Well developed electrical estimating software will either prompt you for this information or already have generator specs stored in its database.

Tips on Fuel Tanks - On fuel tanks, skid or belly mount tanks will usually be factory mounted and will be included in labor units for basic self contained generator set. Separate fuel or “day” tanks will require additional labor and material to set in place and connect. Fuel piping from remote tanks to generator may be by Plumber or Electrical Contractor. You should verify this item. The main fuel tank fill up may be by Owner or Contractor. You should verify this. This is a big cost item!

Determine the weight of generator with fuel tank, housing and other factory attached items. Make allowance in your direct job expenses for necessary cranes, forklifts and other equipment. You may want to get a quote from an equipment mover for your electrical estimates if the equipment is exceptionally large or heavy.


Automatic Transfer Switches (ATS) - Take off the ATS by amp and voltage size. Take off mounting equipment and supports and list any special features such as isolated by pass. This will basically double the size and price of the switch. Also, list any other features or options such as engine starting controls, weather proof enclosure, remote ATS status annunciator, etc.


UPS Systems (Uninterruptible Power Supply) - A complete list should include:

1) Control cabinet with connections to normal power and remote annunciators.

2) External or internal maintenance bypass switch (This is an additional labor item as the control cabinet will be larger and heavier).

3) Battery cabinet for labor to install the cabinet and the batteries. You should determine the number of battery cabinets and number of batteries.

4) Accessories such as battery containment basin, eyewash station, remote annunciators, etc. for additional material and labor.

PDU Systems (Power Distribution Unit) - These are usually associated with data centers or computer rooms. A complete list should include:

1) Weight and accessories for labor calculation. Some PDU’s have transformers built in which are factory wired but will contribute to the weight. A heavier unit will increase the amount of labor needed to install the PDU.

2) Number of output circuits in the PDU panel for wire termination labor.

3) The ampacity, type of receptacle, conduit and wire size and length of branch circuit under floor whips or overhead data equipment connections.

Tip on PDUs - Most PDUs installed on raised computer floors will require an under floor equipment support unit. These are not always included in the PDU pricing. Get a quote on this item.

Ground Grids - Take off grounding grids for raised computer floors on electrical estimates. Raised computer floors require additional electrical work and since we are discussing PDU’s and UPS’s this is a good time to consider it.

In electrical estimates, raised computer floors often require a grounding grid under the floor connecting all or some of the floor supports together. This is usually a #6 copper connected to floor supports with ground clamps designed for this purpose. Usually, there is a ground buss assembly on the wall below the floor. It would have with a (larger) wire in the conduit back to the main building ground. The labor units for the wire under floor should be different than wire installed in conduit. It is more difficult to work the copper wire around under the floor with supports at 24” on center than pulling in a conduit.

Raised computer floors usually have a fire extinguishing system with smoke detectors and a control panel. There might also be a water leak or moisture sensing system. These systems are often furnished and installed by others but you should verify any electrical connection requirements that might be in your scope of work.


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