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lylehartman · Oct 6, 2011, 02:06 PM

I need to calculate the load demand for our veterans' memorial building. We have one stand up freezer, three refrigerators, two stoves with ovens, one hood vent fan, lighting and one small exhaust fan. This is needed in order to purchase the correct generator. We are a designated site for the red cross emergency prepardness. Can some one give me the formula? Thanks

tkrussell · Oct 7, 2011, 02:42 AM

The formula is add up the total wattage of the devices that need to be powered by the generator. Each appliance, device, light fixture, draws power measured in amps or watts.

If you can provide a detailed list of loads and the watts or amps each needs, we can help from there.

ma0641 · Oct 7, 2011, 10:09 AM

We will need more info than you have provided. Are all these appliances 120 or are some 240VAC? Then, you need to look at the appliance plates to determine the Amperage and/or Wattage of the appliances. After that info is supplied we can help. Each appliance is different as to the wattage required, you can't just put in a "refrigerator". No microwave ovens? Lighting needs to be added. How big is the building? Total wattage demand is more than the items you listed. Who will be installing the generator and transfer switch
Wiring? You can't just plug into the generator.

lylehartman · Oct 7, 2011, 02:24 PM

All of the appliances are 120 volts. Hall lights are fluorescent, four bath lights are incadessant, (sp?). There is nothing in the building which is 240volts. I would need to go and count the lights, check the plates on the refrigerators and two over-the-door fly fans. These fans blow down and keep the flys out, we never have used them but that is what they said they were there for. There are two 40 watt outside bulbs over the doors. The generator will not be a standby. We will pull the main and plug in the generator. We will have to install an outdoor all weather 240 receptacle into which we would plug in the generator. We are a very small, mountain community. Thanks for your help.

tkrussell · Oct 8, 2011, 05:06 AM

Simply shutting off a Main Breaker and powering the system with a generator is illegal according to the National Electric Code and I am sure your electric utility.

If you can provide the name of your utility I should be able to find their requirements on line.

I understand you know you cannot send power back out into the grid, and that you promise to open the Main, however, safety involving electricity does not allow for promises.

One mistake of closing the Main while under generator power will send lethal power out onto the grid and can kill a lineman. If the utility detects power on a supposed dead line, they can trace the source of power to your building, cut you free from the grid, you will be the last to be re-connected, after they visit with the electrical inspector to insure your system is installed properly before re-connecting. If a death or injury is involved, criminal investigators will be visiting also.

You will need either a manual or automatic transfer switch, or a interlock kit on the Main Breaker.

Once you get back with a detailed inventory of lights, appliances, etc that need generator power, we can arrive at a total wattage to size the genset.

Miscellaneous items such as fans, etc, we can make some assumptions of loads.

lylehartman · Oct 8, 2011, 07:39 AM

PG&E is the electric company. Thanks, I see that we will have to install a transfer switch. I will take an inventory and send it by Monday. Thanks again.

lylehartman · Oct 10, 2011, 11:24 AM

I inventoried the hall. Everything is 120v, no 240. There are 23 double 40 watt flourscent fixtures; 2 "Air Door" with 5.1 amp motors, (used only one time in past four years); 1 ceiling fan, 5 blade household type; one exhaust fan for a 6' hood over the gas range; 1 ea 100 cup coffee maker; 1ea 60 cup coffee maker; 1 Roper-side by side refrigerator-household type; 1 Gibson refrigerator 5' tall no freezer in it; 1 whirlpool upright freezer 15.9 cu ft; 4 light bulb, two with 60 watt bulbs, two with 40 watt energy saving bulbs; 1 Frigidaire electric stove, 4 burner with oven, household type and 1 Whirlpool refrigerator with a top freezer, 17.1 cu ft. There are no industrial type pieces of equipment, all are standard household types. PG&E is our electricity provider. Any other questions, please let me know.

lylehartman · Oct 18, 2011, 08:09 AM

All of the appliances are 120 volts. Hall lights are fluorescent, four bath lights are incadessant, (sp?). There is nothing in the building which is 240volts. I would need to go and count the lights, check the plates on the refrigerators and two over-the-door fly fans. These fans blow down and keep the flys out, we never have used them but that is what they said they were there for. There are two 40 watt outside bulbs over the doors. The generator will not be a standby. We will pull the main and plug in the generator. We will have to install an outdoor all weather 240 receptacle into which we would plug in the generator. We are a very small, mountain community. Thanks for your help.