INADEQUATE POWER SERVICE

A.  INADEQUATE POWER SERVICE:
Inadequate power service means that the service panel and entrance wiring are too small, in terms of amperage capacity, for the amount of power the house needs. A rough estimate of a house’s power need can be computed by adding the major appliance loads, the minor appliance loads, the general lighting loads, and multiplying by 80%.  For most houses, 30 amperes for minor appliances and 30 amperes for general lighting, figured at 3 to 4 watts per sq. ft. of floor space, will suffice.

The amperage drawn by the major appliances can generally be approximated. Average sized air conditioners, dryers, and water heaters draw about 20 amperes apiece. Electric ranges draw about 40 amperes and electric forced air heat or heat pumps 60 amps and more. Add about 7 to 10 amperes per electric baseboard heater or window air conditioner. For more precise calculations simply divide the appliance wattage rating by the operating voltage to compute the amperage of the appliance.  The wattage is usually stated on the name plate data.  This demonstrates that houses without any major electric appliances can often get by on approximately 60 amperes of service, which was the typical installation from the 1920s to about 1950.  Those using gas for cooking, heating, and domestic hot water can have an electric dryer and central air conditioning and still get by on 100 amps of service.  Those with a full load of major appliances but utilize gas for space and water heating should have 150 amps of service while those homes with all electric appliances should have approximately 200 amps of service.

WARNING:  Older houses that have had electrical appliances or room enclosures added without upgrading their service panels often have INADEQUATE POWER SERVICE.

A typical schematic layout for an all electric house with a 200-ampere service shows the entrance cable (Fig. A1, Item A), electric meter (Fig. A1, Item B), main service panel (Fig. A1, Item C), branch circuits for the heat pump compressor (Fig. A1, Item D), supplemental heat coils (Fig. A1, Item E), major appliances (Fig. A1, Item F), kitchen receptacle, (Fig. A1, Item G), and general lighting/receptacles (Fig. A1, Item H).

Fig. A1

Another way of figuring the power needs of a house is to add up all the wattage in the house and then use the simplified electrical code computation. This figures that power is needed at 100% for the first 10KW and at 40% for all power after that.

WHAT TO:  HOW TO:
A “Heavy Up” is called for when a house has inadequate power service.  This means, that the cable from the street into the house, including the meter base and the inside distribution panel, are replaced with thicker ones.  In many jurisdictions the electric utility company handles installation and pays for the wiring from the street to the electric meter.  In other jurisdictions, the electric utility company may only handle installing the wiring to the house exterior and require the house service cable from the electric meter to their electric service to be provided by the homeowner.  In almost all cases, the homeowner is responsible for the wiring from the electric meter onward. A heavy up installation requires coordination with the electric utility company as well as an electrical permit from the local governing jurisdiction.

There is wisdom in spending a little extra money and purchasing a high quality distribution panel.  The quality of the connections within the panel is the primary consideration.  Beyond that, make sure there will be enough expansion room for any additional circuits needed in the foreseeable future.

REFERENCE: E1, E2, E3, E4, E5, E17