Determining Existing Loads

Here’s some useful information that can be considered for determining existing loads for a single phase service smaller that 100 amps.

The calculation of a feeder or service load for existing installations is permitted to use actual maximum demand to determine the existing load under all of the following conditions:

(1) The maximum demand data is available for a 1-year period.

Exception: If the maximum demand data for a 1-year period is not available, the calculated load is permitted to be based on the maximum demand (measure of average power demand over a 15-minute period) continuously recorded over a minimum 30-day period using a recording ammeter or power meter connected to the highest loaded phase of the feeder or service, based on the initial loading at the start of the recording. The recording is required to reflect the maximum demand of the feeder or service by being taken when the building or space is occupied and is required to include by measurement or calculation the larger of the heating or cooling equipment load, and other loads that may be periodic in nature due to seasonal or similar conditions.

(2) The maximum demand at 125 percent plus the new load does not exceed the ampacity of the feeder or rating of the service.

(3) The feeder has overcurrent protection in accordance with 240.4, and the service has overload protection in accordance with 230.90.

Why bother? Whatever the existing loads are, a home inspection report on a home with less than 100 amp service is going to recommend an upgrade, anyway.

There are many existing services still in use that are 120/240 V, 60 amps that may not be in need of an increase in size, this thread was meant to be considered and discussed as a could be an “or” option.

If the local sales, bank, VA, city, or insurance rules requires the upgrade, that would be the main factor.

I have friends nearby who are living in a home protected with fuses and a range and main setup that is in great shape.

Naturally, if they add any major loads, then that service could become overloaded and require a change.

I talked with a NY Home Inspector today at length, and he too agreed with the existing 60 size, with certain reservations as described above.

How would a home inspector know what the demand is GOING to be on a 60 amp service before his client inhabits the building?

The existing equipment here in this publication give some guidance for adequacy.

The Home Inspector could base his or her comments on the following part of this CDC publication.

"Residential Wiring Adequacy
**
**The use of electricity in the home has risen sharply since the 1930s. Many homeowners have failed to repair or improve their wiring to keep it safe and up to date. In the 1970s, the code recommended that the main distribution panel in a home be a minimum of 100 amps. Because the number of appliances that use electricity has continued to grow, so has the size of recommended panels. For a normal house, a 200-amp panel is recommended. The panel must be of the breaker type with a main breaker for the entire system (Figure 11.4). Fuse boxes are not recommended for new housing.

This type of service is sufficient in a one-family house or dwelling unit to provide safe and adequate electricity for the lighting, refrigerator, iron, and an 8,000-watt cooking range, plus other appliances requiring a total of up to 10,000 watts.

Some older homes have a 60-ampere, three-wire service (Figure 11.10). It is recommended that these homes be rewired for at least the minimum of 200 amperes recommended in the code. The 60-amp service is safely capable of supplying current for only lighting and portable appliances, such as a cooking range and regular dryer (4,500 watts), or an electric hot water heater (2,500 watts), and cannot handle additional major appliances. Other older homes today have only a 30-ampere, 115-volt, two-wire service (Figure 11.11). This system can safely handle only a limited amount of lighting, a few minor appliances, and no major appliances. Therefore, this size service is substandard in terms of the modern household’s needs for electricity.

Furthermore, it is a fire hazard and a threat to the safety of the home and the occupants."

I think that’s what I said, originally.:roll:

True, but this is where I am at with my original post:

*“The 60-amp service is safely capable of supplying current for only lighting and portable appliances, such as a cooking range and regular dryer (4,500 watts), or an electric hot water heater (2,500 watts), and cannot handle additional major appliances.” :slight_smile: *

Electrical Inspectors, such as yourself, are focused on safety and there is nothing unsafe about a 60 amp service, by itself. As long as I remember not to operate all of the burners on my stove at the same time I do laundry, I will probably not have to replace a fuse.

Home inspectors, however, are tasked to describe the conditions of the systems of the home and convenience is a factor. Current building standards require a minimum of 100 amp service and a 60 amp service, no matter how safe it is currently carrying its present load, would probably be described as inadequate.

This is another case that points out the difference between a home inspector and a code inspector. You are evaluating a house for a new buyer, not saying it is inadequate for the current resident. My neighbor gets along just fine with 60a but she is an old lady living alone who has a $50 electric bill. She bought the house from another little old lady. If a family moved in they would be blowing fuses all the time.

Agreed, but let’s look at these two links::

http://www.carsondunlop.com/OBS/60amp.htm

http://www.maine.gov/pfr/insurance/cancellation/archives/2003/2003-13680.htm

Minimum Minnesota VA/FHA

**Electrical Service Requirements
**
By Douglas Pencille
[Minimum Service Requirements](http://www.dspinspections.com/minimum.htm#Minimum Service Requirements) | [Adding Loads To A 60 Amp. Service](http://www.dspinspections.com/minimum.htm#Adding Loads To An Existing 60)

[Requirements For Electrical Outlets/Fixtures](http://www.dspinspections.com/minimum.htm#Electrical Outlet Requirements)

Just not something required by the HI to do. If they determine the house is provided with a 60A service…they would venture into dangerous waters to say the 60A service is not adequate…while they could say in the future if you added lets say modern appliances ( figuring the dwelling was older and letting the buyer know the costs they may incure to modernize it ) they sure inform them about the 200A service recommendation…heck 100A might be fine.

Just remember HI’s deal in safety…not load calcuations as heck i know enough Electricians who dont know how to do the load calculations much less expect HI’s to deal with it.