# Can a single phase supply from a 3 phase outlet result in excessive power meter readings?

Here in Turkey typical residence supply is single phase at 230V.

Years ago a friend's father built a residence and arranged for a three phase supply as he felt that this would provide a more stable supply. Not normal I know, but he was a fanatic about 3 phase supply apparently. There was no large motor usage or such but it seems that he did install a 3 phase water heater.

Power for the water heater was supplied by a dedicated 3 phase breaker panel. In April the 3 phase heater was replaced with a single phase heater from the same supplier. Since then the power meter has been recording approximately triple the consumption that was typically seen before the replacement. The electrician doing the connection removed the panel and wired the water heater directly using just one 'hot' wire and a neutral, I guess.

All the circuit breakers in the house panel were turned off and consumption can still be observed. The meter was recording the equivalent of 6 kW being used over an hour. Only when the 3 phase circuit breaker was turned off directly above the meter did this consumption stop.

Is it possible that the connection made for the new single phase water heater was done incorrectly resulting in a wrong consumption reading by the meter?

• Are you sure that the heater rating is the same? Sounds like a 6KW unit has been installed. Commented Oct 24, 2022 at 9:51

There could be two possibilities:

1. A 230 V, 6 kW heater has been installed instead of one rated 230 V, 2 kW.

2. The new 230 V, 2 kW heater has been connected between two lines (415 V) instead of between line and neutral (230 V).

The resistance of a 230 V, 2 kW heater = 230 * 230 / 2 / 1000 = 26.45 Ω

The wattage of the same heater connected across a 415 V supply = 415 * 415 / 26.45 / 1000 = 6.5 kW.

The second possibility appears to be remote, considering the non-failure of the new heater.

There could also be the remote possibility of excellent heat conduction from the heater element to the water to prevent that.

• Thanks for the answers. I was told the new heater rating is the same as the old. Commented Oct 25, 2022 at 7:48