# [SML] sparky math problem

Jerry Durand jdurand at durandinterstellar.com
Wed Aug 12 07:25:17 UTC 2020

```In our new house the electrician is wiring up an electric heater* in our greenhouse for extra cold nights.  The head scratcher is this:

1) heater mains power = 380v, 3ф, 5 wire wye
(We've got 3ф in three different rooms!)

2) heater has 3 visible heating elements, as expected.

3) power switch has OFF, FAN, 2.5kW, 5kW

How, with the above combination do you get exactly half power?  I presume the heating elements are identical.  Could they possibly drop diodes in series with all three phases?

Of course I'm still in California so can't actually see the heater in person before we get there...whenever the border opens to us Americans.

* it was originally a gas heater, then the building code got stricter and nixed that.  So then it was tied into the house hot water system.  THAT just got nixed over the weekend so it was either electric or a wood stove and I'm not into tending that all night on cold nights.  Our house fireplace is at least designed for heat storage, circulation chambers built in and a lot of rock.  Heat it up during the day and it stays hot all night.

Came out a "little" fancier than we had imagined, it's what happens when you hire an artist.  Picture of it with the creator (and his gift of scotch).
https://durandinterstellar.com/photos/Our_New_Home/2020-08-07_Peter_Fireplace.jpeg

⁣---
Jerry Durand
www.DurandInterstellar.com & www.DurandInterstellar.ru​
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