On Thu, 17 Mar 2005 11:35:36 -0600, Bud wrote:

Paul wrote:
Can someone refresh my memory as to why 240V electric baseboard heaters are
"more efficient" than 120V? In my application I am looking at install one
750W electric baseboard in a bathroom, on a dedicated 20A 120V circuit, but
the heating man strongly suggests I use a 240V model. Problem is the
breaker box is completely full, and I'd have to run a subpanel just for this
circuit if we go 240V.
You can hang more electric heaters on a 240V circuit. Some heaters are
also too high a wattage for a 120V circuit.



240 V. Heaters are more efficient in that there is less voltage drop
(=wasted power) in the line to the cb panel with the higher voltage.

Since the voltage is double, the ability of the 240 V. circuit has a
higher capacity to deliver more current for a given resistance than at
120 V. The power output is I squared x R for both. (R will be
specified at a certain value for 120 V. heaters and a different value
for 240 V. heaters - In general, they are designed with different
heating elements that are matched to the input voltage).

Although you can buy high wattage 120 V. heaters, the 240 volt
versions are generally going to be more robust, heat up the room
faster, and have a higher capacity (wattage).

A double-ganged 240 V. GFCI is expensive and generally not used in
these applications. Safety is provided by the regular grounding wire
of the heater. Here is an example of a two-pole GFCI that is used for
hot tubs:

http://www.sea.siemens.com/reselec/product/rzgfci.html

The hydronic electric heaters are similar to the oil-filled deLongi
portable units. They heat up a little bit slower, but the heat
delivered stays fairly constant as they continue to give off heat even
when the thermostat cycles off. Use this model if you prefer a
gentle heat delivered at a constant rate.

The purely radiant electric heaters (with the glowing red coils) stop
delivering heat as soon as the thermostat cycles off.

Beachcomber