I have a 1KW panel heater that I'd like to control with a remote
electronic thermostat. Thermostat switch contacts are rated 5A 250V
resistive and 3.5A 250V inductive. Should I consider the heater a
resistive or inductive load??

TIA

wrote in message
...

I have a 1KW panel heater that I'd like to control with a remote
electronic thermostat. Thermostat switch contacts are rated 5A 250V
resistive and 3.5A 250V inductive. Should I consider the heater a
resistive or inductive load??

TIA


Its a resistive load but I'd guess that a 5A switch is not enough.

Assuming 230 volts supply, the heater will draw 4 and a third amps

Thats a bit close for me.

I could and probably will be wrong

fray

In article ,
wrote:
I have a 1KW panel heater that I'd like to control with a remote
electronic thermostat. Thermostat switch contacts are rated 5A 250V
resistive and 3.5A 250V inductive. Should I consider the heater a
resistive or inductive load??

It's mainly resistive but like all heating elements and filament lights
will have a much lower cold resistance than the hot one, so will draw more
current than its working rating at switch on. Which I'd guess would be
dangerously close to the thermostat's maximum. You could measure the cold
resistance and work it out, though.

--
*Can atheists get insurance for acts of God? *

Dave Plowman London SW
To e-mail, change noise into sound.

In article ,
"Dave Plowman (News)" writes:
In article ,
wrote:
I have a 1KW panel heater that I'd like to control with a remote
electronic thermostat. Thermostat switch contacts are rated 5A 250V
resistive and 3.5A 250V inductive. Should I consider the heater a
resistive or inductive load??

It's mainly resistive but like all heating elements and filament lights
will have a much lower cold resistance than the hot one, so will draw more
current than its working rating at switch on. Which I'd guess would be
dangerously close to the thermostat's maximum. You could measure the cold
resistance and work it out, though.

Most heaters don't have any switch-on surge -- temperature
coefficient of Nichrome is pretty near zero (as compared with
tungsten anyway), and it's not normally heated through the
same temperature change either.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

Hi
Whew whatever happened to manufacturers putting 5A dc 3.5A ac on their
switches.
As for your heater its impedence depends on the manufacturing process some
panel heaters have a punched strip (looks like a row of hairgrips on a
plate) these have a lower impedence compared to the coil wound fan panel
heaters.
In any case i would recommend a 10 or 13A rated stat due to the start surge
of the heater and the back EMF at switch off under load.

HTH

CJ

In article ,
says...
*Can atheists get insurance for acts of God? *

Just because we atheists don't believe in him doesn't mean he doesn't
exist.
--
Skipweasel.
Never knowingly understood.

In article , cj
writes
Hi
Whew whatever happened to manufacturers putting 5A dc 3.5A ac on their
switches.
As for your heater its impedence depends on the manufacturing process some
panel heaters have a punched strip (looks like a row of hairgrips on a
plate) these have a lower impedence compared to the coil wound fan panel
heaters.
In any case i would recommend a 10 or 13A rated stat due to the start surge
of the heater and the back EMF at switch off under load.

As Andy G points out there is no switch on surge and a quick fag packet
calculation suggests the inductance of a 300 turn coiled, air cored
element would be of the order of 500 microhenries so there's not really
enough energy flying about to call up the inductive rating of the stat.

It's nice to derate contacts by quite a bit to extend life but there's
really no need to do overboard. 5A vs the nominal 4.35A is a little less
margin than I'd like but this sounds like a Horstmann/Tower programmable
stat so I wouldn't be expecting 20 years out of it in any case.
--
fred
Plusnet - I hope you like vanilla

In article ,
fred writes:
It's nice to derate contacts by quite a bit to extend life but there's
really no need to do overboard. 5A vs the nominal 4.35A is a little less
margin than I'd like but this sounds like a Horstmann/Tower programmable
stat so I wouldn't be expecting 20 years out of it in any case.

Over 20 years ago, I bought a bathroom fan heater (Dimplex).
Although it was set down to just 1kW (could be set to 1kW
or 2kW at installation time), the integral pull cord switch
burned out in about 3 months. I cleaned up the switch and
fitted a small contactor into a cavity inside the heater
which was for a shaver isolating transformer in a different
heater model, with the switch operating just the contactor.
It's been running fine ever since. Apart from the inadequate
switch, it was very well built.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

In article , Andrew Gabriel
writes
In article ,
fred writes:
It's nice to derate contacts by quite a bit to extend life but there's
really no need to do overboard. 5A vs the nominal 4.35A is a little less
margin than I'd like but this sounds like a Horstmann/Tower programmable
stat so I wouldn't be expecting 20 years out of it in any case.

Over 20 years ago, I bought a bathroom fan heater (Dimplex).
Although it was set down to just 1kW (could be set to 1kW
or 2kW at installation time), the integral pull cord switch
burned out in about 3 months. I cleaned up the switch and
fitted a small contactor into a cavity inside the heater
which was for a shaver isolating transformer in a different
heater model, with the switch operating just the contactor.
It's been running fine ever since. Apart from the inadequate
switch, it was very well built.

Fan motor - now that's a candidate for both inrush and back emf.
--
fred
Plusnet - I hope you like vanilla