Switching AC loads - induction loads
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--- In basicstamps@yahoogroups.com, "nuclearspin2000"
<nuclearspin2000@y...> wrote:
> Specifically, what I want to do is automatically switch a 5400 BTU
> window air conditioner (120VAC) on/off during the summer which
> doesn't already have this capability. The nameplate specifies 5.5A,
> although it also says to use a 15A time delay fuse or circuit
breaker
> but I'm assuming the 5.5A rating is the continuous steady state
> current rating. I've already worked out the finer electronics
points
> to make it work, now I just have to switch the power safely and
> reliably either using triacs or power relays/optos with switching
> transistors for relay coils if used. The finished unit will be in
its
> own enclosure BTW for obvious safety reasons. I know relays can get
> warm (dissipate pwr) but is a heatsink necessary as long as you
don't
> overload the relay beyond it's rated specs? Thanks.
>
> -Dave
The problem is that motors are induction loads and you need to
address them differently than a lightbulb.
Make sure the device has a rating for inductive loads and don't
exceed that.
Also, the Air Conditioner will have a high starting amperage as the
load is a compressor and needs the high powre to start the
compressor, more than the motor.
Also, after it shuts off, the gasses need time to equalize before it
can be started again. 2-3 minutes should work. That is not an
option, it is a requirement. You are not going to get the motor to
start immeadiatly after a shut-off, period.
The unit probably has an internal sensor to handle the re-start so if
you have too short of a time, you'll know it.
For the cost, buy two units and list all the parts inside for when
something fries.
My exoperiance with X-10 has been that you get years of life, but
life is only years, they will self destruct. For the price, they are
really cheap control!
Dave
<nuclearspin2000@y...> wrote:
> Specifically, what I want to do is automatically switch a 5400 BTU
> window air conditioner (120VAC) on/off during the summer which
> doesn't already have this capability. The nameplate specifies 5.5A,
> although it also says to use a 15A time delay fuse or circuit
breaker
> but I'm assuming the 5.5A rating is the continuous steady state
> current rating. I've already worked out the finer electronics
points
> to make it work, now I just have to switch the power safely and
> reliably either using triacs or power relays/optos with switching
> transistors for relay coils if used. The finished unit will be in
its
> own enclosure BTW for obvious safety reasons. I know relays can get
> warm (dissipate pwr) but is a heatsink necessary as long as you
don't
> overload the relay beyond it's rated specs? Thanks.
>
> -Dave
The problem is that motors are induction loads and you need to
address them differently than a lightbulb.
Make sure the device has a rating for inductive loads and don't
exceed that.
Also, the Air Conditioner will have a high starting amperage as the
load is a compressor and needs the high powre to start the
compressor, more than the motor.
Also, after it shuts off, the gasses need time to equalize before it
can be started again. 2-3 minutes should work. That is not an
option, it is a requirement. You are not going to get the motor to
start immeadiatly after a shut-off, period.
The unit probably has an internal sensor to handle the re-start so if
you have too short of a time, you'll know it.
For the cost, buy two units and list all the parts inside for when
something fries.
My exoperiance with X-10 has been that you get years of life, but
life is only years, they will self destruct. For the price, they are
really cheap control!
Dave