is it possible to power on a 7500 BTU/h or 2200 W air condiotioner through this arduino relay module below?
I can't find any manual from that module. Relay sizing I think it's ok, but the wiring that connects the module and relay seems to be undersized.
When I say wiring, actually it is the printed circuit that connects relay terminals to the module itself
It's a mechanical relay , not a solid state relay. Powering it on is not a problem but when you power it off, the 10A of current will want to continue to flow (at the speed of light) so as the relay contacts separate at maybe 10 or 20 ms time frame , the electrons will jump the gap between the separating contacts and what will result is internal arcing (this is plasma, very hot) and will heat up the relay. If the module has a snubber circuit, this phenomenon may be surpressed. It is usually not possible to get the schematic of these modules but I can see the flywheel diode but there's no snubber cap so that could be a problem. It is possible to add an external snubber that would supress the arcing by supplying an alternate path through a series resistor/cap circuit but even so,
you are already at the maximum current for this module or a 10A SSR so I think you're pushing it on the safety side. If something bad happens at that voltage it is probably going to involve fire. You should probably look for a solution that has a higher rating so you won't be courting disaster.
be careful with turning an AC on and off.
once the compressor is off, the gasses have to equalize.
trying to turn it on with high gas pressure will draw excessive current.
a/c cannot be cycled more than few times per hour. They are not able to obtain any sort of precision temperature control.
one of theses days I am going to post engineering notes on HVAC temperature control.
amazing your explanation about current and relay switching off problems that can occur . So , you think it 's better and safer using a solid state relay. I did a websearch and found this one. Can I buy that one?
Perfect. No problem. good to go ...
Word of advice though, the bottom of that is a metal heat sink. It is supposed to be mounted with white themal paste on an adequate heat sink , preferably with cooling fins. The way that works is a standard heat sink is a block of aluminum that has had
the metal removed between the fins leaving a thick plate at the bottom. You turn the heat sink upside on the workbench, place
the SSR on it, mark the mounting hole centers, then center-punch those and drill and tap for whatever hardware you prefer.
Use 3-in -1 hole while tapping. Clean off the surface with IPA alchohol and apply the thermal paste before mounting the SSR.
dave-in-nj:
be careful with turning an AC on and off.once the compressor is off, the gasses have to equalize.
trying to turn it on with high gas pressure will draw excessive current.
a/c cannot be cycled more than few times per hour. They are not able to obtain any sort of precision temperature control.
one of theses days I am going to post engineering notes on HVAC temperature control.
Thanks for the information Dave. I will take care. I will cycle 1 time once 24hours. What do you think about that situation. I have an air conditioner that doesn't have a timer. I need to power it on at 6am and keep it working until 8am everyday. My bedroom wall is east positioned. So, sun begins heating up the wall at 6am. When it is 8am my bedroom is too hot.
Should I buy a SSR relay instead using an arduino one?
raschemmel:
Perfect. No problem. good to go ...Word of advice though, the bottom of that is a metal heat sink. It is supposed to be mounted with white themal paste on an adequate heat sink , preferably with cooling fins. The way that works is a standard heat sink is a block of aluminum that has had
the metal removed between the fins leaving a thick plate at the bottom. You turn the heat sink upside on the workbench, place
the SSR on it, mark the mounting hole centers, then center-punch those and drill and tap for whatever hardware you prefer.
Use 3-in -1 hole while tapping. Clean off the surface with IPA alchohol and apply the thermal paste before mounting the SSR.
Great, I will take note of it for keeping all things well done and safe. is plasma arch begin only when relay is triggered to off position? I will turn the relay on at 6am and turn it off at 8am. Rest of the day, the system keeps shut off. Is the relay gonna heats up through that duty cycle?
No, it's rated high enough but I don't know if that rating includes a heat sink.
