Today I tried to put a shelly 1pm between the group-switch and the 3 airco units I just had installed. These units can just about fit in the 16 amps for that one group, but when they get power, it seems the shelly just shuts down. So while I believe the setup could work with a 16amp shelly (like there’s any other) 1pm device, the “turning on” part turns off the shelly. Is there a way to connect this or insert something that can make turning on palatable for the shelly?
My other option is to rewire the airco units and put a shelly 1pm between each connected airco, thus limiting the power to that of just 1 unit. This is a lot of work though… Plus I only have 2 spare shelly’s. I might just split those in 1 and 2 units per shelly… Just one would be best, if I could get past the startup phase.
Shelly units, I have the plus 1pm, have device protection as part of the firmware. This is not hardware protection, but as the unit measures current, voltage, and internal operating temperature, it will shut off the power if any monitored parameter exceeds the defined safe limits.
My unit has max power protection at 4480W, max voltage at 280V, and max current at 16A. These are adjustable, but I have them all set at the maximum permitted value. I have suffered ‘over voltage’ trips before with lower settings since my UK voltage can range up to 250V at times…
Aircon units are, basically, a big fat motor that drives the compressor. Motors have considerable startup current, particularly when attached to a heavy starting load. Traditionally things like fridges and freezers will draw, for a very short period of time at startup, up to around three times the rated running current. If you have one A/C that will draw up to 4 amps running, assume that this could be 12 amps for a short period (milliseconds) at start.
The ideal solution is to only load one A/C unit on the Shelly. For motor-compressors down-rate the Shelly to, say, 5-6A. You might get away with two - clearly not three [and if your Shelly is complaining, then the consumer protection fuse/trip might also trip occasionally too].
In industry one solution is to have interlocking between devices so that only one can start at any one time. Unfortunately, motor-compressors for A/C and the like can stop and start repeatedly during duty cycles, so the one Shelly per A/C is probably the only/best way forward.
These are almost certainly running as motors. This highly inductive load will very likely blow out a 15 amp device like a shelly 1. This will never work.
You need appliance rated devices to control inductive loads like that. And one per…
If you insist on using non appliance rated devices on motor loads, use a device that is rated at at least double what the appliance says it needs. So a 7 amp motor needs at least a 15 amp rated switching device for a motor load like an aircon. The ratings on normal (non appliance) smartplugs and devices is a resistive rating.
Thanks, I guess you’re both saying that one shelly is the safest option per unit. And then still it might overrun the limits for a short time. I really would like to have this in my monitoring, so I’m going to have some planning to do…