Hello. I bought 3 Matter/Thread Grillplats sockets.
I plugged it to monitor my Ariston dishwasher, which consumes 2000W in resistive load and 200W inductive load. The Grillplats socket is largely sized for this device (it supports 3680W resistive support and 300W inductive support). But it makes a strange and very audible buzzing sound (when the water heats up I guess and the noise stops and then comes back during the wash cycle). Otherwise, there are no problems when these sockets are used on low-energy appliances (e.g. computers).
I tried it out on my dishwasher and did not hear any strange noises at any point in the cycle. However my dishwasher is only 0.74A / 90W motor plus 7A / 840W heater. Fwiw I do have a 1200W roof heater and a 1900W microwave (1900W input, 1000W output), and neither of those caused a strange noise either.
Hardly anyone has these yet I think. I’ve been watching Ikea US website and finally saw and picked them up yesterday.
Good to know it’s only 300W for motor loads, that’s much lower than I assumed!
That rules out several devices I wanted to monitor. I see my US version is rated 1800W resistive / 300W motor. For my 120V / 60Hz power, that’s max 300W÷120V=2.5A. Devices I can’t monitor after all:
6A→720W clothes dryer (gas heater, not electric; still too much!)
8.8A→1060W dehumidifier (measured 3.8 A / 24.1 A inrush)
9.7A→1170W sump pump (measured 9.2 A / 15.3 A inrush)
12A→1440W clothes washer
3A→360W fridge (maybe ok since it has digital inverter? Idk. I measured 2.4A / 2.6A inrush, but I’m not sure how to trigger the worst-case operating mode)
Only a few of my devices with motors are still ok:
Hm, I’m confused on whether that 300W rating is the appliance amps limit, or the motor power limit. 300W electricity into a motor will produce much less than 300W of mechanical working power, and a motor rated for 300W of mechanical working power will draw much more than 300W of electricity.
In terms of the motor full-load current (FLC), this 300W rating could mean I am limited to 300W/120V=2.5A FLC as I said earlier.
Or it could refer to the motor mechanical power, which per US National Electrical Code (NEC) Table 430.248, looking at the 1/3HP single-phase AC motor at 115V and the 1/2HP motor, means I am limited to 300W=0.402HP = somewhere between 7.2A and 9.8A FLC. The NEC says that an appliance with a 1/3HP motor must be marked either with that horsepower rating or 7.2A (and volts). By linear interpolation (which is not technically allowed), a 0.402 HP motor would be it’s roughly 7.2 + (0.402-0.33)*(9.8-7.2)/(0.5-0.33) = 8.3A FLC.
I am reaching out to Ikea to see if they can clarify for me. Maybe “HP” ratings on plugs are talking about the output mechanical power, i.e. a 1/3 HP rating would correspond to 7.2A and 850W of electrical power. And maybe “W”/“A” ratings on plugs are talking about the input electrical power, i.e. a 300W rating corresponds to less than 1/6HP (that’s the smallest motor listed in the NEC table and but still consumes 4.4A).
Additional context on NEC (available from NFPA for free)
Article 422 Appliances Part V. Marking 422.60 Nameplate. (A) Nameplate Marking. Each electrical appliance shall be provided with a nameplate giving the identifying name and the rating in volts and amperes, or in volts and watts. If the appliance is to be used on a specific frequency or frequencies, it shall be so marked.
… 422.62 Appliances Consisting of Motors and Other Loads. (A) Nameplate Horsepower Markings. Where a motor-operated appliance nameplate includes a horsepower rating, that rating shall not be less than the horsepower rating on the motor nameplate. Where an appliance consists of multiple motors, or one or more motors and other loads, the nameplate value shall not be less than the equivalent horsepower of the combined loads, calculated in accordance with 430.110(C)(1).
… (B) Additional Nameplate Markings.
… (2) Alternate Marking Method. An alternate marking method shall be permitted to specify the rating of the largest motor in volts and amperes, and the additional load(s) in volts and amperes, or volts and watts in addition to the marking required in 422.60.
… Article 430 Motors, Motor Circuits, and Controllers Part IX. Disconnecting Means 430.110 Current Rating and Interrupting Capacity. (A) General. The disconnecting means for motor circuits rated 1000 volts, nominal, or less shall have a current rating not less than 115 percent of the full-load current rating of the motor.
… (C) For Combination Loads. Where two or more motors are used together or where one or more motors are used in combination with other loads, such as resistance heaters, and where the combined load can be simultaneous on a single disconnecting means, the current and horsepower ratings of the combined load shall be determined in accordance with 430.110(C)(1) through (C)(3). (1) Horsepower Rating. The rating of the disconnecting means shall be determined from the sum of all currents, including resistance loads, at the full-load condition and also at the locked-rotor condition. The combined full-load current and the combined locked-rotor current so obtained shall be considered as a single motor for the purpose of this requirement.
The full-load current equivalent to the horsepower rating of each motor shall be selected from Table 430.247, Table 430.248, Table 430.249, or Table 430.250. These full-load currents shall be added to the rating in amperes of other loads to obtain an equivalent full-load current for the combined load.
The locked-rotor current equivalent to the horsepower rating of each motor shall be selected from Table 430.251 (A) or Table 430.251 (B). The locked-rotor current shall be added to the rating in amperes of other loads to obtain an equivalent locked-rotor current for the combined load. Where two or more motors or other loads cannot be started simultaneously, the largest sum of locked-rotor currents of a motor or group of motors that can be started simultaneously and the full-load currents of other concurrent loads shall be permitted to be used to determine the equivalent locked-rotor current for the simultaneous combined loads. In cases where different current ratings arc obtained when applying these tables, the largest value obtained shall be used.
