I want a power monitor for my oven. Will 16A one be enough?

[feral compass]

I have an oven with a gas cooker on top in the UK. I've checked the oven label and it shows 2.3kW. The cooker has no label. There's a fused switch nearby that switches both off.

I'd like to install a in-wall zigbee power monitor just to add the oven consumption into my energy dashboard. Something cheap like this. I've used this model for a standard plug.

These switches support 16A. I'm just looking for confirmation that it will be enough and ok for this application.

[harsh nexus]

for very high power stuff that's going to be on for a while then a ct clamp solution may be better. i use a shelly device with ct clamps for tracking my oven.

[feral compass]

I had a look at them, but too pricey. I'm uisng a Shelly mini EM 16A for my EV, which draws 2kW or so

[harsh nexus]

also the one you linked is tuya which is always a problem. granted the zigbee stuff is better than the wifi stuff but in general it should be avoided.

i would lean towards something more reliable like the shelly, in theory a 16a monitor should be enough but in practice sometimes its better to error on the side of caution.

[feral compass]

it's £4 or £60 for a clamp Shelly setup :S

really hurts. I know of the Tuya hate, but I have plenty of Zigbee Tuya and tbh I'm perfectly happy

[short solar]

There's this "powered by shelly" option with power monitoring rated 25A, for €30:
https://www.shelly.com/products/ogemray-25a-smart-relay
It is still a relay rather than just a power monitor though

[feral compass]

yeah, most are switches too, it's fine

[harsh nexus]

cost vs safety/stability trade off i guess

[short solar]

The Shelly PM mini G3 (€14) / EM mini G4 (€16.50) are both 16A if you don't mind a little less safety margin. Both just power monitors, no switching

But. Those use shunt resistors, they're not non-contact like a clamp meter

[feral compass]

yeah, the gen3 is the one I have for the EV. For the car, I did want to pay a bit more for the safety

[harsh nexus]

i use the gen3 em mini's for appliances dishwasher/washing machine

[feral compass]

for those I have (tuya zigbee) smart plugs. 🙂 But the oven is wired directly. That's why

[harsh nexus]

eek, relays on inductive loads can cause issues (not saying it 100% will but i dont want to risk it)

[feral compass]

hmm I didn't know that. I'm not that good on electrics. What are inductive loads? Why? I don't ever switch them though. They're just there for power monitoring.

[short solar]

Motors, predominantly

[feral compass]

but I ugess the issue is when switching them on/off?

[harsh nexus]

yeah motors mostly it can cause false triggering of the relay and cause it to arc

it will arc if you switch it under load. but if you dont then you just have to worry about potenital false triggers

relays work via electromagnet and inductive loads mess with magnetic fields.
i am over simplifying a bit but thats the general idea.

[short solar]

And if you want to see what that looks like, this is the fan controller out of a piece of HVAC equipment at work, and the relay we had to replace (because the PCB wasn't manufactured anymore):

This one hadn't failed yet, but you can see the soot buildup from the arcing, versus the brand new replacement relay sitting behind

[feral compass]

but that's IF I'm using it to switch, right?? Please put my mind at ease xD

[harsh nexus]

if your appliance is on a fuse spur (most likely) then you put the EM mini behind the spur (on the protected side)

[short solar]

Yep. And only if it's switched on load too; if the appliance was in standby / off any time the relay was switched you'd also have no issues. Only if the motor is running when you switch off, or would start spinning immediately when switched on

[harsh nexus]

it is possible that noisy inductive loads can cause false triggers on relays too which means they get switched unintentionally

[feral compass]

dishwasher and washing machine are into normal sockets. I don't see they have a fuse. Oven does have a fused switch for itself.

[harsh nexus]

athom make a smart plug without a relay which is wifi and rated at 10a if you prefer that form factor.

[feral compass]

that's actually my plug, just a knock off

though mine is 16A. 10A would be on the short side

[harsh nexus]

but that one specifically does not have a relay so cannot switch

[feral compass]

oh, got it

it looks exactly the same

[harsh nexus]

yeah most of them look the same/siimalar. i suspect the shells are mostly made on a single production line with correct tooling. for cost saving

[feral compass]

so this is good info, as I wasn't sure where to install the PM, if before or after the fuse

[harsh nexus]

in thoery it shouldnt really make a functional difference but having it on the protecteed side means if the pm dies a violent death for some reason there will be the extra protection of the fuse

I tend to go a little more overkill with some stuff to error on side of caution. and in general my recomendations reflect that. some people have stuff less overkill that works fine. but also i do hate it when someone does something that's not really designed to do it then they make angry posts blaming the device when it fails. seen too many people with dodgy setups make posts all over the palce saying warning xyz device is dangerous and the manufacturer doesnt care and just said i was using it wrong... when they were in fact using it wrong 😛

[heavy forge]

If it’s inline with your cooker on a 32A circuit, a 16A smart plug or relay wouldn’t be legal under BS7671

Perhaps more pertinently, it’s dangerous and could cause a fire

And if it does cause a fire, your insurance will likely tell you to pound sand because of the non-compliant wiring

If it’s a 13A or 16A circuit with a suitable circuit breaker then a 16A Shelly etc would be fine in theory although personally I wouldn’t do it with an induction cooker - inductive loads can spike much higher than the rating

[feral compass]

yeah no I appreciate the info, I didn't know that about plugs and inductive loads

[feral compass]

no it's a gas cooker

how can I know the circuit rating?

my home has old wiring anyway, and prob due for a rewiring (that I won't do as it's been renovated recently, and it works good))

the fuse in there for the oven+cooker is 13A

if I add the pm/switch "after" the fuse, wouldn't that be ok?

[frigid plinth]

some ovens are multiface.. thus you have to tjeck the lable first

[feral compass]

not sure what that means. But I did check the label and it says 2.3kW. It's in the OP.

[short solar]

I think they mean multi-phase

[feral compass]

ah. Well I don't think so. I don't have any weird stuff in my circuit board. And that fused switch has just the normal cables.

[short solar]

On the wiring front, for anything under ~50 years old the size of the wire ought to be printed on it.

Here in NZ, regulations are something along the lines of 10A/1.5mm², 20A/2.5mm², 32A/4mm², etc, with thicker wire for long distances from the board to the outlet (not 100% sure but something like >20m you have to go up a wire size). Presume yours won't be a world apart from that.

8A/mm² is probably a good rule of thumb.

[feral compass]

I'd just find when I'd open it

[feral compass]

chatgpt said 1.5 mm² ~15–16 A

that's what I was planning to get

you think it's worth upping to 2.5?

man I hate electrics. It's always looming danger and fear everywhere xD

[short solar]

My oven's wired with a 20A breaker, but 4mm² wire

Cooktop (electric) 32A breaker, also 4mm²

[feral compass]

wow

[short solar]

But the oven's feed also supplies the microwave

[frigid plinth]

My oven can run 1phase 16 amp... ore 3 phase 10 amp..

[fathom helm]

My oven is monitored by Nous A1T WiFi Smart Socket with Tasmota. Works just fine.

[fierce vortex]

What boggles my brain is seeing the word “cheap” when talking about these applications. Really? You want to run the risk of something awful going on when you go on holiday for a month? It’s odd. That would make sense if you have some passive monitoring (forget the name) but anything which is inline… umm. Good luck.

[vale aurora]

100% true. Taking the risk for pass-through cheap measurement that can blow up your home and insurance won't pay is mega risky.

[hushed trout]

I have seen this time after time after time. Cost vs safety is a no brainer ... for me

[heavy forge]

Or worse, when you're upstairs asleep

My house burning down when I'm away is an inconvenience, but better than when my family is home

But yeah, high quality only for mains powered devices