Was sent here by the electrical engineers so credit to them for not being known it all types, they said electrician hang out here. Heres my problem below, will get a socket monitor thingy tomorrow and test draw on the socket.

So we've been renovating (virtually new everything) a 1930s semi that hasn't been modernised since it was built and hadnt been lived in since the 70s. Naturally a full rewire was high on the agenda which is 90% complete now, but my suspicion began when the 3000W fan heater I bought seemed not to be chucking out much heat. At first I thought nothing of it putting it down to a poor quality appliance. But when a new kettle I tried took around 7minutes to boil, I started pondering if there was a fault somewhere causing a limit to max power these appliances were generating/drawing. I had the plugs tested and they are producing 230v but before researching ohms law, I suspected a resistance issue. To double check, I took the heater home and plugged it in and hey presto, belting hot heat. I am awaiting an updated fuse board from Northern Power, which I'm sure will fix the issue but, I wanted to rule out any problem with my installation before I sign off with the sparky ideally.

The only other info I have is the original power was a shared supply to ours and next door and I wondered if some sort of phase drop was present grid side of our board. Is my next logical step testing resistance between board and consumer unit? Can you do that with a normal multimeter? My electrician who looks to have done a fantastic installation seems to be brushing it off like there's no problem but the house will be electrically heated and rented out so I can't have 2k worth of underperforming rads getting overworked.

All ideas, practical and theoretical appreciated. Sorry for essay.

  • 3
    It should be a simple matter for your "sparky" to measure the voltage at the outlet when your heater or kettle is plugged in and turned on.
    – jwh20
    Mar 8, 2021 at 10:37
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    @brhans I don’t believe they don’t have split phase power more likely ring’s. I agree with jwh20, but I would check at the panel also. It would not be the first time I saw a transformer that needed to be tapped up a few volts due to the load. Verification at both points rules out bad connections in the home.
    – Ed Beal
    Mar 8, 2021 at 14:35
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    @EdBeal - yeah, my eyes missed the 230V reference - this is probably in the UK.
    – brhans
    Mar 8, 2021 at 17:58
  • Yeah sorry, this is the UK yes. And yes, we have low resistant at the earth board side. So the next test is to measure draw so I'll get a socket monitor device and report back.
    – StvC
    Mar 9, 2021 at 8:21

1 Answer 1


You need to perform measurements while the loads are applied. There are plenty of power test devices that are pass-through: one end plugs into the outlet, and the device itself has an outlet you plug the load into. It'll display the real power, the mains voltage, etc. If you worry about any voltage drops/sags, you'll want one of those. One brand (with some copies) is Kill-A-Watt. It appeared first on the US market, but you can find very similarly looking devices for the UK market. One of them is called Hopi, as used by bigclivedotcom.

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