Two night storage heaters, one of which trips the MCB when it comes on overnight.
Simple way to eliminate the duff one is to switch one on every night & see which one trips.
If the d*zy c*w tenant could remember to do that.
So, if I use my DMM, what resistance setting should I use? I figure I don't need accurate readings as on will be vastly different.
highest range (megaohms) between L&E while it's completely disconnected.
Maybe, maybe not - fault may only show up with a high voltage e.g. with an insulation tester rather than a multimeter.
Indeed. Surprised Dave doesn't have a proper megger, here's one not too far away:
And check for leakage/short betwixt N and E as well...
Won't do any harm to check, but with the element being 15ish ohms for a
3kW heater, on megaohms range I wouldn't expect to notice the difference between L->E and N->E readings.Also of course things move inside when hot. When they put mine in the guy cursed one of them for blowing the breaker and he took some bricks out and a lump of electronic stuff and shoved another bit in and its worked since then. I did not think they were very sophisticated, at least most of them are not. Brian
Ideally a Megger. But don't overlook the possibility of moisture that moves around when the heater warms up. Not an untypical scenario when tenants dry washing on storage heaters and water drips into heater. If so it may test out ok until warm.
Andrew
Single MCB with two heaters? I guess they are small ones, what's the nominal max loading on 2.5 mm wired spur, 4kW ish? Maybe they are wired with 4 or 6 mm?
Even with two 3 kW heaters I suspect it's borderline economic having E7, you just don't use enough night rate to balanace the highly priced day rate. May well be better to have thermostaticly controlled convectors and a cheap ordinary tariff.
Well if on the heater will be pretty low resistance but you have to know the heater is actually demanding heat and as other have said it may require a proper insulation test.
In the abscence of an insulation testerI might be tempted to make up a 13 A plug to open ends, operate the isolator on the night rate CU, wire the open ends into the live and neutral bus bars, switch off both heaters, plug in and switch on then switch on one of the heaters. If the MCB stays in, switch that heater off and switch the other on. If the MCB still stays in switch both on, the 13 A fuse in the plug top won't blow straight away and should last longer than an overloaded MCB.
Making sure that both heaters are actually demanding heat might be a problem but by the sounds of it both are stone cold as the tenant lets the MCB trip...
MCB or RCD?
Disconnect heater A at its wall switch.
Seal consumer unit.
Go back next day and see if tripped.
If not, reconnect A and disconnect B and repeat test.
Charge landlord accordingly as "tenant unable to switch heater on/off for testing"
Owain
First question is:- Is there an RCD device? because if there is it would trip on earth fault (or should). If there is, to eliminate this, the test button should be pressed to be sure its working and the earth arrangemnt checked out.
Assuming everything there is working OK, we are talking overload or faulty MCB If it has worked in the past faulty MCB is most likely. (Check if there is some recent alteration has been made thatr affects the loading of the circuit) Short circuit live/neutral are quite rare.
If the d*zy c*w tenant could remember to do that.
I'm only on site once a week & don't have time to go in.
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