water heater fault finding

[Karin]

evening guys, the forum has been reminding me it's been a while since i posted, but everytime i think to post about something it turns out most everything is actually in those yellow tomes and associated texts if you actually look for it :lol:

just looking for a bit of advice on faultfinding really, specifically the unit is a hyco 2kw 20L undercounter water heater (power in, thermostat/rotary dial, neon indicator, element).

it was installed at a friends by an electrician (someone's brother doing a favour.. ) who wired it directly into the back of a double socket outlet with just the instructions "don't turn the ring back on until someones plumbed in the water".. ?! apparently someone else came along and wanted power and it's now bust.

figured i'd have a look as it'd be an interesting exercise and based on the above info it most likely it is a burned out element that is replaceable. so just playing with the tester and wanted some advice..

there's no obvious damage to any connections (haven't actually dismounted element yet to see it directly as i'd have thought i should be able to get an idea through testing?)

i isolated the element from the rest of the circuit and for kicks checked IR on the circuitry L-L and L-E, all fine.

figured if the element was likely burned out it would either fault to earth (though no protective device was said to be tripping) or have no continuity (or have i overlooked something there?), but L-E IR test was >199MΩ and there was continuity, which showed..

the resistance of element was 26.2Ω, which is near enough the calculated resistance of 26.45Ω (R=V²/P, 230²/2000)

so, as it all seems okay so far, i guess i'm asking, have i missed anything in a sequence of faultfinding tests?
i don't think i'd get anymore info out of my friend as it was disconnected a few months ago - i just thought i might be able to prove it forensically!
is it possible the neon is bust and they were too quick to assume it's broken because there was no light, and if so how would i prove this?
could the element be burned in a way that wouldn't show through testing but that would affect the ability to actually heat the water?
does it work fine and i just need to get wet to prove it.. :lol:

any thoughts/lines of investigation/further reading suggestions very welcome
cheers

 

[telectrix]

if the element reads at wahat you said. 26 ohms, that's fine. IR test L-E and if it's OK tghen immerse it and power it up.

 

[Marvo]

If it was switched on with no water in it then the element will be blown. I can't believe the idiot connected it and just hoped nobody would power it up, they could simply have left a terminal off the element with instructions for the plumber to put it back on when he'd finished.

It's possible that the damaged element won't show up on testing although it's fairly unlikely. If the element is testing 26 ish ohms anD the IR tests are fine then you could try filling it with water, retest it and if it tests good then apply power. Just make sure the CPC is connected and preferably use power from a circuit that's supplied from an RCD.

 

[Karin]

cheers for the responses guys. looks like tomorrows project will be digging in the plumbing box, or involve a funnel and a jug

 

[davesparks]

Looks like you've done everything right so far, better than the bloke who installed the supply!
The supply should have been taken via a switched fused spur if it is to be connected to the ring circuit, or a suitable isolator if it was on its own dedicated circuit.

Some new water heaters have boil dry protection or low water cut-off type circuits.

Look for overheat protection in the element circuit, which is often in the form of a round metallic disc with a ceramic backing and two spade terminals on it, many of them have a reset button in the middle of them which you press to reset after it trips. They are usually fixed with two screws/rivets.

Feel free to give me a call if you want, but don't forget I'm not exactly at my best before lunchtime.

PS. Ive been meaning to call you for a couple of weeks now to get some bank details from you so that I can get you paid for the work you did with us!


Sent from my iPad using Tapatalk

 

[davesparks]

This is what I was trying to describe, push the knobby bit in the middle to reset it.

 

[Bobster]

As Dave says, look for a little thermal cut out.

Some cheaper ones don't have a reset button, and once they pop need replacing.

 

[telectrix]

check for continuity including the stat and cut-out (if there is one). should read same as the element .

 

[Karin]

thanks again for all the suggestions. i didn't see any obvious thermal cut out reset, but there was continuity through the stat. filled it up with water and the L/N-E IR came back fine still so i checked water temperature and powered on. another thermometer reading about five minutes later showed an obvious increase in temperature so it seemed to be all working. however the neon indicator that used to light to show the element is on and heating is definitely bust.

reading the posts back i just checked the stat again closer and there is in fact a tiny little raised bit that could well be the thermal cutout, so possibly at some point between the heater being taken out and finding it's way to me it may have been pushed back in and reset - the bottom cover plate is missing so it could have been accidental or someone maybe tried to reset it but then got thrown by the lack of indicator light. either way, it'd explain why the element wasn't cooked!
so cheers again for the help.

PS davesparks, that's the kinda call that's never going to be inconvenient for me to take! or if it's just the basic details you need i can message you them over?

 

[Marvo]

Sounds promising.

If it's working properly a 2kW element in 20 liters of water should raise the temp by around 8 degrees in 5 minutes. This would be a noticeable temperature increase. If the water started at 15 degrees (room temp) it would take around 30 mins to heat to 60 degrees C which is pretty damn warm and steamy.