cable under sized?

[paul b b]

Hello old friends,

I'm back after a longer than antisapated illness, and blow me down the first phone call i get is from a guy i did some work for a while ago with a fault (nothing i did befor you start lol)

ok so fault is...swimming pool heater keeps tripping, the manual says it will trip from time to time but at the moment it wont stay on for more than a few mins.

he has had a guy out to quote already and his views were that the cable supplying the pool (detached from house) is under size (and poorly installed, ie...no glands etc) and is now tripping because the volts have gone from 240 to 230 (pool is 221) and has increased the current. it seems plauseable but just want to clarify.

there is apparently no breaker (or rcd) in the house for the swa, just an on off switch.

then goes into pool boiler room where there is a cu with rcd and breakers. its the breaker on this cu that is tripping.

just want to clarify that this could be the fault, my thoughts were faulty boiler but i know of the othere guy and he has a good rep. i have been called because i know the guy and other spark gave an inflated quote.

oh..im viewing tomorrow so will get some pics and more details etc.. anything i should test whilst im there? ive not done much on boilers.

thanks guys xxx

 

[ProDave]

he has had a guy out to quote already and his views were that the cable supplying the pool (detached from house) is under size (and poorly installed, ie...no glands etc) and is now tripping because the volts have gone from 240 to 230 (pool is 221) and has increased the current. it seems plauseable but just want to clarify.

If you are talking about a resistive heating element, then reducing the voltage will REDUCE the current that flows, not increase it.

I have a similar ongoing problem with an electric boiler that keeps tripping the MCB. Current whenever I measure it is less than the MCB rating. Swapping the MCB made no difference. I'm now on the third MCB, but this time I moved it to the end of the CU with a vacant position either side, after a FM suggested it was just getting to hot snuggled up in between 2 other MCB's. I'm still waiting feedback to see if that has cured the problem (but I doubt the boiler is working very hard with this warm weather)

 

[davetheglitz]

I think the undersized cable is a red herring as far as the fault goes. It may be poor - but it can't produce an over-current fault.

Suggest you follow Canoeboy's advice and also check the RCD trips.

If all checks out OK then it might be worth checking the control panel - there's probably an interlock to prevent the heater operating if there's no water flow - and there must be a thermal cutout if overheating. Is it possible that there is a fault when this occurs?

 

[m4tty]

Did you test the pool voltage whilst the circuit was under load or not?

 

[paul b b]

i've not been matty, going tomorrow for a look. the results were given to the customer by another spark. my first thoughts were that it would be a fault on the water heter (what ever type it may be) but i thought the other spark had a good rep so was thinking his thoughts were correct. i can sort of see his idea but am swayd towards a fault on the heater, also if its a 16A mcb on 2.5 depending on cable runs etc then i could pop a 20A in there anyway. will take photos tomorrow.

thanks for the info chaps

 

[kme]

Tip: ignore what the other spark said - it can leave you "blinkered", as it were. Go in with an open mind, as though you`d been told nothing, and try to find it for yourself.

similar to: "Yeah, that circuit is off - you can work on it now"

"Oh, okay............: bad day explode

 

[paul b b]

Good point kme. Thanks

 

[park1]

I think the undersized cable is a red herring as far as the fault goes. It may be poor - but it can't produce an over-current fault.Suggest you follow Canoeboy's advice and also check the RCD trips.

If all checks out OK then it might be worth checking the control panel - there's probably an interlock to prevent the heater operating if there's no water flow - and there must be a thermal cutout if overheating. Is it possible that there is a fault when this occurs?

What if the cable size has allowed the insulation to degrade?

 

[davetheglitz]

What if the cable size has allowed the insulation to degrade?

The breaker is at the end of the cable - so not possible.

 

[a1]

Any update and PICS on this, Paul bb?

 

[paul b b]

Have the pics now...what a mess lol. will upload them from my phone later

 

[paul b b]

ok photo time!

i forgot to take one of the supply end. it was swa cut off by a clip, then the inner cores were loose going to an isolator (type with the fuse in). this was fed from tails straight into the isolator (no rcd).

this is the rest of it

View attachment 3779View attachment 3780View attachment 3781View attachment 3782View attachment 3783

 

[Steve3948]

Not working ?