Amptec 12kw boiler melted incoming cables

[Vivatriumph]

Help! The 10mm cable going into boiler melted. It heated up so much that it made the connector start to bubble? Have checked cable it seems fine. Boiler is only 2yr 6 months old. I don't have boiler on accessively. It needs new pcb board but no ides what caused it????

Mike

 

[Gasguru]

Probably cheap and nasty connector blocks....loose screws resulted in a small arc welder developing....good for sales of new boards...check connections are tight every 6 months in future.

 

[Vivatriumph]

How much is a new board? If I have an idea might not be as much of a s hock when I ring lol.

 

[mrrigidtool]

mine over heated so we uupped it to 16mm arfter 3 weeks it meted and bubbled the connector. told it wont be covered as its probably wiring fault either loose wire or wrong type of electric, there engineer agreed nothing wrong with wiring and placed order for a new board. next day his supervisor tells me it's not covered as it's probably wiring issue. i screwed them my self whilst the electrician pushed down on them as they only just fitted in no way they were loose. any one know how to get it tested to find the cause.

 

[ddraig]

You really need good quality connectors, remember 12kw on a typical 230 volt supply can pull over 50amps of current, most connectors found in diy or most retailers are 45 amp MAX. make sure all connections are rated at over 50 amps or you will always have trouble.

 

[mrrigidtool]

sorry did not catch the bit about connectors, the cable comes straight out of seperate fuse box rcd straight into boiler cable is 600mm long 16mm straight into the ****y 3 terminal connector soldered onto the pcb, if i change the connector it will mean desoldering the pcb which will no doubt invalidate guarantee.

 

[ddraig]

Do you know the ampage and short circuit rating of the RCD, also is it just an RCD or an RCBO (Combined RCD and MCB)? because an RCD does no actually protect overcurrent situations.

 

[mrrigidtool]

hi it's 80amp 30ma break had it on a 50amp mcb next to rcd however every hour it would trip any ideas

 

[ddraig]

Every hour, wow, well as I said a 12kw appliance could be pulling over 50 amp, As you have this type of heater am I right in assuming you live in a rural or semi-rural location?

 

[mrrigidtool]

no went for electric as the internal chimney liner was cracked behind fitted wardrobes and had been poisioning us for years until we re decorated and relised. tHE MCB WAS TRIPPING OUT EVERY HOUR SO IT WAS WIRED STRAIGHT INTO THE RCD then it behaved however the main cable coming into the head was a bit warm we ran a 16mm armored to the head to supply new fuse box, that was ok did not get hot. still not sure why it has bubbled

 

[aptsys]

Because by bypassing the MCB you have no overload protection! An RCD will only protect against earth faults not overloads.

 

[ddraig]

Ok, you really need to get a good spark there, by taking the MCB out of the loop you now have NO overcurrent protection, if the MCB was tripping it was for a reason, either to protect the circuit or because it had a fault, I really really urge you to turn it off and get it proffesionaly checked ASAP.

 

[mrrigidtool]

i did thats the problem, the electrician says the fuse box is sound and in the manual is says 10mm connected via a 30ma rcd does not specify amps. he has fiitted this and wires were warm he was not happy about using 10mm to start with however its what was in the manual. The connector has melted so unit no longer comes on. engineer visited cant see any fualts with wiring however he claims not to be more quilified thebn the sparky who is a relative and agrees there is something not right and wants to chage the board so he can fire it up and check it is funtioning correct. Aptec flatly refuse there is a fult on there end and blame the incoming electric ( the engineer is a sub contractor for amptec) so i'm being thobed off. I agree with sparky that connectors are quite crapy for a 12kw boiler, if the boiler was functioning correctly and cables were not loose, then how its fused would not be an issue until there was a problem.

 

[Agile]

One of the functions of thick cable is to conduct heat away from any connectors etc.

You mentioned earlier that the 10 mm² cable gets warm!

Without looking up the tables, I think that 10 mm² is usually specificed for 60 amps when in free air.

It makes me wonder if you have got some poor quality cable where the copper is not as pure and low resistance as you expected! Which China was the cable made in?

Tony

 

[mrrigidtool]

hi agree 10mm cable may have been dud however the 16mm cable should have helped it. one theory i had was that 16mm cable was very stiff to a point that the way it wnet into the heater and bent around and pushed into connector was acting like a spring as it now the connector has bubbled its pushing the connector away from the board. Will replace board and change to new 10mm cable will purchase wire my self from BEW and get spark to fit it, is there any way once its on to meter how much it's drawing as if the thermostat was fualty that could have cuase it to over heat as well.