# Problem solved



## 104305 (May 6, 2007)

Regular browsers to the Hymer forum will remember some time ago I encountered a problem with my 240V ac hook up supply. I eventually traced the problem to a faulty MCB on the consumer unit installed in the wardrobe on my Hymer 644G 2002 motorhome. The MCB in question was a solitary 2 pole 10amp unit which in itself is a questionable installation as it supplied not only the transformer/rectifier but the sockets and the fridge. This meant that in the event of a MCB failiure all these items were out of action. Ive since installed 2 separate MCB's to balance out the 240V items. I think this is a better way than what was installed I guess by Hymer. My 240V is up and running now without having to go to Brownhills. After I had initially told them of the problem they said that they would have to contact Germany for a new entire unit costing in excess of £300 inc fitting. My 2 MCB's from a local electrical wholesaler cost less than £20.


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## bigbazza (Mar 6, 2008)

Nice post longdistancerunner. I'm not a Hymer owner but I would definitely check this out if I was. I thought the German engineering etc was superior  
Cheers
Barry


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## pieterv (Feb 3, 2009)

Glad you got it sorted (and cheap as well!).

Not sure if this reflects badly on Hymer quality though. Things do break.

I don't quite see why it is a questionable installation to have all mains go through one MCB, but do agree that 10A is a bit low.


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## LittleGreyCat (Jun 22, 2008)

Interesting - IIRC "Volts * Amps = Watts" so a 10 amp circuit should support 2.2 - 2.4 Kw (depending on where your supply sits between 220v and 240v).

<pieterv>
13 amp domestic ring main is normally fused at 30 amps.
13 amp domestic spur is normally fused at 20 amps.
These are based on 2.5mm twin+earth cabling installed as per current (ever changing) regulations.

I believe there are issues if the cabling is not in an air gap (for instance in a cavity wall with cavity insulation) where the heat from the cable cannot dissipate as well.

It may well be that the cable used and the routing of the cable through the van only justifies a lower total loading.

I would not have thought that most vans would need to support a load of over 2.2Kw - although come to think of it we do have a 2Kw fan heater as a back up to the Truma gas heating.

It also suggests that buying a generator of over 2Kw rating would be a waste of money if you plan to plug it into the normal blue three pin socket on the outside of the van ;-)

I've just looked inside our 2002 B544 and the consumer unit is rated at 25 amps, with an individual circuit breaker rated at 10 amps plus another switch which looks like a circuit breaker but has no rating (could this be protection from reversed polarity?).

Just looked at the manual for our Electrolux Blizzard air conditioning unit and this quotes 715w cooling load and 800w heating load so this is well within tollerance.

<longdistancerunner>
I note that your issue was not the total loading but that you had all your eggs in one basket. Not normal for domestic wiring, and there have beek long discussions on uk.d-i-y newsgroup over the advisability of putting domestic items such as fridges and freezers on their own circuit breakers to guard against them being turned off by a dodgy electrical item tripping a circuit breaker.

Out of interest, did you change the consumer unit as well, or did you have a spare space for the second 10amp circuit breaker?

I agree that the whole system is vulnerable to an MCB failure - but how common is this? The RCD in the consumer unit could also take the whole thing out so there must always be a single point of failure somewhere unless you have multiple consumer units.

[I ended up revising my RCDs and MCBs - electro-technical stuff as I get acronym-blind.]

Cheers

LGC


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