Uncle Bulgaria Posted August 14, 2012 Share Posted August 14, 2012 The 230 Volt fuse went recently on my Combi 6E. The motorhome was new in January, and is regularly used. On site one morning and using mains to heat the water (using 1800 watts input) I noticed the red fault light light flashing away on the control panel and the yellow LED was off on the power selector switch. Interestingly, the (regularly tested) MCB did not trip. The dealer "excavated" down to get access to the mains control circuit board and found the fuse had gone. Replaced the fuse and all well again. We have used the motorhome for a few days since and the mains water heating has worked without any problems. It's a mystery (to me at least) as to why the original fuse went. The MCB didn't trip, so I assume no arching and the replacement fuse has been through some 8 full water heating cycles without any further problems. I think I can rule out a power surge as I have an AVS30 fitted to the incoming supply ahead of the main switch set to operate in the range 230 +/- 20 volts. Incidentally, on one site in Devon I measured the voltage at the hook-up point at 255 volts when the AVS30 indicated a high voltage input so would not connect the van systems to the mains supply. We moved on the next day. The fuse rating at 10 amps seems a bit marginal for a nominal current of 7.8 amps at 230 Volts, which is almost 8.5 amps at 250 volts. Can anyone throw any light on why the original fuse might have failed, or is this type of failure common if infrequent? Thanks for any advice. Richard. Link to comment Share on other sites More sharing options...
WildBill Posted August 15, 2012 Share Posted August 15, 2012 Perhaps the original fuse was not of good quality. Perhaps Dereck has a better idea/answer. Link to comment Share on other sites More sharing options...
onecal Posted August 15, 2012 Share Posted August 15, 2012 Hi,,,Loose fuse connection or poor quality fuse,,,Regards,Brendan Link to comment Share on other sites More sharing options...
hallii Posted August 15, 2012 Share Posted August 15, 2012 1800w at 250v is 7.2 amps as the evoltage rises the amperage reduces. Fuses are simply put, a crude and inaccurate way of providing electricity disconnect under fault conditions. They are not precision items and can blow at all sorts of odd amperages depending on manufacturing tolerences, temperature, continous load (current) vibration, chemical contamination and so on. There are also slow blow and quick blow fuses, slow blow will carry a higher current for a time. A 10a fuse is adequate for 7.2 amps continuous loading. Do not be tempted to increase the value, there is enough extra margin. H Link to comment Share on other sites More sharing options...
sshortcircuit Posted August 15, 2012 Share Posted August 15, 2012 Cannot comment as to why the fuse blew other than quality of fuse. Whilst the fuse was rated at 10A it will carry a good bit more depending on the type of fuse it is. Cartridge fuses are not precise and some leeway is required to take consideration of surges etc. Link to comment Share on other sites More sharing options...
T8LEY Posted August 15, 2012 Share Posted August 15, 2012 As your motorhome is relatively new it's unlikely the fuse has got tired so soon. Fuses deteriorate with age/use/temperature changes/etc. The 10A fuse rating looks ok for a 1.8kW running load, which, as you say, draws 7.8A @ 230V. Fuses are pretty coarse circuit protection and, consequently, stand quite a lot of start-up current. Have a look at this link IRO voltage statutory limits. http://www.bis.gov.uk/files/file11548.pdf I suspect the MCB didn't operate because there is insufficient discrimination between it and the fuse, although you don't give any breaker details. From the above I can only assume you had a faulty fuse. Link to comment Share on other sites More sharing options...
Derek Uzzell Posted August 16, 2012 Share Posted August 16, 2012 Truma's Combi 6E instructions describe the fuse required to protect the appliance's 230V circuitry as "10 A, slow, interrupting capacity “H”, presumably one of these: http://www.amazon.co.uk/T10A-250v-Slow-Glass-electrosmart®/dp/B0036AKIVW/ref=sr_1_9?s=electronics&ie=UTF8&qid=1345098316&sr=1-9 Richard's heater is now working OK, following replacement of the fuse. If that fuse blows in the near future then there's a fault somewhere that will need to be investigated: if it doesn't then the reason for the original fuse-failure will remain a mystery. This 2007 forum thread relates to a Truma C-6002EH heater's 230V fuse (same type as used on the Combi "E") blowing more than once, with the cause eventually being identified as being PCB-related. http://www.outandaboutlive.co.uk/forums/forums/thread-view.asp?tid=6599&posts=16 For advice on whether 230V fuse failure is a well recognised fault with Combi "E"s, the Truma(UK) technicians should be able to say. Tel: 01283 586020 Email: technical@trumauk.com As far as I'm aware it is not. Link to comment Share on other sites More sharing options...
HWO Posted August 19, 2012 Share Posted August 19, 2012 We had the same fault soon after we got our motor When you looked at the fuse it appeared OK, wire inside the glass envelope looked solid. But if you put a meter on the fuse there was no connection to one of the end cap's of the fuse. Replaced the fuse and never a problem again HWO Link to comment Share on other sites More sharing options...
Uncle Bulgaria Posted October 18, 2012 Author Share Posted October 18, 2012 Grateful to everyone who responded to my initial post. Just back from a couple of months in Europe, and, although low amperage sites restricted the use of the electrical side of the Truma heater, we had no further problems when the full electrical heating could be used. So I guess it was just a poor quality fuse or random failure. Only time will tell. Thanks. Richard. Link to comment Share on other sites More sharing options...
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