Truma Combi 6E. No hot water on electric.

Hello

We have a 2019 Symbol Plus (bought from new) fitted with a Truma Combi 6E heating unit. We generally use the Hot setting on EL2 to heat the water for washing up or a shower - not Eco or Boost and hardly ever Gas. Recently the time for the water to heat up has been getting longer and longer, and now the unit no longer heats water at all on electric. Hot water works fine on Gas and heating works on both Gas and on Electric.

The van has only been lightly used (2 or 3 weeks per year) and has been serviced for most of its life. However, I've never descaled the boiler - only just discovered it's recommended to be done annually.  I'm guessing our problem has been caused by a scale build up leading to the electric element failing. We've always lived in an area of very soft water so limescale is a foreign territory for us. I'm going to descale the system using white vinegar which seems to be a popular method, but I doubt this will resurrect the electric element. I have a few questions:

I've checked the trip switch for the heating unit on the Sargent unit and it's fine. The manual indicates 12V and 240V fuse under the electronic cover on the unit itself. The 12V fuse seems just about accessible through the rear opening but I can't see any sign of the 240V one - how does one access that

What is the roles of the two fuses. Is it worth checking both, or would the Gas not work if either was blown?

Assuming the electric element is blown, how easy are they to remove and replace? Is it a job for the professionals and if so does anyone have any recommendations in the East Lancashire area?

I'm guessing on calcium build up on the electric hot water element, especially as you say it has got gradually worse over time.
The good news is it works on gas.
The build up of limescale, if that is what it is on the outside of the heater element may have caused the, now heat insulated, element to overheat and perhaps have killed it.
I'd say this is a job for, perhaps a mobile guy to fix, in addition it may be necessary to disconnect or otherwise interfere with the gas so that needs a professional anyway.
I'm sure the parts will be easy enough to find..

BTW the 12v fuse is almost certainly to power the gas valve and igniter, can't see any use for it on the 240 mains electric element...

I had my elements replaced about 4 years ago, cost over £700. You can buy copy elements off ebay for DIY replacement but genuine elements are now no longer sold separately,  you have to buy a heat exchanger complete with the elements.  The cost of course has increased but the labour time reduced by doing this. Personally I would go to Truma at Derby for them to do it. Maybe make a trip of it. Or of course make do with gas, you can buy a lot of gas for the price.

You say that the air heating works on gas and on electric and if that’s the case your electric elements are working as there are not separate elements for water heating and air heating. 

I’m not aware that the elements are in the water but are in the heat exchanger which transfers the heat to the water tank that surrounds it to heat the water or to air passing over it for space heating. 

The need for descaling the tank is to prevent limescale building up on the tank sides and inhibiting the transfer of heat much like jug kettles were the element is not in the water but in the base of the kettle. 

You really need an engineer with diagnostic tool it could be the control board or a sensor not working. Are you getting any error codes?

I think one of my elements has packed in as the water is  not as hot as it should be and space heating the same, just need to boast it with gas when necessary. Luckily thee is a mobile engineer works from our storage site who will check it out for us.

Mike

Mike 187 is spot on.  If the heating works OK on EL2 then there is nothing wrong with the heating elements.  If the heat output on EL2 or EL1 has dropped by about 50% it means one of the heating elements has blown which means both should be replaced as described by Paulmold.  This is an expensive job that requires the Combi to be taken out and stripped down and then reassembled and refitted and tested on gas and mains.  This happened to mine last Autumn.  For most of us it's not a DIY job.  A way of seeing if the heating elements are on and working properly is to monitor the mains current on the EC700 CP.  On EL1 900W it should be about 3.75A.  On EL2 1800W it should be about 7.5A.  If the van has been used for less than 20 nights a year, which is less than 1/4 of my usage, and perhaps not in the winter, I doubt the heating elements will have failed  

The heating elements are not in the hot water tank so they cannot become furred up with calcium.  If the heating is working and by that I mean actually on and kicking out heat then water in the hot water tank will heat up.  If you have been trying to heat up the water without the heating being on, which is normal at this time of year, and the water isn't heating then that suggests an electronic fault.  A build up of calcium on the inside of the hot water tank will slow down the transfer of heat into it but it won't stop the water being heated just as you have found when the heat source is gas.  That said, if it hasn't been descaled for 5 years it might be worth doing.

Paulmold wrote:I had my elements replaced about 4 years ago, cost over £700. You can buy copy elements off ebay for DIY replacement but genuine elements are now no longer sold separately,  you have to buy a heat exchanger complete with the elements.  The cost of course has increased but the labour time reduced by doing this. Personally I would go to Truma at Derby for them to do it. Maybe make a trip of it. Or of course make do with gas, you can buy a lot of gas for the price.

Thanks Paul. Yes, I agree that if a repair is going to cost north of £700 then it probably makes sense to just go with gas only - especially for infrequent and fair-weather users like us.

DesG wrote:

Thanks Paul. Yes, I agree that if a repair is going to cost north of £700 then it probably makes sense to just go with gas only - especially for infrequent and fair-weather users like us.

But as Mike187 and I have said, if the description of your problem is accurate, the fault is unlikely to be the heating elements which will cost at least £800 to be replaced.  Whatever the fault, it will be picked up when you have your habitation service done and should be picked up when it's time to sell the van.  So one way or another you will end up paying.

Thanks for all the helpful replies.

To clarify, it turns out that heating is not working on electric either - apologies for the confusion.
See my reply to Mike for more details

Des

Daft question and I don't know your van type, but is the electric power switch on?

PLOUGHLIN wrote:Daft question and I don't know your van type, but is the electric power switch on?

Yes, power switch is on and ehu symbol is displayed on control unit.

Thanks

DesG wrote:Thanks for all the helpful replies.

To clarify, it turns out that heating is not working on electric either - apologies for the confusion.
See my reply to Mike for more details

Des

I haven't seen your reply to Mike.  This is what Truma told me last autumn:

Elements on a Combi boiler have a lifespan of approx. 3000-5000 hours so it would not be considered unusual for them to need replacing after 4 or 5 years of medium useage. 
The rrp of the element kit is £396.54 inc vat plus labour costs determined by your dealer.

If you have only used your van for 2 to 3 weeks per year, you have been incredibly unlucky if both heating elements have failed.  I would get it checked out when you have your habitation service if not before.