Kingham Truma Combi heater over heat problem

Hi Karl
In the end we gave up dealing with it as we were on holiday. We ran it on gas and got back Monday.
Will be replacing the fuse later today and will update you then.
I dont think this is a boiler overheat issue for us.
We werent using the heating at the time just the hot water.
An overheat of the hot water should be rectified by pressing the overheat re-set button. This didnt work for us.
The site hook up tripped the night the boiler stopped working on ehu so we think the site hook up had a surge that night which has blown the fuse in the boiler. The fast blow fuse inside the boiler is apparently likely to blow if there is a surge.
The problen is its not easy to get to hence why we gave up and used it on gas for the rest of the holiday.

snow863 wrote:Hi Karl
In the end we gave up dealing with it as we were on holiday. We ran it on gas and got back Monday.
Will be replacing the fuse later today and will update you then.
I dont think this is a boiler overheat issue for us.
We werent using the heating at the time just the hot water.
An overheat of the hot water should be rectified by pressing the overheat re-set button. This didnt work for us.
The site hook up tripped the night the boiler stopped working on ehu so we think the site hook up had a surge that night which has blown the fuse in the boiler. The fast blow fuse inside the boiler is apparently likely to blow if there is a surge.
The problen is its not easy to get to hence why we gave up and used it on gas for the rest of the holiday.

I'm not sure about that. 

Read what Dare-Devil-Dennis said in the link I just posted. The fuse is rated to run at around 25 degrees Celsius. The hot water gets up to 60 degrees Celsius, so the fuse is likely to age, and blow prematurely at less than its rated current.

Too soon to say if the fans have cured the problem - I'll be able to report back next Spring.

I have read it Dave. I just think the ehu surge caused my fuse to blow. Our van is different to Dennis' van and our casing has several much larger vents in it on 3 of the sides and the lid.
If after we change the fuse it blows again I will definitely look at the ventilation but not keen on installing fans unless we have to.

Thanks I will be changing my fuse later, IMO it has a lot to do with how they are installed, they are a big heater in a tiny area, if I close my rear vents to force air to the front it will overheat and trip in a matter of minutes. A very poor install for access aswell

Have changed the fuse. With the under bed storage empty and the bed stripped it was easier to get the casing apart.
Have run heating and hot water for an hour now. No trip so far. Will see what happens. Will update if it doea blow again.
I agree its important not to block the vents to the casing and the heating outlet vents.
I also think it is ridiculous to have to remove all the casing to get to the re-set button and/or the fuse. Definitely not a job you want to do on holiday with bed made up etc. and back doors wide open. We were up on the north west coast of Scotland and had strong winds and rain showers every 10 mins you dont want to be working at the back of the van with the doors open in that.

Karlburn wrote:Thanks I will be changing my fuse later, IMO it has a lot to do with how they are installed, they are a big heater in a tiny area, if I close my rear vents to force air to the front it will overheat and trip in a matter of minutes. A very poor install for access aswell

Karl, doe the Fairford have the 'reducers' in the pipework going to the front of the van like some other models?
this is to allow slimmer pipe to run behind certain appliances before emerging at the front...and as we know from many posts, the heat from these is poor...
if this is so, and you then close the rear vents to force more aire to the front, this air is being forced through pipe that is much smaller than the norm and may cause a build up as the heater produces more oomph than the small pipes can get rid of...
I've seen these installs in a Kingham, I think, and (IMHO) it's asking for trouble....why not make sufficient room for fullsized pipes to run behind/under the kitchen/fridge etc?
with rear vent closed and the two front ones half sized, the poor heater is trying to put all its heat through (in effect) one outlet...
as Mr Mikawber might have said "result ruin"

We have the Kingham and yes the pipes to the front are smaller but I find the heater warms the van well if you leave all the vents open and unobstructed.
When we bought the van the small pipes under the bed had come loose so we werent getting much heat at the front. Once fixed back securely the heat reached the front better.

All done now  it is an absolute PIG of a job but it appears it might be a common one, 16 screws in total and a 20 torx needed
 
My first attempt as just taken approx 2 hrs now I know what I’m looking at this be 30-45min job

It is indeed the same idea, I think the secrect is to leave everything open it just takes 5 mins longer to warm the front, the wet room makes a very good drying room with the door closed.

bolero boy wrote:

Karlburn wrote:Thanks I will be changing my fuse later, IMO it has a lot to do with how they are installed, they are a big heater in a tiny area, if I close my rear vents to force air to the front it will overheat and trip in a matter of minutes. A very poor install for access aswell

Karl, doe the Fairford have the 'reducers' in the pipework going to the front of the van like some other models?
this is to allow slimmer pipe to run behind certain appliances before emerging at the front...and as we know from many posts, the heat from these is poor...
if this is so, and you then close the rear vents to force more aire to the front, this air is being forced through pipe that is much smaller than the norm and may cause a build up as the heater produces more oomph than the small pipes can get rid of...
I've seen these installs in a Kingham, I think, and (IMHO) it's asking for trouble....why not make sufficient room for fullsized pipes to run behind/under the kitchen/fridge etc?
with rear vent closed and the two front ones half sized, the poor heater is trying to put all its heat through (in effect) one outlet...
as Mr Mikawber might have said "result ruin"

Karlburn wrote:All done now  it is an absolute PIG of a job but it appears it might be a common one, 16 screws in total and a 20 torx needed

Good your boiler is working again

So I'm clear, that is 16 AutoSleeper screws and zero Truma screws on a Fairford?   (It is just 6 on a Warwick Duo)

On the Kingham its 6 autosleeper screws to the casing lid under the bed and 2 torx screws on the Truma boiler cover

snow863 wrote:On the Kingham its 6 autosleeper screws to the casing lid under the bed and 2 torx screws on the Truma boiler cover

Hmmmm, I might be thinking about a different fuse because there are no screws on my Truma Combi 6E. The panel just lifts up and off.

I have the same Truma boiler as you. The red arrows on your photo point to the 12v fuse. The 240v fast blow fuse is located behind the black casing below the 12v fuse in your photo.
Check out the diagram in the manual - its the 240v fuse that had blown on mine.

just read this very informative thread and will be adding to my on board service kit in case we endure the same.


Snow863 did you have to remove the entire wooden box in one or in pieces ?


T20 driver
10amp  fast blow glass type 5x20mm (240 V)
Does anyone have the spec for the 12 V fuse ?

Anything else recommended to simplify the task ?

Thanks

You only need to take the top off the wooden box.
However we also unscrewed the rear panel as it makes the access easier via the rear doors and we have now kept this panel loose fitted to improve access to the under bed storage area via the rear doors.
We used a no. 15 torx on the 2 boiler casing screws.
The fuses to the 12v and the 240v are identical ie 10amp fast blow 5x20mm. Truma confirmed this to me over the phone - definitely identical 10amp fast blow.

snow863 wrote:You only need to take the top off the wooden box.
However we also unscrewed the rear panel as it makes the access easier via the rear doors and we have now kept this panel loose fitted to improve access to the under bed storage area via the rear doors.
We used a no. 15 torx on the 2 boiler casing screws.
The fuses to the 12v and the 240v are identical ie 10amp fast blow 5x20mm. Truma confirmed this to me over the phone - definitely identical 10amp fast blow.

 It was the 240volt fuse on mine, you need to take the torx screws out and the panel pulls away, I removed the fuse in the picture just for my own reference and nothing works and you get an error code on the panel.
  
The boiler in the fairford is the same but it’s mounted with the service panel against the side of the van, very awkward access.

snow863 wrote:
The fuses to the 12v and the 240v are identical ie 10amp fast blow 5x20mm. Truma confirmed this to me over the phone - definitely identical 10amp fast blow.

The fact that Truma confirmed to you that the fuses are both 10A fast blow is noteworthy because that fuse spec differs to the spec given in the manual.

Page 8 of the manual states use a "T 10 A" fuse (3 times) which is a slow acting fuse. Also page 8 states "slow-acting" twice which is consistent with the T10A spec.


A slow blow fuse can withstand surge currents (above rated 10A) for a short period of time such as when powering on/off.

I think I can see how using a fast blow fuse where a slow blow is specified could lead to the fuse blowing when no fault is present.

Now you have me confused Don!!
My AS and Truma manuals definitely say 10amp fast blow for both fuses.
You can see the manual here:
[You must be registered and logged in to see this link.]
It also states "F10A" and  "10amp quick acting fuse"
I checked with Truma just in case and they confirmed 10amp fast blow should be used for both. F10A is a fast blow type.

I checked both fuses when I had mine apart and they are both T10 slow blow.
I would not use f fuses as they have been known to blow on switch on and this heater will suck when used from cold

Perhaps we have different models? I have no idea.
 All I know is the AS and the Truma manuals for my van/boiler  both say use 10amp fast blow fuses. I queried this with Truma on the phone last week and they were adamant I must use a 10amp fast blow fuse. Also someone else on this thread said last week that they had used a 10amp fast blow and it had lasted over a year.
Have run boiler since yesterday morning, it hasnt blown yet.
Guess I will have to see what happens.

snow863 wrote:Now you have me confused Don!!
My AS and Truma manuals definitely say 10amp fast blow for both fuses.
You can see the manual here:
[You must be registered and logged in to see this link.]
It also states "F10A" and  "10amp quick acting fuse"
I checked with Truma just in case and they confirmed 10amp fast blow should be used for both. F10A is a fast blow type.

I agree the reference you give says fast acting.
Here is another reference that says slow acting (page 8) [You must be registered and logged in to see this link.]
and so does my paper manual (photo below which you can read if you click the enlarge button)

My van is a 2017 model.

I like the idea of a slow acting fuse if it is hard to access, and they are only a little more expensive. A slow acting fuse is less likely to blow.

I am at a loss to understand why there are different copies of the manual for the same product.
I see that your copy is also for the combi 6e and says T10A but the manual for my combi 6e says F10A.
Its madness!
It certainly makes more sense to use a slow acting fuse which is why I rang Truma last week and queried it. They were adamant that it must be a fast blow fuse!
Will be phoning Truma in the morning for an explanation!

Am now wondering if they have changed the manual since my van was built (2014)? Could they have changed the fuse in later versions of the same boiler model because it blew too easily?

Dug the old fuse out of the bin and found it was a T10A H type fuse.This is a slow blow ceramic type fuse. So I have ordered a T10A H fuse and will change it asap. 
Looking at the tech spec for a T10A H fuse on Amazon here:
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I see that this fuse is apparently designed to operate in temperatures far greater than the F10A. The info on Amazon states operating temps of 55 deg C to 125 deg C which is consistent with the likely temp of this boiler and considerably warmer than the operating temps of the fuse referred to in Dare Devil Dennis' comments in Dave's fact sheet.
Could it be that I am not the only one who has the wrong information in their manual? If so changing the fuse to a fast blow type  F10A instead of a slow blow T10A H fuse could be the reason why many owners have been having problems?

snow863 wrote:Dug the old fuse out of the bin and found it was a T10A H type fuse.This is a slow blow ceramic type fuse. So I have ordered a T10A H fuse and will change it asap. 
Looking at the tech spec for a T10A H fuse on Amazon here:
[You must be registered and logged in to see this link.]
I see that this fuse is apparently designed to operate in temperatures far greater than the F10A. The info on Amazon states operating temps of 55 deg C to 125 deg C which is consistent with the likely temp of this boiler and considerably warmer than the operating temps of the fuse referred to in Dare Devil Dennis' comments in Dave's fact sheet.
Could it be that I am not the only one who has the wrong information in their manual? If so changing the fuse to a fast blow type  F10A instead of a slow blow T10A H fuse could be the reason why many owners have been having problems?

Thanks for this Snow.

It would certainly seem logical to use a slow blow fuse on something that takes a jolt on start up.

As for Messrs Truma giving advice, I think it all depends on who you talk to. Before all this started I was not too keen on having the wardrobe (directly above the heater on ours) heated like a sauna, and asked their "expert" at a show if it would be OK to cover it with some insulation.

He said it would be most unwise, as it would cause the unit to overheat!!! I'm fairly thick with electronics, but I suggested that's why it's fitted with a thermostat, and wouldn't that prevent any overheating. "That's altogether different." he said, but gave no further explanation.

He insisted that the casing is well insulated already . . . which was easily proved to be quite wrong when looking at their cut-out model. If a small air gap between the casing and the internal components can be classed as insulation, then I guess he was right  . . . but how could the casing be fitted without leaving a small gap??
This could become the new "Gassing" thread!!