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Truma Ultrastore Water Heater Element Test Result


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#1 Burgo

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Posted 14 February 2011 - 09:55 AM

Hi all,
i do not know if this will help other or not ??
I had a faulty element on our Truma Water Heater (450W element 2003) and so took the decision to change it not knowing for sure if it was the cause.

These are the results i made for the element and so wanted to pass on.

OLD ELEMENT
Resistance checks only
Live & Earth - 7MOhms
Neutral & Earth - 7MOhms
Element & Earth - 37Ohms
Live & Neutral - 122Ohms

NEW ELEMENT
Resistance checks only
Live & Earth - O/C
Neutral & Earth - O/C
Element & Earth - 2.4Ohms
Live & Neutral - 120Ohms

All the best

#2 iansoady

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Posted 14 February 2011 - 11:00 AM

Those figures between the element and earth look a bit scary to me. Are you sure they're not MegOhms? Or are you measuring between the outside casing and earth? TBH I would treat the difference between 7 meg and open circuit as academic. It would allow a leakage current of around 3 x 10-5 amps.....

120 ohms looks like a reasonable value for the element ie giving a current of around 2 amps hence power of 460 watts or so.

#3 Guest_baccy_*

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Posted 14 February 2011 - 03:07 PM

Those figures between the element and earth look a bit scary to me. Are you sure they're not MegOhms? Or are you measuring between the outside casing and earth? TBH I would treat the difference between 7 meg and open circuit as academic. It would allow a leakage current of around 3 x 10-5 amps.....

120 ohms looks like a reasonable value for the element ie giving a current of around 2 amps hence power of 460 watts or so.



Spot on

#4 Arc Systems

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Posted 15 February 2011 - 11:07 AM

A bit of confusion at first because the capital 'O'hms read to me as a zero tacked on the end of the values?! However, my take is 'element' is the metal case of the element and therefore short to earth would be correct.

Does though prove, now't wrong with the old one! :unsure:

#5 Burgo

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Posted 15 February 2011 - 07:47 PM

I think i am going to regret posting this post !
I was trying to offer readings of a used element and also brand new to help alleviate problems.
I fitted the new element at the weekend but i have been unable to test as of yet.

My problem was that the heater red LED on the temperature control module would come on after about 15s or so of trying to heat the water up.
From information i have received (only by asking questions on forums) the problem was pointing to the element.
As with everybody else at present money is tight and so trying to fault find and problem solve on me tod !.
I'll probably end up regretting this and have to seek professional help and rectification.

ARC Systems - According to my caravan user manual, the heater element will only heat the water to 70 C even though there is a temp control knob, this is for gas only, I have a green LED and RED, green for GO, red for PROBLEM. The heater works perfectly on gas but fails on electric. The ultrastore on my dart has a seperate isolation switch near the water heater and i can confirm this fuse is OK, i can also confirm the fuse on the main fuse panel is also A OK.
Regards
Steve

If i have misinformed people regarding my readings then i apologise - it was unintentional.



#6 dougie

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Posted 15 February 2011 - 08:26 PM

You are correct with the gas operation and the LEDs are for gas only,there is no indication that electric is actually heating water. If you are sure you are getting power to the element then most times it is the element that is duff and is usually a bit blue and distorted when removed.

#7 Arc Systems

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Posted 15 February 2011 - 11:52 PM

Sorry if you thought I was getting at you but certainly not, I was only pointing out a reason for the worry over an apparent short between 'element' and earth and if I'm correct, there's nothing wrong with the old element.

Gas is more controllable and the control switch with green/red etc only concerns operation with gas.
Constant green is all ok, if it is joined/replaced by red after 10seconds or so, then this is the end of the 'start cycle' and it has failed to light, as there is a fault, the gas operation is then shut down

Electric water heating is totally independent and simply fixed at 70degC, the on/off 'fused switched spur' control switch being the only control, given then your figures prove there is nothing wrong with original element the fault is elsewhere.
There are then plenty of known instances of the switches fuse holder being faulty, fuse itself though is fine.

A simple way of testing for this is to directly connect the 'live' output wire leading to the element, to the brown input live wire, this takes the fuse/fuse holder out of the circuit and if the water gets hot then, change the switch.

#8 Burgo

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Posted 16 February 2011 - 08:42 PM

Hi Gary,
no no, your post was absolutely fine.
You have a fair point regarding the switched fuse spur.
As i have already fitted the element, i shall try it at the weekend, and if it still fails then i shall proceed with your recommended tests.
Regarding these green and red lights i am still somewhat confused.....
I have only ever used electricity to heat our water, so i turn the dial to on and a green light comes on and after a while we have hot water.
Of late, when i switch on, the green light goes out (i think) and the red light comes on after about 10/15s, i leave for a while and try again and same thing - end result cold water.
What i have had to do for the end of season is turn the gas supply on to the heater and hey presto - hot water. According to my caravan handbook the red light indicated "a fault".

It would be prudent for me to follow your advice seeing as you are a specialist in this field, as, as i type this i am now cursing myself for spending 65 on new element that was probably not required, only a 10 switched fuse spur.

Anyway, as long as the weekend is dry, i will charge my battery, fill my aquaroll and hopefully make hot water ......................, will keep you posted.
Many thanks
Steve

#9 matadormajor

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Posted 16 February 2011 - 10:16 PM

.
Of late, when i switch on, the green light goes out (i think) and the red light comes on after about 1015s i leave for a while and try again and same thing - end result cold water.


Hi,

If you have not yet removed the water heater gas vent cover from the outside of the van, the unit will register a fault and cut the gas. The light sequence will be as you describe.
The cover has no effect on electric element operation.

Les.

#10 Arc Systems

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Posted 16 February 2011 - 11:03 PM

Regarding these green and red lights i am still somewhat confused.....
I have only ever used electricity to heat our water, so i turn the dial to on and a green light comes on and after a while we have hot water.
Of late, when i switch on, the green light goes out (i think) and the red light comes on after about 10/15s, i leave for a while and try again and same thing - end result cold water.
What i have had to do for the end of season is turn the gas supply on to the heater and hey presto - hot water. According to my caravan handbook the red light indicated "a fault".



I think from the above in bold, that you have been using gas for heating all along but without realising? one main point being, only when the gas was switched off did you fail to get hot water and the red light come on.

The other point is, the switch with green and red lights being for controlling gas heating only, has then nothing to do with the electric heating and should be left switched off while on electric heating, no need to touch it at all!

......................

Also Les makes a good point, Truma use a solid cover over the outside flue, this is to keep the internal clean and free from creepy crawlies!
If that's in place the gas cannot get enough oxygen so will not light, again then this shows a red light fault.

I wonder then if this has anything to do with it failing to heat water?

#11 iansoady

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Posted 17 February 2011 - 01:42 PM

I think from the above in bold, that you have been using gas for heating all along but without realising? one main point being, only when the gas was switched off did you fail to get hot water and the red light come on.

The other point is, the switch with green and red lights being for controlling gas heating only, has then nothing to do with the electric heating and should be left switched off while on electric heating, no need to touch it at all!


Sounds absolutely right to me. I've never understood why the electric switch doesn't have a light though.

But Steve - don't feel bad about posting. The great value of this forum is we can all learn from each other.

Edited by iansoady, 17 February 2011 - 01:43 PM.


#12 Burgo

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Posted 25 February 2011 - 12:02 AM

Don't i feel a right plonker.
I now have hot water - i now have a new element installed, but my guess is, the old one was fine - as quite rightly pointed out to me.
I turned the temp control knob on and again after 10s the red light came on indicating fault (i now know this is for Gas only and failure to light)
I was so sure that i had the gas isolation valve off to the heater as i have always used the electrical side.

Upon reading the manual (not something i like to admit defeat to !!) it did seem to make a bit of sense.

Once again, big thank you to all who posted with help / information
Cheers

#13 iansoady

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Posted 26 February 2011 - 04:39 PM

i now have a new element installed, but my guess is, the old one was fine - as quite rightly pointed out to me.


Well at least you now have a spare....




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