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Truma UltraHeat - Relay PCB connectivity?


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I have a small, but maybe an important question, to ask relating to the Truma UltraHeat  - model S3002? - dating from 2007 (Bailey Ranger Series 5)

The small pcb with the 3 relays that sits at the back, down near the floor, (difficult to get to!) - the transformer (that supplies 12v to the green LED, etc.)  has blown (now replaced) and now I'm wanting to re-install the board. I notice there are two black wires that go into the fire itself that need reconnecting. I'm a little concerned as to which black wire goes to which of the connectors, given that one connects (within the pcb) to the 'live' mains input.

The wire colours are (from the relay edge of the pcb) Green, White, Black, Red, Black (connected to 'live'), Blue (connected to 'neutral'). And on the mains input connectors are the two green/yellow earth wires, Brown ('live'), Blue ('neutral').

I've hunted Google for a diagram but can find nothing relevant. Can anyone assist in identifying which black wire is which - or does it make no difference and are internally (within the fire itself) connected together? (Not easy to physically check as the 'van is in storage).

Any help/comments would be appreciated. TIA.


 

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You do indeed have a problem.   All I can tell you is that of the six wires which lead from the terminal block and disappear through the grommet, four of them attach to the electric element, and two to one terminal on the two  temperature limiters, with the other terminal being attached to the element.

 

P1000453.JPG.bdd563bc78fb22782651ea4a6e4bb179.JPG

 

The six wires terminate (under the cover plate) as shown by the red rings, but as regards which colour goes where, it's impossible to say without looking.   And of course it doesn't help to say that you should never remove wires without marking them and photographing reference points.

 

Citroen C5-X7 Tourer+Avondale Rialto 480/2
https://jondogoescaravanning.com

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I have that model of heater and my van is accessible now, so I will go and have look , it may be the temperature sensor  for the auto speed control of the fan - I will get back to probably tomorrow as I have to go out soon.

In the meantime could you take photos of the top and bottom side of the PCB?

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Posted (edited)
1 hour ago, IAN2880 said:

In the meantime could you take photos of the top and bottom side of the PCB?

 

Ian - Here's a picture of the Control Board - but it doesn't help.  

 

P1000905.JPG.c74881084dd7b0d35e93b049431650b4.JPG

 

The OP needs to know which way round the two black leads attach to the terminal block.   The only way to see where they connect is to remove the cover plate and have a look.   To do that, you need to remove the fire first.

My first picture was taken after the flue had been detached and the fire removed.

Edited by Jaydug

Citroen C5-X7 Tourer+Avondale Rialto 480/2
https://jondogoescaravanning.com

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Thanks Jaydug, however I did take photos before removal, not expecting that the two black wires went to/from differing points on the board, especially when one of them is to the mains 'live' input. It wasn't easy to see what went where in such a confined space behind all the clutter that is the heater and its fan and not until the board had been disconnected and removed. I don't feel as though I would want to remove the fire if I can possibly avoid it (not gas qualified to do the refit).

Maybe there would be a resistance path through the element (or some other item that is accessible from the back of the fire) back to the pcb for one of the black wires that could be measured that I could compare. You quoted... "four of them attach to the electric element, and two to one terminal on the two  temperature limiters, with the other terminal being attached to the element." - that's 7 wires, I've got six. Maybe I'm misunderstanding that. Either way, moving on...

Looking at a photo of a replacement element there are red, green, white wires with "soldered" ends and a blue-spade wire. Maybe the "soldered" wires correspond to and are those that connect to the pcb. And one of the black wires (the wire that is 'live') "might" go to the temperature limiter(?). I may be barking up the wrong tree here, but it's an idea.

It's such a nuisance that Truma, in their wisdom (?), fail to produce/publish such a critical wiring diagram. No doubt copyright stuff -  and use the same colour wire for potentially two functions. And to use black as a 'mains live' wire colour - what BS are they working to?

Thinking out loud on the page and as I look at the pcb...

pin1 (green) goes to relay1 n/o - - - - - element1 end b (with blue spade wire to a limiter???)

pin2 (white) goes to relay2 common - - - element2 end b

pin3 (black) goes to relay2 n/o, relay3 n/o and ......

pin4 (red) goes to relay3 common & n/c (pcb tracked) - - - element1&2 end a

pin5(black) goes to mains live, transformer and ......

pin6(blue) goes to mains neutral, transformer and  ......


I've tried to follow the (possible) power pathway from the main 'live' black wire and if that wire should goto the temp limiter (does it?) the  via the blue spade element wire to the element and the green wire back to the pcb.....


If I were to measure between one black wire and the red wire (with the power off) should I be able to read one element value? and via the green wire giving a zero resistance? while the other black wire goes to I've-no-idea-where and no idea of what resistance I might find to any other wire.


Looking at www.caravantalk.co.uk/community/gallery/image/9301-dsc-0205/ it shows two temperature limiters, one with two black wires either side of the switch, the other limiter with one blue wire (from the element?) and an open connector. Does this now point me to the conclusion that it makes no difference which black wire connects to which connector on the pcb (and the other limiter is out of circuit and just a "wire holder" for the blue element wire)? If so, and the two black wires go to either side of the limiter switch, simply measuring between the two I should measure zero resistance (or close to it).

 

I think that makes some kinda sense - unless someone can prove me wrong before I blow myself (or the 'van) into a cloud of molten wires.

 

I've tried to work through how the relays are switched and the wire connections but fail to see where the blue wire from the pcb connects in the fire - unless it's missing on the limiter in the photo with the element blue wire on the other side. That could make sense but that might then lead to everything being "live" should that second limiter go open circuit as it effectively breaks the mains neutral connection.
 

And to Ian2880,

thanks for the hint at mentioning the limiter and heading me off in yet another direction that might have led me to the above possible conclusion (via the web link). Images attached of the pcb.

 

Forgive the ramble, but it helps me to write thoughts down, read it though and see if it makes sense. Hopefully these words might also help someone else figure it out also - even if my conclusions are wrong.

 

20220524_143221_1.jpg

20220524_143232_1.jpg

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I,ve just opened mine up and the two black  wires are a dead short and one comes from the live feed  and the other goes to the relays, which suggests that this is a thermal switch which prevent overheating of the element and and as such it is irrelevant which  terminal they go to  hence why the designers gave them the same colour

White  to Blue(neutral )   500W element,  Red to Blue(neutral)   is 1500 Watt.

 green to blue is also a dead short , which I also assume is the second thermal switch, but on the neutral side of the circuit.

Jaydug, my PCB must be an older version as you can clearly see the top tracks -see photo.

 

Truma-Ultraheat-PCB-wiring-001-s.jpg

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Posted (edited)

Looking at Monkey-Mark's other pictures in his gallery, it would seem that the two black wires in question both go to the two terminals on the bottom of the two temperature limiters.  

 

Monkey-Mark.jpg.a54d9347e83a7b9ee668eecee077d7c5.jpg

 

Question is - which way round do they go on the terminal block?   Does it matter?   Is it just a question of wrong way round and the fire just doesn't work as it should?

Edited by Jaydug

Citroen C5-X7 Tourer+Avondale Rialto 480/2
https://jondogoescaravanning.com

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If the two black wires simply go across the switch/cutout then it seems to make no odds as to which is which.

 

So many thanks to you both for putting up with and responding to my otherwise simple question - but it could have been so different had the wires gone elsewhere.

 

At least the question has been raised and it may help someone else further down the line if (when) they have the same issue.

 

Again, cheers to you both.

 

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When I bought my twenty-two year old Avondale, ten years ago, the previous owner's daughter told me the Truma fire had a fault.   Eventually, I tried it out and it did work - but later I discovered that when it reached a certain temperature, the fire automatically switched off.   The fault was that one of the temperature limiters had failed, and the fire wouldn't work again until it was manually switched off, the power removed, then switched on again.

It might be that should you get the wires the wrong way round, the fire won't work correctly.   But trial and error will maybe prove that theory.   My best wishes!

Citroen C5-X7 Tourer+Avondale Rialto 480/2
https://jondogoescaravanning.com

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12 minutes ago, Jaydug said:

Monkey-Mark's other pictures in his galler

Jaydug  how do I access his gallery I searched the forum  but it didn't produce any hits.

DGc88 :- Always happy to help and I enjoyed finding out more  about my heater in the process.

I took some readings of the current draw  at the various settings ,

500W = 2,2A , 1000W = 4.3A and 2000W = 9.0A, if you don't get  these readings  ( approx as they will vary with supply voltage),  you could swop the back wires over 

and please let us know how you get on 

and one final question  how did you release the wire from the mains terminal blocks , mine have funny little plastic 'T'   pieces sticking out, I didn't want to tug on them too hard in case I broke them

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Simply by pressing down pretty hard on the T part of the tag - it seems the only way. Some are harder to get the wires to loosen than others - or maybe that was just me also not wanting to break them. And thanks for the current draw for the various settings, not that I'm likely to want to check them. But always useful to know. Its all a learning curve and we never stop learning.

I'm still waiting for the transformer to arrive from Germany (via ebay); as soon as it arrives I'll get it fitted and then tested when I'm next on a site with EHU hook-up (no mains power on the storage site and not easy to bring the van home to test). Once tested, I'll add a comment or two on here as to how it all went, especially if anything else had gone faulty at the same time as the transformer (primary winding gone open circuit). So I'll be watching the thermal cut-out as a potential issue.

 

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7 minutes ago, dgc188 said:

I'm still waiting for the transformer to arrive from Germany (via ebay); as soon as it arrives I'll get it fitted and then tested when I'm next on a site with EHU hook-up (no mains power on the storage site and not easy to bring the van home to test). Once tested, I'll add a comment or two on here as to how it all went,

 in one of my jobs  I designed a control pcb  using a similar pcb mounting 12V  3VA transformer to power a microprocessor heater control systems ( no not for a caravan heater systems).

The first batch was of 500 and once installed in the student accommodation  about  30% failed , it turned out that  a batch of transformers  was faulty and the primary windings  failed after about 9 months continuous use.

We had to change all the boards on site and fit new transformers,  which  we sourced from another manufacturer and the new ones  were short circuit proof- I wonder?

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Just figured out the wiring for the electric heaters  see attached pdf

Why there are two thermal cutouts  I  don't know as they both effectively cut power to all the heater elements.

Truma S3002 heater wiring diagram.pdf

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6 hours ago, IAN2880 said:

Just figured out the wiring for the electric heaters  see attached pdf

Why there are two thermal cutouts  I  don't know as they both effectively cut power to all the heater elements.

Truma S3002 heater wiring diagram.pdf 38.69 kB · 2 downloads

The only reason I could think of for the TC's on both live and neutral phases would be to isolate the neutral side of the elements in the event of when an O/H event occurred and the van was connected to an opposite phase supply ?

Common sense isn't a gift, it's a punishment because you have to deal with everyone who doesn't have it.  :rolleyes:

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13 hours ago, IAN2880 said:

Jaydug  how do I access his gallery I searched the forum  but it didn't produce any hits.

 

Copy the address - www.caravantalk.co.uk/community/gallery/image/9301-dsc-0205/

that dgc188 put in his post.

Paste it into your browser.

Monkey-Mark's complete gallery will be displayed.   Unfortunately Monkey-Mark appears not to be a member of the forum now.   His last appearance was in 2019.

Citroen C5-X7 Tourer+Avondale Rialto 480/2
https://jondogoescaravanning.com

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10 hours ago, IAN2880 said:

Why there are two thermal cutouts  I  don't know as they both effectively cut power to all the heater elements.

 

The lower one switches at 125C and after it has cooled down will automatically reset itself.   The top one works at 175C and will remain off until the power is removed from the heater, when it will reset itself after a few minutes.

Assuming that both cut-outs are functioning correctly.

Citroen C5-X7 Tourer+Avondale Rialto 480/2
https://jondogoescaravanning.com

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Just now, Jaydug said:

 

The lower one switches at 125C and after it has cooled down will automatically reset itself.   The top one works at 175C and will remain off until the power is removed from the heater, when it will reset itself after a few minutes.

Assuming that both cut-outs are functioning correctly.

:Thankyou: I'll add that info to my drawing

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16 hours ago, IAN2880 said:

Just figured out the wiring for the electric heaters  see attached pdf

Why there are two thermal cutouts  I  don't know as they both effectively cut power to all the heater elements.

Truma S3002 heater wiring diagram.pdf 38.69 kB · 6 downloads

Interesting diagram, many thanks Ian. Given the limited time I had available, I hadn't worked it all through - but I did make a start. So you've saved me some time and at last, there's a published wiring diagram (no thanks to Truma).

I still can't figure out the reasoning behind one cutout being in the neutral line. If the power leads are wrongly connected (as they occasionally are - or were - "sur le continent") and the first cutout goes open, then that one is in the neutral line. Always pays to check the polarity of the mains input and have a reversing plug available to keep "live" where it ought to be. Maybe there's a valid reason, I just can't see it. Maybe a mod coming up here - put both cutouts in the "live" side of things (and check the mains input polarity!). I just hate the idea of the neutral going open circuit leaving the rest of the kit "live".

Slightly different scenario, a few years ago our street had a cable fault where the underground "neutral" went open; this resulted in the" live" not being referenced to anything; the "live" voltage went quite high, did a lot of equipment damage (TVs, alarms, you name it). That's one reason I don't like the idea of a "neutral" going open - leaving the rest of the fire (in our case) being "live". 

Call me paranoid if you wish, but.....

 

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Just now, dgc188 said:

Slightly different scenario, a few years ago our street had a cable fault where the underground "neutral" went open; this resulted in the" live" not being referenced to anything; the "live" voltage went quite high, did a lot of equipment damage (TVs, alarms, you name it). That's one reason I don't like the idea of a "neutral" going open - leaving the rest of the fire (in our case) being "live". 

Call me paranoid if you wish, but.....

Yes I've seen that in industrial electrical installations where the neutral is lost  at the either the main switch room or in subsequent distribution boards, and  because the installation is three phase, one phase  will always increase in voltage wrt to neutral, and all the poor 240V single equipment - mainly small motors and fans and electronics  go pop. 

 And re the drawing  I'm a  bit OCD when  analysing   electrical and electronic circuits ,  I always make CAD diagrams rather than back of fag packet sketches as you never know when you will come across the same  kit again and its best not to start from the beginning again.

I hope the transformer  sorts the problem for you

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