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  • Author Author: koudelad
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Repair of a CNG boiler control board

koudelad

Hello,

 

(Note: I know I am posting this a month after a deadline, but I thought it is worth mentioning as I am very happy about it.)

 

Previous month's theme was Simple Electronic Repairs Project14 | Earn a $100 Shopping Cart for Your Simple Electronic Repairs! . I didn't have anything to repair that time, but a coworker approached me one week before Christmas, because he noticed I was talking about electronics to another colleague. He has got an almost 16-year old Vaillant CNG boiler for a heating of his entire house (including a water tank). The trouble was that a control board couldn't switch the burner properly. He did a good job examining the control board and finding out, that after knocking on one of the two relays present on the control board, the relay switches the contacts and the heater is turned on. This was his daily job for a few weeks, in fact, turning on the electronics every day after coming from work, knocking on the relay, heating the house and water (thermostat was bypassed for obvious reasons, max. output was delivered to the heating system) and switching everything off in the evening.

 

The servicing company said that another board (probably used) would cost ca. € 400.

 

I requested a photo of the board and especially the relay and their surrounding:

image

 

The relay is identified as EE Electronic E3206S (for switching 250 V, 10 A), working with 24 V DC and resistance of the coil 1100 Ohms. I haven't found a way to buy a new one from common distributors, but I found a seller on eBay that had two unused relays (probably in the past). It took about 2 weeks during the Christmas time to get it from Australia to Czech Republic.

 

Yesterday I visited my colleague with a soldering iron and a simple manually operated "pen style" pump and replaced both relays. I am glad the board was originally soldered using a lead solder, so I could do the work easily. I have no I idea whether I would be successful if the lead-free solder was used (need to do more research on that, I only have one bad personal experience).

 

image

After replacing the relays and plugging everything back again, a magical moment came. The boiler started as before the breakdown.

 

We are both happy that we gave a meaningful life to the board again, for about € 10, saving € 390 + price of the work.

 

This was not the end of this evening image I also repaired a toaster (burned temperature fuse soldered inside) for about €1 (new could cost ca. € 30 - 50) and rewired his house lights in one room (after a not very successful change of a power switch), so it could be switched on and off from two places.

 

I don't have a video, because there wouldn't be much to see, as the device is well covered and the flame is not visible.

 

David

  • in reply to koudelad

    I can't find a datasheet for the relay to compare this value with an expected life.

    It wouldn't matter ....

     

    Given that your friend was able to 'knock' it into life, suggests the contacts are the issue, not the failure of the coil or the mechanism.

    If the load was slightly inductive, there would be some pitting, and this might be able to be polished out ... but it would come back again later.

     

    At least you know what the cause is, and it's a relatively easy fix, even if you need to do some tricky wiring next time to fit a different style relay.

     

     

     

    Mark

  • By the way, I forgot to add an important information. The regulator reported that the heater switched 27 000 times before failure. This is probably true, 16 years, meaning ca. 1 700 times switched per year. This is ca. 4,6 switches a day (during summer, only water is heated, but the boiler is operable for the whole year).

     

    I suppose the reported value is only for turning the heater on, which would mean 54 000 switches of the relay in total. Unfortunatelly, I can't find a datasheet for the relay to compare this value with an expected life.

  • Hi David,

     

    Awesome job(s)! This series on repairs is really great. And good seeing the massive savings by not throwing out hardware. Spare parts for boilers are really expensive, and of course schematics are not always available, so the system is often against those who wish to self-repair : (

  • I am glad the board was originally soldered using a lead solder, so I could do the work easily. I have no I idea whether I would be successful if the lead-free solder was used

    Just add new solder and treat it the same way as you normally would.

     

    Mark

  • in reply to tariq.ahmad

    Oh, I wasn't aware of that. Thank you for pointing that out.

     

    I haven't even thought about it, because I "knew" that the project theme was over. As I wrote above, I didn't even film a video for this blog post as the only difference would be in a few clicks of the relay and the heater, but nothing else visibly changes. Rules need to be followed, so this shouldn't be taken as an entry.

     

    Anyway, I have a warm feeling about this repair, but definitely not as warm as the owner of the boiler image