Heatline Compact S24 boiler issues

11 Oct 2014
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United Kingdom
Hello to everyone, first post after reading many many posts on similar subjects...

I have a Heatline Compact S24 boiler which recently cut out owing to water leaking from the 3-way valve (the diverter valve) and shorting the actuator motor. I ordered a new actuator motor & diverter valve repair kit and fitted it over the weekend. I'm still seeing a couple of issues which I'd be grateful if anyone could lend some advice towards.

1. Firstly, the Heatline service manual never once mentions the 3-way valve as being part of the hydroblock - so if anyone is ever wondering what the thing is or where it is - now you know; it's located on the left part of the hydroblock (the right part being connected to cold water inlet and CH return via the pump assembly which includes the PRV and the automatic air vent). This first part just in case anyone gets puzzled by the service manual appearing to suggest the actuator motor is the 3-way valve - it's not, it's the motor for the valve. Incidentally if you have dirty water in your system it'll eventually kill the 3-way valve and let water into the motor which will either blow the main PCB fuses F1 and F2 (both marked F3.15L250V, so I'm assuming are both 3.15A rated) or it'll trip the MCB in the consumer unit.

2. With respect to the 2 fuses on the main PCB, I've had them both out and checked for resistance and continuity and they both appear to be still functioning. I get continuity on both with a digital multimeter, and a lowish resistance level on the 200Ohm setting (near zero, but not quite, neither fuse appears to be open circuit and as I mentioned both beep using the continuity check on the diode setting of the multimeter). What's puzzling me here is the MCB on the consumer unit is rated at 6A/6KA - it's a Protek single pole MCB 106/2B type B MCB and did initially trip when the actuator motor shorted out, and (maybe foolishly in hindsight, although I wasn't sure at this point that the motor had water ingress from the 3-way valve leak) when I flipped the switch on the MCB back to ON, and went back to the boiler to switch it on it immediately popped something somewhere (there was a quick clicking noise/popping nose and a smell of burnt...something...coming from the actuator motor). I went back downstairs to the MCB after turning the boiler off and noticed the MCB switch was still up in the ON position - but no power to the boiler of course (a quick on/off check - no LED lit to indicate power).

So, after replacing the 3-way valve (a total pain in the buttocks mostly cos despite draining the system down via the drain valve downstairs, there was still a little water in the secondary heat exchanger and 3-way valve which made life tricky when I was trying to take them off for replacing the 3-way valve, mostly owing to the boiler's proximity to the wall and difficulty in getting a couple of containers behind the left and right parts of the hydroblock to catch the remaining water) and cleaning out the secondary heat exchanger with the high pressure washer (suboptimal I know, but I thought it would be better than not doing it) I managed to refit everything and refill the boiler. I thought possibly - given the fuse continuity and the replacing of the motor, along with the MCB not tripping again, things might be ok but I was too optimistic.

3. Once I had the system full again and no leaks from the secondary HE or the 3-way valve I was at least confident the refit was sound mind you, but again - no power to the boiler.

Question: Is it not strange to see an MCB remain in the ON position if it's gone? I removed connector X15 on the main PCB to disconnect power 'supply' to the boiler - power still off at this point - I checked continuity between the L and N pins on the X15 PCB connector (that is, on the PCB pins themselves and not the now-disconnected jumper which goes into them) and got another beep. I know electronics can be a bit more puzzling to properly work out whether something is really shorted or supposed to be connected but I'd have thought I shouldn't be seeing continuity between L and N pins.

Checking - with the MCB still ON - the power supply at the wall beside the boiler (X15 jumper still disconnected) I see no voltage between Live and Ground, which is making me think the MCB is faulty. Ive ordered a replacement Protek MCB since I read that one shouldn't try to mix manufacturer parts in the consumer unit (I also understand swapping an MCB for one of the same type doesn't violate Part P regulations, but I'll be enlisting the assistance of a spark mate for that part and would appreciate whether I've got my facts right with respect to this bit, i.e. can I replace myself or with assistance without breaking any regs?

I notice this morning that the boiler has lost a bit of pressure - around 0.3/4 bar - on the front unit gauge, and there's been a wee bit of water leakage on the 'top' half of the boiler. That is, the Ch outlet pipe from the main heat exchanger/combustion chamber has a bit of water leaking (I only attribute this to the CH pipe as that's the only pipe leaving the combustion chamber on the left, the other is the CH return on the left hand side above the pump, ignoring the gas inlet in the centre).

There are no visible water leakages from the lower part of the boiler where I replaced the 3-way valve and refitted the secondary HE with new O-rings, just a wee bit collecting on the thin aluminium plate separating top and bottom halves.

Anyone be able to figure out why I'm seeing this water collecting from the top half? (I realise obviously something is leaking slightly, but I can't see just where it would be coming from. Access to the side of the boiler is near impossible - it only allows a cursory squint if I try to jam my head down the side, which makes determination of the leak position quite difficult).

One last thing with the water - the automatic air vent cap is missing - I don't ever recall having seen one on the damn thing, and there's a tiny bit of water egress from the top of the vent. Given it's position on the opposite side of the leak (and on the bottom half of the system) I'm hopeful I can use an old car tyre valve cap to cap it off - I tried a bicycle tyre dust cap and it's a little too small. Purely to save replacing the vent you understand, although if I'm told that should be done then I'll go order a new one.

I had the system flushed professionally a year or two ago, and a spirotrap filter installed on the filling loop, or near it I should say, but I have noticed form the cleaning of the secondary HE that there's obviously still a bit of crud in the system.

I'd go all out and replace the whole thing with a new flush if we weren't planning on extending the place in a couple of months and moving the entire system (well, replacing it but relocating it downstairs I mean) so any advice to keep things ticking over for the short term would be very much appreciated - and thanks for sticking with the post this far!

Quick summary of questions:

1. What might be the cause of the leak on the top half (and where exactly, if anyone has experience of similar situations)?
2. What are the odds the MCB replacement will fix the power supply?
3. Is my concern at the L-N continuity on X15 (the PCB side, not the jumper which goes into it) justified?
4. Why would the MCB have blown and died but not the fuses on the board?

I've included a few pictures:

(These images mostly to show the replacement 3-way valve/motor and show there's no water leakage from the bottom half of the boiler.

Thanks again!

1. The top half separated by the aluminium plate, left hand side - water is collecting here and running down the CH outlet pipe

View media item 838882. Closer pic of the CH outlet pipe with small drip showing behind hydroblock

View media item 838873. Pump and PRV and air vent

View media item 838864. New 3-way valve and motor - note the drip on the CH outlet pipe above the union (this water coming from somewhere above)

View media item 83885
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Well those reading all they ( if they did not get bored or die ) will now realise all that a boiler engineer has to do to repair boilers!

However, you have opened the combustion chamber and no one should do that unless they are gas registered.

So you now need to call a competent boiler engineer who can come and check it for safety and he will also advise on your supply problems which I suspect are associated with a switched fused spur.

Hi Tony,

Thanks for the reply - d'you mean removing the silver face plate on the front, which covers the primary HE and associated gubbins?

I thought the combustion chamber was 'that' part behind the silver plate rather than the plate itself + all the stuff behind it...I had to remove that to get the sides off as it screws into the side panels

I haven't opened the bit in the photos, although I fear that's not what you were referring to, was it?

(Just to confirm - it's not possible then to get the sides off without opening up the combustion chamber?)

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