Ravenheat CSI85T - No Main Burner Ignition - Gas Valve?

[topskins]

Hi,

My Ravenheat CSI85T is now no longer igniting the main burner for either CH or DHW. Well, it does, but only once in a blue moon.

With heating on demand, and main front cover off, I hear and see the following:

* Click of a relay on the main PCB board
* Fan starts up and continues running
* Pump running (to touch, can't hear)
* Pilot burner visible through glass window on combustion chamber
* Clicking spark ignition sound for around 30-40 seconds together with pilot burner

...but then, no main ignition. After about 50 seconds everything switches off, a short while later I hear a faint "ping" from roughly where the APS is top-right, and finally the flame failure light comes on and the boiler needs to be reset. This seems to happen about 29 times out or 30 post-reset. Occasionally either CH or DHW is successful, but this has usually been first time after a night of the boiler being switched off (could be coincidence?) and thereafter it seems to be the same as above.

I've checked the obvious things, at least to me. The flue is clear, the condensate drain compartment at the back is full in one cavity and empty in the other where the water "trickles" over to the drain outlet i.e. same as it has always been, and the sensor is on the empty side.

From searching here, am I right in thinking that this is most likely the gas valve? If so, it's certainly out of my own personal "safe scope" for repair, and at £120 for the part anyway vs. £450 for what the boiler cost new, I think I might look at getting something a bit more reliable installed instead as this isn't the first of my problems.

Before that though, is there anything else I can test/look into here? Is a faulty APS likely, some other sensor, or is the gas valve the obvious candidate?

TIA.

 

[gas4you]

Check for 230V at the gas valve terminals.

 

[topskins]

Thanks Dave... I have multimeter in hand, but not 100% on what terminals should be checking on the valve. Here's a pic (it's a Honeywell gas valve):



Basically the top block of connectors, from the manual, look to be the power-supply to the valve itself from the main PCB i.e. the ones pulled away in the pic, but I'm not sure which terminals I should be checking for 230V against. I've since looked at the fault-finding section in the manual and it says "Is there 230V at pin ML connections". What does ML mean in this context

Added Later

Ehhh...now that I look at my own picture properly, I don't suppose it's the two purple ones connected above with the thing that looks like a valve behind it ?

If so, I just disconnected them and popped the multimeter probes onto them - no voltage. I guess this means that the fault lies elsewhere then, or am I jumping the gun?

 

[gas4you]

I'm not an expert on these but I think this is the ignition pcb.

You should be able to trace the wires from the wiring diagram in th MI's

 

[topskins]

Thanks Dave. That's where the Ravenheat fault finding eventually takes you too...but then they also mention a fuse on the ignition PC...when there isn't one, as it's on the mainboard . Since the original post I've checked the APS and it seems to be fine, with tubes/venturi clean and unkinked.

As an aside...I see you're located in Norwich too. I know Ravenheat aren't the most popular boilers around, but do you know of anyone that does deal with them in the area? If the fix isn't an obvious, non-directly gas related thing, then I think I'm looking at just getting someone to get this boiler going in the short-term and then arranging to get it replaced with something a bit more of a "known-quantity" in terms of reliability...

 

[topskins]

Actually...this is all seems a bit odd. I've been looking about for replacement ignition PCBs, just on the off-chance that the price makes them worth a punt. However...the Ravenheat manual part-numbers don't seem to match to anything in my own boiler when I find pictures on-line. I have 0012GEN05005 listed in my manual, which apparently looks like this:

However, what I seem to have is a black and red coloured Honeywell S456STF, if that means anything to anyone, and it slots into the Honeywell gas valve it's clearly designed for. It's one of these:

...hence also my confusion above about the manual talking about a fuse on a Ravenheat ignition board, when what I have is no-fuse on a Honeywell board.

 

[c128]

[Ooops...ignore. Can't seem to delete a mistaken post on this forum ]

 

[topskins]

As a further update on this...

Got up this morning, tried the boiler (which had been switched off overnight) and it fired up first time in response to demand for CH when I artificially turned up the temp on the external thermostat. Ran CH for about 20 minutes, and also DHW for a bath/washing up during this time - all fine. Turned the thermostat back down, shut down as expected, turned it up again...exactly the same as in my first post, main burner doesn't light and eventually I get the flame failure warning.

So...I guess I'm not convinced my original comment about "it works first thing in the morning when it has been off overnight" is a coincidence now.

This time, I found that the (purple wire in first pic above) terminals to the gas valve itself had flip-up covers to so you can stick multimeter probes on them when in-situ. On first (successful) run, no voltage to gas valve initially, then voltage and it successfully starts up and the main burner ignites. Second run, and those after that, (unsuccessful) no voltage to gas valve full-stop.

Does this then rule out both a problem with the gas valve and the ignition board?

 

[topskins]

Follow on question from the above [and apologies in advance for folowing my own posts ).

Just so I can absolutely rule-out a pressure issue within the combustion chamber, is there an obvious way that an APS can be confirmed working electronically during the start-up sequence without having the combustion chamber cover off e.g. multimeter on continuity on terminals from APS before and during fan start-up? I'm assuming it is fine, as I hear it "ping" when the process in the first-post goes through a cycle, but I'd like to be absolutely sure.

 

[topskins]

Can I just check this approach for checking that my APS is working correctly with the collective knowledge on here?

Basically, I just disconnected the APS' Common, Open and Closed wires from the combined APS+Fan connector block that goes to the ignition board and attached a multimeter in continuity mode to the now disconnected Common and Open wires going to the APS itself. I then shorted the Common and Closed APS connections at the ignition board, so that the ignition board would assume Closed, and hence correct pressure hadn't been reached. Here's a pic:



What I found was that, on CH demand, the fan starts and, after a few seconds, the multimeter indicates that the pressure switch switches and seems to stay open for as long as I leave it running. Obviously the main burner doesn't light, as expected, but when I remove demand then, after a few seconds, I hear the "ping" I originally heard and thought was the APS, and the multimeter shows that the APS has closed. From this can I definitely rule out pressure issues in the combustion chamber?

 

[EliteHeat]

Well yes, you've proved the correct operation of the APS.

 

[topskins]

Thanks, I guess that seems obvious, but I just wanted to make sure... . I think that just leaves me, in terms of things I feel safe checking, having a look at the condensate sensor, and then just assuming an issue with the ignition board as gas4you plumped for above?

 

[topskins]

Bah! It was the condensate "sensor" (read as "screw"). Condensate trap was fine, nothing was blocked, but for some reason when the "sensor" is screwed into it together with the earth then there must be some continuity there somewhere or other as it prevents fire-up. I'm assuming it worked in the morning because of "drying out" overnight...possibly? Doesn't really explain why it still didn't work when screwed into a cleaned and relatively dry trap, but there you go..."sensor" removed, it seems, in common with lots of other Ravenheat owners, when you search for that specifically .

Thanks all.