Boiler tripping out

[Bob Smith]

I have a boiler that is cutting out. I don't know the model number, but it has a "ravenheat" logo on it.

It is a gas boiler, I have the system pressurised to 1 bar, and it does instant hot water. All the radiators have TRVs on them (yes, all), and there is no room stat. (Ex council house, cheap council installation)

I have tried putting one radiator valve on full to see if it is overheating and tripping out, but it still does. I have also tried altering the water temperature (both tap and rads), with no effect.

After the CH has been on for a while, I notice the rads are cold, and the boiler fan is going, but the flame is not burning. Lowering the rad thermostat on the boiler until it clicks, then putting it back resets it, and it fires up fine. Also, clicking the time clock off and on does the trick.

Any ideas?

Thanks

Bob

[Set Square]

Well one thing's clear - the boiler's overheat stat is tripping - and has to be manually reset before the boiler will fire again.

What isn't so clear is *why*. This could be due to any of several causes, which need investigating, including:

• faulty overheat stat (possibly the prime suspect)

• insufficient circulation to carry the residual heat away after the main stat turns the flame off (This could certainly be the case if *all* the TRVs are closed and *may* be the case if only one TRV is open. There could also be an intermittent pump problem - but that doesn't sound too likely.) [If circulation *is* the problem, I would expect turning down the boiler stat to improve matters - since there's more leaway for the temperature to rise before tripping the overheat stat].

• incorrectly wired pump (This is probably the least likely, and would only really apply if the whole lot were turned on and off with a room stat - in which case it must be wired to keep the pump running for a while after turning the boiler off)

Do you have a means of measuring flow temperature. [If not, it may be a good time to invest in an instant reading non-contact IR device from CPC for £30 - I don't know how I ever managed without mine!] If you can check the boiler outlet pipe temperature immediately after it trips, you can see whether the temperature *is* excessive. If it's not, it points to the overheat stat. If you suspect the overheat stat, try bridging it - but keep a very close eye on the system while running bridged! If this cures it without any side effects, fit a new overheat stat. If you get lots of gurgling and banging, , turn it off a bit smartish! In this case, it really

*is* overheating and you need to look at some of the other possibilities.

[Bob Smith]

Some useful ideas, thanks - I never get to it just after it has tripped to take a temperature though.

The pump has a 3 minute overrun. If there *is* a (can't remember the name - thingy in case all rads are off) would the boiler stop heating in time for the small amount of water to not overheat?

If it has tripped out because of too much heat, would the act of turning down the radiator temp knob until it clicks, then putting it back be enough to reset it? (the boiler in my last house, you had to take the case off and open a metal enclosure to get to the thermal cutout reset).

I will turn the temp down, and leave 2 rads on full to see if it cuts down the frequency of tripouts.

Bob

[Set Square]

You could try to induce it to misbehave though, by turning off the CH at the programmer when the boiler is running at full chat. Verify that the pump continues to run, and monitor the outlet temperature for a couple of minutes.

You're probably referring to an automatic by-pass valve. If you had one - which you probably don't - it would open if the pump were running but the water had nowhere else to go because all the TRVs were closed. As long as the pump kept going for a little while after the boiler stopped firing, this should be sufficient to carry the heat away without the trip operating.

Probably. There are various designs of over-heat stat. On my MkI Baxi Solo boiler, a little button pops out which has to be pushed in to reset it. On more recent versions of the same boiler, the reset procedure is to turn the thermostat knob right down and then back up again. Yours is probably like that.

Let us know how you get on!

[Bob Smith]

Well, I turned the heat down, and put 2 rads on full, and it still cuts out. I think it is even more than before, but it is a seemingly random thing anyway.

I think the thermal cutout thing is working, because it can go for a couple of hours, and the rads do feel hot, so i don't think it is cutting out early.

I fiddled with the pump. It has 3 speed settings, and all three sound different, although it may not be fully functional. When the switch is between settings, the pump stops (break before make switch), and the water sounds like it is boiling, although it did not cut out (I didn't hold it there long).

I don't have a thermometer to check the water temperature.

The firing up sequence sounds like:

Demand for heat flame light comes on dull small click: fan starts pause flame light goes bright large click (gas valve) whoomph (gas lights) flame light goes off (as though it is a "request to light" indicator)

When I find it has cut out, the fan is going, and the light is on bright, and no gas is being used up.

Bob

[Set Square]

This is all very interesting! I'm no longer convinced that it *is* the overheat stat operating.

When my boiler cuts out on its overheat stat, it cuts power to everything - so no fan, no LEDs, no ignition.

Unless the internal wiring of your boiler is different from mine (and it may well be!) the fact that the fan is still running suggests to me that the prpblem is downstream of the fan - like the pressure switch or ignition system - or even the main PCB. Whatever it is, it seems that turning it off and on resets something and gets it going again.

Can you remind me of the make and model of your boiler. Do you have an installation manual with internal wiring diagrams? Does it have a fault-finding chart?

[Bob Smith]

It is a Ravenheat, with no model number or identification (unless it is under the plumbers "call me" sticker). There was no manual when we moved into the house. I could take a picture with and without it's front cover on (ooer missis!) if that would help.

Bob

[Set Square]

It might help someone identify it - not me, I'm afraid - I only know about the boilers I have owned.

Since you don't have an installation manual, my thoughts were that we may be able to download one from the maker's website. But we *do* need to know the model. There may be a plate inside the casing, if it doesn't say on the outside. -- Cheers, Set Square ______ Please reply to newsgroup. Reply address is Black Hole!

[Bob Smith]

OK, will look for a plate, and peel the plumber's sticker off. Failing that, I will take some piccies. Then I could find a PDF or something with te wiring diagram in.

Bob

[Set Square]

Just had a look at the Ravenheat site. They do have downloadable manuals - at least for their current boilers. Have a look at

[Bob Smith]

casing. Failing all other methods of ID (peeling sticker, finding plate etc.) I could go to the factory and ask. The address on those leaflets is in Morley, Leeds, and that's where I live. I know the place, thinking about it, but just thought it was a ravenheat stockists.

Bob

[Bob Smith]

Right, I found a 1"x1" sticker inside with RSF 82 ET and a barcode on it. The PDF is online (they still make this thing?) and the picture of the guts looks like the beast. (

)

The PDF says it is auto modulating though, does this mean it varies the flame, because I am sure mine burns full blast in short bursts?

Anyway, what's next?

Bob

[Bob Smith]

Just noticed there is a troubleshooting flowchart. The "screen version" is a bit blurry. I will get the printable version and print it at work

Bob

[Richard Faulkner]

In message , Bob Smith writes

Have you followed the fault finding flow charts on page 40 and 41?

[Bob Smith]

I am getting the printable one right now. (the screen version one was a bit blurry and unreadable).

Bob

[Bob Smith]

Right, I followed the flowchart, and in normal operation, I fall off the bottom of the flowchart, everything being hunky dory most of the time.

When I find the boiler in it's "stupid" state, it either has not turned the gas on, or not lit when it tried to turn the gas on. The flowchart suggests checking the gas valve or the spark electrode respectively. Also could be a pilot injector blockage.

Are any of these items known to be intermittently faulty? I can't see the gas valve being affected by temperature, and the pilot and spark electrode are only required at the beginning of each lightup (and so should have cooled a bit)

Any ideas?

Bob

[Ed Sirett]

If the ignition becomes marginal then a slight change in the conditions (such as temperature, gas pressure, supply voltage perhaps) can make all the difference between working and not working.

The gas valve is probably the least likely item to go wrong. The spark electrode, pilot jet or gas pressure and likely items.