Boiler tripping frequently

[Nutkey]

I've got a Vokera Synergy 29. It trips more or less daily with error code 8, which indicates (from the manual)

==== Fault code 08 appears if the burner thermostat has been activated. Check gas pressures Check burner thermostat Check wiring continuity ====

I am suspicious of the gas pressures, because it typically trips early evening (when I might expect gas usage to be higher). The feed to the boiler is 22mm followed by a 1m length of 15mm. The 15mm includes two s-bends to get past some other pipes. There is also a tee (from the

22mm section) for a hob.

When the boiler trips, I turn it off and on, and it always starts up again. It has never tripped immediately afterwards.

The boiler tripped two or three times in the first year of its life (2006) but now trips nearly every day. It's being used a lot more too, as the house is now occupied during the day.

As for wiring continuity, I see no reason why this would cause an intermittent problem with this regularity, but stranger things have happened. However, I also don't know which wires I should be checking for continuity. There are a lot of them....

Are there any tests I can run to narrow the problem down?

[YAPH]

Not familiar with this boiler but if it's a combi the gas pipework is definitely undersized. Even with no drop in the 22mm pipework a 1m length of 15mm will drop the permissible 1mbar. Add two elbows in 15mm and you've got the equivalent of 2m of 15mm pipework.

Whether that's causing the problem is another matter.

Your gas usage in the evening theory is not likely to be correct unless the supply to your (and other) houses is such that the incoming gas pressure is too low for your meter regulator to put out the required

21mbar.

Without a manometer and the know-how to use one correctly and safely (not rocket science but I'm not going into it here) there's not much you can do to test it yourself. If your regulator is one of the dodgy types that the gas emergency service people routinely replace when they come across them then they might come out and do that: you could phone and ask nicely (0800

111 999). Be prepared to describe the regulator to them.

[Nutkey]

System boiler - but isn't it the power that matters rather than the type? Anyway, according to the datasheet, max gas rate is 2.64m3/h. Every table I've seen says for a flow of 2.9m3/h, up to 3m of 15mm pipe is allowable. In my case, the s-bends are swept 30 degrees (and that makes 4 bends, not 2), so call that 1.3 90 degree bends, plus an elbow further up. I make that the equivalent of 2m of 15mm pipe. That's 2/3rd of my pressure loss right there - the rest is in 22mm, and looking at the tables again, I'd normally be allowed 8.7m of that, so 1/3rd gives me nearly 3m. In practice I've got more than that - more like 4m, with a couple of elbows and bends.....

So I'm under specced on the pipework. Interesting. Considering the guy who put it in replaced all the gas pipework because it was underspec, I think he might have brought it up to a real spec at the same time.... Mind you, he clearly didn't test the release valves on the pressurised cylinder, because when I did water came out of the compression joints he'd forgotten to tighten up....

As it happens, I do own a manometer...

Ben