Evohome -Boiler Lockout - Help !!

[erik]

could it just be the by-pass not fuctioning? So it wouldn't be a temperature issue really, but a water flow issue? And of course, no flow = getting high temperature inside the boiler from residual heat. Can you see or hear water going through the bypass when all the valves are closed?

[top brake]

I don't think it ever has been . We asked a plumber once and he basically said there's nothing they really service in these models so didn't touch it.

I've recently had a failed DIY attempt to stop it kettling so I may call this new plumber out that we've used once to sort that and ask him to give it a service and see what he says.

Servicing older boilers is even more important that the high importance of servicing new ones so that you can get the combustion efficiency and safety checked and certified. CO is a killer. Older boilers not room sealed.

First thing to do before considering a controls upgrade is make sure the existing system is operating at maximum efficiency.
And you don't want a 'plumber' to service your boiler, you want a gas safe registered heating engineer.

[jonstatt]

The only time I have seen lock-out on the Suprima 50L that I have, is when something strange happened and the radiator valves were all closed, but the BDR91 was still on. The bypass loop is short, so it won't take long for it to heat faster than the boiler expects resulting in a lockout. However, the boiler always recovers from the lock-out on it's own a few minutes later.

After the BDR91 cuts out, the pump over-run keeps the water circulating through the bypass loop. The lockout doesn't just indicate "over-heat", it also indicates insufficient water flow if memory serves correctly. What I am wondering is happening here, is that the water is unable to flow quick enough when it is forced only through the bypass loop. This would happen if the bypass loop balancing valve was not set correctly.

In my home the bypass balancing valve was not set correctly as it was left "wide open" resulting in me always heating up the bypass loop. Unfortunately the charts have all disappeared online due to age for the valve and pump so I had to guess mine by listening to the flow of water when in bypass loop only mode.

[f1arp72]

Thanks everyone. I'll have to get the thing checked over properly. Definitely sounds like a flow issue when it's simply circulating through the bypass valve. The BDR91 and boiler do cut out so the water that circulates shouldn't be getting hotter. Never liked my boiler from the day it ended up on BBC Watchdog !!!!. Maybe it's time for a new one !!

[jonstatt]

Thanks everyone. I'll have to get the thing checked over properly. Definitely sounds like a flow issue when it's simply circulating through the bypass valve. The BDR91 and boiler do cut out so the water that circulates shouldn't be getting hotter. Never liked my boiler from the day it ended up on BBC Watchdog !!!!. Maybe it's time for a new one !!

There is nothing wrong at all with this boiler when it works right, and if you have v3 of the controller board, then most of them are alright. Some of the Siemens (v3) boards develop an issue where they cut out (as if thermostat had been reached, no error lights) even though temperature has not been reached. This is not what you are seeing at all. So I think your boiler is fine and healthy. The issue is more likely what I said about the flow issue with the bypass loop, which is external to the boiler and plumbing related.

[paulockenden]

@f1arp72, can you hear the water being pumped through the bypass loop? Does the bypass loop pipe get warm? If you have a thermometer of some kind (those spot IR ones are good for stuff like this) can you monitor the temps on the boiler's in and out pipes when this fault occurs?

[f1arp72]

@f1arp72, can you hear the water being pumped through the bypass loop? Does the bypass loop pipe get warm? If you have a thermometer of some kind (those spot IR ones are good for stuff like this) can you monitor the temps on the boiler's in and out pipes when this fault occurs?

I'll have to investigate further. Heating is off at present so I may wait and get it services and checked later in t he year ready for winter. I don't get a lock-out when HW is being heated though which is using the same bypass ?