Evohome -Boiler Lockout - Help !!

[f1arp72]

Hi

I have a major issue and I'm not sure how to fix it.

I have set my Custom Override to boost 3 radiators downstairs (temp set to 23) for when the wife pops home and may need some instant heat in the rooms she uses.

However, when the override is subsequently cancelled, the first thing it does it to close the 3 radiator valves, after which the BDR91 it turned off. However, I now have extremely hot water being pumped around the system with nowhere for it to go as all radiators are now closed. I have a bypass valve (have been told never to touch by a plumber) so I understand water should flow back to boiler via that route.

However, after a 30 - 60 seconds the boiler light goes red indicating a lockout which I've been informed means it's overheated at the flow as the water isn't flowing properly !!??

This is an S Plan system and the pump definitely continues to run after DBR91 switches off.

What can I do to solve this. At the end of the day, Evohome closes the valves before it sends the Heating Off command so this is happening every time I try it. Any help would be appreciated.

Thanks

EDIT: I should add, I'm turning the custom override on/off via the mobile app on iPhone, not that I can see it should make any difference ?

[paulockenden]

Evohome closes the valves before it sends the Heating Off command

With an S Plan system boiler demand should be driven FROM your heating valve. The boiler should only fire up once the heating valve has opened. And should power down (apart from the overrun) as soon as the heating valve starts to close.

Or do you have your system arranged in a manner not as per the installer manual? With a boiler relay, for example?

P.

[f1arp72]

With an S Plan system boiler demand should be driven FROM your heating valve. The boiler should only fire up once the heating valve has opened. And should power down (apart from the overrun) as soon as the heating valve starts to close.

Or do you have your system arranged in a manner not as per the installer manual? With a boiler relay, for example?

P.

Nope. All installed "by the book" and I do not have a Boiler Relay, but the valves do seem to close first. The DBR91 turns off the instant the valves close. It's not like it continues with "heating on" for 1 minute or two. They close and the DBR91 turns off at the same time (albeit at the end of the close cycle as opposed to when they start to close).

[paulockenden]

As I understand it, with S Plan wiring the BDR91 controls the valve, and the valve controls the boiler. The microswitch in the valve head should only fire the boiler when the valve is fully open. Perhaps one of the 'proper' experts will correct me if I'm wrong!

Perhaps there's a problem with the 2 way valve on your heating circuit? You can buy new heads if you need to test that, no need to change the 'wet' part.

P.

[f1arp72]

As I understand it, with S Plan wiring the BDR91 controls the valve, and the valve controls the boiler. The microswitch in the valve head should only fire the boiler when the valve is fully open. Perhaps one of the 'proper' experts will correct me if I'm wrong!

Perhaps there's a problem with the 2 way valve on your heating circuit? You can buy new heads if you need to test that, no need to change the 'wet' part.

P.

Well, watching the DBR91 and listening to valves, the valves definitely open first, send request for heat, then DBR91 turns on. Then, when they close, the BDR91 turns off.

Can someone please confirm that's correct on an S Plan. I definitely do not have a "Boiler Relay" and I'm 100% sure set up was completed without any issues at all (having spoken to and followed guide from Richard at Evohome shop). As mentioned before in another post, there is nothing I would or could do differently when setting up system.

[paulockenden]

Well, watching the DBR91 and listening to valves, the valves definitely open first, send request for heat, then DBR91 turns on.

I don't understand how that can physically happen as it's the BDR91 that supplies power to the valve.

[paulockenden]

Just a thought - did you clear the default boiler-relay binding on the BDR91s (15 second press)? If not they might be double bound.

P.

[f1arp72]

Just a thought - did you clear the default boiler-relay binding on the BDR91s (15 second press)? If not they might be double bound.

P.

Sorry, when I say valve, I'm talking about the radiator valve. They turn off first, then BDR91 turns off which yes, turn off the "S plan" heating valve (hence water has nowhere to go, except bypass) and then there's an 80% chance my boiler will lockout

[paulockenden]

Sorry, when I say valve, I'm talking about the radiator valve.

Ahhhhh!!!! Sorry. Cross porpoises!

They turn off first, then BDR91 turns off which yes, turn off the "S plan" heating valve (hence water has nowhere to go, except bypass) and then there's an 80% chance my boiler will lockout

I understand now.

I think there might be something wrong with your boiler. The internal thermostat should kick in before it gets to the 'lockout' state. It's perfectly normal for a boiler to cut out when the return water is hot - that's how they are supposed to work.

P.

[f1arp72]

I think there might be something wrong with your boiler.

I hope that's not the case. Can't afford a new boiler after shelling out for this Evohome system

Unfortunately, I do have a 15 year old Potterton Suprima 40L (I can hear all the laughter as I type).

Never been that happy with it.

[f1arp72]

The internal thermostat should kick in before it gets to the 'lockout' state.
P.

Actually, thinking about it, the boiler has already cut out as the DBR91 has switched off. The pump overrun continues to push water round the now closed circuit via the bypass valve so the lockout occurs when the boiler is effectively off (it's definitely not heating the water at the time). Therefore the internal thermostat wouldn't kick in and turn off boiler as it's already off !!

[paulockenden]

I've got an even older Potterton Kingfisher, so I'm not laughing.

If it's your temp sensor that's gone they are very cheap, and easy to replace. Don't even think you need to be Gas Safe registered to change it, because it doesn't involve opening up the combustion bits of the boiler.

That would certainly be the first thing I'd try, if you're on a budget.

If not, you might need a new logic board. see http://www.diynot.com/forums/viewtopic.php?t=76759
P.

[f1arp72]

If not, you might need a new logic board.

That brings back memories. My boiler ended up on Watchdog 13 years ago when I first got it (not quite 15 years yet as I first thought) as everyone was complaining it kept cutting out but Potterton were refusing to take responsibility. Watchdog provided a letter on the internet which loads of people downloaded and sent to Potterton. In the end, a very grumpy engineer turned up and replaced the logic board for free !!

Not had any major issues with it since and don't usually get red light, but this "Quick Action" seems to trip the lockout more often than not.

Thanks for the link.

[paulockenden]

It's a shame on these old boilers you don't get a code telling you what the problem is! So it's just a matter of trial and error replacing things.

That's why I suggested the temp sensor first - it's the cheapest thing. Although if your boiler is doing proper temperature cycling then it probably isn't that.

When was the last time you had your boiler serviced?

[f1arp72]

When was the last time you had your boiler serviced?

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.