Baxi Bermuda backboiler - central heating iffy after water

[Fitzchiv]

Hi,

I'm a novice when it comes to central heating and boilers so forgive me for any daft statements/questions in this.

Bought a property over the summer with a baxi backboiler heating system. Had been serviced in March, and works (worked) fine. Plan was to leave it until Feb when we're looking at green deal opportunities and having a new kitchen put in.

Anyway, the last week or so the call for heat has been playing up for the central heating. The water works fine, in that it responds to the call and we get hot water as needed. The issue is the central heating call seems to be ignored, and only intermittently works.

My first thought on this was the control unit (a pretty rickety looking Drayton Lifestyle LP112) was playing up. So, I forked out £25 for a new one which arrived today and - whilst the new unit works fine - hasn't solved the problem.

To put it into simple terms, we were away over the weekend and upon returning we clicked the heating to "On" and, good as gold, on it came. We ran this all evening, with wife clicking the water on later on for showers before bed - again, worked fine.

This morning we got up, clicked the heating to "On" and again it worked. Then comes the issue - wife again called for Water to heat before putting both off before we went out and now....nothing. Water will heat, but heating won't respond. This has been the issue for a while now.

To my thicko non-plumber/expert brain it seems like something gets "stuck" with the water heating cycle meaning the heating won't engage, and only when that comes unstuck (be it through time or the cycle completing) will the heating respond.

I've taken a look in the immersion cupboard and uploaded a photo of the motorised valve, zone valve actuator and a bit of kit above them . The motorised vale and actuator both have a black lever which is currently extended and to the right (meaning I can put it in, and left, and manually get water moving through it). Needless to say I've no idea what I'm doing when holding it one way or the other, just hoping one of you folks can glean a bit of info from that.

Any ideas? I don't really want to go big bucks repair on this considering I'll be making decisions in the new year on whether to go for a combi and ship the backboiler out (it's 27yr old).

Any help or advice much appreciated

Untitled

• Fitzchiv
• 23 Dec 2014
• 1

Untitled

• Fitzchiv
• 23 Dec 2014
• 1

Untitled

• Fitzchiv
• 23 Dec 2014
• 1

 

[ChrisR]

CHeck the pump isn't sticking. With CH on, if you switch the speed changer between 1,2,3 you should hear the difference.

In the first pic there's a black indicator on the LHS of the valve head. it should move end to end when you switch between ch only and hw only.
These valves tend to stick. The Manual lever poking out of the top will allow you to open the valve from HW only to mid/both CH & HW. The HW will mostly short out the CH though as the cylinder pipe's an easier route for the water to go through, than all the rads.
Cylinder thermostat needs to be Satisfied for the valve to go to CH only.

It's also very possible the system was never wired properly or there's a bad connection inthe programmer. Was there a wire on the HW OFF terminal? Turn the whole system off, and just put the CH on, with the cylinder temp turned down as well - try that.

Other route is to find out how it should all be wired and check that the valve moves to where it should when it should. But that's more to learn...

 

[Fitzchiv]

Tried seing if Pump was sticking, by holding manual level on valve head to the left to force water through and changing the speed settings. Could hear the difference so don't think it's that.

As for the black indicator, it's hard to tell what it's on - if I push it there are no identifiable steps. Just goes in and comes out again.

In terms of the manual lever, where should that be set? Right now it's up and right. Cylinder thermostat is set to 70, currently quite a bit of hot water in the tank. Turned the system off, changed it to lowest setting, put system back on again just on CH and no joy.

Could it be a CH thermostat issue? I.e it doesn't answer the call for heat because it thinks the place is already at the required temp? (I've already tried putting thermostat to max/min to see if it will spark things, with no joy)

 

[ServiceNumpty]

At a guess it will probably be that Drayton Motorised Head.

 

[ChrisR]

I agree the valve's stuffed.

SOrry I 'm confusing the valves in the earlier post which is therefore wrong - I thought it was two pictures of the same 3 port - you have 2 x 2 ports which is simpler..
Locate which is the CH valve - ie not the one on the pipe which goes to the HW cylinder.

Now use the longer black lever to latch the CH valve open. You should have to push against a sproing but if it's seized/stiff, it might not spring anywhere.
That might turn the heating on, it depends on the valve. I don't think it will. But while the boiler is on, you will get some heat in the radiators.

To get the boiler on:
Turn the HW cylinder stat right UP
Turn the boiler stat on the boiler, DOWN to about 1 out of 6 .
Turn the HW ON at the programmer.
The system will now try and fail to get the HW up to the set temperature, but all the time it's trying, you'll be getting some heat in the radiators. Assuming you can't get the valve fixed tomorrow, it should keep you warm enough over xmas!


CH timing and room thermostat will do nothing.


Watch the HW temperature at the tap. It might get quite hot.

 

[Boilerman2]

Errr that is not a 3 port valve, it is a pair of 2 ports, I suspect the actuator or valve is seized on the Heating valve

 

[ChrisR]

Yeah I just noticed slightly before you posted!

 

[Fitzchiv]

ok thanks all, so the general consensus seems to be the valve from the CH is goosed (just to confirm, the black lever works fine on both so nothing is seized)

Would you expect one of these to just go full stop, or work intermittently? As I said, it tends to be a case of works sometimes and stops others. Usually as soon as we put the HW on, the CH won't come on after it.

Not too worried about the heat really, we've got a coal fire in the front room and a full bunker of fuel - very christmas card!

 

[ChrisR]

With the black lever you should be able to shove it open against the spring then hear it clockwork-style zzzzzing close in about a second.
If it's seized it'll be much slower or not go full travel, but you won't be able to tell much.
Ther's a lot of slop in the lever, go by the sound/resistance.


They either seize or the motor dies. Otherwise - loose/ wrong wires somewhere


You should be able to tell if the electric is opening it when it should (it's slow to open, maybe 15 seconds)

 

[Fitzchiv]

yeh if I push it open it whirrs back into the previous setting

out of interest, what's a rough going rate on replacing one of these? Or is that a bit of a "how long is a piece of string" question

 

[ChrisR]

If the £20 motor can be changed, callout & 1 hour should do it. If access is awful (doesn't look it) and it has to come out and if it has to be drained, maybe a couple of hours tops + £50 for a valve, ballpark.
Easy ones take 10 minutes.

Motor change is a DIY job.

 

[Fitzchiv]

nice one.

Have had a play around with that valve and if I hold the level across in the open position (has to be all the way across mind) it engages and I get some heat into the radiators. Unfortunately seems like it's got to be held in place like that though, as latching it across doesn't hold it open enough to trip the pump.

 

[ChrisR]

yes that's what I meant about not knowing whether it would start the boiler or not. Some do, most don't. Therefore you have to go through the rigmarole withe HW stat up, boiler stat down, etc.

Sometimes you can wedge them with a lump of cardboard, but not usually.

 

[Fitzchiv]

any risk of knackering things further if I do wedge it?

 

[ChrisR]

Not that I can think of, go for it.