PLATINUM 40 COMBI ERP Radiators always heating

[newbie910]

Since last evening, the boiler has been constantly heating the radiators even when the thermostat is off. The thermostat's battery indicator shows full, and the receiver's green LED blinks when I adjust the temperature on the thermostat.

What could be wrong, and what can I check?

 

[CountryFan]

It’s getting a switched live from somewhere by the looks of it. The grey button on the receiver - has it been pressed in, as iirc, this shows a demand for heat. Do you have any motorised valves?

 

[newbie910]

It’s getting a switched live from somewhere by the looks of it. The grey button on the receiver - has it been pressed in, as iirc, this shows a demand for heat. Do you have any motorised valves?

No i don't have any motorised valves. what else it can be if thermostat and receiver are working properly as when i increase the temperature the receiver do blink green LED light so its communicating to receiver. Also this indicator of radiator is always green if i do not switch off the boiler and radiators are getting warm so not sure if its boiler or is it receiver. I did took an advise on phone and one of the qualified person told me it may be receiver which is fault but i am little skeptical about it.

 

[RandomGrinch]

I would start my investigation with the BDR91 receiver - although it may blink, the green LED means the relay is operating and calling for heat from the boiler.
With the power to the BDR91 safely isolated, can you post a photo of the wiring behind it?

 

[newbie910]

The issue has been intermittent, so I’ve purchased Hive to replace the BDR91. However, I’m not sure which wires need to be connected to the Hive receiver. I’ve attached the wiring diagram for reference.
Please advise?

 

[CountryFan]

It appears the L and N for the BDR91 come from somewhere other than the boiler, perhaps the spur.

However it’s L to L, N to N, A and B to 1 and 3.

 

[newbie910]

Thanks for the response. There is also underfloor heating installed in the property. I’m not entirely sure how it's set up, but I’ve posted some pictures for reference.
It appears that the Heatmiser UH8-RF controller is connected to the Honeywell Home receiver, and the wiring passes through the main ON/OFF switch. I have different thermostat or UF ( heatmiser) and Raidators (Center Programmable)
The boiler itself is under warranty, but the receiver and controller are not. The gas engineer mentioned that it should be fairly straightforward to switch to Hive, but I want to be sure before proceeding.

 

[newbie910]

It appears the L and N for the BDR91 come from somewhere other than the boiler, perhaps the spur.

However it’s L to L, N to N, A and B to 1 and 3.

In the uploaded image for HIVE NC is under terminal 3 ? I am confused now.

 

[CountryFan]

In the uploaded image for HIVE NC is under terminal 3 ? I am confused now.

Yes I spotted that, but 2 looks like it should be normally closed, and 3 normally open - which is how previous hives were wired. If it doesn’t work that way, then it’s no harm changing it.

 

[DP]

I would resite that BDR

 

[Madrab]

As far as the UFH is concerned then the zones should all be separately controlled via their own room stats. If the system follows any reasonable wiring setup then the UFH controllers Switched Live (SL) output will be connected into the wiring centre and will send a live to the boiler when any of the UFH stats call for heat, turning it on. That same channel for that switched live to the boiler could also have the SL from the room stat so when it calls for heat it sends its own SL down the same cable to the boiler. Given there is only one set of switching wires into the boiler then it should all be connected into the wiring centre but must be checked.

It will all depend on how it's all been wired. There are a few things that need to be understood first though as to how the system is actually wired through the wiring centre and where each components gets it's live from and then how it's wired to the boiler. It is running @ 240V so it all needs safely isolated and tested to confirm before anything is re-wired firing in there. So circuit testers etc and being comfortable with testing/checking mains wiring is essential.

All that being said the single channel Hive receiver would be a direct replacement for the BDR receiver - Is it a Hive or a Hive mini? Given the Baxi Platinum runs off a 240v SL (don't believe it has OT, would need to check) then on all thr manuals for the OTR1, then A/B should connect to Channels 1&3 (Com/heating on) but the diagram on the Hive (MINI?) suggests otherwise. May be an idea to give HIVE a call to check.



BTW - it may not be your room stat that's the problem, the Heatmiser controller may be the one calling for heat, it happens sometimes when the RF stats lose battery power and lose their comms to the controller.

 

[newbie910]

I’m using Hive (not Mini) . I’ve tried connecting the B wire to both terminals 2 and 3 on the Hive receiver, but the heating still doesn’t start. Pairing with the thermostat is successful, so that’s not the issue.


For troubleshooting, I also tested with another BDR91, but it didn’t work with the previous thermostat either — same result.


This issue started after the last engineer’s visit, when I called him to check why the heating wouldn’t switch off. He checked and re-screwed some wiring at the boiler panel. Since that visit, the boiler no longer starts heating. Hot water is working fine.


What else could be wrong?

 

[CountryFan]

Is the selector on the front of the boiler on heating and hot water?

 

[Madrab]

Since last evening, the boiler has been constantly heating the radiators even when the thermostat is off.

Since that visit, the boiler no longer starts heating.

I'm confused, which is it? Obviously we are 5 months on now.

This all needs electrically tested and the switching live out (240V) from the boiler needs to be traced around the system. It also needs checked at the wiring centre above the UFH controller. There should be a common switched live back to the boiler (blue). The UFH controller should have it's own live and shouldn't be using the live out from the boiler.

If, as per the original post, the boiler is always getting a signal then that needs to be found - either from the UFH controller or the stat.

 

[Madrab]

Is the selector on the front of the boiler on heating and hot water?

There is only one setting on the newer Platinum, the old HE had the right just HW and left HW/CH -

as per post #1 last pic