Wireless boiler demand

[rchez]

Hi, I'm looking for some advice on a control issue with my central heating setup.

System components:

• Vaillant ecoTEC Plus 630 boiler
• Unvented cylinder with 2-port zone valve controlled by cylinder stat + Drayton Wiser HW schedule
• UFH with Heatmiser UH8 wiring centre
  (Yes, the mix of Wiser + Heatmiser just happened over time!)

The problem:

After a recent service I was told the system isn’t wired correctly. Neither the Wiser (DHW) nor the Heatmiser UH8 (UFH) is sending a call-for-heat signal to the boiler. Instead, the installer appears to have left the boiler on permanent demand (permanent live to the boiler’s heating call input). So the boiler is effectively uncontrolled: it only fires based on its internal flow-temperature logic, even when no zones are open.

I've been told that is isn't ideal and can cause:

• short-cycling
• the boiler heating with no open circuits
• inefficiency and potential long-term wear

Unfortunately the boiler is on a different floor on the opposite side of the house, so retro-running control cable from the manifold area would mean major disruption. So I’m looking for a wireless way to provide a proper call-for-heat.

My idea:

1. Install a Heatmiser RF Switch v2 at the boiler as a wireless boiler demand receiver
2. Replace the UH8 with a UH8-RF, which can call the RF Switch (I think?)
3. Feed the Drayton Wiser hot-water call into the UH8-RF so that both UFH and DHW can trigger the RF Switch/boiler

Questions:

1. Is the Heatmiser RF Switch + UH8-RF solution a valid and reliable way to provide a proper boiler demand?
2. Is there a better wireless option I should consider?
3. Any issues with integrating the Wiser HW call into the UH8-RF?

Thanks for any guidance!

 

[CountryFan]

Are you sure that it's not the factory link that's been left in on the boiler PCB? This would keep it activated regardless of any demand.

 

[rchez]

Yeah thanks, I think that's what they've done. My understanding is that this should be removed and there should only be a call for heat whenever a zone calls for it?

 

[CountryFan]

My understanding is that this should be removed and there should only be a call for heat whenever a zone calls for it?

Correct. Might be worth checking before considering any other control setup, especially if it's not needed

 

[rchez]

Just checked my notes from what the service guy told me and I can confirm it's definitely the factory link that has been left in, putting it into permanent demand mode and that this should be removed and replaced with signals when there is actual demand from the various other system components

 

[CountryFan]

Ok. So what might be best for you to do (if you feel confident/comfortable), have a look inside the control box - fairly easy. See if the original installation has been wired up, if it has, remove the link and test it all works correctly. If it works you've just saved yourself some money. If it doesn't you haven't lost anything and can consider how best to approach. Wiring could be there to be used.

 

[rchez]

Ah nice suggestion, I've just had a look and there's nothing at all connected to the "Heat Enable" part of the control box so I guess I do need a wireless solution

 

[CountryFan]

You probably do need wireless, but it’s ultimately the motorised valves that send the switch live back to the boiler for a demand. So you’d either need cable to the boiler or possibly a wireless relay.

 

[rchez]

I'd like to avoid a cable to the boiler so a wireless relay it is then. On that, isn't that what the Heatmiser RF Switch is, a wireless relay? Do you know if my idea would work?

1. Install a Heatmiser RF Switch v2 at the boiler as a wireless boiler demand receiver
2. Replace the UH8 with a UH8-RF, which can call the RF Switch (I think?)
3. Feed the Drayton Wiser hot-water call into the UH8-RF so that both UFH and DHW can trigger the RF Switch/boiler (if that's fesible?)