Heatmiser UH4 and LLH

[SJB060685]

@Brambles

Hi mate. I'd like some advice from you please.
Have a fellow engineer who is thinking of putting a LLH on a system due to primary boiler pump not man enough for CH index circuit.
I dont know which boiler (he hasn't got back to me) but its a 30KW combi.
Currently there is an UFH circuit and 11 radiators.
He would like to know how would he go about wiring up this new layout so the CH circuit pump only energises when the stat is calling for it and no back feed from system at other demands.
I've had a look at the wiring and have an idea but not sure if its correct. My idea was to take out radiator 2 port altogether and call from stat supplies a feed to new pump along with neutral and earth and also supply feed to a relay. The grey wire would be the common to relay output and orange the switch live, that way the pump only runs when being called for.
Please can you confirm mu idea or correct me if I'm wrong so I can get back to him.

Thanks

 

[ShaunCorbs]

If it’s only the ch circuit that isn’t man enough I would cct the heating circuit and then you can install your bigger pump after and either wire it direct to the heating controls or use a port valve depending on pump you might need to use a relay depending on amp draw

and then leave the existing circuits on the standard pump

 

[SJB060685]

If it’s only the ch circuit that isn’t man enough I would cct the heating circuit and then you can install your bigger pump after and either wire it direct to the heating controls or use a port valve depending on pump you might need to use a relay depending on amp draw

and then leave the existing circuits on the standard pump

Hi Shaun. Yes CCT's is an option but its the wiring I'm trying to get my head around. Whether its CCT's or LLH a backfeed needs to be prevented, hence the need for a relay.

 

[ShaunCorbs]

Hi Shaun. Yes CCT's is an option but its the wiring I'm trying to get my head around. Whether its CCT's or LLH a backfeed needs to be prevented, hence the need for a relay.

2 pole relay

heating switch eg prog or room stat to a1
Neutral to a2

Perm live and switch to Load side of relay
Pump feed to outlet and switch

if your using a port valve tie the pump into the brown and orange to boiler

this will isolate the boiler switch from the pump

 

[SJB060685]

The problem I see with the pump feed tied into brown of zone valve is the pump will energise even if the motor has seized or failed, meaning pump could be dead heading if it were.
My idea of the relay coil live was feed from programmer/stat with neutral and the switched output was grey common and orange boiler live

 

[ShaunCorbs]

Yep that will work or install a bypass / trickle valve

 

[SJB060685]

Yep that will work or install a bypass / trickle valve

Thanks buddy. Yes if one was to wire pump feed into zone valve brown a bypass would be needed in the event of motor failure