UH3 to boiler connection help please...

Colin33 · Feb 26, 2014

I am wiring a UH3 to a Grant Vortex Pro internal combi. The heating system is underfloor only, no rads, and no DHW storage. I have stats and a time clock wired into the UH3. I have a supply to the boiler.
My question is, where do i terminate the UH3's 'boiler in/out' wires within the boiler itself? Boiler instructions only give diagrams for their own stats/programmers. Within the boiler there is a room stat link wire (terminals 25 & 26), and also a link in terminals 19 (ch timed on) and 20. I'm assuming it's gonna be one of these but and advice appreciated....

Colin33 · Feb 27, 2014

Surprised no one knows the answer to this one!

Swcfisher · Feb 28, 2014

Take the link out of 19 and 20 then connect your in and out to those terminals. You might need to link the live to the in at the wiring centre check the manual for the boiler

Colin33 · Feb 28, 2014

Swcfisher said:
Take the link out of 19 and 20 then connect your in and out to those terminals. You might need to link the live to the in at the wiring centre check the manual for the boiler

Thanks, that's reassuring as I did this yesterday...I will be on Holiday when the plumber turns up to commission the boiler so hopefully it'll all work! I didn't link a live to the 'in' at the UH3 though, the boiler instructions didn't mention this.
Cheers :smiley2:

Geordie Spark · Feb 28, 2014

What's all this "hopefully it'll all work!" business??

telectrix · Feb 28, 2014

choice of 3.

1. it works.

2. it don't work.

#3. it goes bang.

what's the problem?

Colin33 · Feb 28, 2014

Geordie Spark said:
What's all this "hopefully it'll all work!" business??

Ha ha...you know what it's like...if anything is gonna go wrong it'll happen while you're away and not there to sort it out! Maybe I'll turn off my phone while I enjoy the ski slopes :smiley2:

MrTrance · Mar 2, 2014

I'd personally say 25 and 26 and keep the link in 19 and 20. Don't link a live just in case its a clean pair of contacts!!

Reason i say 25 and 26 is becuase when the 19 and 20 contact closes (when the heating set to come on if using there programmer), it will then look at the stat terminals... just like any basic heating diagram (series circuit), hope this helps.