Frost and pipe stats on WB combiboiler - JW's wiring diagram

[JayN]

Hi, I am a bit baffled, I wired frost and pipe stats to WB combi, exactly as per John Wards diagram, I wonder if I'm missing something or understand the diagram wrong. Diagram is found here

I have the same thermostats and connected to earth wires too.

FR brown wire
FS blue wire

FR goes to frost 3
from frost 1 blue wire goes to connection block where it's connected to
pipe stat wire going to C
and pipe stat 1 wire connects to the wire going to boiler FS.

I did the connections with wagos in junction box and 3-core flex.

However, whern I tested it by having the radiator pipes cold and cranking up the frost stat, boiler comes to life but the blue light does light up and the radiators get no action ie heating does not come on. But something is happening.

Both stats were tested in another installation 3 days ago and worked fine. Is there something else to consider, something so obvious JW did not bother telling us?

Thank you.

 

[JayN]

Hi again, any advice would be greatly appreciated.
Worcester Bosch manual says
FS 230v out frost stat out
FR 230v in frost stat in

and I found a smaller print saying
the live supply is terminal FS
the switch live is terminal FR

And this on JW's website

 

[ericmark]

It seems to be wired in series, would have expected to see it wired in parallel as if either pipes or room go under temperature then want the boiler to run.

However not used frost stats for some time, as the modern room thermostat is programmable, so turns down temperature rather than turning off as with old programmer and thermostat, the frost stat should circulate water at a lower temperature to normal, so can see the point with some installations, but never worked on boilers where they can get that cold.

But hopefully if I put @flameport in this reply, JW will see the post and answer you direct. And also explain why in series rather than parallel.

 

[flameport]

The concept is that the frost thermostat closes when the air temperature falls, the boiler runs, but only until the pipes have heated up.
If just using the frost thermostat, the boiler would run until the air had heated, which would take much longer and use far more gas.

The purpose of a frost thermostat is to ensure the boiler and pipes don't freeze, not to heat the house.

boiler comes to life but the blue light does light up and the radiators get no action ie heating does not come on. But something is happening.

Possibly some configuration option in the boiler needs to be changed, or your boiler only operates in hot water mode from the frost thermostat terminals, which is pointless as that would only protect the boiler.

Connect between L and the LR with the radiator symbol instead.

 

[JayN]

......

Connect between L and the LR with the radiator symbol instead.

Thank you very much, I'm actually the nutter who emailed you twice, got it all wrong in my emails but then got it right in the end. Just checking that I'm understanding you correctly,
I have L live going to honeywell T3R's L then a link from L to A and switch live coming back from B to boiler's LR radiator picture.
I will move wire from FS to that L and FR to LR radiator port?

Sorry for being so dense, really appreciate the help.

 

[JayN]

I bet that's what he means.

As an observation, first time being under the combi boiler bonnet, everything is very cramped and tight, using 5-core would help, and also would need some planning ahead on the length of wires for each flex. Then there are the grommets just in front of the connector blocks. I found it easier using the grommets on the right then feeding the wires to the left where the connector blocks are. A logistical nightmare for a clumsy one.

Thank you also to ericmark for summoning the big man.