New froststat clicking/lighting up but no response from boiler

[Ron S]

Hi, I switched my old Honeywell froststat (it had a broken mount and was firing up boiler) to the cheap Greenbrook TH90F. This is clicking and lighting up when i turn the temp gauge up, (currently 13 degrees C), but no response from boiler. Frost thermostat terminals are wired as instructions (live to t1, neutral to t4). Boiler is older Ideal Baxi.

So, why no boiler response I am wondering? (Does boiler only respond itself if temp drops further??) There are no other wires from froststat.

Any ideas? Thank you.

 

[yorkspark]

you have connected the switch live to term 3 haven't you? where was the earth core connected to on the honeywell?

 

[flameport]

(live to t1, neutral to t4)

No thermostat could ever work with only those connections.

Where is the switched live?

 

[Ron S]

The old Honeywell was wired in this way too, there is only a permanent live and neutral wire to froststat. A separate switched live goes to boiler from the bolier switch. Greenbrook diagram atached.

 

[Ron S]

there was no earth connection to older (or new) froststat.

 

[flameport]

there is only a permanent live and neutral wire to froststat

Impossible.

The thermostat connects two wires together when heat is required.
If they were live and neutral, the result would be a big bang the first time the thermostat was used. Fuses would blow, things would be destroyed, nothing would work ever again.

 

[RandomGrinch]

The old Honeywell was wired in this way too, there is only a permanent live and neutral wire to froststat.

No, if your existing stat had only two wires, you have a live and a switched live.

Instead of using terminals one and four, you need to use one and three.

The way you have it connected, the return to the boiler is acting as a 'false' neutral, allowing the illumination of the indicator on the stat.

 

[Ron S]

it is a blue and brown wire. I don't understand this comment. The instructions refer to wiring the neutral to term 4. Should I try the permanent live into teminal 3 of the stat?

 

[Deleted member 267285]

Boiler is older Ideal Baxi.

Never heard of it. Ideal or Baxi yes, but not a hybrid.

 

[Deleted member 267285]

it is a blue and brown wire. I don't understand this comment.

Just because the wire is blue, doesn’t make it a neutral wire. Although, manufacturers don’t help by stating it connects to neutral.

 

[EFLImpudence]

 

[EFLImpudence]

Doesn't it need a neutral just to work the light?

 

[Ron S]

ok so you are saying the blue is the permanent live? Please be clear if possible. See instructions on the neutral to term 4...

 

[RandomGrinch]

Doesn't it need a neutral just to work the light?

...and the accelerator to limit hysteresis, so not hugely important.

 

[Ron S]

here is the old honeywell, brown was in t 1 (top right), blue t 5. Does this help to solve?