Have I killed my 'boiler'? Help please.

T

tam203

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I have air source heat pump (ashp) system, model Yutaki S .

Recently I replaced the wired thermostat (a relay one) with a Tado wired thermostat.

I turned the ashp system off at the kill switch. Swappef the thermostat, and it wouldn't turn back on. I have check the switch board and the circuit breakers aren't tripped. I put the old thermostat back using the photos I took so I'm confident in that wiring but the system still will not turn on.

By not turn on, I mean no power no lights no nothing, hence checking the circuit breakers.

Have I broken something serious?! Would that be possible if I'd wired the Tado thermostat wrong (defaults to relay mode it said in the manual)?

Any advice really appreciate. No heating, no hot water.

Photos of thermostat wiring below.

Original thermostat:

! PXL_20211009_082045376.jpg


Tado
PXL_20211009_095930805.jpg


Thanks.
 
@ianmcd good suggestion but I definitely stayed away from the 'max 36v analogue/digital' side.

I used the no nc com ports (and thought in the correct manor, matched up circuit diagram that's on the two thermostats).
 
The Tado only needs 2 wires - brown and black into Com and NO, which is the same as L and NO on the old one.
The blue neutral isn't required.

If you connected the blue neutral to any of the terminals, it's likely that you have created a short circuit between L&N which will have blown a fuse somewhere. Possibly in a fused connection unit adjacent to the heating system, or internal to it somewhere.
 
@flameport that sounds highly likely (I connected 3 wires), thanks, I'll have a dig. I really hope it's just a fuse

I wonder if there might be some fuses inside the heat exchanger unit? Will have a look later.

If the Tado just needs 2 wires, would the 3rd go in parking?

Many thanks!
 
Yes Neutral would just go in a parking terminal. When you wired the old one back up, did it work then?
 
@CBW no it didn't work when I wired the old one back up. Just still dead (no lights, noises, errors, nothing)

@flameport There were four fuses inside the unit but non were blown, I got almost 0 ohms accorss all of them with my multi meter


Do either of you know what this is:
PXL_20211009_181249296.jpg PXL_20211009_181300625.jpg PXL_20211009_181306610.jpg PXL_20211009_181326601.jpg PXL_20211009_181317318.jpg

As said above the fuses are fine but this switch/box has a push buttton on it with a hole that alows you to push it without needing to access the electrics , I'm wondering if it's some sort of fuse/trip/reset. I've not dared to press it because I don't know what it is but any ideas?

Thanks.
 
Well I dared to press it and... nothing. A slight click noise, but only the sound of a button depressing. Doesn't stay depressed or seem to do anything. Tried turning unit on, still nothing.
 
tam203 said:
I'm wondering if it's some sort of fuse/trip/reset. I've not dared to press it because I don't know what it is but any ideas?.
Click to expand...
Looks like it’s an overheat thermostat.

With regards the boiler not working, have you checked the 3 amp fuse in the spur? Have you checked for voltage at the thermostat?
 
tam203 said:
Well I dared to press it and... nothing. A slight click noise, but only the sound of a button depressing. Doesn't stay depressed or seem to do anything. Tried turning unit on, still nothing.
Click to expand...

Overheat trip and if it didn't make an obvious click, then it wasn't tripped.
 
@CBW - thanks

> Looks like it’s an overheat thermostat.

Yes I'm sure you are right on that one.

> have you checked the 3 amp fuse in the spur?

I can't find any fuse box between the 'boiler' (actually a heat exchanger but I cant get out of the habit of calling it a boiler') and the main consumer unit (it's got it's own Miniature Circuit Breaker on the unit, that's not tripped).

> Have you checked for voltage at the thermostat?

No voltage - backed up by the fact the little read light doesn't come on when twiddling the thermostat dial.
 
Look for a switch like this somewhere on the system - it'll have a 3a fuse in it which could have blown

BG850.jpeg


Other than that, some MCBs trip to a mid position for Neutral faults, so look at them really closely as it's a bit harder to spot. You need to push them all the way down then back up to reset
 
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