Bypass Nest Thermostat/Heat Link to turn on heating - Vaillant boiler?

[Cable Tee]

Hi everyone,

I hope you are all doing well. Just wondering if it is possible to turn on the heating from the boiler only as the nest heat link (3rd Gen) seems to have stopped working - no lights. We have an engineer coming round next week to change the heat link, in the meantime we wondered if there is any way to get the heating on? Hot water is working fine, but the system seems to rely on a command from the nest to the boiler via the heat link. Nest thermostat (3rd Gen) working fine, boiler also fine.

The boiler is a vaillant ecofit pure and only has the standard controls, no timer on the unit.

Thanks everyone, very much appreciated

 

[CBW]

Have you tried the override on the Nest? If that has failed, the only other way would be to join the 2 switch wires together and use the temperature control at the boiler.

 

[Cable Tee]

Hi CBW,

We tried to switch to manual but the heat link isn't responding. It's a know issue so google are replacing it for free, but its cold!

 

[RandomGrinch]

but its cold!

As CBW said above:

join the 2 switch wires together and use the temperature control at the boiler.

With your 3rd gen heatlink, there will be wires connected to terminals 2 and 3.
Connect these two wires together in one of those terminals.
If you want some reassurance, post a picture of the wiring in your heatlink.

 

[Cable Tee]

Thank you RandomGrinch,

Will changing the wiring affect the hot water at all?

 

[RandomGrinch]

Will changing the wiring affect the hot water at all?

No, it shouldn't effect the hot water.

Remember to turn the power off first, disconnect the yellow wire from 2 and stick it in with the yellow and green wire in 3 ( or vice versa!)

As said earlier this will keep the C/H on for the time being - use the controls on your boiler to adjust the temperature and turn the C/H off manually.

Good luck

 

[Madrab]

Naughty Naughty, whoever wired your system up made a bit of a key error using the earth wire - green/yellow - as a switching wire. It should never be used unless the cable colour is changed with shrink wrap/tape at both ends.

 

[Cable Tee]

Thank you so much everyone, I’m going to give this a go tomorrow. Thanks Madrab for letting me know, thank goodness as I would have not know it wasn’t installed correctly. Hopefully the engineer from boxt will have done enough of these to do the job properly!

 

[clayton]

Hope the OP doesn't mind me jumping on his post but my heat link failed Saturday and is due to be replaced by Boxt on the 9th, I've got the week off and would rather not spend it in the cold, is it still terminals 2 and 3 to connect to get my BG 330+ boiler up and running again, I seem to have a few extra red wires on my setup.

Thanks.

 

[Madrab]

No, you have a different system, you don't have a combi. It also looks like you may have a Y plan going by that wiring, so it's a lot different and not just a case of joining 2 wires.

One way it may work is locking the 3 port valve in mid pos and then bridging a live to the boiler switched live in the heat link but then that would get the CH system and the HW running all the time so the hot water wouldn't shut off so it would get as hot as the boiler temp would be set to. Not the best approach but the boiler could be turned down to a max flow temp of say 55deg.

What type of hot water cylinder do you have?

 

[clayton]

No idea on the make of the hot water tank, I think its quite old but I do have a valve to shut off the water flow to the cylinder.

 

[ianmcd]

No idea on the make of the hot water tank, I think its quite old but I do have a valve to shut off the water flow to the cylinder.

Wrong that valve you refer to with the red handle is to restrict the flow through the HW coil the valve that @Madrab refers to is the silver square box at the right hand side of your pic looks like a 2 port but not really clear post a pic of that motorised valve

 

[RandomGrinch]

Honeywell 2 port I believe...

 

[clayton]

Better pic.

 

[CBW]

Better pic.

Yep, 3 port as per @Madrab