Nest - Central Heating Problem

tesla2020 · Post by **tesla2020** » Mon May 18, 2020 6:35 pm

I have a Nest gen 3 Gas C/H system in a standard size semi. Up until a couple of days ago, the hot water and central heating worked fine. The schedule and app on phone triggered as should. Nothing has changed in the house whatsoever. The thermostat and the Heat-Link(receiver) are paired so I happy with that.

As of now, the hot water works but not the central heating. If I set the temp on the thermostat up beyond current temperature then the pump kicks in and the Thermostart turns Orange and the display shows 'heating' but the Boiler doesn't fire up. However if I press the button on the Heat-Link(receiver) this sucessfully turns on the hot water and heating and so I get both heating and hot water but not if I scheduled the heating or turn up the thermostat.

Nest Customer Care point me to the valve being the possible issue but the Honeywell V4043H valve is a 2 way port Auto/Max Open which is for the hot water only. I am certain this is not a mechanical issue of a kind but must admit I am somewhat unclear.

Any ideas or what I should be looking for would be welcomed if you would please?

ericmark · Post by **ericmark** » Fri May 22, 2020 10:59 pm

I can only guess, but my guess is the micro switch inside the 2 port valve. The normal way to wire is Nest opens the valve then the valve fires up the boiler.

ericmark · Post by **ericmark** » Sat May 23, 2020 6:29 pm

If you have posted this on two forums then it seems likely you have a three port valve, I had it with my daughters house many years ago, previous owners had a problem and had got around it by latching the leaver used to bleed the system on so it is held in mid position, my son-in-law had tidied up airing cupboard and has un-lached the leaver, so no central heating, it took ages to find, and cured with new three port valve, however it is likely you can keep things running by latching the valve, not a cure, but will mean you have central heating until you can get some one to change the valve.

Down side is every time hot water called for the radiators get a little warm, but it should get you out of a whole until lock down ended.