Constant call for heat from cylinder thermostat?

[jamojamo]

Hope someone can shed some light.

To cut a long story short when I turn my ideal logic heat boiler on it immediately starts heating water (flame icon).

Can't override with HIVE, in fact the only thing that stops it is turning the Danfoss cylinder thermostat down to near zero.

If left running it just seems to keep going even when water is well above the temp set on the Danfoss.

3 way is brand new, is the issue the cylinder thermostat?

 

[Murdochcat]

did it do this before the 3 way valve was replaced?

 

[jamojamo]

The boiler was doing the same before the 3 ways was replaced, first place I looked was the 3 way, and it wasnt behaving correctly so was replaced. Boiler still doing the same. Further investigation led me to the cylinder thermostat.

 

[Exedon]

I would suggest you stop throwing parts at the problem get a multimeter and have a good look at a Y plan wireing plan check if it's wired correctly.
Honeywell even do a wireing app with a really good fault finding section.

 

[JohnD]

Is the thermostat touching the cylinder?

 

[jamojamo]

The pin was stuck, the motor was gone and the gearing was knackered. Think it needed changing.

Very simple like for like replacement.

 

[jamojamo]

Yeah it touching the cylinder mate, although I did just go and check.

 

[RandomGrinch]

Can't override with HIVE, in fact the only thing that stops it is turning the Danfoss cylinder thermostat down to near zero.

With the Hive removed from the backplate, does the boiler still fire?
As @Exedon suggests, looking at a Y plan wiring diagram, (good information here);

Y Plan central heating system

Y-plan central heating system operation and wiring diagram

flameport.com

the Hive should definitely override the call for heat.

 

[jamojamo]

Im assuming you mean the hard wired part of the hive. Might take a look tomorrow. Thanks.

Further info, when the hive says off (no call for heating on stat or lights on on the hardwired part) it's still firing. The only thing that stops it firing is to turn the Danfoss to near zero. (It's like it does on and off but doesn't recognise temp I guess)

Although I appreciate if it's wiring it could be anything.

 

[RandomGrinch]

Im assuming you mean the hard wired part of the hive. Might take a look tomorrow.

Yes, we can perform a couple of troubleshooting steps by removing the Hive receiver from its backplate.

With the receiver removed and the power isolated, you could connect a short link wire between L and terminal 1 on the backplate.
When the power is reconnected, the HW should be off.
With the link wire then connected between L and 3, the HW should be calling for heat.
If this works correctly, the Hive will likely be at fault.
If there is still a call for heat with the link between L and 1, there is likely to be a wiring issue elsewhere.

 

[jamojamo]

Interesting. How would this explain what's going on with the cylinder thermostat?

Or is it a case of although the hive may not show on, it is stuck on. And the Danfoss it the reaction?

 

[RandomGrinch]

Or is it a case of although the hive may not show on, it is stuck on. And the Danfoss it the reaction?

Yes, exactly that.
Relays can fail, get sticky, and the contacts can weld themselves together.
This may not have happened, but it is a troubleshooting step we can take to try and narrow down the problem.

 

[Deleted member 267285]

Something is sending an immediate Live to the boiler to fire - with a y plan that comes from the cylinder stat and out on orange to boiler and pump live.

 

[jamojamo]

So CBW you're thinking it's the cylinder stat?

 

[Deleted member 267285]

So CBW you're thinking it's the cylinder stat?

Could be. I’m thinking it needs proper testing with a multimeter