Danfoss cylinder thermostat problem

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I have installed a new Grant Euroflame condensing central heating boiler.
I have wired it up to a Danfoss heatplan controls pack containing:
1-FP715 Si Programmer,
2-HP22 2 Port Valves,
1-RMT Room Thermostat RMT 230,
1-AT Cylinder Thermostat,
1-WC4B Wiring Box.

I am having a problem in that the boiler will fire up even when the programmer is switched off on both the central heating and domestic hot water buttons. The problem seems to be with the AT cylinder thermostat. When the temperature falls below the ambient setting the boiler will fire up even when it is switched off. I have to turn the thermostat down to near zero to knock the boiler off.

I have followed the wiring diagram attached. I am not an electrician but the wiring diagram seems pretty straightforward to me.
Any suggestions as to what might be causing this problem.
 
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Wow what an awful and complicated drawing you've got :rolleyes:

You have a standard s plan system. There's loads of proper clear drawings on Google for these.

Andy there's no off signal on an s plan.

Have you fitted / removed the correct links in your joint box?
 
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Thanks for your quick reply Andy. As I said I am not an electrician. I followed the wiring diagram provided. On the programmer there is no provision for a hot water off connection, just on. Terminal 3 on the programmer to terminal10 on the board. I presume there is an in built switch that would operate when the desired temperature is reached.
 
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RF LIGHTING Thanks for your reply too.
I have fitted the correct links. Removed links. No ????
Have I missed something?
 
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Some heating joints I've seen come with more links fitted than you require so they can also be used on other layouts of heating systems. You need to check there aren't any links fitted which are not shown on your diagram.

It certainly sounds like the cylinder stat is picking up a feed from somewhere it shouldn't be.
 
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ok then,


so what wires do you have connected to the h/w thermostat.

I would have thought one would be to the timer H/W on
and other to the motorized valve brown wire.
 
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It should be ;)

OP can you post a photo of your joint box to see if you've missed something obvious?
 
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I will take that photo in the morning and post it up. I have to shoot off now.
Thanks for your help so far.
 
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RF,here are photos of the junction box, thermostat and programmer wired connections.

Andy, atc wire terminal 2(nc) goes to junction box terminal 14 which has a permanent link to terminal 8. The brown wire from the dhw motorised valve goes to 8 on the jb, so these two are connected.

atc wire terminal 1 goes to terminal 15 on the jb which has a permanent link to terminal 10. Dhw on on the programmer goes to 10 on the jb, so these two are connected.

Assuming all the wiring connection are correct, am I dealing with a faulty thermostat and / or a faulty programmer? Which of the two would be more likely to cause the fault?
 
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Don't know why the photos didn't display in the comment box, but if you click on my user name they are in the album "danfoss".
 
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I cannot make out which wire returns from the room stat and connects to the bottom of terminal 2.

Have you used the CPC(earth wire)?
 
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Anyway, the tank stat would appear to be correct and

should not have any power (at terminal 10) when the programmer is not calling for heat.

A sticky valve would cause the symptom you describe.
 

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