Honeywell ST699 power keeps tripping

R

Richard Edgar

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I have the above programmer, but it is currently causing problems. When it is set to HW only it runs fine no problems, however when I switch to CH on was well the programmer will trip and go dead after a couple of minutes. To get it working again I have to press the reset button but it will trip again after another couple of minutes. It is quite old around 20 years since the house was built so the internal battery has died too. Also I can only get heating if the water is on as well just CH does not fire the boiler. I suspect the programmer is on the way out but I am worried there is an overload somewhere. Does anyone have any ideas?

Thanks in advance

Rich.
 
The programmer seems to lose power and the only the only way to get it back is to push the reset button on the unit. The mains fused switch to the system is not affected. Hope this is more clear.
 
No heating without hot water is a plumbing issue, nothing to do with the programmer (assumption is you have gravity hot water system)

Internal battery is replaceable unless you have current 699

Fuse in the spur/ plug should be 3 amp- check.

Programmer can of course be defective- I would check listed items first though
 
Thanks DP for your reply.

Will check these.

Internal battery on my 699 is soldered on, but when I checked I noticed some obvious burn marks on the circuitboard around what look like resistors and in the mounting plate. I think I will replace it just because of that.

Yes it is a gravity system in Y-Plan, if I set the programmer to CH only should the valve not move to feed radiators only and fire the boiler?

The valve was replaced around 18 months ago (not by me), so I suppose it could have been wired wrong judging by the mess in the junction box.
 
The valve should open. if controls are wired correctly, will fire boiler and pump.
 
A "y" plan normally refers to a fully pumped system with a three port motor valve.

Of course there are many variations of how these can be fitted.

Tony
 
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