ERRATIC OPERATION OF BOILER

[sailor]

Good morning all,
My mother had a new Potterton Suprima 30L Boiler fitted about 3 months ago and has had constant problems with it. Thankfully most have been sorted but one fault remains which the installers seem incapable of curing.
The problem is as follows:
When the system comes on in the morning all is fine (but see note!!), the boiler switches on normally, the water in the cylinder heats up and the radiators warm up. However, when the water cylinder thermostat switches off, the boiler goes berserk - the red/green leds on the control panel flash on and off like christmas tree lights not following any sequence at all and the boiler switches on and off every few seconds.
To cut a long story short, a bloke from potterton came to sort it out at the request of the installer, and he says that the problem is the 'switching live'
voltage at the boiler dropping to approx 190-210v in the 'fault' condition
which is apparently insufficient to fire the boiler hence the erratic LED
sequence and boiler operation. He spoke to the installer and suggested a wiring fault and I am now waiting for the contractors Electrician to attend.
As the Electrician has been back on two occasions already without success
I do not have a great deal of confidence in him to sort it out on his next visit, although I am assured he is well qualified...
My own checks/observations are:
1/ The 240v switching voltage measured at the room thermostat appears
OK and switches on/off normally as measured with a meter.
2/ The switching voltage at the boiler ONLY drops off when the cylinder
thermostat switches off.
3/ The operation of the 3-way motorised valve actuator appears fine
(I have lifted the actuator off the valve and observed its operation and checked the free movement of the valve spindle) but NOTE that the radiators still get hot even if the room thermostat is set at Zero!
I assume this is caused by leakage through the valve and does not particularly concern me unless of course it is contributing to the fault.

I would very much appreciate any input/comments/suggestions as this is driving me barmy!

Thanks for reading....

Sailor

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[CH4]

Check the wiring to the cylinder stat. The wires to terminal 1 and terminal C may have been transposed (terminal C should be connected to the programmer and terminal 1 to the boiler).

I've posted a wiring diagram (only in ASCII art) here.
NB There's a mistake in the voltage table provided - the orange wire voltage, for CH only, should read 240 V. Also, your pump is probably connected via a connector block within the boiler.

 

[sailor]

Thanks CH4,

I will check out your suggestions/voltages later today, although after further checks yesterday I am convinced that the problem lies with the Danfoss actuator. If I measure the voltage at the Orange (SW Live?)
wire from the actuator in the connection box, the level fluctuates between about 205-220v, when the Cylinder stat switches off, and never the expected full 240v. If I monitor this voltage whilst switching the cylinder stat on and off, I can actually see the level change from the full 240v (water on), reduce to virtually zero as the actuator motor moves and the microswitches change, and then increase to 205-220v as the actuator moves to CH only. (At 220v the level actually seems sufficient to fire the boiler, but any less than this and the boiler cuts in and out every few seconds and as I mentioned in the original post the LED's go crazy)

Can I therefore assume that the Danfoss HS3 actuator is faulty (available
locally for about £48) or is my logic flawed??

Thanks again for any suggestions.

Sailor.

Stop Press!
Checked out all voltages as per your table and all ok apart from Orange wire / CH only which as indicated above is 205/220v and fluctuating.
Phoned Danfoss with symptoms and they concur that HS3 actuator is probably faulty.
As I also mentioned leakage through the valve itself it looks as if I may as well order the Valve/Actuator complete.
(£50.94 from Screwfix delivered). I'll be cheesed off if it's something else.

Sailor.