Grant oil boiler hunting

[George J]

above was HW
and with CH
2(N) - 1 240v constant
2(N) - 4 all over the place
2(N) - 7 240v constant

 

[Johntheo5]

Just confirm that I've got this right.

From post 26
HW+CH??
2(N) - 1 240v constant
2(N) - 4 all over the place. Probably about 58. is most consistent reading
2(N) - 7 240 through cycles. Shows OL for split sec when switching back on

From post 30
HW only?
2(N) - 1 240v constant
2(N) - 4 all over the place
2(N) - 7 random figures as low as 6v and up to 180v
I don't have a room stat just TRV on rads.

From post 31
CH only?
2(N) - 1 240v constant
2(N) - 4 all over the place
2(N) - 7 240v constant

 

[George J]

Yep. That looks right.

Happy to repeat any

 

[Johntheo5]

OK George, thanks, I've found a more complete wiring diagram, attached, including the burner, so will have to digest this later.

 

[Johntheo5]

Has your boiler control box got 13 terminals, if so, just probe between ter 10 and N with CH&HW on and then with CH only.

 

[George J]

Thanks John. No rush.

Really grateful for the help and enjoying all the learning.

 

[George J]

just 7 terminals

 

[Johntheo5]

Right, try and identify and write down whats written on the boiler terminal block, especially referring to the burner.

The puzzling bit, to me, is that terminal 1 is the switched live from the MPV irrespective of what position its in but this voltage is rock steady (ter1 to N) in all three positions, which is indicitive of no MPV fault, however ter7 to N is a bit erratic with HW&CH on, its ( ter7 to N) steady in CH only but in HW only varies 6V to 180V, yet no problems with HW only on.

 

[George J]

1. Live
2. Neutral
3. Earth
4. Burner Lock out
5. Burner Earth
6. Burner Neutral
7. Burner Live

Just off out for a couple of hours. When back I'll have another look at diagram. For me its hard enough when everything is working normally.

 

[George J]

What diagram are you looking at ?

 

[Johntheo5]

I think THIS is the correct one (it includes your boiler terminal block), you can forget about 4 to N crazy readings but two things you might do is with the boiler powerd up but neither HW or DHW on, test for voltage between 1 & N and 7 & N on the boiler terminal block, I wouldn't expect any reading on 1 to N (switched live) but would expect a steady 240V between 7 and N as this should be the boiler permanent live. Also with CH & HW on try and locate the wiring centre and test between 10 and 2,