Boiler Problem - Potterton Netaheat Mk2 F 16-22

[Mutley1955]

The above boiler starts up on room stat demand, the fan runs, the pilot lights and about twenty seconds later the main burner comes on. All is well for four about minutes or so (timed) Rads just start to get luke warm. Pump would seem to be working ( ie screwdriver to ear against body of pump and spindle rotating behind vent cover) Header tank full and rads venting water with no sign sound of air.
After four minutes the main burner goes off but pilot remains on, obviously it has not reached working temp.
I have replaced the Mercury vapor switch, the pilot assembly, and the 11 pin relay. I have tested the boiler stat in two different temperature water and it seems to react accordingly.
Having waited a week for Priceright Heating to 'next day' deliver a new PCB but they now tell its obsolete.
1.Anyone know someone who stocks the PCB
2.Any other ideas[/b][/i]

 

[corgiman]

hasnt got a pcb

has got a igintion generator thingy but no pcb

 

[corgigazza]

I would say that the gas valve may be faulty would need checking electrically, follwing circuit diagram.

 

[Gasguru]

The "pcb" is very basic - look carfully for broken joints.

Did you thoroughly leak test the pilot connections?

Does the main burner fire up again?

 

[corgiman]

The "pcb" is very basic - look carfully for broken joints.

Did you thoroughly leak test the pilot connections?

Does the main burner fire up again?

where is the pcb guru

I can honestly say I have never changed one EVER, cos I didnt know it was even there

 

[baxpoti]

hasnt got a pcb

has got a igintion generator thingy but no pcb

pcb = printed circuit board

Printed Circuit Board
Part No. 205295
G.C. 358 911

Extract from maintenance manual
5. PRINTED CIRCUIT BOARD

5.1 Isolate the main electricity supply to the boiler and turn off the boiler main gas inlet cock.

5.2 Pull off the thermostat knob, then unscrew the single screw securing the controls cover and slide the cover from the boiler.

5.3 Disconnect the leads from the two terminal blocks on the printed circuit board.
5.4 Disconnect the flying leads from their respective components noting the order of the connections.

5.5 Unclip the printed circuit board from the five supporting lugs by pressing the barbs inwards so release each lug. Remove the printed circuit board.
5.6 Remove the relay and the fuse and install them on the replacement board.

5.7 Replacement is the reverse of removal.

 

[Gasguru]

The "pcb" is just a bit of board linking the relay base with the connectors (AFAIR)

 

[corgiman]

well I be

I have always thought that that was a spark generator, never occured to me to call it a PCB.



I have changed loads of them, in fact I have one in me van

live and learn

Cheers Baxi and Guru

 

[gasmick2]

hi i had a couple of these boilers where the main gas seemed a long time coming on then it did not stay on for long i found it was the brass restrictor on the palstic pipe to the A P S i took it out and there was a lot of dirt in it i blew it out and bingo all worked fine after the hole is very tiny and soon gets partialy blcked up

 

[ChrisR]

That's there to delay ignition so the fan pumps any unlit gas out before the sparks arrive. So in theory it shouldn't be responsible for putting the boiler out once it's on. Well that's my theory anyway.

Yes it has a pcb, but it's just a board with copper tracks on, no electronics. If the fan fails to low resistance, and the 3A supply fuse goes, and someone comes along with 13A fuses to see what happens, then your pcb's in trouble! Have "mended" them with bits of wire soldered on the back.

 

[Mutley1955]

Corgiman

Thanks for the input, according to Potterton it has a spark generator and a PCB albeit basic on this model. Strange that you've got something that doesn't exist in your van.

 

[Gasguru]

Yes but does the main burner come back on again?

Does it cycle every few minutes or once the main burner goes out does it stay off forever?

 

[bengasman]

I have always thought that that was a spark generator, never occured to me to call it a PCB.

We tend to think of a pcb as something resembling a computer motherboard, but when taken literally, any board that has so much as one line connecting two parts electrically, technically qualifies as a printed circuit board

 

[corgiman]

Corgiman

Thanks for the input, according to Potterton it has a spark generator and a PCB albeit basic on this model. Strange that you've got something that doesn't exist in your van.

It didnt say that

I have a spark generator in my van, which as far as I can tell has this "pcb" in it.

as I said you live and learn, great old world aint it

 

[Mutley1955]

Once the main burner goes out it stays out. If you switch the whole thing off and leave it for a while (about an hour) it will go through the sequence again.