Potterton Suprima 80 - Lockouts, PCBs, Components & Drain Down

We now need to do something about our boiler - a notorious Potterton Suprima 80. Lots of red lockouts over the past year or so getting progressively worse - a common pattern from what I have read (and that's an understatement if ever there was one!). I/we've (I from now on) read lots about the bad PCBs and have tried to check that aspect out (see below).
The problem now is:
A. On power on at the fuse, the red LED either blinks 2 per sec or does so after a reset
B. A relay clicks, the green LED is on (steady) but after about 30 secs, it goes out and the red LED flashes again, usually with green LED going off. No fan no ignition.
If, after about 1 hr off at the fused switch (adjacent to the programmer - this powers the pump and Honeywell 3 way valve too I believe), the Suprima does start, it then just cuts out again within about 5 minutes with the same red LED flashing. Other times it has run for a few hours and then just stopped, with some intermittent bursts for a few mins, cut outs, and so on. I suspected a) a bad component or b) bad solder pads.
I know:
1. The fan works (when the boiler does start as above, I've seen it run) 2. The pump works (after fixing a bad solder pad - see below) 3. The motor on the Honeywell V4073A 3-way mid position valve works (althoug see below). 4. The room thermostat works.
I replaced a duff motor in the actuartor head on the Honeywell 3 position valve, but the valve itself is still a bit stiff. This side seems to work (although the manual level only goes back to mid position on the actuator, not all the way over to AUTO as it does on my ready-to-be- substituted new V4073A 3-Way valve should I l earn how to "drain down" - can anyone can advise here?. I realise it *could* be the microswitches on the actuator head that are part of the problem, but don't want to risk the new actuator on the old valve.
It was all temporarily fixed after a pump-power solder pad re-soldering job done on the J8 connector on the notorious Suprima PCB recently, and/or after the synchronous motor swap last week. We had hot water and central heating back for several days. We thought the problem was solved. Alas no.
5. The PCB has been checked for solder pad cracks and dry joints, several times now. It's has been re-soldered and put back. First big problem must have been one of the pins on J8 as some new solder on a clearly bad joint (vaporised solder?) got the pump running again after the boiler was literally boiling (kettling) because of no water flow. If one looks the wiring diagram on p. 32 of the "Potternon Suprima Installation and Service Manual" J5, J6, J7, J8, J9 and J10 have all been checked and resoldered, I even had a go at what might be the pads for the three big relays K1 - K3 although I can't be sure where they are. Whilst solder pad problems on J8 could lead to problems on the pump, soldering problems on J6 can affect a) the gas valve b) the fan and c) the overheat stat as this feeds all of these! I've tested the connection between the upright pins (for all the leads connectors) and the solder pads and the connections seem 1) sound and 2) make a connection using a meter. As far as I can tell, the connections are OK. There *may* be dodgy components, can't tell. If anyone has any suggestions as to what to look for on each component, and how to test it, please say as it would be nice to know which, if any component is aqctually faulty. It would be nice to be able to exclude the PCB altogether now.
BOILER SENSORS/COMPONENTS
5. The temperature sensor *may* be faulty - not checked it - need a spare to do so.
6. The air pressure switch may or may not be faulty - again, not tested, no spare for comparison.
7. The Overheat Thermostat has been replaced - so it's unlikely to be the problem.
BOILER WIRING
One anomaly is that the mains wiring INTO the boiler doesn't look 100% right to me. Note, this has not been touched so it was like this when we moved in. I have always had a feeling that there is something wrong with how the CH/DHW is wired up though, been something odd since we moved in. Can't put my finger on it, and with the problems we have had over the last year, it's all too muddled now to say exactly what. Repeat, the wiring has always been like this - odd?
Looking at the same Potterton Suprima 80 Functional Wiring Diagram on page 32, it shows what should be the correct wiring. Looking at the Live, Neutral and Earth connections for the P U M P and M A I N S coming in (two three core shite wires), the diagram on page 32 corresponds with our wiring on the B O I L E R PCB WIRING side, but NOT on the P U M P M A I N S side.
On the 7 way terminal connector shown below, we have a yellow/green (earth) attached at position 1, which is clearly labelled L on the terminal block and on page 32 of the manual!
B O I L E R PCB WIRING
y b g/y r b br g/y o o o o o o L N E SwL N L E 1 2 3 4 5 6 7 P U M P M A I N S
| | | | | | | | | | | | | | | | | a | | b |
a+b TWO WHITE 3 CORE MAINS WIRES
No idea why that has been wird that way of what, if any, the consequences might be. It doesn't look like a sensible thing to do, but ......
If anyone any bright ideas apart from (call Potterton, British Gas, and/or a plumber), or replace the PCB altogether, all of which seems like the last sensible option if nothing else - please let me know.
To recap:
1. How to "drain down" so I can replace the Honeywell 3 position valve 2. How to test the air switch, temperature sensor(s), PCB components 3. Advice on the wiring anomaly. 4. Other suggestions.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I had a similar problem and after replacing the pcb, stats etc found out that it was an intermittant fault on the gas valve whereas it would work then the gas valve would fail, it would then try to light and after a few attemts go off on the red light. I was lucky enough to be stood in front of it when it went off and I could hear the igniter trying to light the boiler

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
That's certainly another option I guess. Last night, just aftyer the CH and DHW was programmed to come on, the boiler leapt into life for about 1 minute and then cut out again - leaving the red LED flasshing 2/sec, and no rssets would clear it. The only time the red will stay off is if a) power is turned off *and* the room thermostat is turned down so low that there is no call for heat. The HW is harder to "turn down".
The one thing that really bothers me at present is that looking through the Fault Finding Guide for 30-80 Models on page 35,it says if the red LED is flashing on power on and reset doe snot work, them "Switch Live in or Permanent Live is connected to Pump Live output terminal. Check wiring.
Given that we have always thought something wrong, and that we had a problem on a solder pad which resulted in the pump not working, and that the wiring into the 7 pin terminal block is:
(Note that in the manual, the L N E sequence on PUMP is not the same as the N L E sequence on MAINS)
B O I L E R PCB WIRING
y b g/y r b br g/y o o o o o o L N E SwL N L E 1 2 3 4 5 6 7 P U M P M A I N S
|| || || || || || ||
E N X L N L E
y/g bl - br bl br y/g
(y/g = yellow/green = Earth) (bl = blue = Neutral) (br = brown = Live)
On power on at the fuse, the first connector, which the E is attached to, certainly goes LIVE.
The wiring diagram on page 18 of the manual shows a three core going to PUMP, with, as one might expect, a dark grey wire (brown) going to that point, a blue to the N and a y/g to the E.
In the next set of 4 wires coming from a 4 core cable, it's much harder to say what they are depicting as the diagram is in greyscale.
Main concern is on the PUMP side. This must have been done a couple of years before we moved in.
| | | | | | | | | | | | | | | | | a | | b |
a+b TWO WHITE 3 CORE MAINS WIRES
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Wed, 15 Mar 2006 01:14:10 -0800, adriennebottomley wrote:

When you have replaced the PCB with a reconned unit (or a new one if you are rich). Then all other symptoms will either disappear or their true nature will be come apparent.
I'm sorry that your resoldering efforts did not fix things.
--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.