Baxi Solo 3 50 PF overrun problems

[Geronimo W. Christ Esq]

Hi all,

I have finally completed the rewiring efforts to my central heating/HW suggested to me ages ago here, by Roger Mills, Ed Sirett and other kind folks. Previously the whole system was controlled by a single crappy mechanical 24 hour timeclock. I've now replaced it with a Honeywell Y-plan setup, including a wireless room stat/programmer (CM67), cylinder stat, 7-day full programmer, and three way motorized valve. The electrical side of things all works beautifully, exactly as it said on the tin.

I have one problem though, and it's pump overrun on the boiler. The people who installed this boiler when the house was built did not know (or care) about the pump overrun requirement, and wired it in parallel with the pump :

everyone here predicted, when I run the boiler with the boiler stat up full, the boiler cuts out with overheat after a few hours, during the period when the wireless stat begins doing it's modulation. The problem goes away when I turn the thermostat down to around 11 O'Clock - but then it takes a good bit longer to heat the house to the 20.5deg temp I've set on the room stat.

So I decided to change the wiring so that the overrun would control the pump. I've heard that the Baxis have notoriously wobbly overrun boards, so I tried wiring up a permanent live to the left hand terminals, and a

60 watt light bulb to the right hand L and N terminals as a test. When I power it up, I the lightbulb oscillates on and off very quickly and the relay chatters, sounds like it's on and off at least ten times a second (have I wired this the right way around ?)

Am I right in assuming that it's replacement PCB time ?

[I've now restored the wiring back to where it was so that I can have some heat. But now the relay chatters a few times each time the system fires up, and then settles a second or two later.. it didn't do that before .. ]

Is replacing the PCB a reasonable task for someone not qualified in gas ? (I don't want to mess with gas-carrying parts. If it comes to that I'll get someone who knows about it..)

Cheers

TGS

[Ed Sirett]

Follow the book to the letter. It will almost certainly have a PCB replacement section. Make sure the replacement is a recon from cetltd if they do one for this model.

By the book, most replacement procedures end with the mantra "The recommission the appliance in accordance with the commissioning procedure in sect n.n.". Which you should try to do.

[Geronimo W. Christ Esq]

Do you know where I can get a copy of the service manual (I assume that's what you're referring to) ?

[Ed Sirett]

I've put a copy on my web site.

[Geronimo W. Christ Esq]

[Ed Sirett]

Sorry about the broken link try

[Geronimo W. Christ Esq]

This is fantastic, thanks.

Are there many differences between the Solo 3 PF and the Solo 3 PFL ?

[Ed Sirett]

The ultimate test is the Gas Council Number (GCN) which uniquely identifies the gas appliance.

Letters in boiler names are a bit like letters in Car models they often refer to specific features but there is no guarantee of course.

CF = conventional flue. BF = balanced flue. RS = Room sealed. PF or FF or Turbo = fanned flue. L The boiler complies with part L of the building regs. HE = high efficicency i.e.condensing. SE = "standard" efficiency i.e. non condensing. MF = Multi-flue.

numbers are usually power ratings ( 10kBTU/hr) or (kW). or sequel numbers (e.g. Kingfisher II).