Central Heating question

[D4B]

Hi All,

Just wondered if there are any heating engineers on here who might be able to point me in the right direction?

Have a Baxi Solo 3 50 PF boiler which runs our hot water and central heating in the old fashioned way via a copper tank in the airing cupboard....

We were having a problem where the boiler would struggle to fire up, and after changing a couple of things, the independant heating / gas engineer who we have used for a few years, said he wanted to try changing the PCB in the boiler, and would do this at no charge as he had a known good secondhand one.

This solved the problem. The boiler now fires up lovely, without hesitation. However, since then, the central heating pump runs continuously, 24 hours, and is keeping us awake at night.

It's as if the pump is no longer getting the message to switch off.

Any ideas what controls the pump? Or could it just need a new pump?

Any advice gratefully received.

Many Thanks Steve

[steve_earwig]

Where is the pump? I'm guessing it's separate, they usually are.

My only experience of UK central heating is spotting a dry joint on the pcb by having the cover off and watching it in the dark (pure fluke) but what controls our pumps here are the roomstats. The pump runs while there's a demand for heat and the boiler tries to keep up.

independant heating / gas engineer

Isn't it his fault/problem?

[Welly]

I've worked in the HVAC industry for years, I don't work on domestic boilers but know a bit about them. Did the pump used to 'run on' beforehand and always after the boiler shut down? I mean run on for a short while to dissipate the heat from the boiler and then switch off?

If it did run on like this then that's good as it means a constant power supply is sent to the pump from the boiler to protect the heat exchanger from overheating. The boiler then sends a 'satisfied' signal via the PCB to stop the pump when it has cooled down enough.

Sounds a bit like the PCB is a different version maybe and you're getting 24hr power to the pump regardless of what the overall timeclock says.

I guess the only real check is to compare PCB's side by side.

I used a company called 'adlink' in Wembley when our PCB went, they sell refurbished PCB's at a good price and you send your old one back to gain a deposit refund - mine was great and that was 2 years ago with no probs since.

[D4B]

Hi Steve, thanks for your reply,

Where is the pump? It's in the airing cupboard right next to the copper hot water tank.

The pump runs while there's a demand for heat and the boiler tries to keep up. Agreed, but this pump keeps on running even when the timer control turns everything off, so it isn't calling for anything (or shouldn't be anyway) !

independant heating / gas engineer
Isn't it his fault/problem?

Yes of course, but before I call him out again, I want to try to understand what might be happening so I don't get overcharged, it's getting expensive keep calling him out

Cheers

[steve_earwig]

Welly's your man, looks like. If he left it malfunctioning isn't it his fault and therefore his problem?

[D4B]

Welly, many thanks for your reply, (not sure how I missed it oops!)

That all makes sense to me, while I am not sure if the pump used to run on a little previously, perhaps it did, the thing I am sure about is that it never used to run all night.
I think I have the original PCB in my loft from when it was replaced five years or so ago, if so I will send that off to be rebuilt.

Many thanks, I will let you know how I get on.

Steve: Yes normally it would be down to him, but he did say to me that I could try his used PCB for free, but if he had to come back to it that would be chargeable......

Having said that he is usually fairly reasonable. You live and learn huh?

[Doggy]

It's also possible there's a pump control relay in the new PCB that's got the contacts welded together, the pcb is a different version, or is configured differently. Equally something could simply have been incorrectly connected, if swapping the pcb involved disturbing the external wiring connections.

I downloaded your boiler manual here: http://theinitiativegroup.org.uk/fscini ... System.pdf

Look at the electrical connections on pages 30 & 31
Verify the pump is correctly connected
Also check the permanent and switched lives have not been exchanged

If all else fails, here's a cheapish pcb: http://www.ebay.co.uk/itm/Baxi-Solo-2-3 ... SwpDdVIRyA

[D4B]

Cheers Doggy, that's a great help, will probably try the ebay board!

Thanks for taking the time to help, very much appreciated

[Doggy]

No problem, hope you get it sorted.

[D4B]

Just an update, been a while i know! Sorry!!

It was the PCB, though the first one I ordered was faulty
however they sent a replacement quick enough, then all is well again!

Thanks for all your help on here