Baxi Bahama 100 flow switch problem

[londonerOK]

The boiler stopped firing so I followed the flowchart in the manual which pointed at the two flow switches. I noticed that scale was emerging from the left hand one and it was dripping slightly. I unscrewed it (they're hand-tight), cleaned and replaced it - sorted the problem for a few weeks.

This morning the boiler won't fire again. The flowchart test is to use hot water only and if the boiler won't fire it must be the flow switch. I can hear everything else working OK so I suppose I need to replace one. The manual says they are a matched pair - the GCN is E02-764. Part number 241159. According to one supplier this part has been superceded by 240753. The suppliers seem to sell them individually, here for instance or here (select Bahama 100).
According to the manual, at least one needs a spring - does anyone know if both switches need springs as it looks like I'll have to order them separately?
Is there anything else I can test in case that doesn't fix it?
Thanks in advance
Chris
North London

 

[ChrisR]

They aren't a matched pair exactly - they're both the same so you can try swapping them for diagnosis. I think the spring stays where it is.

 

[burrell8nhp]

Hope you don't mind me joining this post, but I think I have one problem the same as londonerok on a baxi genesis. The boiler has been nothing but trouble since I have had it (approx 5 years). It's had many problems such as temp sensor fault, 3 way valve sticking, and flow switches getting scale on them (this seems to stop them working, and cleaning them in the past seemed to fix it). At the moment it keeps losing water, after much checking over of the ch system the leak is actually coming from the pressure relief valve and is venting outside. Doesn't leak all the time, it just seems to make a noise and dump a load of water out then stops again until the next time (seems to happen when a tap is turned off, ((but not every time)) but can't be sure) can anyone help?.
Back to the flow switch, mine have not got any type of spring in them from new, should they have ?, the hot water keeps cutting off then on.
I looked on a web site yesterday and as you say they seem to be superceded by a new part # is this because the original are no good ?
Heres hoping somebody may be able to help
ATB.

 

[londonerOK]

Appreciate all the help given by you guys - it makes a difference.

I bought a new flow switch from MJT (good suppliers - I asked a question on their website and got a phone call in reply. Ordered on the web and got it within two days - that's what I call service for a £17 ex VAT part).

According to MJT, it has the spring built into the underside of the cap, so it seems an improvement over the version that may have had a spring around the central spindle (according to the manual, although there was nothing on the old one I removed...).

It fixed the problem and I attach a photo of the one I withdrew - it looks like some kind of magnetic switch - when in situ the spindle pokes into the bit shown detached in the photo, which was coated internally in what look like gungy iron filings - bits from the installation four years ago maybe? I've also fitted an external hydroflow de-scaler as north london is a hard water area. I hope this will reduce faults and de-scale the boiler and rads over time - does anyone know if I should add some sort of inhibitor too as I've now emptied and refilled this thing several times.

The only thing wrong now is the fact that the pump seems to run for a really long time after the thermostat cuts the heating off - I don't understand why.

I also had the pressure relief valve problem and fixed it by monitoring the outflow - the valve behaved differently depending on how it was handled. The Bahama has a spring-loaded one that can be turned from the outside by hand. When you release it it is supposed to close but mine wasn't. It was as if there was a bit of scale wedging it open, resulting in constant mild overflow. Opening it briefly and then listening for overflow showed that three times out of four it was not sealing properly after being handled. So I just make sure that it is properly closed now, which has fixed the problem for me.

If you've had lots of problems surely you're invincible now, aren't you? You can fix any fault yourself, can't you? My problem is I cannot identify the clever plumbers. I want one who has fixed lots of Bahama 100s - how do you find such a person? They really ought to get themselves together on the web, open to public examination, in a forum like the IT freelancers, rentacoders etc do, then bid for work...

I'd also like to see which are reliable components, like is done for cars by independent reviews like the Which Reliability surveys - surely that should exist for boilers, shouldn't it? Baxi must realise that growing their industry will grow their business - wonder why the old fashioned, backward looking atmosphere that seems to surround everything connected with UK plumbing still persists? The design of the boilers reminds me of early car design - mechanical fail-safes for everything, electronics mistrusted.

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[ChrisR]

Pressure relief valves tend to leak once they've let water through. They usually first do so because the pressure vessel precharge has leaked away so they need pumping up again. A search should find plenty on that.
Boilers are crap because they are too cheap. . 20 years a go a Vaillant combi cost £850 and they're still going and very serviceable. Now you can buy one for £under 600. Other makes are as low as 400 inc vat. That's the same as a non combi, which has a hell of a lot less in it. All combis seem to suffer a lot from sludge in the heat exchangers. Often caused by plumbers throwing the things on the wall and leaving all the flux in the system. SO the combi degrades a bit, maybe gets one thing go wrong, and it gets changed. BG charge something like £2500 for a combi swap but pay the subcontractor £200. etc etc etc.

Most combis now are old models, which are usually better, but when a new model comes out it's the customer who has to find the bugs in the first year or so. Some baxi's were disgracefully awful and you have to advise people to cut their losses and bin them early. But the current baxi 105 is very good. You just can't tell.. Both the last two Vaillant models had lousy diverter valves, but they're apparently sorted now.
I steer clear of all new models. Soon we'll all have to have condensing boilers and gawd help us. There are a couple of designs getting stable now but there are still long term worries. eg many of them use aluminium alloy heat exchangers, which slowly dissolve in the condensate... No Industrial cond boiler has ally - all stainless steel.

There's no wonder plumbing is a "conservative" trade. Most of the new stuff is crap. Like plastic pipe, which just barely stands the pressure and temp in a combi system - sometimes it bursts if things go wrong. Then the push fit connectors all rely on a single O ring. How many of those are going to be leak free if thermal cycling moves the pipe a bit in 20 years time - answer none. We'll be ripping them all out and putting the next generation of crap in. You can get a combi and 6 rads put in for about £1600 - so who wants to pay double that or more .

WE don't have to be good to be busy. There's so much scope for bad work and ripping people off that people hold on for years. One guy I know reckons that if you get a recommendation you didn't charge enough. There's so much work out there that he has a point. But what a state for a trade to be in!

 

[burrell8nhp]

After checking over my boiler again this week, I have found that the expansion vessel is losing pressure. Don't know what effect this has on the system but I ordered a new one along with 2 flow switches and a pressure relief valve from MJT on monday and they have arrived today. They seem to be a good company to deal with.
I plan to fit them over the weekend and will let you know if it has been sucsessful.