Evening everyone,

After some help with my boiler please…

Worcester Bosch 280 rsf combi fitted and for some reason when using the shower the water temperature fluctuates.

Starts off fine then temp seems to increase before becoming pretty damn cold, temp then warms again before the process cycles through again.

Would suggest the whole cycle (warm – cold – warm) takes about 2-3 mins.

No problems with central heating at all.

Can anyone point me in the right direction for a repair?

if other hot taps are fine it suggests a blockage in the pipework to the shower or most likely in a filter fitted to the inlet elbow?

I tend to spend more time in the shower than the amount of time that other hot taps are running so thinking this is why it isn’t presenting itself in other taps???

Definitely something worth looking at though

I don’t have any problems with water pressure or volume which may be something I’d expect if I had a blocked filter? However where exactly would I be looking for the filter that may fitted in the inlet elbow, would this be located around the boiler?

Thank you for your input

The 280 is an odd layout inside for the DHW. It’s either a blockage in the calorofier, or the plate heat exchanger if it’s had the conversion, or it’s one of the thermisters out of range.

Either way you’ll need a gas man.

edit, re-read this properly now, but probably still right. You need to see what it does on prolonged DHW running at the tap, does it cycle the same, if it’s fine, then I’m back on Bear’s side 🙂

Paulsoxo and Bear,

Thanks for your help, looks like I’ll be putting a call into worcester bosch in the morning then…

Sunday wobbler

Yup, check another tap first before you do anything else.

Whats the general opinion on Worcester Bosch boilers? I’m thinking of replacing my current boiler to one towards the end of this month.

Update:

Just had the hot tap running in the kitchen and it happened 2 in 5 mins…

Water running hot lovely then boiler goes out, water gets cold and boiler re-fires heating water up again, cycle repeats.

Does anyone have any ideas?

Sunday

I have one and it has been generally fine
5 yr guarantee if installed by an approved engineer.
A washer split so they fixed that but forgot to rebuild it properly so hot water only worked when the heating was on so they fixed that – more accurately plugged the bit back in.

nowt really to compare it to
it works , its very efficient and you get a 5 yr guarantee
Better off with a trade opinion I would assume

Flow sensors? I had a Baxi that used to et them. Now have a Worcester Bosch and its good.

Must admit mine (the boiler) is a few years old, at least pre 2000 (based on the paperwork I’ve found since owning the house) I would say and thus far has been amazing.

I need to replace the kitchen next year and was planning on replacing the boiler at the same time, finances don’t allow doing both yet hence I would like to keep mine going for a while longer.

FWIW I have only heard good things about bosch worcester

I’m no expert but I had a similar problem with mine.

The CH worked fine but the hot water would go very hot and the boiler would overheat and trip, before firing back up again.

It was just caused by low pressure on the CH, just needed topping up back to its working pressure with the valve on the bottom. I had a very slight slow week on CH, which I never saw but lost enough water over a few weeks to cause an issue.

Thanks Winston,

Are you talking about low pressure on the water side or within the pressure vessel inside the boiler?

If so could I do this with my track pump? I’ve seen a schraeder valve on the pressure vessel so I might check this tomorrow?

It is really a slight lack of water in the CH and a loss of pressure.

What does the pressure gauge read on the front of the boiler? I think it should be be between 1.5 to 2 bar – it should have a green sector marked.

You top it up by the the filling loop valve that is on the bottom of the boiler. I have had 3 Worchesters in the last 3 houses I have been in and the valve is always been on the bottom of the boiler. You need to use the plastic T piece that is clipped inside and insert it in the hole. This will allow you to add water to the system from the mains. Keep an eye on the pressure gauge on the front of the boiler and just allow it to gently rise up to the green sector.

It should explain how do this in the manual.

This should help from their website

It’s almost certainly what I said above.

Flow sensors? I had a Baxi that used to et them. Now have a Worcester Bosch and its good.

That’ll have been a Bahama, and they work very differently to a 280 RSF, the 280 has a paddle flow switch.

Thanks Winston,

Are you talking about low pressure on the water side or within the pressure vessel inside the boiler?

If so could I do this with my track pump? I’ve seen a schraeder valve on the pressure vessel so I might check this tomorrow?

What are you checking for then? No offense, but leave it alone, it’s only for the expansion vessel, and if the pressure relief is not dripping water outside, then it’s not the vessel that’s the issue. The system pressure can be checked by checking the pressure gauge, however, that’s not very likely to be the cause if everything else is ok. Do check it though. It should be 1, to 1.5 bar when cold.
The T bar Winston is talking about is on the newer CDi’s. Yours will have a filling loop if it’s a sealed system. There were an awful lot of 280’s fitted to open systems though.

@Paulsoxo,

Mine has got the filling loop and as you have also said it is a sealed system, pressure gauge is reading fine at just over 1 bar, a nice big one on the front, even the O/H has noticed that!

Heat exchanger inspection on the way I think…

I’ve had this on mine:Take the front panel off, run the hot tap..after half a minute or so do you hear a little click? If so, then the micro-switch (that tells the boiler there is a hot water demand) has swiched off.
It is probably doing this because the diverter valve diaphram has failed.
You can get reconditioned ones on Ebay but you have to strip half the boiler to replace; will be expensive I’m afraid.

Be aware if diaphragm some of the older Worcester boilers needed the whole valve needs changing.

Sorry, syntax error; you need to replace the whole valve!

Believe it or not I have had BG out for a WB junior 28i which is going into fault when using hot water,they have replaced the printed circuit board and are going to replace the air sensor switch, but he was saying that the burner uses more gas heating water as opposed to heating the radiators, the other thing we noticed today were the hoses on the air flow sensor had started to crack possibly letting air into the system (trimmed back and refitted) but these things are working an tiny differentials so the littlest difference can knock a sensor out and kick the boiler on its arse.

definately a plate heat exchanger issue.. swapped out you should get it for about 170 from wb or about the same from BG

yes the 28i ( and many others combis) use more gas when heating the hot water than the central heating in fact for the last 18 months wb come packaged with an alternatice ‘chip’ that reduces ch gas usage to 15kw leaving the hot water at the original level..

Gweilo, Worcester is a great boiler.
Also fit Vaillant or Glowworm.
The boilers are all good.
It’s down to who you have fit and maintain it (see British gas thread).

My perants just had the same symptoms from their WB. As above, it was the small plate, or what i’d call the heat exchanger. It was partially blocked causing the hot side to overheat and the boiler to trip off until it cooled enough to fire up again, thus the oscillating output.

That’ll have been a Bahama, and they work very differently to a 280 RSF, the 280 has a paddle flow switch.

You know your stuff! 🙂

The biggest pile of poo I ever saw. When I finally got rid, after the low sensors went, again, replacements leaked and part of the plastic tubing started dripping I got a W-B. Told all those who came to give quote for new system that I would consider any but Baxi. One refused to quote (think he got Baxi cheaper) the others all suggested W-B.

BTW: never ask BG fo a quote: they quoted > £5000 for the same boiler I got for ca. £2300!

I had this problem about a year ago with a wb 240 and it was the diaphram in the diverter valve it had a little tear in it and had perished. Im not a plumber and dont know the difference between your model and mine but hope this is of help. I did however have to replace quite a few other seals as a result of disturbing things while doing the repair I supose this is par for the course with a 15+ year old boiler. I got an exploded diagram of the boiler and part numbers from the wb website.

Thanks for all the replies folks, it is amazing the information that is available on STW!!

Diverter valve has been replaced, recently, as it wasn’t closing properly causing the radiators to heat up when the hot water was used.

Going to see how much I can get a replacement heat exchanger for before just replacing. Might also do a ‘test’ fix and see if I can clean it out and refit to see if it fixes the fault…

The standard mountain bike rider tight ar$e when it comes to anything apart from bicycles 🙂

I have had this problem with quite a few combi boilers that use plate heat exchangers to heat the hot water. The plate heat exchanger can be removed and descaled using blockbuster drain cleaner or similar acid drain cleaner.Be careful use protective gloves and glasses, the acid only needs to be poured into the primary side of heat exchanger and left for approximately ten minutes.You may need to renew the o-rings between the plate heat exchanger and the hydraulic block. Good luck.

Sunday – did they replace the whole valve or just the diaphragm? As I mentioned earlier, think the whole valve needs changing on this boiler.

@ bear, the whole valve was replaced, the drayton motorised unit is the one which has been replaced.

Must admit the gas side of the boiler has not been touched as I am presuming the problem is more on the water side than the gas as the gas side of the boiler seems to be working ok just tripping out when it goes overtemp…

Thanks again to everyone for their help so far, it has been ace!

sunday.. a couple of issues.. your boiler is a minimum of 15 years old, swapping the heat exchanger out on this model is a pig of a job on a 15 year old piece of kit its like open heart surgery on an 80 year old doing it yourself is not realistic.
the expansion vessel has to come out to get to the thing and every o ring / seal will have to be replaced as the old will be dry/ flattened/ in more than one piece. use plenty of silicone grease on every surface and every seal when re assembling

i understand the desire for constant hot water but if your convinced this is the work req. ( which i believe it is likely to be) it is no small undertaking..

I understand the boiler is pretty much a relic and does need replacement but do not want to do this until I replace the kitchen next year and replace with new, I’m sure you understand not wanting to move things all around once I’ve (well the O/H probably) decided where things need to go…

Must admit it does look like a bit of a pig to get to but on the plus side unlike some trucks and most cars at least I can see it and the manual I’ve got with the boiler does detail how to replace, in fairly broad terms at least.

It is also the original heat exchanger (cylindrical type) so replacement will be of the modified plate type by the looks of it means modified pipework too and around £160 is purchased off t’internet.

Going to have a look and see if I can get it off and give it a clean out in the week before biting the bullet and replacing, yes I’m a tight ar$e.

@ Totalshell I appreciate and understand your concern but without meaning to sound condescending I’m fairly hopeful my ability and experience will allow me to complete this, although probably with a few choice words involved (note to self, make sure the O/H is out)…

Where do you live Sunday Wobbler?

Paul, I live in the best mountain bike area in the country, sunny suffolk 😀

Tongue firmly in cheek of course

Miles away then, I was going to offer getting one of my engineers round and giving you a quote.

I’m guessing the travel costs might make it a little prohibitive 🙂

Thanks for the offer though, I’ll keep on with my pig-headed stubborness 😯