Britony Combi 80 SE - DHW valve/filter

[thescrapyard]

Our marvelous combi boiler has 'issues' again, when its cold as usual


Long standing problem was hot water microswitch on changeover valve wasn't always being fully activated when valve activating to get hot water. Changed diaphram and seals but not 100% solved, got worse recently with hot water being very poor and a bad habit of switching off when running hot taps or running bath

Changed microswitch a couple of days ago as that had got wet when I changed the diaphram ages ago, and noticed the changeover valve was now not closing enough to activate the new microswitch, so looked into why water pressure didn't appear to be enough to operate the changeover valve

Pulled out the filter/valve assembly that is at the bottom left of the changeover valve block, and noticed a spring that was jammed sideways and a small plastic plunger that was also rattling around in this block, so I assume thats my problem with water flow as it was somehow jamming/restricting flow. Removed these parts, now no hot water as I assume the valve is permantly shut, hence no water pressure is being diverted to operate the diaphram and moving the changeover valve to operate the switch give us hot water and diverting the water for the DHW system

Just ordered a new filter/valve assembly, won't be here 'till Monday morning so I'm popular with the wife who moans 'at least we had some hot water'

This is the 'only' part I pulled out, the changeover valve operates smoothly by hand as I also changed that 6 months ago and was very badly scaled up and only operating partially and was a pig to remove due to scale build-up, which I assumed was causing the hot water switch issues, until now

What I'm asking is how this simple looking spring/very tiny plastic plunger can cause the changeover valve to now not operate at all and its function as the diagrams I can find don't explain much

And any other suggestion if this doesn't fix it, as I'm at a dead loss as to why the changeover valve is only operating partially


Luckily heating still works, as obviously the changeover valve can't move



Now I've said if we can coax it through to next year its a new boiler time, after 3 circuit board in 3 years and all the other parts. Local parts factors suggested Vaillant ecotec 24/28 as I said I was thinking Vaillant Ecotec 831 as recommended by "which", but at a £800-£1200 for boiler is stretching the budget, not including install and power flush


Reading past comments and the suggested "your lucky to keep it going its an old design now", but wife insists its new and was installed as a new central heating system about 6 years ago now, I suggested it may have been a brand new boiler but how old is that design ......

 

[Agile]

Since 2005 all boilers installed needed to be condensing.

Your boiler sounds as if its at least 12 years old!

I suspect this spring and plunger were not there by accident! But have become displaced from their proper operating place and causing your problem.

Have you even considered getting a boiler engineer?

Tony

 

[thescrapyard]

Looking at other diagrams it appears to be a by-pass valve, but the spring/plunger was jammed so allow partial closing/opening of the changeover valve with some but not full water pressure getting through. Yes I knew they were meant to be there but not doing much good rattling around and the spring jammed sideways doing nothing

And the mesh water filters in the pipework may also be partially blocked with scale reducing flow even further


I've found the Baxi Genesis intructions as its mentioned these are virtually identical, should have changed the boiler last year really, and your comment about condensing boilers suggests it may be a minimum of 12 year old design, I thought at least 10 years. But nobody ever really does anything until you notice its just too damn cold and you haven't the warmth and comfort of instant heat/water anymore when its really needed


Getting hold of the engineer who fitted it 6 years ago, isn't easy. Maybe he knows what a fantastic design (cheap) the boiler is so avoids coming back to it, never seemed too impressed when we could get him to come back after he changed the PCB about 2 years ago after changing the first replacement PCB which failed within 12 months

The wife's ex did a great job of 'doing the house' up and paying out as little as possible to contractors but taking as much as he could off her for the building work, like leaving rubble under the floorboards when they pulled a non-supporting wall down for the bathroom as I found out when the bath outlet pipe starting leaking



What your thoughts on the Vaillant combi boilers, I read about internal rubber pipes bursting and other issues, but these seem to be on boilers that are 2 years old or more and appear to have been resolved when new ones are built or as and when the faults appear on already installed systems

We only have a 2 bed terraced with 4 radiators and bathroom radiator/towel rail, so its not as if a boiler will be overworked

 

[thescrapyard]

Changing the water control valve solved the problems, but still annoying to find a simple spring and cheap thin looking piece of plastic piston can cause so much aggrevation. What a great design ... not

 

[Agile]

It may be a little part to you but these devices often use them to create a pressure differential which is then applied to the large diaphragm which then does the pushing.

If the differential pressure is higher with a good flow then the spring loaded part opens to prevent the diaphragm pressure getting too high.

Tony

 

[thescrapyard]

Thats makes sense, I knew it was a difference in water pressure that caused the diaphram to move the valve to block the central heating supply but couldn't work out why there wasn't enough pressure for the diaphram to move that valve enough to activate the DHW microswitch and divert the water for the hot water supply


Whats your views on the Vaillant EcoTec Plus 24, the local suppliers says they are good boilers and could get me a good price for the boiler/flue and wireless room thermostat and magnatec filter and a registered fitter is happy to fit a boiler I bought as he says the warranty would still cover any boiler issues, but can give me a quote for him to buy the same boiler/flue and extras as well as giving the old setup a powerflush

Another local registered company claimed they flush the system out with cold water to get rid of any old sediment or crud in the system and said the Vaillant EcoTec Plus 24 was a good choice


I know I could get much cheaper boilers but do I really want to go through yearly breakdowns or some kind of faults all over again

 

[Agile]

The Ecotec Plus is a good average boiler.

But there are other boilers with a five year warrantee that I would choose in preference such as the Intergas or Viessmann.

Installers are not happy with the appalling lack of replying to calls to the Vaillant tech help line within a reasonable time.

Tony

 

[RichieRich73]

Hi Tony, I have the same boiler and think I have the same problem, so would just like to check how you fixed it.
I have replaced the diaphragm and plastic housing as one unit, but the 3 way valve still doesnt go down enough to operate the microswitch. Is the 3 way valve unit easy to remove? In the manual I have it says to take off the diaphragm unit and just twist off the 3 way valve. I would like to take it off to remove scale etc. You can buy a replacement valve (part 61302411), which is just the slider and not the housing. Is this the part you replaced?
Any help you can give would be useful.