Valliant pressure problem

Over the past couple of days our valliant boiler has developed a strange problem. When the ch comes on in the morning and the hw is being used at the same time, some how water is getting into the ch system and the pressure in the ch system goes upto about 4 bar and then starts overflowing via the over flow pipe, at the same time the boiler is making a funny noise. What we have been doing when this has been happening is reducing the pressure by opening the ch drain valve and once we have done this, then its OK and continues to work. We have had problems in the past with the boiler, its started off when the pilot light kept going out and that sorted itself out, then its was the rads getting hot when the ch system was off ? the only part we have changed since having the boiler is the diaphram. I changed the filler loop just the other day but that didn't help, could this be the diverter valve ?
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I'm not quite sure I understand the type of system you have. Could you answer the following:
1. What sort of hot water system do you have? (i.e. hot water cylinder/combi boiler)
2. Is the primary circulating water sealed and pressurised, or gravity fed? (you mention an overflow pipe, which suggests a feed/expansion tank and a filling loop, which suggests sealed operation).
3. What is the model of your boiler?
Christian.
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Its a Valliant combi boiler turbomax 282
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Mayur wrote:

I'm guessing you have a VCW? I would greatly suspect that your new filling loop is continuously topping the primary circuit. The diverter valve is having problems but when the primary pressure is brought under control things may get better?
ACTION: 1) Fix the inlet loop problem. 2) Add corrosion inhibitor to the circuit ASAP. 3) Get the air out. 4) Check for correct operation of the diverter valve. Replace as necessay.
How long since this boiler was properly [1] serviced?
[1] I don't mean sniffed at by BG with a combustion analyser.
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I'm a bit confused now, let me clarify a few things
On Sunday the reason I changed the filler loop is because I thought the valve had stopped working properly. On Sunday the handle on the vavle snapped off and then when I used a set of pliers to turn it, it just wouldn't open or close. I thought it was stuck in the close position so I left it but come Monday morning it started topping up ? I'd suspected that some how the valve had become open and started the topping up process.
Monday evening I changed the filler loop. On inspection, the filler loop looked valve was ok ? using pliers open and closed the valve ?
Tuesday morning same problem !
It did it Weds morning but this morning it was fine. Inhibitor was added to the system around the same time last year and all the air from the rads has been removed. What is a VCW ?
Thanks
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The filling loop should include a flexible hose, which should not be left connected. That way you can be sure there are no leaks. OTOH, some bungled installations just use fixed pipework.

A VCW is an Vaillant boiler that was common a few years back.
Christian.
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Mayur wrote:

A particular model of Vaillant combi which has (IME) a tendancy to run the CH on its own accord. Fixable with a new PCB.
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How about the pressure vessel - if the diaphram splits and you top it up you can get very high pressures. I had exactly that with a Worcester a few months back. Incidentally, it doesnt take long to screw the overflow valve up when the system goes over pressure.
Steve
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Sorry folks but that should read Vaillant turbomax 828
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Mayur wrote:

IIRC the pilot is electric ignition? It's quite a new model. Check out all the SealedCH FAQ then sort the other problems.
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Ed Sirett wrote:

It also has a built-in filling loop, have you checked this one isn't "open" ?
Lee
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The boiler itself is about 5 yrs old. I'm pretty sure it has electronic ingition but how do you tell ? If this system has a built-in filling loop, where is it located ? as the only I know and use is external and connected between the mains and one of the ch system pipes. Also, regarding the pressure vessel, I know that they are usually red in colour and round but looking inside the Vaillant I don't see one ? any pointers ?
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Mayur wrote:

Unless yours is a different model from our 828 Turbomax, then it's an 8mm or so braided hose that is joined to the incoming mains water block. There is a screwdriver slot in the water block to operate the filling loop.
Again, on ours the pressure vessel is red and sits at the very back of the boiler, against the wall. You can't miss it... ;) It has a car-type valve on the top, so you can check the pressure.
Lee
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Just looking at the servicing manual, I can confirm that the boiler is a turbomax VUW 282/1E
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Mayur wrote:

Sorry I forgot that they called some of the earlier combis 'turbomax' as well. It is nigh on certain that it has only an external filing loop.
The expansion vessel may be long and rectangular and to the side of the boiler. Anyway you now have the instructions...
So back on the main job. Check for water and pressure on the dry side valve of the expansion vessel. Check for a filling loop that is letting by when off.
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Mayur wrote:

It has. Also it does not have a push button sparker for lighting the pilot.
If this system has a

Is this a boiler with a digital numeric display or with a ladder of Leds?
If its the former it is a turbomax+ which IIRc started around 2000. I suspect it is the plain turbomax. These have external filling loops.
Also, regarding the pressure vessel, I know that they

It's big round and red/brown but it is also hidden right at the back behind the combustion chamber.
You might find the dry side valve if you look down from above at the back.
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Ed Sirett wrote:

snip
Forgot about the earlier ones, sorry to be misleading.
Lee
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Lee Blaver wrote:

Earlier models had just one filling valve but later models have two which both need to be operated to allow water in.
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