Vaillant Turbomax 282e diaphragm

[Johnking]

I think the diaphragm in my diverter valve needs replacing. The little white arm that activates the microswitch moves fully when the downstairs hot tap runs (12l/m) but when the upstairs shower runs (6l/m), the arm barely moves. The specs say that the minimum DHW flow is 2.7l/m so am I right in thinking the arm should do a full movement even when called by the shower?

There are no leaks, and the microswitch is OK. I replaced the diverter about 10y ago and it's worked fine until recently.

According to the manual, the steps to replace the diaphragm are:

7.15.1 Replacement of water section diaphragm (fig. 72).
• Turn off boiler as in Section 7.1.1.
• Remove bottom cover as in section7.1.3.3.
• Open hot water taps. • Remove clip (2), undo union (3)
• Remove 6 screws (4).
• Pull water section base away from DHW heat exchanger and dropdown.
• Remove diaphragm.
• Replace in reverse order.
• Carry out electrical checks (see section 5.1).
• Refill and repressurise the boiler(see section 5.4)

Is this really correct? No need to drain the boiler, just turn off electric, gas, CH and DHW valves? I assume opening the hot tap is to allow water to drain. Seems like a quick job, which isn't what I was expecting after last time doing the DV!

 

[Gasguru]

Unfortunately that rarely sorts out the issue in my experience...
The plastic lever that operates the microswitch can go weak.
The top section (that diverts primary water) can partially seize.
Behind the large brass hex plug in the lower section is a plastic spring valve arrangement...these can break up and it's not part of the service kit or available.
The venturi needs pulling out and cleaning, can't remember if the seals are included in the kit.
The microswitches on these diverters are almost the worst of any manufacturer and fail for fun.
The filters break up and can clog.
There is a limited adjustment on the microswitch plate..you can rotate to lower the operating point.

The quality of these diverters has worsened over the years and when I last worked on Turbomax's I was seeing failures after just a couple of years.
You used to pick these valves up for new for £60 on ebay but not any more...I'm not sure I'd trust any "refurb" claims.

 

[Johnking]

Thanks, though that's ruined my morning!

Got to be worth doing the diaphragm first I think, even if it might not work. The white arm works well for ground floor taps, it just doesn't move enough when it's the top of the house calling for hot water, where the flow is less.

However, even when I get hot from the tap, I've noticed that the CH outlet is getting hot, and I'm not clear on whether that is a diaphragm symptom, or indicates the deeper issues you've mentioned.

I'm prepared to replace the DV if I have to, but it does look expensive. My previous one was indeed 60 quid off eBay, but that was a long time ago. I might still have the old unit, could look at refurbishing it but I imagine the cost of bits would make it uneconomic. So it's 200 quid new or 60 quid for a refurb.

 

[gas112]

Im with gasguru on this always better to change the whole valve on these and if your heating flow is getting warm when hot water on then diaphragm will not cure this valve is worn internally.

 

[Johnking]

I can see that would be the best approach as a contractor, but as a diy-er would you really not give it a go with the diaphragm, given it's a quick job?

 

[gas112]

I can see that would be the best approach as a contractor, but as a diy-er would you really not give it a go with the diaphragm, given it's a quick job?

Nope as you have already said its passing to heating so new valve search ebay you sometimes pick them up at reasonable price

 

[Johnking]

Nope as you have already said its passing to heating so new valve search ebay you sometimes pick them up at reasonable price

Well that's the afternoon ruined now.

Are these repair kits worth a go?

VAILLANT TURBOMAX VUW 242E & 282E DIVERTER VALVE REPAIR KIT 140352 | eBay

VAILLANT TURBOmax VUW 242 E(1995-1999). VAILLANT TURBOmax VUW 242/1E(1998-2001). VAILLANT TURBOmax VUW 282 E(1995-1999). VAILLANT TURBOmax VUW 282/1E(1998-2001). VAILLANT VUW 242 E (1995-1999).

www.ebay.co.uk

 

[Gasguru]

The problem with all the repair kits is that you don't get all the parts included. eg. the white sprung valve (I've had several that break up).

 

[Johnking]

Well, I found one for £140, new in box, nothing cheaper available unless you go for a refurb and it sounds like there's plenty that they would miss out. Oh well, the boiler owes me nothing, it's been a trooper for >20y.

I see the DV comes with a few o-rings and washers, but I imagine there are some other unions that will need them replacing, am I right?

 

[Gasguru]

The kit doesn't contain all the o rings you need afair...too long ago to remember which ones. You might have to chance reusing a few seals. Be ultra carefull fitting the correct screws back onto the pump..it's possible to get them mixed up and piece a pipe behind.
Replace the air vent on the pump...often leak. It'd just the top section off a standard 1/2 Caleffi aav.

 

[Johnking]

The kit doesn't contain all the o rings you need afair...too long ago to remember which ones. You might have to chance reusing a few seals. Be ultra carefull fitting the correct screws back onto the pump..it's possible to get them mixed up and piece a pipe behind.
Replace the air vent on the pump...often leak. It'd just the top section off a standard 1/2 Caleffi aav.

Thanks so much for your advice - I'll feedback once I've done the job! Probably flush out the heat plate while I'm at it, very hard water here.

 

[Justin Passing]

..

 

[Johnking]

OK, I changed the diverter, no issues, no leaks after recommissioning, hot water working fine. Or so I thought. After running the tap for a few minutes I noticed the water temp fluctuates a bit, and the burner cycles at the same time. It's always done this, and I assumed it was normal - the burner runs for a bit, then goes off, then back on and so on. BUT after a while, the water started to run cool, and the CH flow pipe is really hot.

I disassembled the old diverter valve and really there seems to be nothing wrong with it. Is there anything else that could be causing this? Blocked heat exchanger? Something overheating?

Edit: Decided to clean out the DHW plate, used spirits of salts but it looked remarkably clean. Had a bloody mare getting it resealed. What was interesting though was that there was a small plastic flow restrictor on the DHW inlet. Is that meant to be there, is it safe without it? I can't find it referenced anywhere and I wonder if it's aftermarket. Anyway, it wasn't really blocked, but I took it out to see if it made a difference. Seems to have, though temperature still does fluctuate and the burner still cycles, but it didn't run cold this time, just varying degrees of hot.

 

[Johnking]

@Gasguru @gas112

Sorry to bug you, any comment on the last message? Current behaviour is that the upstairs shower does start hot, but after a few mins ran cold and would not come hot until the tap was turned off and back on.

 

[Johntheo5]

Turn the shower temp control to fully cold with full flow, the boiler should not fire up, turn it then to fully hot with full flow, the boiler should fire up and stay running, measure this water flow.