Vaillant turbomax hot water problem

[mavisravis]

I have a problem with the hot water, basically the hot water will turn on the first time the boiler is switched on, then after that will either not come on at all or just heat up for a few seconds. boiler is a turbomax with green buttons. pressure is 1.1 bar. Reading through previous posts it sounds like it could be the diverter valve (green microswitch fitted) About 3 months ago the diaghragm was replaced as we had a similar problem.
Is the diaghragm in the diverter valve, and if it has why has it failed so quick ? The plumber who fitted the diaghragm won't come back to look at it so I'm stuck. Any ideas?

 

[namsag]

Could well be just a faulty diaphram again but have had a couple of turbomaxs that needed the whole valve as new diaphragm still wouldn`t allow proper movement of the arm to operate microwitch

 

[mavisravis]

Thanks, Is it safe to test this by manually closing the contact on the microswitch?

 

[Dan Robinson]

Not without running water - totherwise the boiler shall go pop!

 

[Agile]

As I do come back as we guarantee our work, we would usually only fit a complete new diverter valve on this model.

You could watch the microswitch when water is being taken and see if its staying made. If it is then the indication is that its a different fault.

If the switch is going off then it is the diverter valve.

There is a screw adjustment underneath which has an effect on the operating point of the valve but I have never seen any instruction on how it should be set.

Tony

 

[namsag]

Missed that bit.... As agile says it is not unusal for faulty microswitch am reaches it and it makes but the contacts within dont.

 

[Dan Robinson]

You can test the microswitch by looking at the front of the boiler If the demand light goes out then the microswtich has failed/released depending on what the stupid white plastic foot is doing.

This thing is made of flimsy plastic that (has happened a few weeks ago on my brothers boiler) can wear away where the diverter pin pushes on it.

The designer must have been hung over on that day.

 

[Agile]

I didn't really mean that as the switches are very reliable on that model.

The initial movement of the lever does sometimes have a little overshoot and thats what I was wanting him to check.

The switch also has some adjustment in its mounting and that has to be correctly set to coincide with the lever movement.

If the diaphragm was really replaced it would be unusual for it to fail so soon.

I do have to say that the whole senario sounds like a cowboy who, faced with a failing diaphragm, just bodged the switch adjustment to keep it going for a while, get paid and then refuse to come back!

Namsag, dont you know how the screw underneath is meant to be set?

Tony

 

[namsag]

Agile remember reading something about it years ago, but have not got a clue now.

 

[Agile]

Turning it clockwise uses a spring to push upwards on the diaphragm.

I would guess that its intended for setting the turn on flow rate to about 2.5 li/min.

But so far I have never met anyone who knows for sure and I dont think its in the MI but as I rarely read them then it may be mentioned..

Tony

 

[Dan Robinson]

I stripped down my borther's when we changed the valve, and Idid figure out what it was for - can't remember now though - I aqm about to ride over there (11 miles ) for a BBQ so will ask if he remembers - I seem to remember it was a flow limiter of some sort...

 

[mavisravis]

thanks for that feedback guys, The diaphragm was definately replaced as the old (holed) one was left in the box, so I also have the part number. I'll go back and have a look and see if I can see the microswitch lever moving

 

[mavisravis]

Update!! I switched the hot water on and off at 20 sec intervals, and I can clearly see the lever arm moving OK. On about the 6th time the hot water failed to come on, so I held the arm with a screwdriver with the water flowing and the water then went hot. I reckon it's just the adjustment of the switch, but it looks difficult to get to the mounting screws, Any tips?

 

[Gasguru]

Disconnect the connector on the microswitch wires and connect a continuity meter. The microswitches can fail with poor contacts. If replacing the switch it is very easy to damage the plastic carrier the switch sits in.

A few years ago Vaillant were suppling sub-standard diapgragms in their kits that did hole within 18 months.