Vaillant VCW 20/1 T3W No hot water

[Agile]

I was surprised when I went to one of them on Tuesday!

Both the water section AND the Flow Switch ( diverter valve ) were both working!

I even got it working for her yet again within my fixed diagnostic fee with no parts used.

Keep giving her quotes for a new boiler but as long as I keep repairing it she stays with it!

Tony

 

[gorselands]

Thanks for all the info. Will report back when job done.

Mike

 

[gorselands]

Help. Took off thermostat housing, cleaned and carefully reassembled using new seals. Ensured all joints seated and positioned (red ring) properly and went round tightening gradually. Refilled and water pouring out of triangular thermostat housing. Extra little turn on screws made no difference. Taken it of again. Is it ok to use some LS-X or silicone grease on seals? Can't tighten any more and baffled as to why its leaking.

Mike

 

[Agile]

Are you talking about the housing for the wax stat in the Flow Switch ( diverter valve ) ?

I would guess you may have two washers instead of one somewhere and its not screwing up tight somehow?

Always difficult to say when we cannot see it!

Tony

 

[gorselands]

Yes, housing on wax stat in flow valve (diverter)

No, all washers - seals came off and ensured seats were clean.

So is it ok to use a sealant? Vaillant says not to.

Mike

 

[Agile]

Are you 110% sure you dont have two washers above the waxstat?

One left attached to the underside of the housing and a new one you added?

I dont see any reason not to use a sealant BUT I think its never necessary and that there is something else badly wrong!

Tony

 

[gorselands]

Thanks Tony. 200% certain no washers left behind. If there's never a problem the only thing I can think of is that the larger washer may have slipped/kinked when I offered it up. Will try again and get back.

Mike

 

[gorselands]

All assembled/bled and adjustments made - no leaks.

Still no hot water. The spindle in the flow switch is not moving as freely and operating the micro switches compared to the other boiler. The spindle on good boiler moves very quickly to operate micro switches.

Spindle partially seized, or another problem?

Thanks

Mike

 

[gorselands]

All seems to be working now!! Removed gland on F/S spindle, WD40 and using 2 nuts and 7mm socket turned it back and forth a little. Adjusted M/S plates. Still a bit sluggish compared to good boiler but, as I said, all seems to be working. The hot water comes on when set to H/W only and seems hotter.

I can't thank you gentlemen enough - The 831 Bunny, Bunnyman and Agile Tony.

One last request (for the time being). The boilers (spares) are coming to an end and I don't know how long I'll be able to keep them going. In your experience what should I replace them with when the time comes?

All the best

Mike

 

[Agile]

You did not actually say it but I assume that you put in a new wax stat.

Did you test the removed one by immersing in a cup of boiling water?

With the new one the shaft should rise fairly quickly when the DHW flow stops.

Unfortunately perhaps these boilers are pretty reliable and can go on for years!

If you do decide to replace them then I cannot say much as I have not seen your installation and dont know why you have two boilers. The obvious solution would be a single boiler.

As for makes then Viessmann or Intergas would be the current favourite.

Tony

 

[gorselands]

Thanks Tony. Did replace with new wax stat. Haven't tested the one I took out yet. As I had a new one decided to change it anyway.

Why two boilers - big old house, and in when I bought it 24 years ago. Between them they run 20 rads on two circuits - basically one for upstairs and one for downstairs. They have been great, just a pity about the spares.

If and when I do replace them I will have to relocate as presently they are flued up the chimney. Have thought about one boiler (zoned) but it will need a big output and to be honest I just don't know enough about it.

Thanks again

Mike

 

[Agile]

Many boilers now are 30 or 35 kW. Or more if required.

As long as they are working they do work surprisingly well!