Advise required r.e.Vaillant VCW-sine 18

[AND1234]

You have a lot of mixer taps /showers.
Check the temp of the hot water pipe coming out of the boiler.
You could well have cold water mixing in with the hot somewhere along the line.

I think these boilers are generally worth repairing.
Most parts are still availlable and mainly cheap.
Of course it wont be as economical as a new condenser in gas bills alone however no new boiler will last the 25 years plus that these old beasts have.

Two monoblock mixers downstairs. One bathroom upstairs with a monoblock on the basin and a thermostatic bath/shower diverter mixer, wouldnt say was excessive?
How would I check the temp coming from the boiler accurately? I know the routes of all pipes within the house. I'm not sure how cold water could be "mixing" in somewhere?
Closest HW take off (shower/bath) is only three lagged meters of 15mm copper away...

 

[mrgas]

In my experience showers are the worst for allowing cold to hot leakage.
Holding the hot pipe should give a fairly accurate guide to the temp!
If the pipes to shower are accessible, run shower until hot then open a hot tap further away whilst feeling the shower hot pipe. If this pipe becomes cold quickly then non return valve may have failed in shower.

 

[AND1234]

In my experience showers are the worst for allowing cold to hot leakage.
Holding the hot pipe should give a fairly accurate guide to the temp!
If the pipes to shower are accessible, run shower until hot then open a hot tap further away whilst feeling the shower hot pipe. If this pipe becomes cold quickly then non return valve may have failed in shower.

Its funny you say this. Ive just got out the shower.

Still had to heavily gag in but I decided to leave it running when I got out and try the HW tap in the same bathroom (I'd tried this tap 10mins earlier with shower off and luke warm) and its hot! Very hot indeed! Yey!
I then put downstairs tap on and thats hotter too. But not as hot as upstairs. (closer to boiler upstairs) the shower goes very cold when trying any tap...

Hmmm... Does that mean the showers had it inturnally? Cant really get back to the unit. (all in the wall)

 

[AND1234]

In my experience showers are the worst for allowing cold to hot leakage.
Holding the hot pipe should give a fairly accurate guide to the temp!
If the pipes to shower are accessible, run shower until hot then open a hot tap further away whilst feeling the shower hot pipe. If this pipe becomes cold quickly then non return valve may have failed in shower.

Its funny you say this. Ive just got out the shower.

Still had to heavily gag in but I decided to leave it running when I got out and try the HW tap in the same bathroom (I'd tried this tap 10mins earlier with shower off and luke warm) and its hot! Very hot indeed! Yey!
I then put downstairs tap on and thats hotter too. But not as hot as upstairs. (closer to boiler upstairs) the shower goes very cold when trying any tap...

Hmmm... Does that mean the showers had it internally? Cant really get back to the unit. (all in the wall)

Ive just google'd my mixer and found this

http://forum.plumbingpages.com/-img...title-view-latest-post-border-0--vp36744.html

Hope i'm allowed to post links?

Mines the very same Metro Mixer from B4th st0re.c0m.

Does this new cartridge sound feasible or do you guys think a check valve on hot feed could do the trick? Its just over a yr old now and dont fancy having to replace internals every year...?

 

[mrgas]

Its hard to be certain without been there..
What it does show is that your boiler can produce hot water, and that that hot water may be been cooled by the introduction of unwanted cold water somewhere else in the hot/cold water system.
The boiler may have an intermittant fault, or a shower mixer, mixer tap or blender valve may have an intermitant fault.
Further investigation should be carried out before replacing anything.
If you have isolation valves going to shower then isolate the cold and try the hot elsewhere would be my first port of call.

 

[Agile]

Most showers should be installed with non return valves on the hot supply and ideally on cold as well to comply with the water regulations.
Few installers bother though.

Its often easier for a DIYer to fit them than try to diagnose whats wrong.

Tony

 

[AND1234]

Most showers should be installed with non return valves on the hot supply and ideally on cold as well to comply with the water regulations.
Few installers bother though.

Its often easier for a DIYer to fit them than try to diagnose whats wrong.

Tony

The shower installation manual says check valves are already within the unit inself so none fitted in feeds. I'll get some tomorrow and do hot and cold just to be sure. Ive seen double and single check valves does it mater which I use...

Damb sight cheaper than a new combi anyway... HW flow still not brilliant in winter but I can put up with it now I no the showers at fault. I'll be ringing to complain tomorrow also as its gone faulty after less than 12months use. Pity it was bought more than a year ago...

Thanks to all that helped figure this one out... Thanks again

Andy

 

[Agile]

Whilst some showers have NRVs within the casing they easily get blocked and I would always fit expernal ones regardless.

Remember WE do not know exactly what your problem is but cold water crossover sounds very likely.

Tony

 

[AND1234]

Its definitely cold water getting into the hw through this shower valve. I isolated cold to said shower and hot taps hot again. Open isolation with tap open and flow to tap increases and it goes cold.
You can hear it flowing through isolation valve as you open it up.
The key to the answer was in my first post. "Better pressure at HW taps but colder"

 

[ChrisR]

The integral ones are likely to be ni the inlet area of the mixer. Prise or drill them out they're a pain. Very restrictive even when they are working. External 22mm cpmression single check valves with reducing sets are good. Much bigger - I have a pic I think....

 

[AND1234]

The integral ones are likely to be ni the inlet area of the mixer. Prise or drill them out they're a pain. Very restrictive even when they are working. External 22mm cpmression single check valves with reducing sets are good. Much bigger - I have a pic I think....

A pic would be good. Not sure if I can remove existing ones as the valves pretty much stuck in the wall.