heat exchanger

[blacksmith]

could anybody tell me is it simple to fit a secondary heat exchanger on a
vaillant combi approx 10yrs old. as i have been quoted £175 plus by BG and it looks iimple? regards.

 

[geoff@cetltd]

Are you changing from the old black plastic to the new "sardine can" one ?
Fairly simple, ( if a little fiddly) as long as you have spanners to fit,

 

[blacksmith]

yes thats correct. thanks for your help.

 

[bogstandard]

YOu get a kit of pipes to connect to the "old" out/inlets Check out ebay £20/30 Make sure it comes with the connecting pipes!

http://cgi.ebay.co.uk/Vaillant-heat...048011450QQcategoryZ42234QQrdZ1QQcmdZViewItem

http://search.ebay.co.uk/vaillant_W0QQfkrZ1QQfromZR8

 

[Gasguru]

May require a mod to circuit board and if TRV's fitted the diverter valve may also need a strip down (to replace disc).

Unless you know what your doing leave it to BG. Occasionaly you can find the control tubes block, the servo valve plays up, aav leaks etc.

Sounds a reasonable price for the genuine part and pipework to be fitted.

 

[chrishutt]

if TRV's fitted the diverter valve may also need a strip down (to replace disc).

If TRVs fitted? What's it got to do with TRVs? I thought the disc change was required because the original disc has by-pass grooves to allow a small flow through DHW H/E when in CH mode to maintain a small hot store.

The new plate H/E, having a lower water content, cannot absorb that heat input without overheating (scale deposition), so the grooved disc has to be replaced with the new plain one. If BG (or anyone else) does it, make sure they do the Diverter Valve dismantle as well (in which case £175 isn't too bad).

 

[lor]

Are you changing from the old black plastic to the new "sardine can" one ?
Fairly simple, ( if a little fiddly) as long as you have spanners to fit,

this job took hours, not only do u replace the plate & pipes but the internal plate on divvlv and cut link on the pcb .

£170 sounds too cheap for BG

 

[chrishutt]

cut link on the pcb .

Only if it's a hybrid model!

 

[Gasguru]

I spoke to one of the Vaillant tech. guys a few years ago - he said only change disc if TRV's on most of the rads - didn't ask exactly the reason behind this.

Link on board is cut on hybrid (HY) models only.

 

[chrishutt]

I see why Vaillant might say that, but what if TRVs are fitted later? It still isn't good practice, especially if you don't understand why!

 

[Gasguru]

Agree. Normally always replace disc but it was getting very late and tenants needed water back on.

Had spent hours getting siezed screw out to replace diaphragm in water section.

No chance of TRV's being fitted (L.L too tight)

 

[Agile]

The first and last time that I did that job I allowed one hour and it took at least TWO !!! Its NOT so simple, but not impossible either.

Kit was provided by owner and there were no instructions just a load of bits in a bag!

Beware there are some "copy kits" but they do not come with any washers or little bits".

Tony