Advice required - Vaillant vcw 242 eh - Is it a hybrid?

[Sig10]

Hi Folks,

I am about to change the dhw heat exchanger from the old style plastic one to the newer metal plate version. I am unsure if my boiler is a hybrid model or not. I understand that a hybrid has a plastic spindle on temperature control knob - does this refer to the DHW temperature control knob on main water valve or CH temperature selecter that sticks out of middle front of control box? Also, I think a hybrid has HY printed on front of die cast control box. My boier has a plastic spindle on CH temp control knob, a brass spindle on DHW temp control knob, and does not have HY printed on control box. Does anybody have experience of identifying whever this boiler is hybrid or not?

Thanks in advance for any help.

Sig

 

[ChrisR]

HY only refers to the technology used on the pcb's so no need to worry, afaik.

 

[namsag]

It is the spindle on temp contorl knob that gives it away wether its hybrid or not. You will be asking because it tells you to cut a wire on the board when changing heat exchanger and change the disk in divertor..

If it needs wire cut, cut it but don`t bother with altering divertor as it won`t make any real difference for all the extra work and problems you will get trying to get it running again

 

[Terrywookfit]

If it needs wire cut, cut it but don`t bother with altering divertor as it won`t make any real difference for all the extra work and problems you will get trying to get it running again

What was the reason for changing the disc ??
I have tried with and without and it does not seem to make any difference!!

 

[ChrisR]

ChrisH knows, he told me once - something to do with bypass, scaling, expansion...? Nope it's gone!

 

[chrishutt]

You've remembered the gist of it ChrisR. The old diverter disc had grooves on one side to allow a small flow of central heating water to by-pass to the secondary HEX so keeping the hot water preheated ready for a quick response when a tap was opened.

However the new plate-to-plate HEXs have lower water content and so the same by-pass flow would more quickly give higher temperatures which could result in scaling of the HEX. So a replacement disc is provided which does not have any by-pass grooves.

At least that's my deduction. I don't think I've ever heard anything official to confirm that, but it seems plausible. As namsag says, it's a lot of extra work to change the disc and I wouldn't be surprised if most people don't bother.

 

[bengasman]

Recently swapped old model for new plate exchanger without any other alterations. Seems to work fine

 

[namsag]

We done several hundred and after the first few , thought what the F is the point of changing the disk, we never had one come back for anything other than a everyday fault

 

[Sig10]

Thanks for all the good advice. I have now changed the HE to the new plate one. Kit didn't have a disc so that kinda solved that one for me anyway. Although having read everybodys advice I don't think I would have taken on all the extra work (just taking the boiler cover off is a bit daunting!). I didn't cut the wire on the pcb - I'm still unsure if it's a hybrid or not but it's all working fine, so best left alone now. Many thanks again to everybody.

Sig

 

[Frimly Greendish]

Many people (me included) believe this to be the finest combi boiler ever constructed. The problem is, it is feendishly complicated and operates through a unique combination of hydraulics and electrics. The skills needed to service these boilers properly have largely been lost, as production stopped in the late 1990s. However, the original inventor of the VCW series, Horace Gripe (ex-Vaillant, now an independent boiler trouble-shooting consultant - hourly rate £50), can be contacted through this forum.

Hope this helps!

Grimly Feendish

 

[Rob]

Many people (me included) believe this to be the finest combi boiler ever constructed. The problem is, it is feendishly complicated and operates through a unique combination of hydraulics and electrics

So complicated you couldnt spot a faulty flow switch