Worcester-Bosch heatex replacement

[stewamax]

My daughter's W-B 34CDi combi is showing signs of age and either the diverter valve or heat exchanger will need replacing soon.
Looking at W-B's catalogues for new boilers shows the 29CDi and 34CDi having a heat output from 7.7KW-30KW and the 38CDi and 42CDi with 9.4KW-30KW.
The notable difference between the models seems to be the domestic hot water (40degC) flow rates with the 29CDi giving 11l/min and the top-end 42CDi giving 15l/min.

However, looking at prices of replacement heat exchangers shows one heat exchanger and sump fitting all of them - which I find a bit difficult to understand...

So DAK how, for models with the same heat exchanger and the same heat output, they are capable of giving substantially different hot water flow rates (apart from perhaps just having a more enthusiastic pump!)

[Itsallaguess]

My daughter's W-B 34CDi combi is showing signs of age and either the diverter valve or heat exchanger will need replacing soon.

Looking at W-B's catalogues for new boilers shows the 29CDi and 34CDi having a heat output from 7.7KW-30KW and the 38CDi and 42CDi with 9.4KW-30KW.

However, looking at prices of replacement heat exchangers shows one heat exchanger and sump fitting all of them - which I find a bit difficult to understand...

So DAK how, for models with the same heat exchanger and the same heat output, they are capable of giving substantially different hot water flow rates (apart from perhaps just having a more enthusiastic pump!)

Are you sure they use the same heat-exchanger plates?

When I look at the 29CDi Classic parts-page on the HSP website and compare it to the 34CDi page, they seem to give different part numbers, and when you drill down into the parts, they do specify one being specific to the 29CDi, and the other being specific to the 34CDi, with something like the expected boiler ranges listed for each part -

29CDi Classic Parts Diagram - https://www.heatingspareparts.com/boile ... ?gid=24876

29CDi Heat Exchanger - https://www.heatingspareparts.com/boile ... ?id=228047

34CDi Classic Parts Diagram - https://www.heatingspareparts.com/boile ... ?gid=24887

34CDi Heat Exchanger - https://www.heatingspareparts.com/boile ... ?id=230176

Not sure if that really helps at all if you're using manufacturers information (you might not be...), but I just thought I'd have a quick check on the HSP website, as it's my go-to site for boiler-parts, given the great exploded diagrams for a huge range of boilers.

It might be worth giving them a ring and see what they say?

Cheers,

Itsallaguess

[stewamax]

Tnx Itsallaguess.
HSP's link for the 34CDi appears to say that the one part 87161082120 - HEAT EXCHANGER PLATES - that I assume is the DHW exchanger and not the primary CH exchanger - covers the 34CDi Classic, 38CDi Classic, 42CDi Classic ERP, Combi 35 CDi, Combi 37 CDi HE, Combi 40 CDi and CombI 42 CDi HE. Odd - but perhaps I am misreading it.

[Itsallaguess]

HSP's link for the 34CDi appears to say that the one part 87161082120 - HEAT EXCHANGER PLATES - that I assume is the DHW exchanger and not the primary CH exchanger - covers the 34CDi Classic, 38CDi Classic, 42CDi Classic ERP, Combi 35 CDi, Combi 37 CDi HE, Combi 40 CDi and CombI 42 CDi HE.

Odd - but perhaps I am misreading it.

I don't think you're misreading it, but just to be clear, I only really posted because you seemed to be under the impression initially that a single heat exchanger specifically catered for both the 29CDi and also the 38CDi and 42CDi range, which didn't seem to be backed up by the evidence on the HSP website.

Yes, it looks like there's some cross-over between the two individual heat-exchanger parts I linked to, but that cross-over doesn't seem to include the ranges you initially thought were covered by a single heat-exchanger in your opening post....

Going off the HSP links, if you bought a heat exchanger from them for the 29CDi (https://www.heatingspareparts.com/boile ... ?id=228047) then you could not use it on any of the models above the 30x range.

Given that your initial post seemed to suggest that you thought the 29CDi heat exchanger could be used on the 38CDi to 42CDi range, I just wanted to point out that this didn't seem to be the case when looking at the HSP website details.

Cheers,

Itsallaguess

[stewamax]

Tnx again Itsallaguess
It appears to be a strange quirk of W-B's range but there will be rational explanation.
Is Mike4 still out there somewhere?