Worcestor Bosch Boilers - Which one?

[Peter Woodhouse]

I'm considering a WB combi boiler to replace an exisiting boiler.

Could someone tell me the basic differences between the various series that they manufacturer.

For the size of house I have (3 bed mid-terrace), I think I have the choice of

24i Junior 24i 24CDi BF or OF or RSF (or are these the same - different flues?)

What makes them different?

British Gas have recommended a Brit Gas RCH 24CDi (manufactured by WB) which they claim is similar but better than the comparable WB model... but they would say that! They have also recommended a powerflush at £200+VAT. Is this a good idea when replacing an existing boiler?

Any help appreciated

Pete

[John Stumbles]

...

compact lightweight unit different from:

Yup, flue options. I think the the i and CDi are mechanically similar but different controls (clock/programmer?)

The latter types are 'conventional' combis having one gas->water heat exchanger and a diverter valve & (plate type) water->water heat exchanger for DHW.

The Junior has no diverter valve or plate exchanger, but both primary and DHW are heated in the gas->water exchanger assembly. Someone (Ed?) said Ferrolis are like this too.

[Pete]

Thanks for the reply John. Space is not really an issue so it makes no a compact unit has no real plus points over a non-plus one. Given this, should I be looking at the 24i/24CDi? Does the fact that they have 2 exchangers make them a better unit or is the 1 exchanger of the Junior a new idea? Maybe this is a cost cutting measure which means a weaker product? I'll check out the controls of the i and CDi and see if I can see where they differ.

FYI, I had a quote from an installer yesterday. They said that the Junior has a smaller expansion vessel and they recommended adding an additional, external vessel to the system to ensure it supports the radiators satisfactorily (we have 8 which he said was "border line"). He also said he could try and get hold of the older 24i which has a larger vessel. It seems a bit daft to get a non-compact one which needs "extras". Can anyone comment on this?

As you can tell, I'm a bit of a novice when it comes to combis!

Any additional comments most welcome.

Pete

[Andy Hall]

.

Yes.

The Junior has an expansion vessel of 6 litres which is pretty small. At the normal operating pressure of 1.5bar, that would allow a system capacity of 30 litres, so I think that your installer is probably right - it would be marginal at best. You would have to calculate radiator volume from the radiator manufacturer datasheets to be sure. Obviously volume depends on the radiator sizes and number of panels.

50-80 litres for a system is pretty typical

The 24i has an 8 litre vessel and the 24CDi has 10. You can scale up the capacity of system that these will support linearly.

If you have to add an additional expansion vessel to the system it can go anywhere that is convenient.

You can download all the information from the web site if you go to the installer area.

.andy

To email, substitute .nospam with .gl

[Ed Sirett]

And "Fer" which is a badge of some Ferrolis. I suspect the down side is that due to hot spots you could get a big limescale build up in the DHW heat exchanger. I guess for a soft water area it might be a good choice, although ideally you would then want a s/s heat exchanger.

[Pete]

Thanks to all for the replies. I think I'm going to go for the 24Si. Seems to be an update of the 24i. Basically my pipework, both gas and water, are a bit sub-standard for anything with more power.

SHould be fine.... I hope!

Pete

[IMM]

Some Ravenheats are like this, but being crap they also use a 3-way valve.