Thoughts on Worcester CDi Compact vs CDi Classic

[jonnyw]

We're getting quotes to have a conversion to a combi boiler, replacing the old boiler in a slightly oversized kitchen cupboard. We've had quotes for a 34 CDi Classic, and a 36 CDi Compact.

The Compact would fit straight in the cupboard without modifications. The Classic would require some modifications to the cupboard to bring it out a bit, and would leave it looking worse off (and worse case removed - which I really don't want), so here the Compact (which I'm leaning towards) would be much more suitable.

On paper it seems the Compact is marginally better on the hot water (14.7 l/min compared to the Classic's 14.3 l/min). However, the Classic seems to have heating up to 30kW vs the Compact's 24kw

The Compact at least would be installed by a WB approved installer, so would come with a 10 year warranty (as I realise would the Classic if I use an approved installer).

My main questions are,

1. is the extra 6kW of heat the Classic can use of significance (20 year old 4 bed detached, 1 bathroom + 1 en-suite with shower, 11 med-small rads)?
2. Are there any major other differences between the boilers I should be aware of.
   
3. Is the Compact as good as the Classic?

Whilst I realise there are other great products out there by manufactures beginning with V, I'm pretty much decided on WB (as I can't face starting this process again!)

 

[Dan Robinson]

If you must have a Wooshitter POS, then get the classic.

 

[Hot&Cold]

We're getting quotes to have a conversion to a combi boiler,

Why are you wanting a combi boiler ? you have not mentioned your current heating/hot water set up,requirements and future expectations.

do you want your new combi to match the hot water production of your existing system ? sometimes its worth discussing with the end users the pros & cons of going to a combi.

which ever boiler you chose.please dont skimp on cost and trying to shoe horn it into a cupboard.

 

[petit_pablo]

Go with the Cdi Classic.

 

[jonnyw]

Why are you wanting a combi boiler ? you have not mentioned your current heating/hot water set up,requirements and future expectations.

I purposely didn't go into too much detail, as I didn't want to get into discussions about whether a combi was suitable. My main questions where how much difference there was between 24 and 30kW CH, and if there were substantial differences between the Compact and Classic.

do you want your new combi to match the hot water production of your existing system ? sometimes its worth discussing with the end users the pros & cons of going to a combi.

A candle under a pipe would match the hot water production of our current system!!! I've had 4 separate engineers here whom I gave my requirements to, each of which has (independently) recommended a combi (two of them did go through the pros and cons).

which ever boiler you chose.please dont skimp on cost and trying to shoe horn it into a cupboard.

I didn't mention skimping on cost. In fact looking around at boiler prices, the Compact is more expensive than the Classic. Fitting it in a cupboard however would be advantageous!

 

[Terry lambert]

I’d fit the Classic if I had the space and a Compact if I didnt

I’ve fitted lots of compacts and not had any issues

As to the heating output, have any of the engineers carried out heat loss calcs ? From your description I’d be amazed if the 24KW to heating wouldn’t be ample, if anything you may well be range rating the output down to be more efficient and more closely match the load

With either you may well need an additional expansion vessel

I take it they have measured your incoming mains performance ?

 

[jonnyw]

Cheers Terry.

No engineers have carried out heat loss calcs, or measured incoming mains performance (as far as I'm aware).

The one who we've used for work on our CH previously (so knows the house) was confident ANY CH output would be sufficient to heat the house. I have no idea about these things, hence posting on here!

 

[Terry lambert]

I think your engineer is right about the heat reqirement.

No point in fitting a high flow rate combi @14/15litre min if your incoming main is only 10 so worth knowing

For actual flow rates you will need to have a look at there spec for a 40degree temp rise as they will have a flow restrictor in them for that as opposed to a 35 degree temp rise which is often quoted

34KW will be 12 for instance

 

[muggles]

Of the two, I'd say the Classic, but given a free choice I'd say neither. There are better boilers on the market for less money

 

[Terry lambert]

Different boilers for different jobs, when we say better boilers, depends what your doing. A whipet is fast but I wouldn’t want one as a guard dog


I think the CDi is a decent boiler but over priced. After care is second to none, easy to work on for those that are familiar with them, parts readily available, reliable

In a situation where I need something compact with upward rear piping then I’m going to go with the compact

Reasons for not fitting WB are going to be controls options, average modulation, price

 

[jonnyw]

I've just realised your reference to 'incoming mains performance' is in relation to the incoming water (I think), and not gas.

Again, no engineer has tested this, but I went round and tested it myself a few weeks ago (with bucket and stopwatch) and got the following:
- Shower (set all way to cold) - approx 15 l/min
- Bath (cold tap) - approx 27 l/min
- Kitchen tap (on cold) - approx 10-12 l/min

The 36 CDi Compact quotes 13 l/min @ 40 degree rise, and the 34CDi Classic quotes 12 l/mi.

Do these two boilers seem sensible for the above flow rates?

Would they allow for example, the shower to run, and the kitchen sink to be filled simultaneously?

 

[Terry lambert]

27l min at bath ? Is your bath cold on mains ?

You would only ever advise a customer that a combi is one tap operation

 

[muggles]

Combi boilers are only really designed to run one outlet at a time, maybe two with the 40kW+ models. An unvented hot water cylinder would be more appropriate for you if you want to maintain those flow rates

 

[Terry lambert]

Could fit one of these to an Intergas for higher flow rates, not sure if WB can take pre heated water you’d have to check

https://theintergasshop.co.uk/combi...tlcs50.html?search_query=Combi+flow&results=6

 

[Dan Robinson]

Could fit one of these to an Intergas for higher flow rates, not sure if WB can take pre heated water you’d have to check

https://theintergasshop.co.uk/combi...tlcs50.html?search_query=Combi+flow&results=6

They barely take normal water