Which Worcester Boiler

Nikumba

Nikumba

Nikumba

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Joined
4 Dec 2002
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Location
Bourne, Lincs
I have a two quote to replace my old combi with a new Bosch Worcester was quoted for a 32cdi and a 34cdi with less than £90 between the two.

Live in a mid terrace with 3 bedrooms, and only have a shower no bath.

Other than 34 being bigger than 32 is they much advantage over either?

Thanks

Kimbie
 
I had something similar - end of terrace, 3bedroom, and was quoted for 28cdi and 32cdi. Difference was flow rate and compatibility with solar water. I asked they guy that quoted for the 28 to use a 32 instead.

It heats the house including a large towel radiator and under floor heating loop.

I had a powerflush, larger gas line fitted and the boiler located into the loft against the gable wall.

2years on and it’s been a good performer.
 
Looking into it a bit more, seems to suggest the 34 is good if you have 12 plus rads, as I only have 7, and a shower might be worth saving the £90 and getting the 32
 
Nikumba said:
Looking into it a bit more, seems to suggest the 34 is good if you have 12 plus rads, as I only have 7, and a shower might be worth saving the £90 and getting the 32
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We have 8 rads, plus the heated floor loop. All the top rooms have temp rad valves.
 
All boils down to water flow rate really in a small house what's yours? The 34 will be wasted on a low flow rate.
 
Nikumba said:
No idea on my flow rate or how I would go about checking it
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Get a large container of known capacity stick it under the closest tap to your stop **** turn the tap full on and time how long it takes to fill. Some simple maths will get you a litres per minute number. Then ideally you want a boikercrated for slightly more than that purely because in the winter when the incomming water is really cold some extra headroom for heating it up is good.

Really the plumbers who quoted should have checked this before specifying a boiler when we had quotes it was a good way of seperatingvtge decent plumbers from the not so good!
 
a1ex2001 said:
All boils down to water flow rate really in a small house what's yours? The 34 will be wasted on a low flow rate.
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This is key, with our flow rate we could have gone up too but the guy said in the discussion you have to have enough water running through otherwise the boiler will cut out/in due to the water temp overheating. Boilers still aren't intelligent in tuning themselves so it's important to get the right size. Our shower is hot as we need it, if a cold water tap starts then we may get some change in hot water pressure that causes the mixer tap (non temperature) to allow the cold to stall the flow of hot - simply because the hot water has to got up before it comes back down. Changing that to a temperature mixer will solve the issue.

I forgot to say they should also fit a magnetic filter in the CH return, so check that's in the quote.

Interesting bit is the CDI defends itself from cold, first circulating water that's in the CH and if it gets colder it will fire up automatically, regardless of the temp setting on the thermostat.
 
I think you'll find boilers are intelligent enough. WB use the flow turbine to monitor the flow rate and adjust the heat generated accordingly. The only thing they don't know is the incoming mains temp. Even boilers that don't use a flow turbine to monitor flow rate, they adjust the output to demand by temperature. And most nowadays can drop to quite a low output, so you can trickle a tap if you really want and a boiler will behave itself. In my mind it's better to have a boiler that's more than capable than be under powered, especially as things can change in the future with regards to mains pressure and flow, even something like changing a shower or tap fitting can increase flow rate. Having a boiler that can't cope is something you'll be stuck with.

I only mention this as it's one of the biggest complaints customers have with combi boilers, especially in the colder months.

Mick
 
totally agree with the above I wouldn't go massively over but I'd always go one up from the minimum to supply the desired flow, the price jumps bettween models are pretty small.
 
yak.h'cir said:
I've just had the 29Cdi fitted, 4 bedroom and 1 shower currently, it runs it all without skipping a beat :)
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Snap.

Actually ended up with this by mistake, was quoted for a 32 but installer ordered a 29. We researched the difference and decided to keep the 29 and took a discount from the installer. Seems fine for our 3 bed end of terrace 9 rads 1 shower / bath.
 
I have quotes for the

Greenstar 30i - hot water flow rate of 12.1l/min
Greenstar 32CDi Compact - hot water flow rate of 13.1l/min
Greenstar 34CDi Classic - hot water flow rate of 14.3l/min

The difference between the cheapest and most expensive quote is £90, all of them include magnetic filter and gas pipe upgrade works.

Given I have a flow rate of 12 litres a minute, 7 rads and a shower which would be the best boiler to go with?

Kimbie
 
Nikumba said:
I have quotes for the

Greenstar 30i - hot water flow rate of 12.1l/min
Greenstar 32CDi Compact - hot water flow rate of 13.1l/min
Greenstar 34CDi Classic - hot water flow rate of 14.3l/min

The difference between the cheapest and most expensive quote is £90, all of them include magnetic filter and gas pipe upgrade works.

Given I have a flow rate of 12 litres a minute, 7 rads and a shower which would be the best boiler to go with?

Kimbie
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I wouldn't go lower than the 32 the flow rates on boilers aren't calculated for raising temp from 5 degrees in the winter! If the 34 isn't much more I'd be tempted!
 
34CDi classic all day long. As mentioned above, a boilers dhw flow rate is calculated normally using a temperature delta of 35c, not much use when you can measure incoming mains at 6/7c
 
When considering radiator numbers do we need to factor in size and whether they are doubles or singles (triples?) or how is the calculation done?

Edit: Never mind I just remembered about the max wattage/KW rating of the boiler.
 
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Although you can set the max temp of the radiators/CH circuit, you want it to be efficient in how it does that - not always burning but also not constantly cutting in/out.
The CDi system with the Honeywell controller limits the number of times/hour it will burn for to ensure it burns efficiently. Also the temp of the radiators varies depending on how much heating is needed to reach temperature rather than being full heat or off.
 
Superficial said:
When considering radiator numbers do we need to factor in size and whether they are doubles or singles (triples?) or how is the calculation done?

Edit: Never mind I just remembered about the max wattage/KW rating of the boiler.
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To do this correctly you need to calculate the heat loss of each room using a heat loss calculator, In the olden days this was done with a mears calculator, nowadays you can get an app on your phone. Once you have worked out the energy requirement of each room you add these up the resulting KW is what the boiler needs to output to heat those rads (add hot water cylinder if required) with some combi boilers you can manually adjust the heating KW in the service settings, most others you can't adjust and they just output automatically up to there max heating output. Bare in mind for most combi boilers the heating output is lower than the dhw KW used in naming the appliance.

If the radiator system is already fitted then you can have a best guess to work out each radiators KW from a radiator catalogue, and work from there.

Mick
 
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