Combi fans: is bigger better

[Andy Hall]

To be a bit more accurate:

The formula for resultant temperature of mixing water is

Vc[Tf - Tc] = Vh[Th - Tf]

Where upper case V=volume T=temperature and lower case h=hot, c=cold and f=final

The store holds 57 litres according to the manufacturer

If the mains water temperature is 5 degrees:

Vc[40 - 5] = 57[60 - 40]

Solving for Vc gives 32 litres and a total of 89litres which is not enough even for an IMM bath of 100litres. For a reasonable bath of

150 litres It is only jut over half way there and at 11lpm will take a further 5 minutes or more to fill.

At 10 degrees cold temperature, you could add 38 litres but still you would be at less than an IMM bath and still at nearly 5 mins to fill to produce a reasonable bath.

.andy

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[Pete C]

Should just do it, the 60l at 60°C in the store will give 100l of bathwater at 38°C, leaving 60l of bathwater required for a 160l bath. The 28kW boiler will give 10l/min at 38°C, so would take 6 minutes to heat the rest of the bathwater.

Fairly high, how long would that be for, 10 mins?

cheers, Pete.

[Andy Hall]

See other post - the shortfall is rather more.

Which overall is pretty disappointing.

I can fill the bath to equivalent volume in about 4 mins max.

Not really - I find that sort of flow rate just about acceptable - typically for 15-20 minutes.

.andy

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[Brian Sharrock]

Leaving aside the type of heater;-

I have a "ComputaShower" computerised bath filler; The system mixes hot and cold water precisely and fills the bath to a preset (constant) level

I've experimented with filling the bath with differing temperatures; it's anecdotes not data, but;- This 43deg C bath is too hot .. This 38 deg C bath is too cold This 41deg C bath is just right ...said the little bear,

[raden]

In message , IMM writes

So what do you think of the 28i Junior DIMM ?

[Capitol]

In our area, it won't do one at 6pm. The flow rate varies throughout the day between 12 and 6 litres/min dependent on the total demand. I have no intention of fitting new input pipes when the existing non combi system can provide >40l/m for the period required to run baths. We also average

facility.

Regards Capitol

Regards Capitol

[IMM]

loft tank facility.

You need to move to an area with proper services.

[IMM]

Also when the cylinder is approx 25% depleted the boiler kicks in re-heating as hot water is being drawn-off.

[IMM]

25 l/min per shower? Absolute irresponsible. The water used and energy used to heat that is ridiculous.

[IMM]

You have clearly never seen a CB50 in action they fill 100 litres baths no problem, summer and winter.

[IMM]

Maxie is Dim Lin the luscious far eastern lovely 28 years old? That is old my boy!!

[raden]

In message , Brian Sharrock writes

Did you mean bare ?

[raden]

In message , IMM writes

I ask you a sensible question and you can't answer it

[IMM]

writes

OK I think she is fabulous, even though she is old.

[raden]

In message , IMM writes

Should be just about right for you then

answer the question

[IMM]

Maxie I did. I think she is fabulous.

[Andy Hall]

No it isn't.

Assuming that I were to use a whole 200 litre cylinder, which I seldom do, the energy required would be 12kWh - cost around 25-30p.

.andy

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[Andy Hall]

It's irrelevant. The machine can't defy physics, no matter how much you would like it o do so. The figures for filling even a drop-in-the-bottom 100l bath aren't brilliant, and if it's a proper sized 150l, the performance is pathetic. THey should either have designed it with a larger store (although then it wouldn't go on the wall) or a larger burner.

As I say - a linsey-wolsey product.

.andy

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[Andy Hall]

It makes little difference because the production rate at 40 degree output is only 11lpm.

.andy

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[IMM]

It is! I will not engage with any defence of such irresponsibility. Mr Blair will be making war on the likes you.