water flow and heating of water per minute

[mattysupra]

Hi, im looking at my options on a new boiler.

When they say 11 litre a minute flow on heating the water, well heating the water from what temp to what temp?

I.e- from 1c upto 30c? does it mean it will heat 11 litres per minute to 30c?

 

[DP]

What it means is, whatever the temperature of incoming cold water, boiler will raise the temperaure by 35 degrees IF boiler is getting the correct pressure of gas and flow through the boiler is what the makers state boiler should deliver at the hot tap.

 

[mattysupra]

i will go and measure my flow then and see what size boiler i need.

I think from other threads that with a combi i need to worry more about how much water it can heat as my 24kw boiler at the moment seems to struggle.

thanks

 

[GaytonTonner]

24kW is small for a combi. For for at least 35kW preferably more.

 

[mattysupra]

i have measured my flow,

My hot tap flows 11 litres per minute.

my present boiler struggles to get it hot enough.

What size combi boiler would you recommened for 11 litres per minute flow?

 

[PRS1]

You need to measure your cold water supply

 

[mattysupra]

You need to measure your cold water supply

O right!


Well then

14 litres a minute out the shower head.
24 litres a minute out the bath tap.

 

[picasso]

whats the flow rate at the kitchen cold tap ?

 

[mattysupra]

whats the flow rate at the kitchen cold tap ?

14 litres a minute

 

[D_Hailsham]

whats the flow rate at the kitchen cold tap ?

14 litres a minute

You say you are getting 24 litres per minute from the bath tap but only 14lpm from the kitchen cold tap. This does not make sense as both are supplied from the same source - the incoming cold main. The only explanations are: (a) you have a valve on the pipe to the cold tap which is closed down to restrict the flow; (b) the tap is very restrictive - e.g. continental types with 10mm or less tails.

Do you have a tap in the garden which is supplied from the incoming mains? If you do, check the flow rate.

 

[mattysupra]

yes its one of them poxy designer looking taps. It connected with micro bore size flexy pipes (kitchen tap that is ) Still there is plenty enough pressure there and you cant turn it on full without water spraying back out the sink.


The garden tap flows 30 litres per minute.

 

[D_Hailsham]

yes its one of them poxy designer looking taps. It connected with micro bore size flexy pipes (kitchen tap that is ) Still there is plenty enough pressure there and you cant turn it on full without water spraying back out the sink.

The garden tap flows 30 litres per minute.

Now the 24lpm from the bath tap makes sense!

The normal criteria is that you need 2.5kW per litre/min. This would mean a boiler size of 60kW, based on the bath tap. But you only get this rate when only the bath cold tap is on. If you have both hot and cold taps on at the same time you will get a total of 24lpm, i.e about 12lpm from each.

Based on your shower flow rate of 14lmp you would need a 35kW boiler, which would also be OK for your bath, assuming both taps are on at the same time.

As for the "which boiler?" question in your other post, based on the info supplied, I would suggest the Broag Remeha Avanta 35C. This will give a flow rate of 14lpm for the hot water and will modulate between 6kW and 30kW for the heating, though the upper limit can be reduced at installation to say 15kW for your installation. These boilers come with a 5 year warranty.

 

[mattysupra]

well thankyou very much for that mate.

So 35kw it will be then.