Minimum incoming flow rate for combi boiler

[sifry]

Hi,

I've had a search around on the forums but can't find any advice on this so apologies if this kind of question has already been answered.

I have a 4-bed victorian house which currently has one bathroom, I am looking to convert the loft and install an additional bathroom, so I had planned to put in a combi boiler to gain the extra space in the loft and the bathroom by removing the hot water cylinder and the cold water storage tank.

However the incoming flow rate to the property is only 16 litres per minute (3 bar pressure). I've had my plumber dig up the ground by the external stopcock and check it there, and had the water board round to check the stopcock and also check the flow rate at other houses in the street, it's all the same.

So my question is:
Is there any type of combi boiler that I can fit that will work with an incoming flow rate of 16 litres per minute? (my plumber tells me not, i have no reason to disbelieve him but just wanted to make absolutely sure!)

If not, would putting in a thermal store be an option? I understand from reading the info on them on these pages that the remove the need for a cold water storage tank and supply hot water at mains pressure? (i'm keen to ensure that the showers in the bathroom work well, as I hate a poor shower!)

Many thanks for any advice you can give!

 

[GeorgeBramwell]

Your plumber should stick to drains. At 3 bar and 16 litres/min most combis below 40Kw will work OK.

If you want a better flowrate all around, hot & cold, then fit a cold water accumulators with the combi. See current thread on accumulators.

 

[kevplumb]

you on commision by any chance

 

[GeorgeBramwell]

you on commision by any chance

If common sense gave commission, I would be a billionaire.

 

[gas4you]

You have loads of choice, but your first choice should be to change your plumber!

24Kw combis give 9-10 l/min
28/30Kw combis give around 12 l/min
35/37 Kw combis give around 14/15 l/min

As there will be some loss of flow in the pipe work to and through the combi, I personally would look at the 35/37 Kw as the maximum you should fit, otherwise you will be paying for performance that your cold mains cannot give.

 

[GeorgeBramwell]

24Kw combis give 9-10 l/min
28/30Kw combis give around 12 l/min
35/37 Kw combis give around 14/15 l/min
40-42 kW 16/17 l/min
approx 50-54 kW 25/26 l/min

 

[kevplumb]

whats the point of the last 2 if the main can't deliver as dave has already stated

ohh let me guess

 

[GeorgeBramwell]

whats the point of the last 2 if the main can't deliver as dave has already stated

Poor reading skills as well. I wrote "See current thread on accumulators."

 

[kevplumb]

ohh i guessed right

 

[GeorgeBramwell]

ohh i guessed right

That is your problem. You always guess and you are a poor guesser too.

 

[Agile]

Hi,

However the incoming flow rate to the property is only 16 litres per minute (3 bar pressure). I've had my plumber dig up the ground by the external stopcock and check it there, and had the water board round to check the stopcock and also check the flow rate at other houses in the street, it's all the same.

Many thanks for any advice you can give!

What you have said is probably NOT the actual situation!

I doubt you have 16 li/min flow AND 3 Bar pressure at the same time!

The 3 Bar is probably the STATIC pressure and the 16 li/min probably the OPEN PIPE flow rate.

What your nupty plumber needs to measure is the DYNAMIC flow rate. Thats the flow rate WHEN a residual pressure remains in the house of about 1 Bar ideally ( although 0.5 Bar would be possibly useable ).

My assessment is that probably the incoming flow rate is inadequate particularly for supplies in a loft conversion although the static pressure is good.

The obvious solution is an upgraded supply from the street.

Tony

 

[kevplumb]

kevplumb wrote:
ohh i guessed right icon_rolleyes.gif


That is your problem. You always guess and you are a poor guesser too.

yup

and you fella are soo predictable

 

[GeorgeBramwell]

and you fella are soo predictable

I know. I do see BS and bad guessers easily.