Kilowatts?

[Peadee]

Yes, they are as follows:-

My shower (Gainsborough 10.5kw) delivers 6.5 LPM
My mains delivers 15.5 LPM
My DHW (WB 24i Junior) delivers 10.5 LPM

There will be 10 rads to heat when I've finished fitting my new kitchen,
1 of which will be heating a conservatory and may become 2!!

 

[D_Hailsham]

My mains delivers 15.5 LPM

Presumably that is with no other tap on. What is it like when you have a second tap running full on, e.g a garden tap of the cold tap in the bath?

 

[Peadee]

No I've not tested the rate with 2 taps running but I will this evening and I'll let you know the result. Is it a big factor to consider?

Maybe I have approached this whole thing from the wrong end. Maybe the question should be "are there any boilers that I should avoid?" As I look around, the choice of boilers available is bewildering. The same could be said for cars and as many people know there are some lovely cars out there, mostly good but there are some that are known to have issues. For me I would never buy a Alpha because of this. The looks are there but it's only skin deep and the one thing they do regularly is, let people down. Is it the same in the boiler world. Are there certain ones, like my current WB 24i Junior, that should be avoided at all costs.

 

[D_Hailsham]

No I've not tested the rate with 2 taps running but I will this evening and I'll let you know the result. Is it a big factor to consider?

Yes. It show what the flow will drop to if someone flushes the toilet, turns on the washing machine etc when the shower is in use or the bath is being filled. The 15.5 litres/min has to be shared] between all outlets running at the same time.

A flow rate of 15.5 l/m would require a 38kW boiler to raise the water temp by 35C at full flow. Presumably you want to be able to get rid of the electric shower and it's measly 6.5 litres per sec. Doubling it to 12 litres/sec would feel like a power shower in comparison. This would require a 30kW boiler

Maybe the question should be "are there any boilers that I should avoid?"

Anything made in the UK and Italy.

For me I would never buy a Alpha because of this.

I think you mean an Alfa. Alpha make boilers and they are even less reliable than the homonymous car.

Edit 12/10/10 Changed 12kW to 12 litre/sec.

 

[Peadee]

Yes, the plan is to eventually get rid of the electric shower and get something with a bit of oomph!! It's like running around under a dripping tap in the winter.
Just turned on my outside tap and ran the cold water at the kitchen sink. I got 9.5 LPM
Is that good or bad!!

 

[D_Hailsham]

Just turned on my outside tap and ran the cold water at the kitchen sink. I got 9.5 LPM

So 15.5lpm on its own but 9.5lpm when another tap is on. That's not too bad.

A 28-30kW combi boiler should do the job.

 

[Agile]

A flow rate of 15.5 l/m would require a 38kW boiler to raise the water temp by 35C at full flow. Presumably you want to be able to get rid of the electric shower and it's measly 6.5 litres per sec. Doubling it to 12kW would feel like a power shower in comparison. This would require a 30kW boiler

D Hailsham seems to have forgotten that you have an open pipe flow of 15 li/m.

Whats relevant is the dynamic flow rate leaving say 1 Bar residual pressure in the pipework to ensure a good shower.

It all depends on your supply pressure but usually the dynamic flow rate is 2/3 or 1/2 of the open pipe flow rate.

I have not read back all the previous posts but you should have been told that the choice of installer is the most important aspect of a boiler reliability. The system needs to be totally clean and the installer should give a full guarantee in relation to system cleanliness.

Tony

 

[D_Hailsham]

A flow rate of 15.5 l/m would require a 38kW boiler to raise the water temp by 35C at full flow. Presumably you want to be able to get rid of the electric shower and it's measly 6.5 litres per sec. Doubling it to 12kW would feel like a power shower in comparison. This would require a 30kW boiler

D Hailsham seems to have forgotten that you have an open pipe flow of 15 li/m.

Are you referring to the 12kW? If so I meant to write 12 litres/min. I have corrected the original. Thanks for drawing it to my attention.

 

[Agile]

Are you under the weather today?

No I was refering to the quoted part where you say a 38 kW boiler is required .

That would only be required if he had a dynamic flow rate of 15.5 li/min. But that flow rate is only the open pipe flow.

My brain auto corrects for most incorrect units like that person who recenly had a whole house heat loss of 10 watts.

Tony

 

[ajrobb]

You could select your shower head and measure the flow rate of your 'desired' shower on a length of garden hose, say. A bit of mucking about now might avoid an expensive disappointment later.

 

[Agile]

You could select your shower head and measure the flow rate of your 'desired' shower on a length of garden hose, say. A bit of mucking about now might avoid an expensive disappointment later.

Thatsa a good idea!

 

[D_Hailsham]

Are you under the weather today?

No I was referring to the quoted part where you say a 38 kW boiler is required. That would only be required if he had a dynamic flow rate of 15.5 li/min. But that flow rate is only the open pipe flow.

I understand dynamic and static pressure, but I don't get what you mean by "dynamic flow rate". You can only get a flow rate if a tap is open, so any flow is dynamic!

I agree that the flow rate from a shower head or from the hot tap in a wash basin may be less than that from the cold tap in the kitchen, but that will be due to different pipe diameters or restrictions in the shower. For example Mira showers have restrictors to limit the flow rate to as low as 8 litres/min for showers designed for combi systems.

If you read my post immediately before yours, you will see that I suggested a 28-30kW boiler.

 

[Peadee]

So, a 28kw or 30kw is what I need and I should stay away from stuff made in Italy or the UK. Is that right?

 

[D_Hailsham]

So, a 28kw or 30kw is what I need and I should stay away from stuff made in Italy or the UK. Is that right?

I'm not going to disagree with what I said earlier.

 

[onlyfitidealboilers]

i blame maggy the **** thatcher for killing apprenticships & hence all these "6 week wonder" efforts of today