will i loose hot water pressure with a system boiler

[Graham SW]

I only have a 15mm pipe from the water main and have been told this may be limiting if i go for a system boiler as some of the water pressure is used to fill the tank while the hot water is being used. Is this correct and would a combi boiler with a high flow rate be better?

 

[gingalig]

I only have a 15mm pipe from the water main and have been told this may be limiting if i go for a system boiler as some of the water pressure is used to fill the tank while the hot water is being used. Is this correct and would a combi boiler with a high flow rate be better?

Ideally you would need a dedicated 22mm supply to an unvented cylinder and then balance the supply via the inlet set, although you can use an accumulator of the correct size if you have the space to help balance any pressure loss. You could consider a 111w viessman or 200 series combi storage boiler, but what ever you choose you would need to know the flow rate and water pressure before you could make any decision. To fit an unvented you would need to be or have a plumber that is G3 registered.

 

[Last Plumber]

I only have a 15mm pipe from the water main and have been told this may be limiting if i go for a system boiler as some of the water pressure is used to fill the tank while the hot water is being used. Is this correct and would a combi boiler with a high flow rate be better?

You need to know the Pressure and flow rate at the first draw off point on the main really. That will help a lot.
I have installed many Unvented Cylinders off a 15mm main. However, I have upgraded all of them to 22mm pipe from the entry point of the main over to the cylinder. In some cases the external supply needs upgrading and of course some areas have poor water pressure and flow either due to elevation, mains size or demand.

 

[SimonG]

Check static and dynamic pressures. That is with outlets closed and a tap open.

 

[fixitflav]

I only have a 15mm pipe from the water main and have been told this may be limiting if i go for a system boiler as some of the water pressure is used to fill the tank while the hot water is being used. Is this correct and would a combi boiler with a high flow rate be better?

Is it an unvented HW cylinder, or conventional type fed from the CW storage tank?

 

[Riley]

Yes what has been specced to work with your system boiler