Choice of C/H and H/W pump

[akist]

How do I choose the size/type of the C/H pump? Is there a method to it? As the H/W cylinder is right next to the boiler, will I need, or benefit, from its own pump, or simply use a 3-way valve?

 

[Mottie]

Do you have fully pumped or gravity hot water?

 

[akist]

Everything will be pumped / mains, no tanks in the loft.

 

[Mottie]

I know next to nothing about flow rates etc but I think a lot depends on how many rads, how big a house, how long the runs, how many floors and where the pump will be fitted but for an average 2 story, 3/4 bed, 12 rad house, just a normal one would be my best guess! You certainly shouldn’t need a separate pump for the hot water cylinder.

I have a 3 bed, ten rad house with a hot water tank and my Grunfoss UPS2 15/50/60 pump is normally used on speed 1. Occasionally speed 2 but speed 3 has never been used.

 

[oilhead]

Using 2 pumps is uneccesarily complicated and can be counter productive with one taking precedence over the other. Using a Y or S plan with a pump matched to the boiler output makes best use of the boiler output and offers a better level of control.

 

[akist]

Thanks. I will go for a simple Y plan with 1 pump.

 

[Exedon]

Thanks. I will go for a simple Y plan with 1 pump.

S plan better system not much more in cost and easier to wire.

 

[JonathanM]

Thanks. I will go for a simple Y plan with 1 pump.

Have you thought about using priority hot water? It depends on whether your boiler can do it. It's becoming more popular and some say it's the way forward.

It lets you have a different temperature for when the boiler is feeding the radiators, and when it is feeding the cylinder.

 

[flameport]

. I will go for a simple Y plan with 1 pump.

Y plan is obsolete. Do not use it for any new installation.
It's also inappropriate for an unvented hot water cylinder as the valve fails open.

 

[akist]

I am going to ask a boiler fitter to come and tell me how he wants it done!

 

[Mottie]

Good luck with that.

 

[fixitflav]

Thanks. I will go for a simple Y plan with 1 pump.

No, go for a simpler W-plan!