central heating and system choice (yet again) (long)

[Jeff]

Measure at biggest mains fed tap - taps can be restriction

Regards Jeff

[Sponix]

He said he *may* rent it out or *may* sell.

If he sells then a cheap boiler is the best option.

If he decides to rent then a cheap boiler is still the best option imo. Firstly, tenants have a habit of breaking things and it's better that they break a cheap boiler than an expensive one.

Secondly, he can replace the cheap boiler with an expensive one five or ten years down the road and presumably offset the cost for taxation purposes.

sponix

[David WE Roberts]

Exactly - which is why I used the bath tap :-)

[Dave Plowman (News)]

Sounds like that's coming off the header tank.

[Doctor Drivel]

You said you have a tank/cylinder arrangement. Is that off the cold water mains? 60 litres/min appears excessive.

>

[Ed Sirett]

Thanks Dave, I'd missed that when I replied earlier. The OP needs to measure the flow rate of cold at the kitchen sink, he'll need 20litres/min to fit the Alpha CD50.

[David WE Roberts]

Hmmm....I'm pretty sure that the cold water is coming from the mains, not the header tank,but I will check. If I am getting this pressure from the header tank (around 8' head from the tank (top of water level) to the bath tap then this is pretty impressive. I thought that in general cold should come from the mains (therefore suitable for drinking), and also there seems no point in taking cold water from the tank as it reduces the amount available for the hot tap.

You obviously need tank fed for applications such as a power shower where balanced input pressures are needed. . . . . . {puff, pant} . . Yep - mains pressure. Checks: (1) I turned the hot tap on and ran it for about 5 seconds. I could hear the cistern in the loft start to fill. This ran on for a bit after I turned the hot tap off. (2) I turned the cold tap on. About twice the perceived pressure, and no cistern filling sounds during or after running the cold tap.

I used the bath tap as a test because (a) I knew there was restricted flow from the kitchen tap (b) From looking at visible pipes I think that the bath is fed by 3/4" cold mains as opposed to the 15mm to the kitchen tap, thus giving a better measure of potential flow.

Still, worthwhile double checking.

Cheers

Dave R

[David WE Roberts]

I prefer to think of it as impressive :-)

As posted higher up, I have checked and it is from the mains.

[Dave Plowman (News)]

No - just means the pipe runs are well done. Remember it's 22mm pipe too.

You drink bath water? ;-)

They're two separate pipe runs, and the header tank holds much more water than the hot water cylinder.

[Capitol]

Seems ok. I,m surprised at the flow rate. If you stick your thumb over the end of the bath tap, how easy is it to stop the flow, compared to the kitchen sink tap? Wear raincoat?

Regards Capitol

[David WE Roberts]

Thank you for your generous offer of late night entertainment but unfortunately I will have to decline.

The pressure does seem high - so high I have no intention of putting my thumb over the end :-)

I will re-check the flow rate as it seems far higher than most expect - but I may just be close to the source of the water with decent piping between me and whatever pressurises the water main.

I assume that people living next door to a water tower (or pumping station) may get awesome pressure/flow rate compared to those at the remoter parts of the system.

It does look as though a larger power combi may fit my requirements, given the potential flow rate.

Cheers

Dave R

[Doctor Drivel]

I am impressed. Always have a mains pressure system.

[Doctor Drivel]

Dave R

Yep. That is the way. Make sure the combi has its own dedicated feed from the stoptap.

[Doctor Drivel]

If using a pump yes. If using the mains then an integral equalisation valve in the mixer will do. They can be external.