Combi boiler - hot water flowing too fast, so cold.

[Adrian]

We've just got the keys back to our house, after a couple of years in a camper van whilst friends lived here. We've noticed something very strange has happened with the boiler - the hot water's coming through FAR too fast, so it's running cold. If you turn the tap way down, the flow comes back to where it always used to be, and the temperature gets back to hot.

It's a Worcester Bosch 24CDi Combi, just prior to condensing taking over. A couple of years ago, a leak meant it had a new heat exchanger fitted.

Before I go ringing British Gas (it's under a maintenance contract), is there anything obvious I can check or poke?

Ta, A.

[Tim+]

I suspect that the flow through the boiler was always limited by a stopcock somewhere (maybe the main incomer) and your friends (or a plumber) has opened it up fully after fitting the new heat exchanger.

Look for the stopcock supplying the combi and try shutting it down until you get back to your old flow rate.

Tim

[Phil L]

Isn't there a temp setting on the boiler for water? - they've probably turned this right down if they had children or elderly people living there

[ARW]

I agree. And it could be a simple as an isolation valve just before the boiler.

[ARW]

BTW Did you have a good holiday then?

[John Rumm]

Well what you describe is normal operation for many combis (unless they include a flow regulator). In these cases one normally throttles the water supply rate with the inlet service valve, and makes final temperature adjustment with the taps at the point of use.

(in this weather, you won'y be able to get more than 9 lpm of usably hot water out of a 24kW boiler).

With many boilers the temperature control for the hot water simply sets the maximum temperature - it can't set a minimum temp.

[ARW]

It's snowing here ATM:-)

[Ericp]

Isn't that boiler one that has a frame you put up and plumb then drop the boiler into?

If so it has a full set of quarter turn taps on the frame at the bottom front plate.

[Adrian]

Utterly wonderful, ta. 22 countries, including Tunisia, Albania, Serbia, Bosnia...

[Adrian]

Trust me, we're getting FAR more than that with the hot tap full open.

[Adrian]

I like that idea. It's nice and simple.

I shall rummage.

[Adrian]

Yes, there is - and it's turned up. When you turn the tap flow down, the water is proper hot.

[Dave Liquorice]

Make your mind up:

" ... the hot water's coming through FAR too fast, so it's running cold. If you turn the tap way down, the flow comes back to where it always

So is this high flow of water "useably hot" or not?

[John Rumm]

Well to quote Scotty, "yea cannea change the laws of physics!", so if its coming out much faster, than that, its not going to be hot. Which brings us back to your original problem.

[David.WE.Roberts]

Been watching this for a while.

Isn't a tap an analogue rather than a digital device?

So what is the problem with turning the tap on just enough to get the water temperature that you want?

Cheers

Dave R

[docholliday93]

On Tuesday, February 5, 2013 11:25:00 AM UTC, David.WE.Roberts wrote: =20

If there's any length of pipe between the boiler and the tap the lag betwee= n changing the flow and observing the new temperature makes it quite a long= process to get the temperature you want - if there's a flow restrictor ups= tream that you can set just the once it makes things easier.