On 12/11/17 11:17, T i m wrote:
On Sat, 11 Nov 2017 16:59:53 +0000, John Rumm
wrote:

On 11/11/2017 11:44, Tim Watts wrote:
I've balancing my new CH - noticed the flow and return to the boiler
were virtually the same - and the auto bypass valve was set to minimum
(0.1 bar = 1m head water IIRC)

Closing it down to 0.4 bar has jumped the differential temperature - but
I suspect that's too high.

The Worcester manual says the pump can deliver 2m head for "21C
temperature rise" - nothing else about min flow rates or bypass pressure.

Any ideas? If I turn it to 0.2bar the flow temperature starts to creep up.

Now this may also suggest I have the lockshields all turned down too low
as well (I've opened 1/4 - 3/4 turn as a starting point).


I have mine set pretty high - based on the assumption that I only want
it to do anything when nearly all the TRVs are closed off. A highish
differential temperature should keep condensing efficiency up as well.

Never actually having CH of my own [1] and only dabbling with other
peoples when helping them out, I am not up to speed on all the rules
re 'balancing' the system, especially on something like a combi /
sealed system.

I have a question / interest though because I was round my mates the
other day when they had the plumbers in because they didn't have any
hot water.

I had previously been told they had the gas boiler AND immersion on
because there were 4 of them showering every morning and the hw would
run out otherwise?

Anyway, I while back (a couple of years possibly) I had helped them
(over the phone) conclude that the immersion had probably gone as it
tripped the ELCB in the CU when you turned it on and I thought it had
been replaced (but it may have and had gone again)?

Anyroadup, the plumbers this time had previously replaced a motorised
valve (apparently, a couple of weeks earlier) and they thought it had
gone again (faulty) but then found a valve marked up 'Balance, do not
touch' that they had been completely turned off and opening it, seemed
to have fixed the problem?

Now the only time I was aware of a bypass was in the two way motorised
valves where when both were off you could potentially short out the
boiler so a 15mm pipe was placed in parallel with the HW cylinder and
before the mv to ensure there was always a path back to the boiler (or
somesuch)?

So, my question is 'could it be possible that a 'balance valve' is
likely to be (nearly) fully closed and for it to be right' please? I'm
asking in case the plumber doing what they did is not a real solution
and it will cause issues further down the line?

It could be a shunt. Normally you use a designated radiator. Or if you
don't want to (or don't trust it not to be fiddled with), you could do
as I did and put a pressure bypass in, which should only open to protect
the boiler pump.


FWIW they have a fairly big HW cylinder and a mix of UF and
conventional radiator CH.

Cheers, T i m

[1] I did actually have the boiler and cylinder fitted here but then
my Uncle's coal fired floor standing CH failed so I took my stuff out
and fitted it (and some more rads) in his. In fact, because it was a
'low capacity' wall mounted boiler with a copper heat exchanger I also
fitted delayed stop relay to the pump and seemed to make the system
run very well (and never went wrong once in probably ~20 years). ;-)