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.
After balancing round 1 (a differential thermometer with 2 pipe clamps
certainly makes this quicker!), I have 10-12 across all rads more or
less at a flow to rad of 56C (boiler indicates more like 65C internal).
Fiddling with the bypass, it seems to start shunting big time at a bit
under 0.4bar - so I have set it a smidge over.
The plan is now to turn the boiler down to about 55C flow - I have
oversized the rads as far as possible with a low flow temperature (and
spare in a really cold winter) in mind.
Think I'll have to go around one more time in a couple of weeks.
Next problem - it's bloody hot upstairs and there are no radiators.
But there is about 50-70m of exposed pipework!!!
It's been quite tightly run (linked Talon clips) and I cannot get 13mm
thick insulation on it. So I'm off to peruse the Internet for either
some thinner tube, or I'll have to box it in (and be damned if the flow
heats the return a bit).
Overall - very happy. I have boiled everyone half to death running it
flat out all day. That is very nice - this house has never been this warm :)
Yup its surprising how you notice heat after a long spell without!
I grew up in place that did not have CH until I was about 17ish.
Getting up on a winter's morning to go to college was a well honed
routine - kettle would boil on a time switch. Chuck water in mug left
waiting from the night before with coffee and milk in it, and turn on
the gas fire in bedroom, before leaping back into bed. Drink coffee and
wait for room to become slightly habitable while marvelling at the
frozen condensation on the inside of the windows!
Then one day I came back up in the evening, and the installers had the
new CH fired up, and the place was warm in winter for the first time ever!
On an aside:
Very pleased that my calculations seem to have borne out.
This is my spreadsheet:
I tried to design the biggest radiators in that I could, without taking
up excessive space. It was nice to have a clean sheet... PS the rad
prices were less via the plumber's discount and over half of the costs
were labour, so in the grand scheme of things not too bad.
Today, Heat Genius showed the kitchen/dining room (a difficult room to
heat - large, 2 big bay windows, no door to side lobby) went from
18.4C at 6am to
20.5C at 7am
with a *flow* temperature (external to boiler) of around 55C - that
would be the green column H on the sheet, delta-T0K
Sadly the WB boilers do not have a simple weather compensation option
(they want you to use their smart programmer to get that and that
doesn't work with an external programmer) - so we're pretty much in the
land of twiddling the knob each month.
However, I'm hoping to reduce that to a simple guide on the boiler -
Novemeber - position 4, January - 5 or 6, or something like that...
On a further aside:
I am *very* impressed with the heat output of Ultraheat Tibrook vertical
rads: (Ultraheat were recommended here last time I asked):
These have been used in a few difficult locations where there was simply
no long run of wall available for a normal rad.
They're baffled at the bottom forcing water to flow up one half and back
down the other half (disadvantage, only bottom entry pipework is
allowed) - seems to work.
The rest, I used Quinn Compact - a normal typical radiator, but heat
outputs for any given configuration are better than competitors. Plus
they are made in Wales with British steel so +1 for home production.
Was warned by plumbers to avoid chrome plated.
So went for https://www.screwfix.com/p/a/28451
which is stainless. Looks the same and the miserable amount of heat it
throws off (it's purpose is for drying the bath towel) surprisingly
seems to keep the bathroom warm (islanded, no external walls)
My WB Greenstar oil boiler has two ways to do weather compensation.
Either via a fancy controller or via a separate sensor (plastic case,
choc block connector, one thermistor, not even a PCB, 26GBP!) with it's
own dedicated terminals on the boiler. Are you sure yours can't do it
That's a shame, I thought that it was one of the big selling points of
condensing boilers that you could do this. Not that there appears to be
any choice about getting a condensing boiler! I suppose an alternative
would be to adjust the flow temperature according to the return
temperature, but it probably varies too rapidly for this to work. How
does the fancy controller do it without any external informaion? One
thing I don't think is common in oil boilers is modulation of heat
ouput, It would I think be dfficult to achieve without multiple burners.
I don't know how modulation in gas boilers is controlled without
external temperature - speed of temperature rise or something?
Some you can easily. Others may require a bit more intervention / invention.
You can do stuff with a controlled blending valve on the output of the
boiler, that mixes some of the return flow back into the output before
its gets reheated. (much as some of the UFH mixers do), but in this case
use the external temp to control the mix (when low temps result in less
mixing, and hotter effective flow temps)
There are a limited set of cases where you can still legally fit a non
In the case of the one on mine, via an external temperature sensor. You
select a response curve on the programmer based on the heat loss
characteristics of the house, and then the programmer picks a flow
temperature on that curve based on the current external (and possibly
current internal) temperature.
IIUC modern oil boilers do support *some* modulation - but not nearly as
wide a range as with gas ones.
Usually based on the return temperature and the flow set point
temperature. As they start to see the return temp start to rise toward
the flow temp, they modulate the power down so as not to exceed the flow
maximum set temp. If they reach minimum power output and still the
return temp is too close to the flow, then they cycle off much like a
fixed output boiler would on its stat.
Never actually having CH of my own  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 /
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
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
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?
FWIW they have a fairly big HW cylinder and a mix of UF and
conventional radiator CH.
Cheers, T i m
 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). ;-)
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.
<snip> >> Anyroadup, the plumbers this time had previously replaced a motorised
As I describe above (but with some control)?
So this would be on all the time, no stat-valve etc?
Ah, that makes more sense and as you eluded to above, less chance of
being 'fiddled with'.
It will be interesting to see how it all went on Friday (when the
plumbers were due back to replace both motorised valves) and whilst
they were there the other day I overheard talk of 'one of the
motorised valves not being moveable by hand' ... but are they all (as
they could have been different makes / designs)?
Cheers, T i m
<snip> >> It will be interesting to see how it all went on Friday (when the
That's what I remember from seeing other peoples systems but I wasn't
sure if it was always the case?
eg, Can you (could you) 'commonly' get a motorised valve where you
can't override it manually? If the answer is 'no', then one that
wouldn't move with the lever was very likely to be stuck?
Cheers, T i m
On Sun, 12 Nov 2017 13:48:20 +0000, Tim Watts wrote:
I believe the primary purpose of the locking lever is to force the 3
port diverter valve to keep both ports open to facilitate draining and
reduce air locks during refilling operations whilst the system is powered
It doesn't (or shouldn't) stay in the latched position once the system
is powered up and running. I can't say whether this also applies to the
two port valves since I only have experience of the 35 yo single 3 port
diverter valve (Y or S plan ?) setup used here.
On Mon, 13 Nov 2017 14:23:56 +0000, John Rumm
<snip> >> It doesn't (or shouldn't) stay in the latched position once the system
So that's 'the two port ones *can* have a similar feature ...' as
that is my question ... are we assured that all makes and models do?
The point was that if someone was expecting some form of manual
control and thought they saw one, but it didn't move, does that alone
guarantee that the valve was faulty / stuck, or could there be some
valves that simply couldn't be overridden manually or can only be
overridden in one direction or some other conditions(s) etc?
I'm not expecting a definitive answer from anyone in particular, just
putting the question out there as a definitive answer may suggest my
friend is being 'duped' by the plumber ... ;-(
Cheers, T i m
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