Central heating auto bypass valve - setting?

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).
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On 11/11/2017 11:44, Tim Watts wrote:

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.
--
Cheers,

John.
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On 11/11/17 16:59, John Rumm wrote:

Thanks John.
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 :)
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On 11/11/2017 18:31, Tim Watts wrote:

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!
--
Cheers,

John.
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On 12/11/17 03:46, John Rumm wrote:

Sounds like my bedroom in Reading, rented off an old polish bloke:
3kW fan heater on timeswitch. Coin meter ran out and I reckon the dT/dt was about 1C/min!

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On an aside:
Very pleased that my calculations seem to have borne out.
This is my spreadsheet:
https://drive.google.com/open?id WOVvFMhbR4i8WAA_pWRCGHjqxguvxZKXpMbXX-PTdk
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...
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On 12/11/17 10:55, Tim Watts wrote:

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):
http://www.ultraheat.co.uk/premier-range/tilbrook.html
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.
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Towel rail:
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)
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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 way?
--

Roger Hayter

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On 12/11/17 13:18, Roger Hayter wrote:

No - I read the installer's manual and rang WB tech. They also confirmed that the CDi fancy "Wave" IIRC programmer could not accept an external control input - so not very fancy.
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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?
--

Roger Hayter

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On 12/11/2017 14:02, Roger Hayter wrote:

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 condenser.

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.
--
Cheers,

John.
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On Sat, 11 Nov 2017 16:59:53 +0000, John Rumm

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?
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). ;-)
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On 12/11/17 11:17, T i m wrote:

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.

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wrote:
<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
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On 12/11/17 13:05, T i m wrote:

Yes.
And with lockshield valves both ends so normal users don't fiddle.

Usually they have an override lever that can be pushed and dropped into a locking slot, for when the motor fails.
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wrote:

Check.

<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
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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 down.
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.
--
Johnny B Good

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On 12/11/2017 15:15, Johnny B Good wrote:

Yup. On many it does not activate the microswitch in the same way normal activation would - so does not provide a temporary fix for all ills.

Yup two port ones have a similar feature (or at least the Honeywell ones do)
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John.
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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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