It's a megaflo 250l. From memory, the stat is around 7pm which I believe indicates roughly 60 degrees. We only heat HW first thing in the morning, and then as and when required if necessary. So I was able to just override the programmer and it called for heat.
Vaillant anti-cycle time question
- Thread starter fezster
- Start date
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L8 would disagree.
Does L8 make a provision for unvented water storage (plus 50c at the taps will be a bit hotter at the cylinder)? For OP so there had been some draw off in the day surprised that it cut out so quickly on return sensing, but was worth a go. Does it behave differently depending on d.0 as maybe you can find a sweet spot as we dont have access to what the actual logic is for the boiler either on the original PCB or the revised. From what I saw the revised still ramps up for 50 seconds but seems to allow a bit of an overshoot of flow temp. I also see from cold the boiler starting at less than 75% of max rated temp but from a hot start it still does the stupid 75% which is a bit daft.
I was kind of hoping this setting might have some effect on how quickly the boiler recovers from s53. Might try that tomorrow (easy to replicate opening a cold zone), but thinking LLH is my next step. The other reason being that the constant extreme temperature differentials at the heat exchanger surely can't be good for its life!
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How much is it going to cost to have a LLH, maybe time to get a new boiler which is a bit more tolerant to what you are asking. Maybe fudge something with 3 port valves as another option with a timer like https://www.parkelect.co.uk/timer-r...Q_zbh-mAyVjSipazTrbjMuV4sSSg5r7BoCt5kQAvD_BwE
Max flow rate @ 20dt - 0.45 l/s.
Header velocity - 0.22 m/s (54mm LLH required).
Interesting - I was just discussing with my father earlier that if I could have a zone valve activating turn off the Switch Live to the boiler for 5-10s, and then reactivate the boiler, this would allow the return temp to stabilise before the boiler fires up again. I haven't had a chance to look at the link you sent properly, but I'd be intrigued if I could put together a relay like that on the cheap.
It's actually comforting to hear that hopefully spending money on a LLH will actually solve the issue! Thanks.
I was thinking the Spirocross AX100 or the Worcester Bosch Greenstar Low Loss Header. I will, of course, be letting the installer decide which to go for, but it'd be useful to know whether either of these meet the criteria you have given. The Worcester is attractive because of it's price. The Spirotech is rated at 0.55 l/s and all I can find on the Worcester is that it is suitable up to 70KW. How do either of these figures relate to velocity?
Found this formula:
Max flow rate 38KW @ 20dt - 0.45 l/s = 0.00045 m3/s
Header velocity - 0.22 m/s
Diameter of header (mm) = (SQRT((flow rate*1.28)/header velocity)) * 1000
Much of the literature I've read says the header velocity should be 0.5 m/s, rather than 0.22 m/s.
How important is the spacing between the header tappings?
Max flow rate 38KW @ 20dt - 0.45 l/s = 0.00045 m3/s
Header velocity - 0.22 m/s
Diameter of header (mm) = (SQRT((flow rate*1.28)/header velocity)) * 1000
Much of the literature I've read says the header velocity should be 0.5 m/s, rather than 0.22 m/s.
How important is the spacing between the header tappings?
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Oh dear.
The timed relays are cheap and can work in various modes (including delay on if you get the correct one). I have used them for pump overun duties just mounted in a 1 gang pattress.
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Worcester LLH fitted to a 438 28 rads on two zones and 210 unvented purrs like a kitten. Just fit it and forget the maths guys.
A picture paints a thousand words 
Thanks. I wanted assurance the Worcester LLH could work with my Vaillant boiler. I saw no obvious reason why not, but good to know someone has done it. Hopefully my installer will be familiar with the combo too.
Thanks. I wanted assurance the Worcester LLH could work with my Vaillant boiler. I saw no obvious reason why not, but good to know someone has done it. Hopefully my installer will be familiar with the combo too.
Ask him to note the use of the two port valves. They act as a high temperature non return valves. The call from the zone powers the secondary pump and activates the valve. The orange is switch live as normal and the boiler controls the primary pump. Piece of cake, but there's a lot of materials and work there, so sit down when he gives you the price.
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