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Old 21st January 2019, 18:59   #11
COLVERT
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Turns out diverter was fine, but the flow cartridge was the cause of the fault
Rich. Your post really does highlight the skills of some of those plumbers out there.--

Fault finding is becoming a lost art.----
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Old 21st January 2019, 23:01   #12
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Rich. Your post really does highlight the skills of some of those plumbers out there.--

Fault finding is becoming a lost art.----
Same in alot of fields these days John,
not many willing to fault find, garages are a fine example. Most ( tradesmen) just replace parts rather than diagnose faults. This is the second time in 2 weeks we have had to call Baxi for the same problem, dont see why this part couldn't have been replaced first time.
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Old 23rd January 2019, 10:37   #13
HarryM1BYT
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75 Contemporary SE Mk II 2004 Man. Sal. CDTi 135ps, FBH on red diesel, WinCE6 DD

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Harry. That passing of the boiler heat to the CH circuit sounds like it might be the temperature sensor. The sensor could be sending an OVERHEAT signal to the circuit board. As a safety feature the board would open the diverter valve to get rid of what it thinks is excessive heat in the boiler.

It's not demand opening the valve, but maybe just a faulty sensor signal.

Could be why the temperature to kill the bacteria will never be achieved.



Colvert.

Yesterday evening I got the bright idea to reset the boiler to factory defaults, followed by setting the system to call for HW. For the very first time it did what it had been asked to do. Just the once so far, I will try it again as more water is used, before calling it a fix and boxing it all up.


I have never touched the boiler settings, apart from tweaking the user setting for maximum output temperature, to get hotter water in the cylinder.


It has led me a merry dance, trying lots of ideas as to why it wouldn't heat the water on demand. I have tried three different valve actuators following suggestions that it might be the actuator which was faulty, or not compatible. I nearly ordered a complete new valve and actuator to fit, which was known to be compatible. I even emailed Vaillant several times to ask if there was any incompatibility issues with the bits I was fitting and the boiler, they responded with no sensible answers, just offers to send an engineer out or buy a set of their very latest control modules.



Yesterday morning I ran several tests to heat HW, it responded each time by moving the 3-port to HW, flashing the call for HW on the boilers display, running a purge on the boiler (as it does before firing), then going into anti-cycling mode, before repeating - never firing to produce any HW.


The VR65 has connections for either a NTC (thermistor) cylinder or a normal bi-metal stat.. The instructions suggest the NTC sensor can only be used on a Vaillant supplied cylinder, which seemed wrong. It will actually work with any type of cylinder and gives better and more intelligent control of the boiler output for HW.
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Old 23rd January 2019, 16:57   #14
COLVERT
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Quote by Harry.

Yesterday evening I got the bright idea to reset the boiler to factory defaults, followed by setting the system to call for HW. For the very first time it did what it had been asked to do. Just the once so far, I will try it again as more water is used, before calling it a fix and boxing it all up.


Keep us posted Harry. Hoping it carries on working for you.---
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Old 23rd January 2019, 23:36   #15
HarryM1BYT
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Quote by Harry.

Yesterday evening I got the bright idea to reset the boiler to factory defaults, followed by setting the system to call for HW. For the very first time it did what it had been asked to do. Just the once so far, I will try it again as more water is used, before calling it a fix and boxing it all up.


Keep us posted Harry. Hoping it carries on working for you.---

Two more water heating sessions and it was perfect


Though I found the boiler was wastefully cycling a bit, when just heating water, so I have delved into the boiler's settings to adjust it so it reduces it Kw output when just heating water. The boiler now has almost 100 operation configuration options which can be set up to optimise its behaviour


Before I added this fancy system, all the boiler knew was that there was an heat demand, it had no idea whether the demand was for CH or HW, or even how big the demand might be. Now it knows the house HW cylinder temperatures and how cold it is outside and can fine tune its response - well that's the theory.



I noticed the difference straight away on the CH, as soon as I had the system working on CH - instead of the feeling the room warm up and cool down, as the heating kicked in and out, radiators got hot, then cold, now they just get warm-ish and remain warmish.


Gone is the tick, tick, tick as the pipes heat up and cool, apart from when the the temperature is first turned up.



Very pleased now with the result! I managed to get the two units needed, at much less than the original cost - new items, but older stock - replaced by the same spec. items with network/phone control, which I just don't need.



It is supposed to save around 6% on the gas bills and some wear and tear on the boiler, so parts cost recovered in say around three years for me. Of course a much longer payback time for anyone paying full price and paying for the install. It is a very much simpler system to install than using clocks and thermostats, which I have just ripped out.
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Fix a poor handbrake; DIY ABS diagnostic unit; Loan of the spanner needed to change the CDT belts; free OBD diagnostics +MAF; Correct Bosch MAF cheap; DVB-T install in an ex-hi-line system; DD install with a HK amp; FBH servicing.

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