On 18/01/2019 22:41, Harry Bloomfield wrote:
My usual server is off line, so I cannot find the original thread..
I have been a bit "off line" myself - flu, and possibly the real thing
rather than the "man" variant!
Today the VRC 470F was delivered, so I got stuck in a removed all of the
old controls and fitted the VR 65 and VRC 470F - this after getting
house and water to a good temperature, in case it took longer than
expected.
I had it all ripped out and new back in, within 3 hours. CH was
obviously working fine, but not so sure about the HW side. CH now runs
much more gently, modulates output down to minimum instead of the near
flat out or off as before, boiler never seems to exceed 50C, so well
inside condensing range.
Yup that sounds like its doing what it should.
I had VRC 470F running on its batteries for several hours, without the
boiler etc. powered and it retained it time and date just fine. Maybe
because the clock is in the 470F and is maintained by the batteries,
your 470 has no battery rather it is powered from the ebus. Power the
boiler down, no ebus power, clock is lost, but the settings are in non-
volatile memory?
Yup, no batteries on mine...
The HW issue...
I configured the boiler to assume a mid position valve, but it seemed
not to make any difference other than the boiler then allowed me to set
a max temp for the HW, but only a max of 50C. Before changing the
control system, I was able to set a max boiler output temp of 75C.
470F Menu Installer Level System Config. seems to suggest a Flow
Temperature Target 40C, though I have seen this show 51C. It does not
allow it to be changed..
The flow temp should just reflect what the "system" is calculating is
the ideal for the circumstances (external temp etc). So you don't set it
directly. If you play with the Heating curve then you can influence the
slope of the mapping between target flow temp based on outside temp.
IIRC the thing comes preset to a curve of 1.2. That would mean with a
external temp of ~5 deg you would see a max CH flow temp of around 50
(if you have the internal temp set to 20 - it will alter the flow temp
in response to the actual temp demanded as well).
Depending on how good the house is thermally you may need to tweak that.
There was a 'desired HW temp' setting in the 470F which could be set to
a max of 70C.
I initially had the HW running on its cylinder stat. and it never seemed
to try to heat the HW, maybe because it was already well over 50C, but I
never saw the valve move at all.
I then swapped from stat., to the NTC sensor. I was than able to see the
HW cylinder temperature on the 470F, it seemed to be just maintaining a
constant 50C, but not much HW was consumed today so I cannot be sure,
but I never saw the valve move to HW or the mid position. Except by
pulling the NTC out of the cylinder insulation and allowing it to cool,
did cause the valve actuator to move.
HW Boost didn't seem to do anything.
That basically gives priority to HW generation even if you have the DHW
programmed off at that time. However it will only fire the boiler if it
sees the cylinder below set point, then once its reached set point it
will revert to its normal programming.
I wonder if the legionella setting, once per day might overrule the
boiler, if it is the boiler holding the temperature down.
I have mine set to 60 for "normal" and 70 for the once weekly cycle.
I set the clock deliberately 5 minutes fast, to see if the DCF77
receiver corrected it, as there doesn't seem to be any indication of
reception. It hasn't corrected it yet, maybe over night reception? That
is probably in the remote outdoor sensor and the 470F is showing the
correct outdoor temperature.
For anyone interested - Boiler is a Vaillant 418 ECOfit Pure, valve
actuator is a Sunvic SDM 1901.
Vaillant have been downright unhelpful (three times), when asked if the
VCR 470F + VR65 + my boiler would work properly together. It seems they
do, if I can solve the HW issue.
The CH temp ought not affect the DHW flow temp - for weather
compensation to be practical its got to be able to run different flow
temps for DHW since it would otherwise only be during fairly server
weather you would be able to adequately heat the water.
--
Cheers,
John.
/================================================== ===============\
| Internode Ltd -
http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/