This was the system at the start of last week and all working fine..
Open vented boiler and HW cylinder with a Vaillant ECOTec 418 Pure boiler (installed last March) + a basic timer + mechanical stats + Sunvic SDM 1901 valve/actuator. That setup meant there was only one setting for boiler flow temperature, which I had set to75C to get the HW cylinder good and hot. 75C meant the boiler tended to run near flat out, or off, when heating for the CH too, with little modulation down.
During the week, I upgraded that by removing stats + timer and installing a VR 65 Control Centre + VRC 470F, including wireless outdoor sensor. CH works great, modulating boiler up and down nicely, but I am obviously still tweaking the Heat Curve value.. (That is apart from Problem 2).
Problem 1 Idea was to be able to split the boiler output to be able to have higher temperature for HW, than needed for CH and run CH in condensing mode. It has enabled split, but the max setting for HW at the boiler is 60C and 75C for CH. The 470F allows the HW desired temperature to be set at a max of 70C. At 60C from the boiler, the cylinder struggles to be got higher than 50C, so demand is never met.
Problem 2 When HW is demanded, it seems to circulate to the CH circuit too. Thinking I might be able to get the water hotter once per day, using the anti-Legionaire facility, I set that up as a test today. Boiler ran very hot (85C) and it did raise the HW from 50C a couple of degrees, but it also got the CH hot too, stiflingly so. The SDM 1901 seemed to be regularly cycling between HW and CH, despite no CH demand. I never actually spotted it in mid-position at all.
I also tried configuring the boiler to use a mid-position valve d.97 to option 1.
Despite the warning to only use a NTC sensor on a uniSTOR cylinder, I tried both my original bi-metal stat and swapping to the NTC to see if that made a difference - it didn't.
Your suggestions please gentlemen?
Is the VR65 Control Centre perhaps incompatible with the SDM 1901?
I emailed Vaillant three times, in my attempts to get their assurance of compatibility of these items before purchase. Three times they ignored my question, only suggesting that VR66 and VRC 700 were the latest models.
Finally, how can I tell whether the 470F has a DCF77 receiver or not and whether it is receiving? Oddly this morning the clock and date (correct yesterday), had changed to 23:00 and 05/05/19 at 08:30 20/01/19. I wondered if it might have received corrupted data from DCF77, though odd if it just accepted it with checking the check-sum..
Open vented boiler and HW cylinder with a Vaillant ECOTec 418 Pure boiler (installed last March) + a basic timer + mechanical stats + Sunvic SDM 1901 valve/actuator. That setup meant there was only one setting for boiler flow temperature, which I had set to75C to get the HW cylinder good and hot. 75C meant the boiler tended to run near flat out, or off, when heating for the CH too, with little modulation down.
During the week, I upgraded that by removing stats + timer and installing a VR 65 Control Centre + VRC 470F, including wireless outdoor sensor. CH works great, modulating boiler up and down nicely, but I am obviously still tweaking the Heat Curve value.. (That is apart from Problem 2).
Problem 1 Idea was to be able to split the boiler output to be able to have higher temperature for HW, than needed for CH and run CH in condensing mode. It has enabled split, but the max setting for HW at the boiler is 60C and 75C for CH. The 470F allows the HW desired temperature to be set at a max of 70C. At 60C from the boiler, the cylinder struggles to be got higher than 50C, so demand is never met.
Problem 2 When HW is demanded, it seems to circulate to the CH circuit too. Thinking I might be able to get the water hotter once per day, using the anti-Legionaire facility, I set that up as a test today. Boiler ran very hot (85C) and it did raise the HW from 50C a couple of degrees, but it also got the CH hot too, stiflingly so. The SDM 1901 seemed to be regularly cycling between HW and CH, despite no CH demand. I never actually spotted it in mid-position at all.
I also tried configuring the boiler to use a mid-position valve d.97 to option 1.
Despite the warning to only use a NTC sensor on a uniSTOR cylinder, I tried both my original bi-metal stat and swapping to the NTC to see if that made a difference - it didn't.
Your suggestions please gentlemen?
Is the VR65 Control Centre perhaps incompatible with the SDM 1901?
I emailed Vaillant three times, in my attempts to get their assurance of compatibility of these items before purchase. Three times they ignored my question, only suggesting that VR66 and VRC 700 were the latest models.
Finally, how can I tell whether the 470F has a DCF77 receiver or not and whether it is receiving? Oddly this morning the clock and date (correct yesterday), had changed to 23:00 and 05/05/19 at 08:30 20/01/19. I wondered if it might have received corrupted data from DCF77, though odd if it just accepted it with checking the check-sum..
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