antonyupward
New Member
Hi,
Hoping someone on the forum knows more about the technical CONFIguration and SERVice menu options for the Viessmann Vitodens 100 B1KA than appears in the "Installation and Service Instructions".
I am looking to see if its possible to adjust the primary circulating pump (the one internal to the boiler) "off-delay" after a call for DHW has ended, i.e. the delay before the diverter valve moves the internal heating loop from the DHW heat exchanger back to the external heating loop.
The table on page 71 of the "Installation and Service Instructions" says this delay is "none", but in practice, although the burner goes out 1-2 seconds after end of DHW call, the diverter valve remains in the DHW heat exchanger position for 35-40 seconds (and the little "faucet" icon remains on the display for this long too).
I'd like to change "none" to 2-3 mins... anyone know if either the CONFI or SERV menus offer this possibility?
Background aka TLDR
During heating season, when there is a call for heat, and there are several uses of hot water in succession, with 1-3 mins between each one, I get a "plug" of cold water at the hot faucet.
Why? Here's what is happening:
(1) 35-40 seconds after the end of the DHW call, the diverter valve switches the diverter valve back to the heating loop.
(2) The hot water in the heat exchanger, at the DHW set point of 50C / 120F from the last call for DHW, is sent into the heating loop, which has a set-point of at 30-45C / 85-110F (depends on Reset calculation/outside temp).
(3) The return water from the heating loop, which is at a considerable lower temperature than the heating set-point (perhaps 25C / 75F), then comes into the boiler for reheating.
(4) The boiler doesn't immediately fire due the latent heat in the boiler and the lower heating set-point. For a short time - 2-3 mins - there is enough heat in the boiler to raise the heating water to its set-point without firing.
(5) Then, within 2-3 mins there is a subsequent call for DHW, and it takes 30 seconds for the boiler to change the diverter valve back to the DHW heat exchanger, and ramp up the temp in the heat exchanger to the DHW set-point.
(6) While the boiler is ramping up, the water sent to the primary loop side of heat exchanger from the heating loop is at best 30C/110F (the set-point of the heating water), and usually lower.
(7) As a result, a "plug" of 2-6l / 0.5-1.5 US Gallons of essentially unheated cold water (in my area 3-5C / 37 -41C) is sent to the open hot water faucet - since it could pick up almost no heat from the heat exchanger
(8) For the faucet user, the DHW pipe has hot water on either side of this cold "plug", which if they have just stepped into the shower, they experience some time after getting into an initially hot shower!
(9) Complaints for the occupants ensue!
I believe the simplest solution to this would be to keep the diverter valve/primary circulator pump set to DHW for 2-3 mins after a call for DHW ends, not the default 35-40 seconds.
Anyone know how to change this via the SERVice or CONFig menu options on the B1KA?
Hoping someone on the forum knows more about the technical CONFIguration and SERVice menu options for the Viessmann Vitodens 100 B1KA than appears in the "Installation and Service Instructions".
I am looking to see if its possible to adjust the primary circulating pump (the one internal to the boiler) "off-delay" after a call for DHW has ended, i.e. the delay before the diverter valve moves the internal heating loop from the DHW heat exchanger back to the external heating loop.
The table on page 71 of the "Installation and Service Instructions" says this delay is "none", but in practice, although the burner goes out 1-2 seconds after end of DHW call, the diverter valve remains in the DHW heat exchanger position for 35-40 seconds (and the little "faucet" icon remains on the display for this long too).
I'd like to change "none" to 2-3 mins... anyone know if either the CONFI or SERV menus offer this possibility?
Background aka TLDR
During heating season, when there is a call for heat, and there are several uses of hot water in succession, with 1-3 mins between each one, I get a "plug" of cold water at the hot faucet.
Why? Here's what is happening:
(1) 35-40 seconds after the end of the DHW call, the diverter valve switches the diverter valve back to the heating loop.
(2) The hot water in the heat exchanger, at the DHW set point of 50C / 120F from the last call for DHW, is sent into the heating loop, which has a set-point of at 30-45C / 85-110F (depends on Reset calculation/outside temp).
(3) The return water from the heating loop, which is at a considerable lower temperature than the heating set-point (perhaps 25C / 75F), then comes into the boiler for reheating.
(4) The boiler doesn't immediately fire due the latent heat in the boiler and the lower heating set-point. For a short time - 2-3 mins - there is enough heat in the boiler to raise the heating water to its set-point without firing.
(5) Then, within 2-3 mins there is a subsequent call for DHW, and it takes 30 seconds for the boiler to change the diverter valve back to the DHW heat exchanger, and ramp up the temp in the heat exchanger to the DHW set-point.
(6) While the boiler is ramping up, the water sent to the primary loop side of heat exchanger from the heating loop is at best 30C/110F (the set-point of the heating water), and usually lower.
(7) As a result, a "plug" of 2-6l / 0.5-1.5 US Gallons of essentially unheated cold water (in my area 3-5C / 37 -41C) is sent to the open hot water faucet - since it could pick up almost no heat from the heat exchanger
(8) For the faucet user, the DHW pipe has hot water on either side of this cold "plug", which if they have just stepped into the shower, they experience some time after getting into an initially hot shower!
(9) Complaints for the occupants ensue!
I believe the simplest solution to this would be to keep the diverter valve/primary circulator pump set to DHW for 2-3 mins after a call for DHW ends, not the default 35-40 seconds.
Anyone know how to change this via the SERVice or CONFig menu options on the B1KA?
