- Messages
- 10
My parents have a Baxi Back Boiler with a pumped central heating system and gravity hot water system with a Primatic cylinder. My Mum's asthma is getting more severe due to the house being unheated at night. I am looking for a way for them to be able to have their central heating on low at night but not have the hot water heating all the time. They can't afford to use the system for longer periods without the controls being upgraded.
From the research I have done to date, I understand that we could change the controls to the Honeywell C-Plan, but that this can't be implemented on a Primatic cylinder because a zone valve in the flow or return to the cylinder would rob the CH system of its provision for expansion. I've seen a suggestion that the way around this is to replace the Primatic cylinder with a conventional indirect cylinder and add a F&E tank. Currently their cold water tank sits above the cylinder in the airing cupboard; it's not in the loft. If we did add an F&E tank I'd be inclined to install where the current cold tank is and relocate the existing tank to the loft as I understand the cold water tank should be above the level of the F&E tank. Is this correct (and why is this)?
The final configuration will be a pumped CH system with a gravity hot water system arranged as per C-Plan with a Programmable Thermostat controlling the CH pump + boiler for central heating and a Single Channel Timer + Cylinder stat controlling the boiler and cylinder zone valve for DHW. I know that the cylinder zone valve will need to a six wire V4043H to work correctly in the C-Plan configuration. I've been referring to the C-Plan diagram at the top of Page 13 in this Honeywell document:
https://heatingcontrols.honeywellhome.com/documents/All/pdf/._Wiring Guide 2018 (Web DPS).pdf
The programmable thermostat will be a Honeywell CM721 (or CM727) and the single channel timer for DHW will probably be the Danfoss 102 timer that current controls the entire system.
Unfortunately we don't have the money to replace the Baxi boiler with anything better, and we probably can't change the location of the pump due to cost. Any comments or suggestions?
The work will be done by a heating engineer, but I'm aware that experience with Primatics, gravity hot water and C-Plan is getting rarer.
From the research I have done to date, I understand that we could change the controls to the Honeywell C-Plan, but that this can't be implemented on a Primatic cylinder because a zone valve in the flow or return to the cylinder would rob the CH system of its provision for expansion. I've seen a suggestion that the way around this is to replace the Primatic cylinder with a conventional indirect cylinder and add a F&E tank. Currently their cold water tank sits above the cylinder in the airing cupboard; it's not in the loft. If we did add an F&E tank I'd be inclined to install where the current cold tank is and relocate the existing tank to the loft as I understand the cold water tank should be above the level of the F&E tank. Is this correct (and why is this)?
The final configuration will be a pumped CH system with a gravity hot water system arranged as per C-Plan with a Programmable Thermostat controlling the CH pump + boiler for central heating and a Single Channel Timer + Cylinder stat controlling the boiler and cylinder zone valve for DHW. I know that the cylinder zone valve will need to a six wire V4043H to work correctly in the C-Plan configuration. I've been referring to the C-Plan diagram at the top of Page 13 in this Honeywell document:
https://heatingcontrols.honeywellhome.com/documents/All/pdf/._Wiring Guide 2018 (Web DPS).pdf
The programmable thermostat will be a Honeywell CM721 (or CM727) and the single channel timer for DHW will probably be the Danfoss 102 timer that current controls the entire system.
Unfortunately we don't have the money to replace the Baxi boiler with anything better, and we probably can't change the location of the pump due to cost. Any comments or suggestions?
The work will be done by a heating engineer, but I'm aware that experience with Primatics, gravity hot water and C-Plan is getting rarer.
