Changing from combi to system boiler with thermal store cylinder

triplefan

I'm not changing the system per se, but I have moved house and brought the Tado with me, I'm looking to install the system when it is warm enough to manage without heating. I have a V3P extension kit which states it will control hot water, does it use the existing thermostat on the cylinder?

To add another twist it is a thermal store cylinder, probably a dumb question but is this type of cylinder compatible with Tado?

Thanks in advance

Andrew

royi

@triplefan The extension kit should work with the new boiler, (provide more details about your boiler) but won't work with the existing thermostat on the water cylinder.

GrilledCheese2

@triplefan if it's a simple thermal store setup with a 2 channel programmer then you can simply swap the programmer with the extension kit to control HW and CH. If it's a more complicated setup with multiple heat sources, then you'll need some expert advice on how the control system works before making any changes.

Note that you'll need the configuration setup so that HW always comes on when there is demand for CH. You cannot have CH only.

triplefan

Thanks for the reply, yes it is a simple set up. I am grateful for any info on the system as every plumber who has looked at it is "not familiar with this set up". I am however slightly confused (easily done😂) with your comment about HW & CH, does that mean I can have HW only?

triplefan

@royi

The boiler is a Baxi Solo HE a. This system is unknown territory for me too, could you explain how the HW temperature in the cylinder is regulated?

GrilledCheese2

A thermal store can be setup with S-Plan or Y-Plan controls where there are motorised valves to provide independent control of CH and HW. Often they are setup without valves. For the latter the boiler ignites and heats the store when the HW circuit is active. The cylinder thermostat controls the water temperature inside the cylinder and this temperature shouldn't normally be adjusted by the homeowner. You might have a thermostatic mixer on the HW output to the taps - this can be adjusted to avoid scalding hot water.

The CH circuit starts a pump that circulates water through the radiators, but doesn't ignite the boiler. It's due to this setup that I mention you need to ensure you don't have the option for CH only. If you want to know more about how your system operates, then find the manufacturer name and model of the cylinder. Thermal stores aren't common but they're often used with alternative heat sources such as wood stoves and solar.

triplefan

GrilledCheese2, great read and thanks, I read it about 10 times and I think I understand. There are no motorised valves, just 2 pumps, yes it has a mixing valve, the cylinder is a IMI range ltd flowmax, the thermostat is set to 80. Since moving in we have had solar PV panels installed along with a Myenergi Eddi.

GrilledCheese2

I'm guessing one pump is on the HW circuit circulating hot water between the boiler and thermal store. The second pump is on the CH circuit to circulate water through the radiators. With this setup you will need Tado configured for the CH relay to be linked to the HW relay. Tado documentation refers to this as gravity fed configuration. You have CH + HW or HW only, but not CH only.

triplefan

Thank you so much for all your help and time spent