Am I choosing the right components?
Hi.
Just want to confirm I understand what to buy to replace my Honeywell heating controls. I've got a Potterton combi boiler, megaflo tank, 3x control valves, and Honeywell ST9100C timer + 2x CM707 battery powered thermostats. I *think* it's connected as shown in my diagram below, but if anyone thinks I've got it wrong please let me know! Not sure what controls the input valve to the Megaflo - the boiler or direct from the ST9100C?
My question is what I should order to replace the Honeywell bits. Suspect I need a starter kit for the boiler/hot water control and a thermostat for downstairs - should I get the wired version so it can connect to the control valve for the downstairs zone? Also need an additional (wired?) thermostat to replace the control for the upstairs zone?
I saw something about using the little terminal blocks supplied to short circuit wired thermostats, but not sure if that's what we're supposed to do for control valves. Presumably this would put them in a permanently open position? I'll be using a bunch of Tado TRVs, but I guess the zone control of the legacy system still has some value.
Thanks in advance for any tips!
Mike
Comments
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The CM707s are wired thermostats and you will need to replace them with 2 Tado wired thermostats.
The ST9100C is a single channel programmer. I assume you use this to set the schedule for the HW cylinder and not the CH? The replacement for this is the Wireless Receiver. It's a dual channel device, so you won't use the wireless thermostat that comes with it.
If the ST9100C is for HW control only then you don't have to replace it - you could just use Tado for CH control and continue to use the non-smart control for HW. To be honest the cost of the Wireless Receiver for only HW control is not going to save you money in the short to medium term. If your cylinder is heated while you are away from home the hot water will stay hot for a long time.
You only need one bridge, so just purchase one starter kit.
If you purchase TRVs you can add them at a later date. The wired thermostats will be the Zone Controllers for the TRVs.
Just to add, your boiler is not a combi. If it was you would not have a hot water cylinder.
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Thanks for replying GrilledCheese.
The ST9100C is fitted to the side of the boiler cupboard in the kitchen. I hadn't thought about whether it controls the HW and/or CH schedule before. The CM707s have their own weekly schedules, so I guess the other unit may well be for HW only. As noted there is a valve on the input to the Megaflo (upstairs) which I assume is controlled by the 9100C - either directly (can't see the wiring path) or maybe via the boiler (if that's possible). Any tips on how I could confirm - switch it to 'off' and see if the HW runs out?
Noted on the boiler not being a combi. Lots of Google results for 'Potterton promax HE plus' suggest it is, but I read that combi boilers aren't compatible with Megaflo units, which was confusing - maybe they come in combi and non-combi variants...
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On the 9100C use the mode button to change from Auto to Off and use up the hot water. Obviously you need to do this when the HW cycle is scheduled to be On.0
