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I have just bought a house with a Vaillant ecoTec 637. The previous owner had some terrible Honeywell system installed but took all the controllers. So I can’t control the system, and in particular I can’t get the hot water on, no matter what I do. I had previously used a tado system, so I have connected this to the eBus as instructed, but still no HW, even if I can now control central heating.

Oddly the boiler doesn’t display the target hot water temp… it seems to be in a central heating only mode. What do I do? I have been through the installer mode for the boiler but I can’t find a setting. Some of the old wiring for the Honeywell evohome is still connected though I have disconnected the thermostat/bridge BDR91… HELP!!
I have all i need for tado, which should work, but doesn’t.
 
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You need a programmer for the hot water, a cylinder thermostat and a zone valve to activate the boiler. Do you have these?
 
I don’t know. How do I tell?
I imagine the whole thing was working fine before the old owners moved out?
The boiler was controlled by a Honeywell evohome system. This was wired to a thermostat BDR91A1000 and a Potterton EP2 controller was attached, but the potterton didn’t seem to control anything - the boiler was on all the time irrespective of settings on the boiler. These are wired to a couple of relay controlled valves via a wiring loom.
 
So your Potterton EP2 is the programmer. Where the hot water cylinder is situated, there should be a small thermostat strapped in place with a wire - a bit like a net curtain wire. Wiring loom? Relays? The relays may bring your hot water on. Also if you’re in need, you may have an immersion heater. A couple of photos at this point might be best.

Cylinder cupboard showing: cylinder, any valves and wiring.
 
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I enclose some pictures below:

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84011A13-B87A-401C-9D93-C6FB1F0B07FF.jpeg
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BB1A552F-07F4-4A12-A228-9F353633470A.jpeg
59457689-B85E-4AE8-BDE3-7434B27E24C1.jpeg
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B12CE18D-3BFE-4F9F-9198-F2D927BF0790.jpeg
 
The potterton unit is no longer attached. This has been replaced by a tado extension attached to the + and - terminals of the eBus as instructed by tado.
 

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