Smart Thermostat

FreeBear

Bendy_House said: Ah, I see what they meant now by one 'wire'. It's more like one 'channel' to control two systems, the CH and the DHW.

Your plumbing would appear to be missing control valves. These are what open (and close) to direct the boiler's flow to the radiators and hot tank. Without these, you will never have individual, independent control over each.

I wonder if your system is even 'gravity' supply to the hot tank? And the pump only comes on to circulate the water around the rads?

Looks like half of an S plan system... Or a half baked Y plan without the three port valve.

Get that boiler serviced, and then ask the engineer to have a look at the whole system and see if it can be converted to a fully pumped Y plan. Get a thermostat fitted to the HW tank, secure those junction boxes to the wall, and fit a Drayton Wiser - It might cost you a couple of hundred in labour, but it will pay dividends in cutting your gas consumption.

Although the HW tank is reasonably well insulated, popping a jacket on it will cut the heat loss a little.

BUFF

apparently a BG UT2 is a Drayton LP711 

Bendy_House

Wow, Kido!

I think FreeBear's on the money - again.

Before you consider looking at upgrading your controls, you really need a decent plumber to sort out what you have. And what you have is a half-baked system.

I don't know if there's a 'good' reason why such a crude setup has been put together - is that the only setup that old boiler will cope with, for example? - or if it's been done by a semi-competent individual, with only half knowledge of what's required.

There is NO point trying to fit a Hive, or Nest or Wiser to what you have - it is not designed for it, and it would be a bodge. It is technically possible to wire it up, but not in the normal way.

The normal setup for a boiler like yours is to have a pump - the red and black thing - which circulates the heated water out of the boiler, and the pipe then splits in two directions; one goes to the hot cylinder, and the other goes to the radiators. On these two 'split' pipes, there is a motorised valve fitted (you have ONE of them). Finally, the CH (radiator) system has a room stat controlling it, and the DHW (hot tank) has a tank thermostat controlling it.

This gives you completely independent control over your heating and your hot water - either, or both, can be turned on at will. Then you can fit your Hive/Nest/Wiser, and programme it to come on and go off when you like, and whatever temp.

At the moment, this is what your system looks like it has: a pump (red/black thing) comes on with the boiler, when the programmer tells it to. This circulates the hot boiler water in to the hot cylinder to heat it up. If you then also turn up the room stat, the single motorised valve will open, and this will divert some of the hot boiler water to your radiators. But your hot cylinder will still be getting some hot water from the boiler, because there's nothing to stop it - there isn't a second motorised valve.

Bendy_House

These are the main parts:

GREEN: Motorised valve. When this buzzes open, some of the boiler's hot flow will go around the radiators.

BLUE: Danfoss WB12 WIRING CENTRE (where everything gets connected). Loose and a bit unsafe.

ORANGE: The hot boiler water FLOW to the hot cylinder, used to heat it up.

RED: The boiler water RETURN from the hot cylinder, after it's done its job.

YELLOW: A gate valve, used to partially restrict the return boiler flow from the hot cylinder, so that some of the 'flow' will instead go around the radiators when the motorised valve opens.

Bendy_House

RED: The circulating pump.

GREEN: The motorised valve.

Thin red arrows: the upwards one shows the direction of FLOW from the boiler. The downwards one shows the direction of FLOW to the radiators WHEN the motorised valve is opened. Otherwise, all the flow goes to the hot cylinder.

Bendy_House

Interesting - this looks like a magnetic filter? Have you been told about it? Have you ever cleaned it out? This catches sludge which is common in older systems, and can lead to blocked pipes and stuff.

What make is it?

Bendy_House

To use a modern control on this EXISTING setup would require a competent electrician, one who can wire it up in a way it was not designed for.

Ie - for DHW, one timer has to work it. For CH, the same timer AND the room stat needs to be controlled together.

And that will still leave the existing issue that, whenever the CH is on, the hot tank will ALSO be being heated. It's all very crude, and very wasteful.

When the CH is on for a while, does the hot cylinder become VERY hot?! This is clearly wasteful - it should be turning off when it reaches around 65oC. What's more, it isn't as well insulated as modern cylinders, so - especially when it's very hot - it'll be losing heat to the air.

This should be quite sortable. It essentially needs a second motorised valve on the orange pipe in the first pic - that will properly control the DHW, and only heat up the cylinder when it's actually asked for. The existing motorised valve can continue to control the CH.

The hot cylinder doesn't appear to have a cylinder 'stat on its side, which would be used to stop heating it when the required max of 65oC is reached - so that would need fitting too.

That's pretty much it! All these gubbins would be wired together in that wiring centre, which should be attached to somewhere securely.

And then you add the controller of your choice, including, I'd suggest, Smart control via a phone App. You'd use this to preset each CH temp you'd want at each time (20oC at 6am, 14oC at 8am, 20oC at 4pm, etc etc), and when you'd want the hot cylinder to be topped up with heat. And you'd have full overriding control over this, even away from the house. So if folk aren't coming home until later, you turn the heating down until you know you are a half-hour away, that sort of thing.