Central Heating Advice

[400bandit]

Hi All,

I'm after some advice if there is anyone out there that can comment. I moved house nearly a year ago and have been blissfully ignorant in my understanding of how my heating system actually works...

House is a decent sized four bed detached which has an external oil boiler and on the roof, evacuated tubes (solar water heater).

In the house we have 2 thermostats, one upstairs and one down.

Before Christmas I bagged a Drayton Wiser smart heating controller and was hoping to use it in place of the two thermostats and to control hot water. Well after taking the existing controller off the wall I was left scratching my head, the wiring didn't match any of the examples in the Wiser instructions (was supposed to be a bit of a plug in and play scenario...) and seems far too simple to facilitate two thermostats and hot water.

What I'm starting to think is the hot water isn't at all controlled by the existing control unit and is not in any way connected to the boiler - I think it purely relies on the evacuated tubes and an immersion heater. Does this sound likely? Seems odd to me to go to the effort of putting in the evacuated tubes only to pick up the slack with an electric heating element?

Here are some pictures:
https://drive.google.com/uc?id=1AgYw28u6XwmQF_xdQANMhvH8IrT6rRHK
https://drive.google.com/uc?id=1AfOh0HbONfYud4dFckG1rrNKJbNMBYtt
https://drive.google.com/uc?id=1Acls38M6zylgGftCNtfViJeL28vTuk6j

Here's the brain box were the hot water from the evacuated tubes:
https://drive.google.com/uc?id=1AlVfWRui8TJK77sH_aaj7pNFTXNba9bn

Any help would be much appreciated!

Many Thanks,

Joe
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[duhawkz]

If you have a problem, if no one else can help, and if you can find him....maybe you can hire The SinghPal."
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[stinkwheel]

Now I'm no expert but I did land up having to rewire my outdoor oil combi heating system and fix my boiler because no other fucker seemed to be able to work out how to make it work properly. Got fed up paying for boiler engineers to come out and scratch their heads, suck their teeth and start replacing random parts because they're "no good at electrics mate".

That centaur box is controlling CH only.

Do you have a combi boiler that does both CH and HW or is it just a heating boiler feeding a heat store (big polystyrene covered tank)? Check make and model.

I suspect what you have is a heat store/hot water tank which can be heated by the solar, boiler or immersion. In which case the centaur box will be triggering the CH pump via the 'stats (with a heat exchanger in the heat store). The HW will be on all the time being pre-fed hot water from the solar, and topping up with the immersion if the boiler isn't on.

Nearing the limit of my experience but I'd guess the boiler is only on when the CH is on (controlled by the white box). So when the CH is on, the HW is using the boiler, when it's off it's using a combination of the solar and topping up with the immersion. I suppose one way to check if that's what's happening is to turn the heating off (at the centaur box) and the hot tap on and see if the boiler fires up after a bit.

Combis are sometimes wired up so the HW is on all the time but I don't think you can use a combi with a pressurised HW system and heat store, they are usually mains pressure and cold-water fed.
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[Sister Sledge]

This ^^

But: Who the F wired that Centaur in? It has DIY written all over it. Why did they run the mains tail out like that instead of running it under the plaster wall? The wire they used is second hand - a kink from a previous use can be seen in it. There are wire whiskers loose around the terminals inside.

I can't help but do think you might be up against a bit more than you're expecting!
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[stinkwheel]

[almostthere]

wheres the pics of the cylinder? that solar install looks an abortion where does the discharge pipe go to you could potentialy have scalding water or steam discharging from it
where does the switched live from the timeclock go looks like it only controls the heating as it a single channel programmer
you are probably right about the immersion and solar controlling the hot water
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[400bandit]

[mentalboy]

[UncleFester]

We have an old gas boiler system where the CH will only get hot water if you have the HW on.

If you put the CH on by itself, it relies on the temperature of the water that is already in the system as all it does is turn on the pump, not the boiler.

We had no end of bother getting a sparky to fit the HIVE system but our plumber managed it just fine.
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[A100man]

My guess is that the water system (hot tank) only has one indirect heating circuit in it (cheaper) and that is used/fed by your evac tubes and as you say in winter they slack is picked up by the immersion.

I don't really see an issue with that but gas is approx 4p/kW and Electric about 15p, more even. so long term it's more expensive. Short term the cost of a dual circuit tank extra valves and controls etc.. might make you re-consider.

Pip pip.
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[A100man]

[MCN]

You can have a hot water tank heated by a coiled tube from the CH (+ an immersion element 3kw or more.)
The HW can heat independent of the CH by a two-way switching valve (controlled by a CH/HW controller).
Either CH or HW or a mix of both.
I would fit TRVs on all but one small rad (to give the boiler a place to send heated water when the thermostat hasn't shut it off yet.)
TRVs are not too expensive and provide a room by room control.
The problem is that once all the wiring has been chased bubthe original sparky it's a job to work out what he's done. Unless you're up to speed in electrics and have a couple of specific testers to simplify troubleshooting.
Don't get electrocuted, scalded or set fire to the hoose in the meantime. And have the doors open ifbyou are phaphing about with gas. Although by law you can't touch gas.
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Disclaimer: The comments above may be predicted text and not necessarily the opinion of MCN.

[UncleFester]

Boyles Law or just Physics lol
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[MCN]