Hot Water and Central Heating at the same time

[MattK90]

Hello,

I’m hoping that someone might be able to help with an issue that’s driving me mad.

I have a conventional boiler set up with a hot water tank. For as long as I can remember when the hot water heater is on at the thermostat, the central heating also comes on. I’ve recent upgraded to a Hive thermostat and still have the same issues.

I have checked the wiring and I’m sure it is all in correctly. I have also changed the mid point actuator and valve body to ensure this isn’t the failure point.

Im starting to run out of plausible options? Any recommendations on what the issue could be?

Thanks!

 

[cross thread]

Possibly it’s piped wrong have you photos

 

[MattK90]

Photo of the set up, I’m starting to think it’s the way it’s plumbed in.

 

[picasso]

Can you take the front off the junction box and post a pic? the 3 port valve looks correctly plumbed in.

 

[MattK90]

Photo attached, top left wire is from the pump, one out the bottom is the tank thermostat, black is the 3 port. Then the three wires to the side that aren’t connected are the old room thermostat that is now redundant. I’ve also added the control panel wiring, this is the old one I replaced but the hive is wired in identically.

 

[ianmcd]

Do you have another junction box somewhere? the HW off wire T1 on the hive is red and should go to grey on the mid position valve, but in your pic the wire is blue ?

 

[MattK90]

There’s no other junction box, the wiring has been replaced like for like, the only change has been the removal of the room wall thermostat and the required change to that.

It has they same issue with the old Thermostat and control panel so I believe that it has always been wired in wrong.

 

[ianmcd]

it is wired wrong then, as said the red wire in T1 on the hive goes to the grey on the MPV if you have a cylinder thermostat , the satisfied on that also goes to the same terminal, without that wire the MPV wont work correctly

 

[MattK90]

So I’m trying to get my head round this. I can’t see where it’s wired wrong.

The red at the top of the junction box comes from T1 on the control panel downstairs, that’s is linked to the grey from the MPV, on the other side that’s linked to the blue of the cylinder thermostat which is (3 on the inside of the thermostat as it’s old, which I believe is port 2 of C,1,2 set up, which should be satisfied?).

Unless I’m mixings satisfied and call up?

 

[ianmcd]

sorry couldnt see the red wire in your pic its not very clear

 

[picasso]

Has the boiler been moved since the problem started ? it sounds like you have reverse circulation .

 

[MattK90]

No it’s not been moved, the boiler has been in since I bought the bought house 5 years ago, but I have a feeling it was changed about 2 years before purchase.
The mid point valve should closing off with the CH or HW circuit, but I haven’t managed to isolate one at a time.

 

[MattK90]

I’ve attached a few extra photos, there is a spur of the feed from the boiler into the hot water tank that bypasses the MPV. He has an open isolation valve on it should this be open?

You can see it as the back of the photos