Heating on with hot water

[matt-drummer]

Hi,

I hope somebody can help me with some guidance before I call a plumber to investigate my problem. I just like to be armed with as much information as I can, it seems to help so I know what is going on.

We moved into a house almost exactly one year ago and I have not touched the central heating/hot water programmer since we moved it. Last week I decided to adjust the on/off times of the central heating and this is when I noticed the issue.

The house was built in the 1980's, detached four bedrooms and the previous owner was a keen diy fan by the looks of things with an electronics background.

The house has solar panels and the previous owner removed some equipment before he moved out (primarily a home made solar diverter to heat the hot water from excess solar power).

All of the wiring is in the airing cupboard with the heating/water programmer together with the hot water tank and the motorised valves.

I cannot see the wiring between the programmer and the valves but looking at the wires and the motorised valves etc I am 99% sure that it is wired as an s plus system.

There are three heating zones and one hot water valve, the programmer is a Siemens RWB29Si. The three heating valves service the front, rear and the conservatory.

The front heating is controlled by a room stat in the lounge and the rear of the house and conservatory are controlled by a room stat in the hallway.

So, there are only actually two controlled heating circuits as the rear of the house and the conservatory are linked together.

Now that I have altered the heating and hot water programs to suit our life style we have noticed an issue.

With the heating off on the programmer and the thermostats set below the ambient temperature, the radiators in the rear of the house (although not the conservatory) are heating up when the hot water is being heated.

So I did a test last night, the three heating valves function in accordance with the programmer and the room stats, closed when off and open when on and heat requested by the room stats.

I then turned the heating off on the programmer and turned on the heating. As soon as the heating is turned on the motorised valve for the rear heating circuit opens, therefore sending hot water to the radiators in the rear of the house. It is not affected by the room stat or tank stat, it remains open as long as the programmer is in a hot water on period

My only conclusion is that the valve for the rear heating circuit is connected to both the heating and hot water outputs of the programmer.

I don't know how that is possible looking at standard wiring diagrams and having done this once before (in a previous house with a Y system).

I am sorry for the long post but it would be difficult for anybody to assist me without all the details.

Thank you in advance for any help or just even for reading!


Matthew.

 

[matt-drummer]

This is not what I was expecting to see!

Is this normal or safe? Has anybody seen it done this way before?

I suspect there might be a `short' somewhere?

 

[CBW]

I then turned the heating off on the programmer and turned on the heating. As soon as the heating is turned on the motorised valve for the rear heating circuit opens, therefore sending hot water to the radiators in the rear of the house. It is not affected by the room stat or tank stat, it remains open as long as the programmer is in a hot water on period

I think you’re getting mixed up, if you turn heating off and then back on it will heat up if the room thermostat calls for it. I think you mean you put the hot water on? Could be let by if the motorised valve when hot water is selected, but could be wired in such a way that is working the way you describe.

Is this normal or safe? Has anybody seen it done this way before?

Seen it that way a few times before, they’re just Wago connectors, and should be safe.

 

[oldbutnotdead]

Reread your post, especially where you turn the heating off then turn the heating back on. Not very clear what you are doing ....

First job is to determine what is connected to what. So a sketch with all the electrical items on then go through that rat's nest and mark the connections on your sketch.

 

[matt-drummer]

Hi Chris,

Thank you for your reply.

Yes, I got mixed up, I meant as soon as the water was turned on with the heating off the motorised valve for the rear of the house opened to allow water to flow to the radiators.

Now I have taken the cover off the trunking the rear heating valve is not opening when the hot water is turned on.

I need to test a bit more.

It looks like a wire is touching somewhere inside the bundle, not that I can see it.

It should be easy to turn the power off and pull the mess out carefully to see where the problem is.


Matthew.

 

[matt-drummer]

Reread your post, especially where you turn the heating off then turn the heating back on. Not very clear what you are doing ....

First job is to determine what is connected to what. So a sketch with all the electrical items on then go through that rat's nest and mark the connections on your sketch.

Hi,

Sorry, yes I meant to say turned the hot water on with the heating off. I was trying to keep it as brief as possible and failed!

I have a diagram of how it should be wired so I should be able to label each Wago connector with the appropriate number and then check from there.

I am pretty much convinced that a wire from the heating valve is touching something it shouldn't so it is being operated by both parts of the programmer.

Thank you for your help.

 

[matt-drummer]

Hi,

I have pulled all of the wires and connectors out of the trunking and inspected for bare wires, there are none.

I have also checked all of the connections between the components, everything is where it should be for an s plus wiring diagram. None of the wires from the two channels of the programmer are crossed and there is no way that the heating could be triggering the heating valve to open.

Putting on the hot water results in only the hot water valve opening.

So my problem is solved on the face of it.

But I can't really leave the wires as they are.

I don't know if this is possible as I am relying on a really low level of understanding of electricity. Could the wires being crammed in to such a small space be creating enough interference or interaction between the wires to cause the hot water circuit to activate the heating just by its close proximity?

 

[oldbutnotdead]

Are any of the cables stranded rather than solid cored? Reason for asking- one single copper strand inadvertently linking 2 terminals together would give you your problem, the current drawn by motorised valve would be carried quite happily by said almost invisible strand of copper.
And unless the original installer has gone mad and put a PLC in somewhere (with high impedance ELV signalling) then no, crosstalk/induction wouldn't give enough current to fire a motorised valve

 

[matt-drummer]

Hi,

Yes, some of the cables are multi stranded.

I am familiar with PLC's, there are none.

I am sure that this situation has persisted since we moved here a year ago, it wasn't really evident as there was a lot to get used to in the house (solar panels, alarm, wired internet all over the house, various underfloor heating, programmable thermostats, etc) and by the time we had settled in it was winter and I just left the heating alone.

it is only since we had a smart meter installed and the weather has got a bit colder that the radiators have come on (they have TRV's) and I couldn't understand why as the heating was off.

The previous owner explained very little to me and when I asked I got very basic replies, it's not that I don't understand stuff, just it's hard to know what somebody has set up without asking. There are cables and boxes everywhere, like a router in the loft but he had removed his and said nothing.

It doesn't help that he was a bit of a bodger, bought nice stuff but never quite finished things, (a new kitchen but when you touch it a lot of stuff is not fixed in place!)

I would have been surprised if there would have been enough crosstalk/induction but I didn't really know.

Maybe there was a rouge strand of cable that was touching, it seems the most plausible explanation. I will examine it all again really closely and see what happens when I put it back inside the trunking.

Thank you again for your help.


Matthew.