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Vaillant 824 Wiring Issues


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Hi there. I am new to this forum, I am hoping someone can help. I recently wired a control box to my 824 combi. Everything was fine initially. A week or so later the boiler keeps wanting to fire even though the control box is not telling it to. When I wired it up I connected the switched live from the control box to terminal four in the boiler and this seemed to work. When it developed the problem i found that both terminals three and four in the boiler are both permanently live even when nothing is wired into them. This can't be right surely, I would have thought that only terminal three should be live and act as the live for a switch back to terminal four or have I got this wrong? Can someone assist please? Is it a circuit board fault?

Thanks, Jim

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Have you left the link in the boiler?

How are you measuring the voltage? In relation to what? 

What is the control box?

Does the boiler have 230v switching, or ELV? 

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Thanks.

No, I removed the link. My understanding is to remove this across 3 and 4 when using external controls.

When I say control box I mean programmer.

With a tester linked to neutral I am getting a live reading off 3 and 4.

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vailant changed their wiring setup it's in the manual buried under some health n safety guff just read the whole thing.

:)

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What's the programmer?

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It's a Drayton MiTime 721R

It's not the programmer at fault I don't think.

Like I say, 3 and 4 act as the switch to activate the boiler. 3 is live out and 4 is the switched return, I think!

With the programmer disconnected from the boiler 3 and 4 are both showing as live without being connected together, that can't be right can it? PCB fault?

This is an old boiler by the way 2009 I think.

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Does the boiler use 230v switching?

or should it have been 24v,? 

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230v is my understanding.

I wired terminal 4 in the boiler to the orange wires coming from the two two port valves. My understanding is that the programmer activates either the central heating or the hot water valve. When the valve opens this triggers a switch in the valve which makes the Orange wire live, this then fires up the boiler via terminal 4.

Have I got this wrong?

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ok, so you have a combi boiler,

why have you a valve for the hot water?

that doesnt make sense

 

actually, why do you have a valve for the central heating?

do you have a large house with 2 heating zones, and NO hot water valve?

.

also, how are you putting a voltage onto the grey at the valve?

to do it properly you should be taking a signal from your boiler out to the grey on your valve,

but, unless you have 2 separate heating zones Im lost as to why you have 2 zone valves,

there should not be a valve on your hot water,

or,

are you heating a cylinder? which seems a bit stupid with a combi.


also,

where is your room thermostat connected to?

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We need to know the exact boiler model.

For buildings with 2 bathrooms and a cylinder, it is common to replace an existing regular boiler with a combi. the combi can run one bathroom/shower from mains pressure, and the second bathroom can be run from the tank/cylinder. So that both can be run at the same time without loss of pressure. If only one bathroom is used, the cylinder need not be heated. If the boiler breaks down, you still have the immersion as a backup. Makes good sense.

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It's a Vaillant 824 combi. I have attached a hot water tank for flexibility around bathrooms etc so there are two valves, one for heating and one for hot water. As I said it was working fine then I noticed that it was trying to heat although the programmer was not telling it to come on. I looked for why and noticed that terminal 4 in the boiler was constantly live without anything connected, is that how it should be? I thought it was the switched live?

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I can't find a 824 combi manual. I can find an ecotec 824 and a turbomax 824.

Again, what is the exact model?

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Rob, sorry, will check as soon as I can and get back to you.

Thanks.

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OK,

Ive just done an 824 ecotec plus today, by coincidence,

Im unsure if its the same as yours,

BUT, is there a link on the 24v controls of your boiler?

this needs removed if you are using the 230v controls.

 

as Rob says,

we really need to know the exact model.

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Don't know if this specific to yours as the other manual didn't show terminals labelled 3,4,5? So take a look page 27 for connections?

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Thanks everyone.

It's a Vaillant Eco Tec Plus 824 R1

Serial 210703308520

There are no links on the 24v side

Like I said it was working fine but now I seem to be getting a voltage from terminal 4 with nothing connected to 3 or 4. My understanding is that terminal 3 should be live and then 4 is the switched live.

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When you wired it originally, you had nothing connected to terminal 3 at the boiler, and the orange wires from the valves were connected to terminal 4?

 

If you take out the wire from terminal 4, does the boiler fire up?

 

(Do you have a by-pass fitted to the pipework?)

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Is your programmer wired correctly?

Is it faulty,? 

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Thanks for your help, I think I have sussed it.

What I did originally was wire the live to the programmer and thermostat direct from the mains. The "switch" from the valves to activate the boiler, ie when they are calling for heat, was then working from that direct mains feed too.

What the instructions say, and what I had ignored, was that any external controls must be wired from terminal three in the boiler and then switched back to terminal four in the boiler, this then turns it on when heat is called for. Obviously the boiler has permanent electrical feed from elsewhere to cater for the overrun.

Quite why I was getting a live feed from terminal four without terminal three being connected I don't know, I suspect my previous mess up had made it throw a wobbly.

Thanks again for your help, maybe this saga will help someone else.

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vailant changed their wiring setup it's in the manual buried under some health n safety guff just read the whole thing.

:)

;)

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What you describe is VERY bad wiring practice

Boilers and their controls should have a single point of isolation

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Sorry to say, either I've misunderstood your post, or I'm not sure you really know what you're doing?

Are the boiler and controls on separate supplies?

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Sorry to say, either I've misunderstood your post, or I'm not sure you really know what you're doing?

Are the boiler and controls on separate supplies?

 

 

not sure, but it looks as though even if they are on the same supply, there may be a live in the boiler even if its switched off

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Not sounding too clever?

Jim wherefore art thou?

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just goes to show, a little knowledge is dangerous. fortunately, in this case, it didnt work correctly, so obvious there was a problem and its been discovered.... before some innocent other person comes along, ensures supply to boiler is dead, then gets electrocuted because someone put a separate live supply to it...

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