Electric Connection for Gas Boiler

[Robin]

Hullo uk.d-i-y world...

I have inherited an old Vaillant VC Gas boiler. It works OK, but the 'built-in' timer control is broken and no-one I know wants to touch it. It's all going to be ripped out in about 18 months, so I want to do a quick fix to get a timer control.

The boiler connects to the mains electric using a switch box. See the picture at:

switch box on the mid left is wired into the double socket above it. The wire that comes out of the bottom of the switch box goes into the boiler.

Would there be any issue if I removed the switch box and put a regular plug on the wire instead?

If I did this I could put a timer on the plug (X10), insert into socket and presto, I've got the boiler on a timer.

Aside: I had this all apart earlier today, the switch box had a 13amp fuse, but the old manual for the Vaillant says the fuse should be 3amps, so I've replaced the fuse and its working ok. This is right isn't it? A gas boiler doesn't draw a lot of current, does it?

Thanks for any advice.

Regards Robin

[Andrew Gabriel]

A couple of issues...

The socket should be an unswitched one if it has a fixed gas appliance connected to it. Also I'm assuming the spur is already wired correctly into it's supply.

The boiler may not like being routinely switched simply by turning its mains supply on and off. That wouldn't allow a pump run-on function to work, or any built-in frost protection, or pump exerciser. (I don't know if your boiler has any of these features.)

Your boiler probably has a connection block to which a timeswitch is supposed to be connected. Do you have the installation manual for it (it's supposed to be left with the boiler after installation and when a house changes hands).

That's correct.

[John Rumm]

A simpler solution would be to replace your room thermostat with a programmable one. This combines the functions of timer and thermostat and also gives added control in that you can choose different target temperatures for different times of the day.

Screwfix do a quite reasonable one for about £22.

[Robin]

Thanks for your help.

Unfortunately, there is no room thermostat. At least not as far as I can see. I'm going have a longer think about this and see what my other options are. As another poster commented, there are some issues with my simple plug timer plan.

Regards Robin

[Robin]

Thanks for your help. I suspected my plan was a bit too simple, and you've confirmed it.

I do have a manual, a connection block and a timeswitch. Unfortunately, the manual doesn't describe the connection of the timeswitch in a way that I can find (or perhaps understand).

I'm going to have another go at reading the f* manual, maybe I'll get it with a bit more study.

Thanks again.

Robin

[Owain]

If you can quote or upload pics of the manual somewhere, the (sadly, remaining) finest brains on uk.d-i-y will collectively ponder...

Owain

[John Rumm]

In which case this seems like an ideal opportunity to add one. Generally very easy to do. If you don't fancy running a cable to the stat position then you can even get wireless stats.

[Robin]

Thanks. I'm going to pursue this a bit.

Now I just need to find out what the (undocumented) 25 year old control panel is doing.

(See new post in this group).

- Robin

[John Rumm]

If you can get the existing control panel to set the boiler to run continuously, then you can let the prog stat do all the work from there. The timer becomes in effect redundant (although no harm in leaving it there in circuit)

[meow2222]

If I understand the system correctly, that control box will control the temp of the primary circuit. If this is so, then removing it, wiring over its temp limits or setting the boiler to run continuously would all be most unwise.

Ideally you want a timer & thermostat to control the supply that feeds the main jet gas valve in the boiler. Most likely you need to design your add on wiring from the ground up, ie think about exactly what youre trying to control and wire things up to do that, WITHOUT removing any of the key safety devices, such as the existing control box's primary circuit temp control.

You'll only know for sure by looking for all electrical parts inside and outside the boiler, and working out which does what. Until you can be sure, it is not appropriate to remove what are likely to be safety components on what looks like a crude system.

The original purchaser saved themsevles a few quid by not buying the timer... I wonder how many times over that saving was gobbled by extra fuel.

NT

[Robin]

Well...

The real odd thing is that I do have a timer!

It was connected to the boiler, not the "control box" (by control box I guess you mean the picture of the thermo nuclear device).

For your amusement, I've uploaded a picture of the timer connected to the boiler. I've removed the plate that covered these connections.

the terminal block, the timer is connected to terminals 7, 8 & 9. The rating is 20v (obscured by the timer cable).

In the manual for the boiler, (and also on the cover plate for the terminal block), it says "Do not use Terminals 7 to 12". !

I'll open the control box up at the weekend and see if there is anywhere obvious to connect the timer.

Many thanks for all the comments.

- Robin

[Robin]

Sorry. For clarity I should add that the timer connection to the boiler didn't work. It was also quite clearly left, by the previous owners, in a state which indicated that it didn't work - randomly switched to go on and off in at hourly intervals.

My guess was that they were very frustrated by it.

- Robin

[Geo]

I can't help with your problem but the workmanship of the wiring is not brilliant - was it modified by the previous owner? Cable clamp on the black cable is not on the outer insulation, there is bare wire showing on it's neutral terminal and the routing of the earth avoiding the clamp seems odd.

Geo

[geoff]

In message , Robin

[geoff]

In message , Robin