Help! Mystery cord/cable!

aintshesweet

Hi
First up, I would like to say I have ZERO knowledge on boilers and how they work (physically). All I know is, it heats my radiators and water.

Would someone with a little knowledge care to impart some wisdom my way?

I want to know exactly what my boiler is doing in connection with my shower and water tank (we have an immersion heater).

I know when I switch on the immersion the water gets very hot. I probably have a (very) hot shower once a month. However, there is a mystery cord next to our shower which alights a red box above it. This puzzles me because I was under the impression our boiler was not combi (it's an old Potterton Netaheat Profile - which I presumed was gas only). When I pull the cable, the water is pretty warm and a regular pressure. When I don't pull the cable, the water is pretty warm (the same temp) and the same pressure. It doesn't really seem to do anything, but it does light up. What on Earth is it for?
It's driving me mad.

Even though it doesn't do anything, I turn it on anyway when I have a shower, because I presume it must be for this purpose... somehow. The water is never cold, anyway, unless the Mister has an extra long shower before me.

So, although we might be using electric for our showers (somehow?), what does this mean in regards to the gas? Surely the gas has to heat up the tank first anyway? So what is the point of the electric cable (if it is for that purpose)? And the immersion is only used in emergencies (when I want to swear at OH for using all the water). (Also - I thought immersion was only used in properties where there wasn't a combi boiler - or is this wrong?)

We do use a lot of gas (I've been sorting out our bills which is what prompted me to post). We used 164 units (5154.98Kw) of gas the past quarter (~£260) but we only used 280 units of electricty (which sounds more but in actual fact is only ~£49 due to cost discrepancies with gas). That's £16 pm - in a 2bed with 2 people who like very long showers...

If anyone might have any idea as to what this cable might be, or the system our house is using that would be FAB because this is driving me mad. I just don't understand how our leccy could be so low if that's what our water is run from. And if there's no way it could be electric, what the hell is the cable for?!

brewerdave

Pull cord could be for either:_
a) extractor fan - have you got one which no longer works? (you would hear it running if it was still live)
or b) isolator for electric shower - have you been in your house very long? If not, did the previous owner remove an electric shower (they cost a fortune to run!!) and use boiler supplied hot water.
or c) Isolator switch for shower pump -Was the shower originally at a higher pressure?

macman

If you have gas CH and DHW, then don't use your immersion heater to heat your hot water. It's nearly 3 times more expensive per kWh to heat it by electricity. Just use it as an emergency backup.
Your shower is fed from the hot tank for two reasons: 1) If it was an working isolator, the shower would not operate if it was switched off. 2) An electric shower heats the water instantly, so the hot water supply is unlimited. If your supply eventually runs cold, it's obviously fed from the hot tank.
So I agree with brewerdave that it's either an isolator from a previously installed electric shower, or some other electrical device in the bathroom. Have you checked at the CU to see if there is a dedicated circuit marked 'shower?
Unless there's a pumped shower (which you'd hear starting up, or notice the difference in noise and pressure with it not starting up with the isolator off)), the isolator is doing nothing, so you can leave it off.
So, in summary, you don't have a combi boiler, and your hot water is heated by gas (unless you use the immersion).

aintshesweet

brewerdave wrote: »

Pull cord could be for either:_
a) extractor fan - have you got one which no longer works? (you would hear it running if it was still live)
or b) isolator for electric shower - have you been in your house very long? If not, did the previous owner remove an electric shower (they cost a fortune to run!!) and use boiler supplied hot water.
or c) Isolator switch for shower pump -Was the shower originally at a higher pressure?

Hmmm.. thanks for this!

Definitely no extractor fan in the bathroom, that would've been my first guess. No idea if the previous tenant had an electric shower - surely that would've left a right mess behind? There are some tiles which appear to have been drilled into, I guess, it could be that there was a unit on the wall.
Definitely no change in pressure - so could be a broken shower pump... wonder how I find out where the pump would be?!

Macman, by CU you mean the circuit board with all the flipswitches?

Definitely no noise when it's turned on (like sounds of a pump or pressure humming), although the red light does go on.

I'm going to go and run more experiments and check the circuit board. Thanks for the input!