Hot water even though ST9400C hot water program is off

[nigelfa]

Hello,

I moved to the UK from India and I haven't used boilers and central heaters prior to this, so this question may be a bit dumb.


The place I moved to in April has an Ideal HE12 boiler and a Honeywell ST9400C. The hot-water program and the heating program on the ST9400C were both off till today.

I setup the hot water and heating programs today and I can deduce that the heating is working fine based on
-green LEDs on the controller, which were off earlier but are now on
-and from my room heaters that are now warm as well

However, I have had hot water since I moved in and I changed the thermostat on the boiler some months ago to raise the water temperature which worked then.

So, what I don't understand is how and why I have had hot water, when it (and the heating) were both switched off at the controller until today?

I did find an immersion switch on the wall next to the controller, but that has also been off since April, so I think that can be ruled out.

Any help or explanation would be most welcome.

 

[JohnD]

I expect you have a hot water cylinder.

It stores water, which the boiler heats up during the "HW on" period.

You can then use it from the hot taps until it is all used up.

The size of the cylinder determines how much there is, and your usage determines when it runs out.

please post a photo of yours, including the pipes, cables and devicesaround it. And of the timer and the immersion switch.

Looking at your Actual gas and electricity meter readings (not estimates) what were they when you moved in, and what were they when you checked them?

 

[nigelfa]

Thanks for replying JohnD









There's no timer on the boiler. The immersion switch is to the left and below the controller. (first pic)

The boiler is in the kitchen (last pic) while the rest of the system is in the utility room.

I haven't checked the meters recently, but these are the last 2 actual readings that I have.

19th may reading
Electricity: 14267
Gas:2436

18th June reading
Electricity:14510
Gas:2465

What would the "HW on" period be controlled by - ST9400C, boiler thermostat or something else ?

 

[JohnD]

your usage of 30 cubic metres of gas in a month would be plenty to heat a HW cylinder in summer (at that time of year you would not have been using the central heating)

You were using 8kWh of electricity per day, which is not much so I don't believe the immersion heater will have been running.

So I expect your boiler has been heating the cylinder.

Did you never hear it start up?

The Honeywell ST9400C is a timer (programmer) that controls the boiler "on" periods.

 

[nigelfa]

Yes I have noticed the a louder hum from the boiler after the hot water taps have run, so I assume it has been starting up . What I don't understand is what's triggering it. The hot water and heating on the programmer were turned off till today, so wouldn't that mean that the boiler should not have come on ? Or does the boiler keep the water at a certain temperature, in which case, does the hot water program on the controller serve any purpose ?

 

[JohnD]

Either the timer was "HW on", or is faulty, or there is some other control. It might have been incorrectly wired if it was done by an unskilled person. The Honeywell control is a good one and unlikely to go wrong.

btw, for economy, you'll use a bit less gas if you set HW on twice a day, for about an hour each, starting just before the bathroom rush.

Your gas bill will be much higher in winter when you have the heating on, it could be five or ten times as much as your summer usage, so if you are used to a hot climate, keep the doors (including internal) shut, and turn down the temperature overnight, maybe 15C. The heating can be off when the house is unoccupied, or turned down to 12C, and use the timer to have it come on half an hour before you will be getting home or getting out of bed.

Don't hang wet washing over radiators, it will cause damp and mould. The upstairs windows should be opened each morning for half an hour or so.