Boiler Hot Water Timer - How long is yours on for?

System

Cardew wrote: »

I get the impression some people think that having the hot water on for one hour a day costs one tenth of having it on for 10 hours a day.

It is the same as standby consumption for TVs etc, some people think that switching them off at the mains is a huge contributor to electricity savings.

I tend to avoid questions like these as no two households are the same so any cost comparisons are useless.

As far as turning things off rather than leaving them in standby is concerned, the overnight cost can be very real. I have a TV, Sky box and a play bar. The measured standby wattage is c.40 Watts. I happen to think that it is worth turning them off overnight.

Cardew

Hengus wrote: »

As far as turning things off rather than leaving them in standby is concerned, the overnight cost can be very real. I have a TV, Sky box and a play bar. The measured standby wattage is c.40 Watts. I happen to think that it is worth turning them off overnight.

40 watts is huge.

We are in danger of getting off the subject(my fault!) I was just trying to make the point about perspective.

reeac

Hengus wrote: »

I tend to avoid questions like these as no two households are the same so any cost comparisons are useless.

As far as turning things off rather than leaving them in standby is concerned, the overnight cost can be very real. I have a TV, Sky box and a play bar. The measured standby wattage is c.40 Watts. I happen to think that it is worth turning them off overnight.

40 watts for 8 hours is 0.3 kWh or 4 pence per night.

System

reeac wrote: »

40 watts for 8 hours is 0.3 kWh or 4 pence per night.

Or £14.50 a year which equates to 5% of my annual electricity bill. Every little helps.

To get back on to the topic, my daily gas consumption for hot water and a gas hob has averaged 7kWhs a day. HW heating is available for 8 hours a day and hot water temperature is maintained in the range 57 to 62C. Storage is a 250Litre unvented tank.

Ilona

I turn my hot water on when I want a bath, and my heating on when I am cold. Don't use the timer. I am not a creature of habit.

Ilona

WobblyDog

At present I've got 2 time windows, but the boiler will only fire-up if the temperature of the water cylinder is low enough:
07:00 to 08:00
15:00 to 15:40
I'm trying to configure it so that it "skips" the afternoon burn, unless the ambient temperature is quite low. There's just me in the house, so demand for hot water is fairly low and predictable.

The boiler is about 10 metres from the hot water cylinder, so my theory is that quite a lot of metal and water in the loop needs to heat up before the water cylinder temperature rises, so minimising the number of burns per day will save money. I'm using a Raspberry Pi to measure temperatures at various points and estimate gas consumption, and so far my theory seems to be right.

System

WobblyDog wrote: »

At present I've got 2 time windows, but the boiler will only fire-up if the temperature of the water cylinder is low enough:
07:00 to 08:00
15:00 to 15:40
I'm trying to configure it so that it "skips" the afternoon burn, unless the ambient temperature is quite low. There's just me in the house, so demand for hot water is fairly low and predictable.

The boiler is about 10 metres from the hot water cylinder, so my theory is that quite a lot of metal and water in the loop needs to heat up before the water cylinder temperature rises, so minimising the number of burns per day will save money. I'm using a Raspberry Pi to measure temperatures at various points and estimate gas consumption, and so far my theory seems to be right.

Two comments:

1. Most HW set ups using a cylinder are based on a temperature set by the user. Each time hot water is drawn off, the boiler kicks in. Boilers often have a pre-burn routine that wastes some gas before the boiler fires. The answer to reduce boiler firings is to have a set up that allows the cylinder temperature to drop some degrees C before the boiler re-heats the cylinder; that is, a temperature range.

2. Most modern boilers have a built in HW over-run to ensure that very hot water is removed from the heat exchanger: usually, in the range 1 to 2 minutes. If a shower, for example, needs a minimum input temperature of, say, 60C then setting the cylinder at 58C during the summer will most likely get the cylinder close to 60C. In the Winter, any HW over-run in a hot water priority set up is distributed around the CH loop.

Blackbeard_of_Perranporth

Boiler for CH on 24 hours a day and water heater on 10 minutes in morning and 10 minutes in evening.