Heat up water tank every night or every other night?

JackieChang · 21-11-2020 08:20AM #1

I have a night meter and one of those E7 water heater control panels: http://www.adverts.ie/333618

The timer is set to come on at 3am and off at 8am. I have a night meter.

I turned it off one morning to test the insulation and found that we had plenty of hot water for two days of showers, all from the one charge overnight. The tank is very well insulated.

Now the question is, would it be more cheaper turn it on for one night, off for the other night, on the next night etc. So instead of it being on 365 nights a year it's only on 180 nights a year? By the second night it would be heating the water up from cold ish.

Or would it make any difference at all? The tank has a thermostat set to 55 degrees so I'm guessing every night it's just topping it up slightly and not actually blasting the water with the element non stop for 5 hours.

I'm in an all electric house and trying to get the bills down a bit.

21-11-2020 08:27AM

Can't answer your questions but you need to have your tank at 60 minimum to prevent the risk of. Legionnaires disease

salmocab · 21-11-2020 08:37AM

JackieChang wrote: »

I have a night meter and one of those E7 water heater control panels: http://www.adverts.ie/333618

The timer is set to come on at 3am and off at 8am. I have a night meter.

I turned it off one morning to test the insulation and found that we had plenty of hot water for two days of showers, all from the one charge overnight. The tank is very well insulated.

Now the question is, would it be more cheaper turn it on for one night, off for the other night, on the next night etc. So instead of it being on 365 nights a year it's only on 180 nights a year? By the second night it would be heating the water up from cold ish.

Or would it make any difference at all? The tank has a thermostat set to 55 degrees so I'm guessing every night it's just topping it up slightly and not actually blasting the water with the element non stop for 5 hours.

I'm in an all electric house and trying to get the bills down a bit.

It would make very little difference really as yes it just heats to the set temp and turns off. A better plan would be to maybe shorten the on time by maybe an hour. Although once the water is warm it probably wouldn’t make much difference anyway.

Pkiernan · 21-11-2020 08:40AM

55 degrees is not hot enough .

You should have it at 65

Wearb · 21-11-2020 09:00AM

The best and most economical use would be just to heat enough water for each days use. Try it for an hour each night to see how that works out.

The heat loss from your cylinder ("wasted" energy) will increase with the temperature it's heated to and quantity heated.

JackieChang · 21-11-2020 09:49AM

Pkiernan wrote: »

55 degrees is not hot enough .

You should have it at 65

Actually it's at 60 degrees not 55, just checked there.

Wearb wrote: »

The best and most economical use would be just to heat enough water for each days use. Try it for an hour each night to see how that works out.

Just checked the manual of the E7 timer, apparently the shortest heating time I can reduce it to is 4 hours. It currently heats up for 5 hours so I can only reduce it by 1 hour max. Oh well. Seems a bit excessive, it's not a huge tank.

Jesus these old night storage / E7 / all-electric apartments are a right pain in the arse. There's so much fiddling around with settings. I can imagine how some people can rack up huge bills if they don't take the time to google how everything works. My uncle who is the worst at technology in the world wasn't using his night rate at all, just the boost at peak times during the day. "Hmm I need to do a bit of washing up, let me throw on boost for 2 hours". Didn't have a clue what the E7 timer knob was for and it was switched off.

Pkiernan · 21-11-2020 09:50AM

Its at least 60 degrees, you should set it to 65, and in a well insulated tank you won't see a noticable difference in cost.

Wearb · 21-11-2020 10:03AM

Surely those horstman timer segments allow for less than 4 hours? If that was the case there would only be 6 segments in that dial.

John.G · 21-11-2020 10:18AM

Don't think 4 hrs on E7 will waste electricity. A 3kw element would heat 260 litres from 25C to 65C in 4 hrs or 100 litres in 1.6 hrs, so assuming a 150 lire HW cylinder the heating time is only 2.3 hrs before the thermostat switches out the element. If you can set your timer to the last 4 hours you will save a few watts.

JackieChang · 21-11-2020 10:31AM

Wearb wrote: »

Surely those horstman timer segments allow for less than 4 hours? If that was the case there would only be 6 segments in that dial.

Just double checked. It's actually a minimum of 4 and a half hours according to the manual.

Wearb · 21-11-2020 10:38AM

JackieChang wrote: »

Just double checked. It's actually a minimum of 4 and a half hours according to the manual.

As you can see from John's reply it's not such a big deal. Just have a well insulated cylinder or good cover.
You could also experiment wit just using the sink element to see if this satisfies your needs.

10-10-20 · 22-11-2020 07:58PM

As it's electrical, has a temperature control and is well insulated, you have few losses. You can heat it nightly.
If you used gas or oil and if the boiler was a distance away from the hot-tank, then the losses might be worth considering modifying the heating frequency for.

Heat up water tank every night or every other night?

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