Please help me understand electric water heaters
July 30, 2017 2:55 PM Subscribe
How are electric water heaters and their timers (UK) supposed to work? Is this one malfunctioning? Or is there something I am missing? timer shown here
I have an electricity tariff where electricity is supposed to be cheaper at night. I have the water heater timer shown above. I have the timer set (little blue pins on dial pulled out, not pushed in) for 4-5am in the morning. My Loop electricity monitor tells a different story. It shows the water heater comes on every two hours ignoring the timer and uses 0.4 kWh power every time. When I switch the timer completely to off on the big white switch the two hourly peaks disappear. When I switch it back on again I get a large immediate peak (eg. 1.43 kWh) like a thermostat is telling it to reach a certain temperature - again the timer which should be determining when it comes on is ignored. Is the timer broken or is there something I just don't understand about how this is all meant to work? Thanks!
I have an electricity tariff where electricity is supposed to be cheaper at night. I have the water heater timer shown above. I have the timer set (little blue pins on dial pulled out, not pushed in) for 4-5am in the morning. My Loop electricity monitor tells a different story. It shows the water heater comes on every two hours ignoring the timer and uses 0.4 kWh power every time. When I switch the timer completely to off on the big white switch the two hourly peaks disappear. When I switch it back on again I get a large immediate peak (eg. 1.43 kWh) like a thermostat is telling it to reach a certain temperature - again the timer which should be determining when it comes on is ignored. Is the timer broken or is there something I just don't understand about how this is all meant to work? Thanks!
Those tooth wheel timers usually work in the exact opposite manner to how you've guessed. 'Out' means Off. Basically you've told it to come on and maintain hot water in the tank for 23h per day.
posted by genghis at 3:51 PM on July 30, 2017 [6 favorites]
posted by genghis at 3:51 PM on July 30, 2017 [6 favorites]
Out means on in the two timers I have (one for a combi boiler and one for a timer light switch).
It does sound like it's behaving the opposite way to what you expect, or that the timer is just being ignored.
In my combi boiler there are dials to set a 'target' temperature for both the heating and the hot water. When the system is running then the boiler will try to maintain that temperature.
In my case the timer is only for the heating, not the water. When the hot tap is running the boiler kicks in to heat the water, regardless of the timer setting.
posted by toamouse at 11:56 PM on July 30, 2017 [2 favorites]
It does sound like it's behaving the opposite way to what you expect, or that the timer is just being ignored.
In my combi boiler there are dials to set a 'target' temperature for both the heating and the hot water. When the system is running then the boiler will try to maintain that temperature.
In my case the timer is only for the heating, not the water. When the hot tap is running the boiler kicks in to heat the water, regardless of the timer setting.
posted by toamouse at 11:56 PM on July 30, 2017 [2 favorites]
According to the manual, out means the "economy period" is on. Which I think means that genghis is right.
posted by flibbertigibbet at 3:57 AM on July 31, 2017
posted by flibbertigibbet at 3:57 AM on July 31, 2017
I have two timers which are similar but for plugging things into. They aren't the same brand as each other or yours. On both out means off and in means on. Genghis is correct, you're setting it to switch your heater on for 23 hours a day and the peaks correspond to it bringing the water up to temperature then maintaining it.
posted by *becca* at 4:28 AM on July 31, 2017
posted by *becca* at 4:28 AM on July 31, 2017
Response by poster: I thought that manual said the opposite of Genghis? Set the economy period by positioning the relevant tappets. In towards the centre is off, out towards the outer edge is on. I've tried setting it the Genghis way but now get a steady 0.3kWh draw instead of the two hourly peaks. I'm baffled.
posted by Flitcraft at 8:13 AM on July 31, 2017
posted by Flitcraft at 8:13 AM on July 31, 2017
Yes, but "economy period" means that it will try to use less/cheaper/more efficient electricity--so "out" means "I want to try to preserve electricity".
posted by flibbertigibbet at 11:05 AM on July 31, 2017
posted by flibbertigibbet at 11:05 AM on July 31, 2017
More questions than answers below I'm afraid but hopefully they can help you track it down.
Have you tested it by making it come on and off during the time that you are sitting in front of it? I'm with you that the manual says the way you have it setup is correct.
Is the system only controlling your water heater or does it do the radiators as well?
It looks like the Loop monitor would be tracking all of the electricity use in your home, not just the boiler - is there a chance that it's picking up some other energy usage and the boiler is a red herring?
posted by toamouse at 11:08 AM on July 31, 2017
Have you tested it by making it come on and off during the time that you are sitting in front of it? I'm with you that the manual says the way you have it setup is correct.
Is the system only controlling your water heater or does it do the radiators as well?
It looks like the Loop monitor would be tracking all of the electricity use in your home, not just the boiler - is there a chance that it's picking up some other energy usage and the boiler is a red herring?
posted by toamouse at 11:08 AM on July 31, 2017
The Economy Period is the time that the energy is cheaper... The point of this system is that you programme it to be on during the economy period so that you can store energy for use throughout the day when it would otherwise be more expensive.
You therefore want it to be off outside of the economy period.
NPowerEconomy 7 periods
posted by toamouse at 11:13 AM on July 31, 2017
You therefore want it to be off outside of the economy period.
NPowerEconomy 7 periods
posted by toamouse at 11:13 AM on July 31, 2017
Response by poster: Have you tested it by making it come on and off during the time that you are sitting in front of it? I'm with you that the manual says the way you have it setup is correct.
By switching the position of the pins yes - when pins are 'out' the blue 'economy' light comes on even though it' s not in the economy 7 time period.
Is the system only controlling your water heater or does it do the radiators as well?
Only water heater
It looks like the Loop monitor would be tracking all of the electricity use in your home
Yes however I use very little electricity in summer and nothing of note when I'm out of the house but the water heater and fridge and by turning water heater off completely I can see the fridge is not causing these patterns (by big white off switch - not timer pins). Put the water heater back on and the patterns re-appear, put it off they disappear.
posted by Flitcraft at 1:20 PM on July 31, 2017
By switching the position of the pins yes - when pins are 'out' the blue 'economy' light comes on even though it' s not in the economy 7 time period.
Is the system only controlling your water heater or does it do the radiators as well?
Only water heater
It looks like the Loop monitor would be tracking all of the electricity use in your home
Yes however I use very little electricity in summer and nothing of note when I'm out of the house but the water heater and fridge and by turning water heater off completely I can see the fridge is not causing these patterns (by big white off switch - not timer pins). Put the water heater back on and the patterns re-appear, put it off they disappear.
posted by Flitcraft at 1:20 PM on July 31, 2017
IANAPlumber, but I'm sort of enjoying digging into the question.
Something that I thought was weird was this line in the manual: "During off peak periods, the economy light will illuminate" - it doesn't say 'during the off peak periods the boiler will be active' - it implies that you are just telling the system when the off peak period is. As in my NPower link above, the period varies across the country so that sort of makes sense.
So - I think your theory that there's a minimum temperature that it is trying to maintain (to avoid Legionnaires' disease) might be right, although I can't find anything to back that up from the information you have given. Is there a model number for the water heater itself? Does it have any controls other than the timer, such as a thermostat?
One thing I'd try is to extend the economy period to cover a longer part of the 7 hour economy period so that the water can get heated for longer overnight and maybe better maintain its temperature throughout the day.
Of course the risk there is that it just uses more energy in total, so up to you!
posted by toamouse at 2:03 PM on July 31, 2017
Something that I thought was weird was this line in the manual: "During off peak periods, the economy light will illuminate" - it doesn't say 'during the off peak periods the boiler will be active' - it implies that you are just telling the system when the off peak period is. As in my NPower link above, the period varies across the country so that sort of makes sense.
So - I think your theory that there's a minimum temperature that it is trying to maintain (to avoid Legionnaires' disease) might be right, although I can't find anything to back that up from the information you have given. Is there a model number for the water heater itself? Does it have any controls other than the timer, such as a thermostat?
One thing I'd try is to extend the economy period to cover a longer part of the 7 hour economy period so that the water can get heated for longer overnight and maybe better maintain its temperature throughout the day.
Of course the risk there is that it just uses more energy in total, so up to you!
posted by toamouse at 2:03 PM on July 31, 2017
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posted by Flitcraft at 2:58 PM on July 30, 2017