Hot water Cylinder help.

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sep11guy

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# 173828 8-Jun-2015 09:39

Hi Team,

I need a bit of help / advice from you regarding hot water cylinder.

for past 2 months i have got quite a high power , and we haven't yet started to use the heaters yet for winter.

So i talked to a few people and figured it must be the hot water cylinder so got the Electrician in, who said the thermostat was faulty and changed it.

There has been a slight improvement but not that much. So i carried out monitoring for a week and this is what i found :

Over night, with no appliances used, the power consumption was aprox 15kwh ( for night duration approx 6-8 hrs )

after changing to new thermostat , no appliances used, over night is now stable at 9kwh ( same as above for night duration approx 6-8 hrs )

Now, Day time when there is again no appliances being used, usage is average 10-11 kwh ( for std 8hr working day )

I did another test with hot water switch off at MAIN Elec Board, and all appliances switched off ( apart from fridge, cellphones ) , power usage was 1kwh

So I kinda have figured out that the issue is hot water. I feel that the "standby " power consumption by the current hot water cylinder is way too high, which is approx 9 +10 = 19-20 kwh for 1 day.

But i just need to confirm that is my conclusion corrrect. What do you think , am i on the right track assuming that the hot water is the cause of this situation.

What would a average hot water cylinder consumer whilst on standby / what would a brand new one consume.

Could any one perhaps take a small reading when they go to office , and one when they come back and tell me whats the consumption.

Reason being this will immensely help me to decide, if its time to get a new cylinder - as this quite a expensive affair. It could cost me upto say $2k for getting new one done.

Appreciate your help,

Cheers !!

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# 1319148 8-Jun-2015 09:52

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to see if it is the hot water cylinder, turn it off and leave it over night and see what happens.

Are you sure that its not leaking? if it is then there will be wasting hot water and needing to be reheated ie using power

sep11guy

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# 1319150 8-Jun-2015 09:53

Jase2985: to see if it is the hot water cylinder, turn it off and leave it over night and see what happens.

Are you sure that its not leaking? if it is then there will be wasting hot water and needing to be reheated ie using power

Yeah I already did that, and mentioned in my original post :: I did another test with hot water switch off at MAIN Elec Board, and all appliances switched off ( apart from fridge, cellphones ) , power usage was 1kwh

Also, additional notes :

House is a small 3 bed home, hot water cylinder is from 1965

timmmay

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# 1319166 8-Jun-2015 10:02

15kwh is heaps. I use 5kwh each weekday morning around the time we're having showers. That includes having two heat pumps on for half an hour. We use around 30 units per day - closer to 40 on weekends, most like 25 on weekdays.

I could give you half hourly usage if that's helpful.

Given switching off your hot water drops your usage significantly I suspect you're on the right track. Get on on the roof and check the overflow pipe - see if there's water coming out or recent evidence of water. Be super careful, rooves can be slippery this time of year.

linw

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# 1319167 8-Jun-2015 10:03

Errm, Jase, he did turn it off.

Electric heating is pretty simple so there aren't many ways one cistern can be more efficient than another. One factor would be insulation. You need to tell the forum about that.

But, generally, greater power in equals greater water temp. Would be helpful if you put a thermometer under your hot water tap to measure that.

There are real experts here who will chime in I am sure.

sep11guy

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# 1319173 8-Jun-2015 10:15

timmmay: 15kwh is heaps. I use 5kwh each weekday morning around the time we're having showers. That includes having two heat pumps on for half an hour. We use around 30 units per day - closer to 40 on weekends, most like 25 on weekdays.

I could give you half hourly usage if that's helpful.

Given switching off your hot water drops your usage significantly I suspect you're on the right track. Get on on the roof and check the overflow pipe - see if there's water coming out or recent evidence of water. Be super careful, rooves can be slippery this time of year.

My last bill , was around 29kwh per day, but going by history, for us its way way to much cause I know that as the bill is higher by approx $80 ( before that it was higher than $160 , which was before i replaced thermostat )

I dont want that intricate half hourly usage - if you could just please take 2 readings for me . 1) when you go to office , pls note down whats the meter reads . 2) when you come back home what does the meter reads. thats all ( this is assuming that no one stays at home during normal business hrs ) .

This would greatly help me to decide if my hot water cylinder is consuming way too much energy for just being on standby

HaggisKiwi

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# 1319176 8-Jun-2015 10:16

House is a small 3 bed home, hot water cylinder is from 1965

40 years is pretty good going for a HWC! We had our 1974 model replaced a couple about 5 years ago when it shat itself, fortunately when plumber & sparky were on site doing our bathroom renovations.

Might be that your HWC has finally given up the ghost & it's internal elements are burning out. What remains is trying to do the whole job & using a lot more power to provide the how water you're used to.

Get a plumber/sparky in to check the HWC, but based on what you've said it looks like you many need to be budgeting to spend >$1k on replacing your HWC.
In our case, our replacement ended up saving us average $20 p/m over the year.

sep11guy

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# 1319179 8-Jun-2015 10:20

linw: Errm, Jase, he did turn it off.

Electric heating is pretty simple so there aren't many ways one cistern can be more efficient than another. One factor would be insulation. You need to tell the forum about that.

But, generally, greater power in equals greater water temp. Would be helpful if you put a thermometer under your hot water tap to measure that.

There are real experts here who will chime in I am sure.

Thanks for your replies, there is no insulation currently, but the home was insulated fully top and bottom few years back and our bills have gone up only for past 2 months.

water temp - last week the elec came and when he changed the thermostat , he first set it to 60C, but then we said it was way too hot, and then he came back next day and he changed it to 55deg C.

andrewNZ

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# 1319181 8-Jun-2015 10:22

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My money is on a leak/overflow problem.

Location: Dunedin

BTR

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# 1319183 8-Jun-2015 10:23

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I am guessing that by the date of your HWC thats it will be low pressure, have a look at the overflow pipe on the roof and male sure water isn't shooting out, if so the temp thermostat isn't working. I know you have replaced it but the replacement could be faulty.

Based on the age of your cylinder I would replace it, with a brand new cylinder. That way you have something thats more energy efficient because its better insulated and its internals are new.

I replaced my old 180L low pressure HWC with a brand new 300L main pressure cylinder 3-4 years ago and my power bills dropped.

sep11guy

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# 1319184 8-Jun-2015 10:27

HaggisKiwi:
Get a plumber/sparky in to check the HWC, but based on what you've said it looks like you many need to be budgeting to spend >$1k on replacing your HWC.
In our case, our replacement ended up saving us average $20 p/m over the year.

A electrician did come in and change the thermostat, which helped the stand by go down from 15kwh to 9kwh on night usage ( when there is no hot water being used at home )

but overall consumption is still high, considering that hot water is consuming approx 9+11= 20kwh just for standing and not providing us hot water ( ie no one using hot water)

sep11guy

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# 1319186 8-Jun-2015 10:29

andrewNZ: My money is on a leak/overflow problem.

Do you think that its worth getting this checked ( would this be a plumbers work ? ) before i assume my studies and go on replacing the whole cylinder . Cuz changing the cylinder is quite a expensive affair ( 1.5-2k approx, from what i have heard )

sep11guy

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# 1319189 8-Jun-2015 10:30

I replaced my old 180L low pressure HWC with a brand new 300L main pressure cylinder 3-4 years ago and my power bills dropped.

Thanks for your help, can you please advice what did it cost you approx to get new one installed.

timmmay

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# 1319191 8-Jun-2015 10:30

sep11guy: I dont want that intricate half hourly usage - if you could just please take 2 readings for me . 1) when you go to office , pls note down whats the meter reads . 2) when you come back home what does the meter reads. thats all ( this is assuming that no one stays at home during normal business hrs ) .

This would greatly help me to decide if my hot water cylinder is consuming way too much energy for just being on standby

The half hourly usage shows that on Thursday I used 3.16 units between 7am and 5pm, and on Friday I use 2.95 units.

Note that because we have showers at 6am and 6pm the water heater has finished by 7am so it's just maintaining temperature during the day. I only see small blips, plus the constant ticking over of things like the fridge. I can see 4-5 units used between 6 and 7am. Most of our power use is 6-7am and 6-10pm.

andrewNZ

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# 1319195 8-Jun-2015 10:33

BTR: I am guessing that by the date of your HWC thats it will be low pressure, have a look at the overflow pipe on the roof and male sure water isn't shooting out, if so the temp thermostat isn't working. I know you have replaced it but the replacement could be faulty.

Based on the age of your cylinder I would replace it, with a brand new cylinder. That way you have something thats more energy efficient because its better insulated and its internals are new.

I replaced my old 180L low pressure HWC with a brand new 300L main pressure cylinder 3-4 years ago and my power bills dropped.

I'm pretty sure they'd know if the cylinder was boiling, and they've stated the usage went down after the thermostat was changed.

That's also not the only reason for water to be coming out the top. If the Ajax valve is dodgy, there may be a small, barely noticable at a distance, amount of water overflowing. This would significantly increase the amount of power used.

Location: Dunedin

Aredwood

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# 1319197 8-Jun-2015 10:34

As Timmay said you have a water leak. Most likely from the cylinder vent pipe on the roof. Or if you don't have an open vent pipe. There will be a relief valve that will be constantly discharging hot water. And if you are unlucky you will have a copper pipe that is cast into a concrete floor slab that has a leak. If this is the problem best long term fix is to abandon the leaking pipe and install a whole new one.

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