Is this logic correct? Off peak hot water heating.

Forums › Home Workshop DIY › Is this logic correct? Off peak hot water heating.

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k1w1k1d

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#2240588 18-May-2019 16:33

Why does he turn the cylinder off?

We are on a day/night plan with Genesis. They turn the cylinder on for several hours, sometime between 9pm and 7am. We don't have to do anything.

We also run the dishwasher after 9pm to get the cheaper power rate.

ubernoob

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#2240626 18-May-2019 18:34

k1w1k1d:
Why does he turn the cylinder off?

We are on a day/night plan with Genesis. They turn the cylinder on for several hours, sometime between 9pm and 7am. We don't have to do anything.

We also run the dishwasher after 9pm to get the cheaper power rate.

We also run the washing machine when we go to bed and it's ready to hangout before work in the morning

k1w1k1d

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#2240676 18-May-2019 22:49

I turn the washing machine on when I get up at 6am, so it has finished before the day rate starts at 7am.

mattwnz

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#2240682 18-May-2019 22:56

What do people think of these Smart cylinders , which apparently can save up to 10% off heating bill?. https://rinnai.co.nz/Product/121/257/water-heating-hot-water-cylinders-rinnai-smart-cylinder-the-rinnai-smart-cylinder

Geektastic

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#2240694 19-May-2019 02:32

Is it possible to fit an insulation jacket to the outside? That would reduce loss further and save money. In the UK, they habitually insulate exposed hot water pipes too. Do they do that here?

Bluntj

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#2240708 19-May-2019 09:47

Geektastic: Is it possible to fit an insulation jacket to the outside? That would reduce loss further and save money. In the UK, they habitually insulate exposed hot water pipes too. Do they do that here?

Yes they do. Surprising they dont have one, yet go to extremes in managing the electricity it uses.

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JuanPerez

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#2242837 22-May-2019 04:54

From Vector's hot water load management FAQ’s:

Does it cost more to heat a hot water cylinder if it has been switched off by a load management system?

No. In fact, there may be marginally less electricity used overall if reheating a cold cylinder than keeping a cylinder at the temperature set point with uninterrupted electricity supply.

timmmay

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#2242888 22-May-2019 07:27

The hotter the water is the high the heat losses, so by switching it off there is less overall heat loss. Given power is cheaper at night I think turning it off at night is sensible. I doubt he'll save all that much, but a little.

He could have a timer installed, but that cost me $250 and was only worthwhile for the Electric Kiwi free hour of power. Even then the break even time is a year or more.

wellygary

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#2242914 22-May-2019 09:33

mattwnz:

What do people think of these Smart cylinders , which apparently can save up to 10% off heating bill?. https://rinnai.co.nz/Product/121/257/water-heating-hot-water-cylinders-rinnai-smart-cylinder-the-rinnai-smart-cylinder

Wow, there is so much spin on that page my head is still turning,

"In vacation mode the Rinnai Smart Cylinder will keep the water at a minimum temperature (6°C) to save power. This will also prevent the water from freezing in colder areas."

Maybe at Scot base this is a problem,

but I've looked after ski lodges on Mt Ruapehu, And I have never seen a regular hot water cylinder freeze (even in the depths of winter with a building being un heated and un attended for weeks....

+keeping you cylinder warm is fine, but what about the rest of your plumbing, which will freeze up long before the cylinder solidifies...

mclean

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#2242941 22-May-2019 09:54

timmmay: The hotter the water is the high the heat losses, so by switching it off there is less overall heat loss. Given power is cheaper at night I think turning it off at night is sensible. I doubt he'll save all that much, but a little.

He could have a timer installed, but that cost me $250 and was only worthwhile for the Electric Kiwi free hour of power. Even then the break even time is a year or more.

Exactly right. There will be less standing loss if the heater is off during the day, but the saving will be small. The only thing I would add is that if you use the HWC cupboard as an airing cupboard then it's the standing losses that provide the heat, so turning it off in the day reduces that. Noticeable but not by much.

raytaylor

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#2245535 25-May-2019 21:12

k1w1k1d:

Why does he turn the cylinder off?

We are on a day/night plan with Genesis. They turn the cylinder on for several hours, sometime between 9pm and 7am. We don't have to do anything.

We also run the dishwasher after 9pm to get the cheaper power rate.

If its just a controlled plan, it will probably be ripple controlled by your local lines company and not Genesis. The lines company is supposed to provide a minimum of ~18 hours heating time per day (depends upon local lines company) and so there is a high chance they will switch it on during the day, with your thermostat kicking it in if you had used the hot water in the morning.

The controlled/ripple control function is a result of your local lines company desire to shed load and move it to offpeak times.

The on/offpeak pricing is more a market feature / pricing game that the electricity companies play, which can often be based on the load shedding desires of your local lines company but they dont always match up.

Ray Taylor

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raytaylor

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#2245536 25-May-2019 21:13

Geektastic: Is it possible to fit an insulation jacket to the outside? That would reduce loss further and save money. In the UK, they habitually insulate exposed hot water pipes too. Do they do that here?

The typical ones you buy from M10 / Bunnings / Warehouse are not very effective.

https://www.youtube.com/watch?v=HJYrMdSiaQU

This is a typical canadian one showing similar results.

Ray Taylor

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Gordy7

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#2245585 25-May-2019 21:46

I have my hot water heating on a controlled plan that has a cheaper rate.

I have a Smart Meter with Pulse Energy.

Does the Smart Meter give the power company the option to switch the water heating to full rate metering during the day?

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nickb800

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#2245751 26-May-2019 06:01

Gordy7:

I have my hot water heating on a controlled plan that has a cheaper rate.

I have a Smart Meter with Pulse Energy.

Does the Smart Meter give the power company the option to switch the water heating to full rate metering during the day?

Short answer, no.

Assuming your power bill details your hot water usage separately, then it will be metered separately, and count all hot water/controlled usage equally regardless of what time it is on. The cheaper rate is more a reflection of their right to interrupt your hot water/controlled supply, rather than a specific time

bfginger

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#2252762 6-Jun-2019 09:16

Bluntj:
Geektastic: Is it possible to fit an insulation jacket to the outside? That would reduce loss further and save money. In the UK, they habitually insulate exposed hot water pipes too. Do they do that here?

Yes they do. Surprising they dont have one, yet go to extremes in managing the electricity it uses.

$55 to buy a Greenstuf polyester cylinder insulation cover.

Copper pipe insulation is cheap. The copper pipes adjacent to the cylinder are radiators if left uncovered.

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