Hot water cylinder timers

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Scott3

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#296389 13-Jun-2022 13:55

Just moved to a time of use power plan (covered in power plan shopping thread).

Plan is (incl gst)

Standard user:

Day: $2.22655

kWh Peak: $0.23207 (7am-11am + 5pm-9pm weekdays)
kWh Off Peak: $0.142945 (11am - 5pm weekdays + 7am - 11pm weekends)
kWh Night: $0.116035 (11pm - 7am every day)

As such a pretty strong incentive to move my hot water into night time (but I think my 180L cylinder isn't enough to consistently last all day, so expect to need a boot in the middle of the day off peak time).

Ideally I would run on from 11:10am - 4:50 pm & 11:10pm to 6:50am weekday's, and 11:10pm to say 6pm on the weekends (As to shift a 5 hour period of hot water use to night rate)

Anybody know of a better product than this to get the job done?

www.kiwisparks.co.nz/products/bluetooth-hot-water-cylinder-control-kit

Should I be looking at more smarts?

Is the timer only staying alive for 8 hours going to mean that every time there is some network event where all the hot water cylinders get rippled out for several hours going to require a reset? Does this happen often?

Scott3

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#2926058 13-Jun-2022 14:06

Here is a wifi alternitive:

www.kiwisparks.co.nz/products/bluetooth-hot-water-cylinder-control-kit

timmmay

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#2926059 13-Jun-2022 14:09

It's generally set and forget, you don't really need any smarts. I have a timer in my switchboard, if I want to change it I get out a ladder and change it there. About three times a year I need to give the hot water a boost, easy, it has an "on" button. If a Bluetooth controller is about the same price as a regular controller then sure as the ability to boost from your phone may be handy occasionally, but don't pay heaps more for it. I could look what kind of timer I have later.

I don't know what size our cylinder is, medium sized is all I can say. Three hours heating @ 3kw will heat it from pretty much cold. Our free hour is 5am, I turn it on from 4am to 6.55am, then boost it 4 - 4.55pm. The afternoon boost isn't necessary most days, but if we all have showers after the 6.55am switch-off time it can be handy.

I don't know if ripple control is every used in practice. If it is then heating overnight is pretty safe. We've never had a cold cylinder.

Don't forget to change the timer's time when daylight savings changes.

Scott3

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#2926082 13-Jun-2022 14:26

My circuit board was full when we brought the house, and we put two lighting circuits on on breaker (no issues with modern eco bulbs) to install a new feed when we had an induction cooktop put in.

Are going to have an EV circuit added (no need for dc leakage protection as it is in the EVSE), likely by changing the bathroom RCD (two bays) to one combined with the breaker.

So I don't think putting anything more in the switchboard is a go, unless we go for a full upgrade (which could be a good call).

We have a child who now likes her bath's deep, so use a lot of hot water. Bit weary that 180L might not be enough to even get us through 5pm - 11pm. But not much else to do other than to test it out.

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#2926085 13-Jun-2022 14:39

Ah, then the WiFi / Bluetooth timer seems good. WiFi has better range so I'd do that one personally.

I think our hot water cylinder is 250L, we typically have two people having baths in the evening most days, you might find the 180L cylinder does better than you expect but it depends on timing of things. If you can do the bulk of your heating at free / night rate then just top up at shoulder rate you should get good savings.

It takes longer to heat the water in winter. The winter water comes in at maybe 8 - 10 Celsius, in summer it's probably closer to 15.

eonsim

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#2926128 13-Jun-2022 15:42

Scott3:

Is the timer only staying alive for 8 hours going to mean that every time there is some network event where all the hot water cylinders get rippled out for several hours going to require a reset? Does this happen often?

Not sure, but at least if it's got wifi/BT with an app, the app can probably save the schedule and push it back out to the timer if it loses it. Better than having to redo the schedule each time...

gregmcc

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#2926151 13-Jun-2022 17:28

Scott3:

Is the timer only staying alive for 8 hours going to mean that every time there is some network event where all the hot water cylinders get rippled out for several hours going to require a reset? Does this happen often?

To take the existing HW off the controlled (Ripple) you WILL need to get your electrician to do this at your distribution board, otherwise the HW will be off when the ripple control is off and no way to do an override boost when your low on HW

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raytaylor

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#2926170 13-Jun-2022 18:44

We have our cylinder running through a ripple controller on the meter board, as well as a battery-backed timer in the hot water cupboard itself.

Being a 180 litre cylinder it has a 3000w element inside it.

Our offpeak power is from 9pm-midnight so I have it set to come on at 9pm and off at 1am.
I also have it come on for about 20 minutes in the morning from 6am to 6.20am.

However what I found is that each night, its always finished by 11pm with 3 guys in the house.
In the 9pm timeslot we always use more than 3kwh but in the 10pm timeslot its always under 3kw - so even with the heatpump running that means the cylinder is not running for the full 10pm hour.

Example

The timer I have used is one of these https://www.trademe.co.nz/a/marketplace/building-renovation/electrical-lighting/switches-switchboards/other/listing/3633234333

TM615-2

Make sure the timer is rated for a resistive load of 2x your actual element size at 230V.
This means if your cylinder is over 3200watts your going to be looking at some more expensive timers such as PDL or Schnider brand.
In my case, I am using a 30amp resistive rated timer for a (3000/230v)=13amp load so I am accounting for some specification sheet embellishments there and knowing that the relay contacts are nice and large reduces the potential for faults.

I had it mounted inside a HAGVD103NT plastic enclosure with a din rail mount at the back of the enclosure. It has enough space inside for wiring to fit around the sides of the timer. (Ideal electrical $25ish+gst)

Its been working really well.

The main reason for me was because our local lines company usually turns on the ripple control around 8pm but I wanted to delay it an hour longer until 9pm.

I have an electrician in the family but if i was paying full price for an electrician, the parts and labour would break even after only a few months.

Regarding wifi and cloud connectivity - if its battery backed you dont need it. The timer just needs to be set to turn on when your off-peak rates kick in, and keep going until the thermostat switches off the element. If you are still heating into your on-peak or shoulder time then sure thats just a cost you will have to deal with but by doing most of the heating during the off-peak then you have saved as much as you can anyway. Cloud control or wifi is not going to be changing the times you run your cylinder.

Interesting note: You can see from my example link above that our base load is 0.5kwh.
At 6am the cylinder kicks in again for a short 20 minute boost. The total hour is about 1.5kw so the extra 1kwh above the base load must be the cylinder element running at 3kw for the 20 minute limit. During that time it uses 1kwh of energy meaning we are loosing at least 1kw of heat between 10pm and 6am out of the cylinder.
I find that interesting because it shows just how much water costs to maintain at temperature even if you dont use it. In our case, at least 3kwh per day is spent on just maintaining the temperature.

Edit: To compensate for temperature losses and not reheating during the day, I decided to initially turn up the temperature of the thermostat by 5 degrees. With 180litres of water in the tank, thats an extra 1kwh being stored that could leak out as heat during the day. It was cheaper to buy that extra 1kw offpeak than to buy it during the day just to cover heat loss.
So with a short 6am boost in the morning, at 8am there is one shower and 6pm its still very hot for 2x more. It would handle much more - especially if anyone decided to have a shower or bath between 8pm and 11pm. It feels like there would be time for a further 70 litres to be heated from 10 to 70 degrees within the 9pm-midnight window above what we currently consume.

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#2926177 13-Jun-2022 19:06

Scott3:

Is the timer only staying alive for 8 hours going to mean that every time there is some network event where all the hot water cylinders get rippled out for several hours going to require a reset? Does this happen often?

Check your local lines company to see if they publish ripple control info. I have read of a couple that state they will guarantee at least 16 hours of water heating per day - or something to that effect.

So it would mean something like your timer is powered off for up to two 4 hour blocks or some other combination and you need to make sure your battery backup will recharge fast enough during the ripple on time. Probably not a concern but is something to watch out for.

I do recommend staying on ripple control though as its usually only turned off in the morning and evening and gives you a discount on your power plan, while you generally only want to heat during the offpeak when ripple is almost guaranteed to be on. So being on both a timer and ripple is a double-win for you.

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timmmay

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#2926181 13-Jun-2022 19:22

A low current timer with a high current relay, installed by an electrician, can work well.

SomeoneSomewhere

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#2926204 13-Jun-2022 20:08

I have a PDL cat 646E7 that you can probably have if you're near Wellington. (I don't think it does day/month/year though, which is necessary for automatically handling daylight savings. Not a major issue if you can lose an hour at either side, more of an issue if you're trying to aim for a free hour.)

Otherwise, a timer and contactor in a surface DIN box (e.g. PDL SE4 or equivalent with a lid) could be an option. Add a DIN switch/breaker (for isolation) if it's replacing the existing switch at the HWC.

Scott3

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#2930134 15-Jun-2022 21:37

Thanks everybody for the information.

SomeoneSomewhere:

I have a PDL cat 646E7 that you can probably have if you're near Wellington. (I don't think it does day/month/year though, which is necessary for automatically handling daylight savings. Not a major issue if you can lose an hour at either side, more of an issue if you're trying to aim for a free hour.)

Otherwise, a timer and contactor in a surface DIN box (e.g. PDL SE4 or equivalent with a lid) could be an option. Add a DIN switch/breaker (for isolation) if it's replacing the existing switch at the HWC.

Thanks, but I am based in Auckland.

I have used that timer before, pretty good functionality. Multiple timers, and day of the week combinations, would meet my needs for sure.

But as with all the timers with screens etc, the install location inside my hot water cup-board facing away from the door, with the space in front blocked by shelves, would be quite a chore to set.

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Scott3

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#2930136 15-Jun-2022 21:40

gregmcc:

To take the existing HW off the controlled (Ripple) you WILL need to get your electrician to do this at your distribution board, otherwise the HW will be off when the ripple control is off and no way to do an override boost when your low on HW

Happy to keep my hot water cylinder on controlled rate, just want to put a timer in series with that.

Will need a sparky to do some unrelated work involving the breaker box anyway.

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#2930278 16-Jun-2022 10:34

The timer doesn't necessarily have to go where the existing HWC switch is. Depending on layout, running a cable to the other side of the wall or in some capping to by the door is possible.

Several of the DIN rail timers are Bluetooth programmable I believe, so that could also be an option.