Digital timer for hot water

Forums › Home Workshop DIY › Digital timer for hot water - which one?

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Kickinbac

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#1497670 23-Feb-2016 11:02

I've programmed a few of these over the years. The small digital timers are a pain, the screen is small and instructions poorly written.

The mechanical timers are very simple and seem to be robust.

timmmay

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#1497773 23-Feb-2016 12:31

How about this: of those who've had timers fail, were they mechanical or digital? I've never used analog, I only have one digital - Theben. It's been working fine for a couple of years, switching a low load, 600W peak usually less.

Shoes2468

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#1497815 23-Feb-2016 13:12

Lemming:

Cant say I agree with a mechanical device with motors and plastic cogs being more reliable than an electronic device..

Electric Car vs Petrol/Diesel car

Lemming

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#1497824 23-Feb-2016 13:24

Shoes2468:

Electric Car vs Petrol/Diesel car

Not sure if you are agreeing with me or not :-)

Theclaytons

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#1534914 18-Apr-2016 12:47

trig42: My parents are looking for timer for their hot water cylinder.
They have solar panels, but not batteries (feeds back to grid).

It makes sense for them to be heating hot water during daylight, and turn it off overnight. I will look into the timers in the OP.

Hi,

I've recently had solar installed with a hot water timer as part of the package. The installer said he set the timer to power the hot water from 8.30am to 5pm every day to take advantage of the electricity generated from the panels. To me, this does not make sense for the following reasons:

1. I have night rate so my rates are 35c (day) and 13c (night) (incl. GST)

2. The HOT water takes about 2 hours to heat and uses around 6kW in the that 2 hours

3. The solar generates anything from 0kW to 3.42kW at any given time during the day - it averages around 1.5kW

So, using the information above, I believe I am better off to heat the HOT water at night using the night rate of 13c as opposed to usin the day rate less the solar generation.

Example 1 (night rate)

6kw of generation at 13c = 78c to heat hot water

Example 2 (day rate)

6kw of generation - 3kw for free and 3kw at 36c = $1.08

There are a lot of variables in solar generation so taking this out of the equation and getting my 10c per kw hour for excess generated i can actually get my effective night rate for solar hot water down to 48c

It seems to me, I'm best to use the solar during the day for everything else except HOT water due to the size of the hot water element. If it was a 1.5kw then it would make perfect sense....

Can anyone see anything wrong with my logic?

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timmmay

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#1534922 18-Apr-2016 12:54

Theclaytons:

Can anyone see anything wrong with my logic?

Suggest you ask a moderator to split your question off to a new thread, it's quite off topic.

You need a solar diverter, though that might not be its real name. This allows all your solar power to go into water heating without using mains power. Friend of mine has one, can find brand if you like. He uses it so it runs his three hot water cylinders and spa pools when the sun is shining.

gregmcc

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#1535114 18-Apr-2016 17:15

Theclaytons:

trig42: My parents are looking for timer for their hot water cylinder.
They have solar panels, but not batteries (feeds back to grid).

It makes sense for them to be heating hot water during daylight, and turn it off overnight. I will look into the timers in the OP.

Hi,

I've recently had solar installed with a hot water timer as part of the package. The installer said he set the timer to power the hot water from 8.30am to 5pm every day to take advantage of the electricity generated from the panels. To me, this does not make sense for the following reasons:

1. I have night rate so my rates are 35c (day) and 13c (night) (incl. GST)

2. The HOT water takes about 2 hours to heat and uses around 6kW in the that 2 hours

3. The solar generates anything from 0kW to 3.42kW at any given time during the day - it averages around 1.5kW

So, using the information above, I believe I am better off to heat the HOT water at night using the night rate of 13c as opposed to usin the day rate less the solar generation.

Example 1 (night rate)

6kw of generation at 13c = 78c to heat hot water

Example 2 (day rate)

6kw of generation - 3kw for free and 3kw at 36c = $1.08

There are a lot of variables in solar generation so taking this out of the equation and getting my 10c per kw hour for excess generated i can actually get my effective night rate for solar hot water down to 48c

It seems to me, I'm best to use the solar during the day for everything else except HOT water due to the size of the hot water element. If it was a 1.5kw then it would make perfect sense....

Can anyone see anything wrong with my logic?

Yes, example 2 is wrong, the timer is not switching between mains and solar simply because the solar can't provide enough energy (6kw),so 6kwh (that's kilowatt-hours) that means you have a 3kw element in your hot water cylinder, solar averaging around 1.5 Kw, it will take twice as long to heat, 4 hours

Does the solar have any kind of battery storage? if so the inverter may also pull from that as well to provide the full 3kw, so heating during the day is free if only been powered by solar.

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MadEngineer

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#1535134 18-Apr-2016 18:08

You what now?

His HWC isn't getting diddly squat from the solar panels. If the panels are grid-tied they will be offsetting the total power usage during the day. Don't think of them as powering the home.

It's better to be using the power generated (hence, the HWC set to use power during the day) because the payback otherwise is less than the cost of the power used.

You're not on Atlantis anymore, Duncan Idaho.