Timer on hot water cylinder?

[p.dath]

What's involved with getting a timer put on your hot water cylinder to stop it heating during the day? I want to use cheaper night time power, 11pm to 7am.

I was thinking if they install it at the hot water cylinder it will keep getting turned off when they ripple the power off and on.

[Edbear]

That's the idea behind ripple, it turns your cylinder off during the day, or am I confused again..? Call your power company.

[jaffaonajappa]

What's involved with getting a timer put on your hot water cylinder to stop it heating during the day? I want to use cheaper night time power, 11pm to 7am.

I was thinking if they install it at the hot water cylinder it will keep getting turned off when they ripple the power off and on.

So, you can plug your hot water cylinder into 240v mains, like a normal plug/socket thing?
If so...theres them mechanical timers - have some on the lights for the fish tank. About $10 from mitre 10. Or $40 from specialist pet shops. (sound familiar....bikers? :P) Theyre a wee bit bigger thana double adaptor - similar concept.

[FJRider]

That's the idea behind ripple, it turns your cylinder off during the day, or am I confused again..? Call your power company.

THat is correct ... ripple control ... they do turn it on for a short period during the day to keep the water HOT ...

Turn it OFF all day would mean it would use a LOT of power to get it hot again ... more than normal ripple control.

But hey ... it's YOUR power bill p.dath

[pete376403]

So, you can plug your hot water cylinder into 240v mains, like a normal plug/socket thing?
If so...theres them mechanical timers - have some on the lights for the fish tank. About $10 from mitre 10. Or $40 from specialist pet shops. (sound familiar....bikers? :P) Theyre a wee bit bigger thana double adaptor - similar concept.
Your HWC element is going to be 2400w at least, maybe 3000w, so whatever timer you put in will require fairly healthy contacts (switching 10-15 amps) - not the sort of thing you'd find in a pet shop.
Also HWCs are permanently wired, so you can't use any sort of plug in device

[jaffaonajappa]

Your HWC element is going to be 2400w at least, maybe 3000w, so whatever timer you put in will require fairly healthy contacts (switching 10-15 amps) - not the sort of thing you'd find in a pet shop.

Ahhh. Good point.
And at ~3kw....i suspect its hard-wired?
Dunno - cant remember a time before instant gas :)

[neels]

Have a look in your meter board

If you've already got night/day rate then there should be one ripple control relay for that. If you've got controlled hot water then there will be one for that, and possibly another if you've got a night store heater.

Most hot water cylinders are hard wired and 2000 or 3000W, so you'd probably need to hard wire a timer and relay into your switchboard.

[St_Gabriel]

Speak to you power company to get switched from your existing un24 cn17/19 tariff to a un24 with a lower cost tariff running on either the ripple relay or a power company supplied timer. I dont know a whole heap of options but do know of what is called a ND16 tariff which usually gives a two register (two counters) meter with cheap power available for 8 hours and dearer power for the remaining 16 hrs (usually used on the likes of nightstore heaters). A sparky would be your only option in regards to a timer on the cylinder if it had to be mounted in the switchboard.

[Indiana_Jones]

If you wanna save a little bit off your power bill, could always lower your hot water temp if you have not already.

55-60C is all you need really

-Indy

[Grumph]

Been there done that - i've got a timer on my HWC and with standard economy all day rate it is a noticeable saving. With a night rate it would be more.
As far as increased usage to heat only once - not so as your cylinder should be well enough insulated to hold the water warm at least. It certainly does so for us.
Used in conjunction with a wetback our water heating costs are minimal. Timer only heats for around 4 hrs in the am which suits us fine - a family with kids would need more.
i used to work for an outfit installing nightstores - that's your main source of high amperage timers. We used to make our own from chinese plug in type which had a relay capable of handling 60amps - god knows why when the plug ins are limited to 10amps...I put 3 position switches on them on/off/manual override - useful if you wanted extra hot water at short notice.

[scissorhands]

Spend the money on insulation, its done in a flash. Do the ultimate job so you have no heat loss. Completly surround cylinder with wool insulation, batts if you dont mind the dust, either way wear a mask and cut the pieces and push behind, under over, all round, no gaps. Fill the whole cavity even 500mm thick is great.

Modify usage and turn down temp, I'm at 45 degrees C

Otherwise switching HW supply on and off can be done by a timer powered off the HW circuit, and not affected by ripple switching

A whole swag of polyethylene farm piping on your roof would heat a HW cyclinder on sunny days

[p.dath]

That's the idea behind ripple, it turns your cylinder off during the day, or am I confused again..? Call your power company.

The ripple relay allows the power company to turn off your cylinder at times of peak load.
I can buy much cheaper power at night, so I don't want to pay for more expensive power during the day.


THat is correct ... ripple control ... they do turn it on for a short period during the day to keep the water HOT ...

Turn it OFF all day would mean it would use a LOT of power to get it hot again ... more than normal ripple control.

But hey ... it's YOUR power bill p.dath

I don't believe it would use considerably more power over a 24 hour period. In fact I believe the opposite, it costs more to try and keep your water heated to a set temperature, than it does to allow it to cool and just re-heat it once.

The main difference being I can get much cheaper power between 11pm and 7am.


Speak to you power company to get switched from your existing un24 cn17/19 tariff to a un24 with a lower cost tariff running on either the ripple relay or a power company supplied timer. I dont know a whole heap of options but do know of what is called a ND16 tariff which usually gives a two register (two counters) meter with cheap power available for 8 hours and dearer power for the remaining 16 hrs (usually used on the likes of nightstore heaters). A sparky would be your only option in regards to a timer on the cylinder if it had to be mounted in the switchboard.

I have a two register smart meter. And the power company said they can give me cheaper power at night time.


If you wanna save a little bit off your power bill, could always lower your hot water temp if you have not already.

55-60C is all you need really

-Indy

I have already lowered it to the legal minimum.


Spend the money on insulation, its done in a flash. Do the ultimate job so you have no heat loss. Completly surround cylinder with wool insulation, batts if you dont mind the dust, either way wear a mask and cut the pieces and push behind, under over, all round, no gaps. Fill the whole cavity even 500mm thick is great.

Modify usage and turn down temp, I'm at 45 degrees C

Otherwise switching HW supply on and off can be done by a timer powered off the HW circuit, and not affected by ripple switching

A whole swag of polyethylene farm piping on your roof would heat a HW cyclinder on sunny days

The cylinder is relatively new, and is barely warm on the outside. It is well insulated. The piping is insulated. I can't do much more to limit heat loss.

I've investigated using solar heating - but the systems cost more than the power I would save, and hence are not worthwhile.

[Latte]

Modify usage and turn down temp, I'm at 45 degrees C


P.Dath mentioned a legal minimum, I thought it was 55^C ? 45 is a tad risky no?

[BoristheBiter]

What's involved with getting a timer put on your hot water cylinder to stop it heating during the day? I want to use cheaper night time power, 11pm to 7am.

I was thinking if they install it at the hot water cylinder it will keep getting turned off when they ripple the power off and on.


Unless you have a high use house hold, the savings would not be all that great.

For all them that say a lower temp is the answer, its not, you use more hot water to keep the same temp for showers dishes etc, the more you use the more cold that goes in so longer heating time.

If you are going though that much hot water then look at getting a bigger one or if you can go gas.

[Virago]

...Modify usage and turn down temp, I'm at 45 degrees C...

Remind me never to shake your hand...

At that temperature your HWC is a perfect breeding ground for bacteria - even 55 deg is not entirely safe. From a health point of view, it's better to store water at 65-70 deg, and use a tempering valve to bring it down to a safe temperature at the tap.

[Smifffy]

I don't believe it would use considerably more power over a 24 hour period. In fact I believe the opposite, it costs more to try and keep your water heated to a set temperature, than it does to allow it to cool and just re-heat it once.


It takes 4.2 Joules of energy to raise the temperature of a gram (or mL) of water (liquid) 1 degree C.

Ye cannae change the laws of fuzzics Jim.

As you say, you do have a (limited) choice of rates you pay for your Joules, and control over how many mLs you want to heat.

[bogan]

Remind me never to shake your hand...

At that temperature your HWC is a perfect breeding ground for bacteria - even 55 deg is not entirely safe. From a health point of view, it's better to store water at 65-70 deg, and use a tempering valve to bring it down to a safe temperature at the tap.

+1 And considering the main use of having hot water at all is for hygeine, you may as well do a proper job of it.


I don't believe it would use considerably more power over a 24 hour period. In fact I believe the opposite, it costs more to try and keep your water heated to a set temperature, than it does to allow it to cool and just re-heat it once.

If it costs significantly more to hold the water at temperature, check and improve your insulation. Also, if you have a decent temperature ripple, and are running it to a low temperature, you might get bacteria buildup during the day.

One thing you could look into for power saving (probly going off on a bit of a tangent here), put a heat exchanger in your shower, so the cold water going in is heated by the warm water going down the drain. Or solar etc, better to lower your total usage than just get into a lower price bracket.

[Smifffy]

A whole swag of polyethylene farm piping on your roof would heat a HW cyclinder on sunny days

You would need to set it up so that it doesn't:

Radiate heat to atmosphere on cold days
Freeze

[scissorhands]

Remind me never to shake your hand...

At that temperature your HWC is a perfect breeding ground for bacteria - even 55 deg is not entirely safe. From a health point of view, it's better to store water at 65-70 deg, and use a tempering valve to bring it down to a safe temperature at the tap.

Mines instant gas so no hygiene issues I think

Its digital temp adjust only goes from 37-50 degrees C

p.dath if your intent on switching your HW circuit via timer, an inspector or regulating authority enquiry may be prudent as electricians like myself have not normally come across this, a manual on off has the advantage of human modulation in regard to load/guests, but the timer is the no brainer esp if manual switch access is poor.

[Virago]

Mines instant gas so no hygiene issues I think

It's a major hygiene issue for someone with a HWC who may follow your advice. At 45 deg the cylinder would basically be a bacterial incubator.

But yeah, instant (non-stored) low temp is fine.

[bogan]

You would need to set it up so that it doesn't:

Radiate heat to atmosphere on cold days
Freeze


Temperature controlled valve or two would sort it, only let water through if it's hotter than the alternative.

[Hellzie]

Modify usage and turn down temp, I'm at 45 degrees C



Careful with that, if you turn it down too much you increase the risk of evil legionella bacteria growing in your cylinder and possibly getting pneumonia by breathing in the little critters. There are different recommended temperatures, the majority recommend a temperature of at least 49 degrees C.

[Smifffy]

One thing you could look into for power saving (probly going off on a bit of a tangent here), put a heat exchanger in your shower, so the cold water going in is heated by the warm water going down the drain. Or solar etc, better to lower your total usage than just get into a lower price bracket.

I think the HX concept would struggle, at the flow rate to fill the cylinder, the exchange surfaces would need to be very large indeed, particularly with respect to the limited duration of operation of the warm side.

Keeping the surface clean of soap scum, hair and other detritus would also be difficult I'd imagine.

Without running the calcs, I'd hazard a guess that cutting one's shower shorter by a minute would save more than an HX, and of course the shorter the shower, the less effective the HX becomes.


Temperature controlled valve or two would sort it, only let water through if it's hotter than the alternative.

Yes, I'm not saying it can't be done, just that there's a little more involved than simply hooking up a length of poly pipe. Depending on storage I'd say it's a good option for the incoming water, if the cylinder is used during the day a lot - better than a heat exchanger on the shower drain. :)

[bogan]

I think the HX concept would struggle, at the flow rate to fill the cylinder, the exchange surfaces would need to be very large indeed, particularly with respect to the limited duration of operation of the warm side.

Keeping the surface clean of soap scum, hair and other detritus would also be difficult I'd imagine.

Without running the calcs, I'd hazard a guess that cutting one's shower shorter by a minute would save more than an HX, and of course the shorter the shower, the less effective the HX becomes.



Yes, I'm not saying it can't be done, just that there's a little more involved than simply hooking up a length of poly pipe. Depending on storage I'd say it's a good option for the incoming water, if the cylinder is used during the day a lot - better than a heat exchanger on the shower drain. :)

Indeed, and the bigger the surface the longer it wuld take to heat, so a fair few temperature adjustements during the shower may be required. Still, essentially free energy once impolemented though.

I guess living in palmy, you get the idea that sun isn't common enough to bother harnessing, wind on the other hand....

Or another idea, just make a water brake dyno, and feed it into a well insulated storage tank. Hell, if I put the bros on there you could have a steam supply for days :lol:

[NighthawkNZ]

Make sure you have good insulation on the cylinder, as it could cool quiker than expected and to heat it again evey day could cost more...

Remember when the cylinder is up to temp the element only has to keep it on the simmer at that temp, if it cools it has to actually heat it for longer periods of time and may cost more.

When they had the power shortages in the 90's and the power company's in their wisdom decided to save power by turning off the cylinders... peoples power bills went up, and it actually used more power...

I would also look into solar heating, gas, wetback...

Example our coal range is a form of warmth, hot water on wet back (and boiling water for coffee) as well as cooking... (not saying install a coal range a modern one is around 10,000g) over all saves money on power bill but some of the money is spent on coal... But there are other options that can lower your power bill

I am not sure on the instant gas thingy neighbor has it in conjunction with Solar... but don't know much about it.

[p.dath]

P.Dath mentioned a legal minimum, I thought it was 55^C ? 45 is a tad risky no?

Yes. At that temperature legionella can grow - and that can kill you!


It takes 4.2 Joules of energy to raise the temperature of a gram (or mL) of water (liquid) 1 degree C.
...
As you say, you do have a (limited) choice of rates you pay for your Joules, and control over how many mLs you want to heat.

Ahh yes, that is to raise the temperature, but that doesn't take into account the constant heat loss, and constant heating required to maintain the temperature in the tank.


Mines instant gas so no hygiene issues I think

Its digital temp adjust only goes from 37-50 degrees C

p.dath if your intent on switching your HW circuit via timer, an inspector or regulating authority enquiry may be prudent as electricians like myself have not normally come across this, a manual on off has the advantage of human modulation in regard to load/guests, but the timer is the no brainer esp if manual switch access is poor.

I think you might be right. I might ring my power company and ask them.

I have a manual switch - but I don't want to wait up till 11pm every night to turn it off.

[MisterD]

It's a major hygiene issue for someone with a HWC who may follow your advice. At 45 deg the cylinder would basically be a bacterial incubator.

Mains supplied water will be chlorinated though won't it?

[p.dath]

Mains supplied water will be chlorinated though won't it?

Heat destroys chlorine. Warm water grows bacteria faster than cool water.

[p.dath]

I am not sure on the instant gas thingy neighbor has it in conjunction with Solar... but don't know much about it.

We have a lot of people in the household. I think instant hot water with gas would suit small users better.

[pete376403]

Have you investigated the heat-pump type HWCs? I'm guessing that they use the heat pump to initially warm the water and then an element to raise the water temp to its final setting.

[pete376403]

We have a lot of people in the household. I think instant hot water with gas would suit small users better.

My experience in a house which had an infinity type (instant gas) hot water supply was that it never ran out, regardless of the length of time of showers.

[BMWST?]

i am sure your power company can provide you withthe hardware necesary to provide you the cheapest possible power for your hot water cylinder.If you can feel the cylinder is actually warm then an extra layer of insulation will definetly help to minimize that loss.If you can feel its warm thats lost heat.Put a cylinder wrap and ask your power company for the plan you want.

[Smifffy]

Have you investigated the heat-pump type HWCs? I'm guessing that they use the heat pump to initially warm the water and then an element to raise the water temp to its final setting.

No, I think they keep cycling the heat pump until the temp. is reached, and maintained. They are hella 'spensive though, you'd need to be heating a metric shit ton of water to ever get a return on your investment. Still a good idea though, and I'd love to have one.

[YellowDog]

My first electricity bill in my present house was $489 and we were freezing cold.

Four years later, my bill for the same time of year is $265 and we are now comfortale 24 x 7.

Fitting a timer on the hot water cylinder and electric towel rails was a good start towards saving money. I recon it saved around $40-$50 per month. I already had them, so they cost me nothing and I simply wired them into the existing switch.

Turning off the Spa Pool heater, which the previous owners left on, helped too :mad:

[chanceyy]

before you make the change trial the 11pm to 7am heating to make sure it fits your household requirement, as a number of ppl who wish to change to nite heating for hot water realise it may not suit .. there may also be a nite boost meter that also comes on between approx 1 -4pm to boost the cylinder for evening showers etc

with day/night metering the day rate is quite high so ensure you also set dishwashers & other house hold appliance to come on after 11pm or before 7am as you auto change to that nite rate (day rate comes on at 7am)


depending on your meter board, current meter set up, and whats available via your network you may be able to have a seperate nite meter or nite boost to soley run the cylinder.

definitely have a chat to your power co & see whats available, and find out cost to either change your meter set up or add another meter & see if its viable. also do not forget to ask if there is a change to your daily line charge as well ;)

what is your current meter set up (on the back page of your bill)

[chanceyy]

We have a lot of people in the household. I think instant hot water with gas would suit small users better.

lol just the opposite, instant esp with the infinity system and continous, with the elect hot water system the hot water being used is constantly being filled with cold once it reaches a certain temp it would come on & reheat

also 45 is far to low a temp it should be as Virago stated

if you have a large household I am not sure that nite only heating would be sufficient & highly recommend trialling it for at least a week before making those changes

[p.dath]

Have you investigated the heat-pump type HWCs? I'm guessing that they use the heat pump to initially warm the water and then an element to raise the water temp to its final setting.

They are even more expensive than solar water heats (I think the price was $8k). There is no way they would save $8k in power, so they are not worthwhile in my case.


My experience in a house which had an infinity type (instant gas) hot water supply was that it never ran out, regardless of the length of time of showers.

The problem is that they use a lot of energy to do the heating. If you have a small number of users they work out great. If you have a lot of users they work out to be much more expensive.

[Smifffy]

The problem is that they use a lot of energy to do the heating. If you have a small number of users they work out great. If you have a lot of users they work out to be much more expensive.

No. The energy required to heat a litre of water is a constant. It doesn't matter where that energy comes from; electricity, gas, solar, geothermal, whatever. All that differs is the cost of that energy, and the efficiency with which it can be stored and transferred to the water.

[p.dath]

No. The energy required to heat a litre of water is a constant. It doesn't matter where that energy comes from; electricity, gas, solar, geothermal, whatever. All that differs is the cost of that energy, and the efficiency with which it can be stored and transferred to the water.

Most energy systems have a concept of paying for peak demand. So if you use 300J of energy in 30s you pay more than if you use 300J in 8 hours.