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How is our Water Heated?

Electric Hot Water

Most properties have an electric Hot Water Cylinder.  This may be located in a cupboard, under the house or even in the ceiling. Think of your HWC as a large electric kettle.  Like a kettle it has a heating element and a thermostat.  A kettle stops heating once the thermostat has reached boiling point (100 degrees).  A hot water cylinder stops heating once it reaches the temperature set on the thermostat (usually 65 degrees).  Once the water temperature drops a few degrees below that temperature the thermostat turns the heating element back on and heats the water back up to the set temperature again.  So once the water is hot the HWC is not using any power until the water temperature drops (by using hot water or cooling over time).


Advantages:  If you use a lot of hot water (eg long showers) then it will work out cheaper than gas.


Disadvantages:  If you use a lot of hot water (eg long showers at one time) then you will run out of hot water and someone will get a cold shower.

So what is “Ripple Control”?

House peak power usage times are in the mornings when everyone is getting for school / work and in the evenings when everyone is cooking tea.  If too much power is used at these times then the power grid can overload and fail.  Power companies have to manage power usage during these peak times.  Over half of NZ electricity users in NZ are attached to a ripple control unit on the meter board.  During peak power usage times the power companies send a signal down the power cable that activates the ripple control unit on your meter board.  This stops power to the HWC for the peak power use period.  Landlords and tenants have no control over this or when it happens.

The ripple control may be on in the off position for several hours (eg cold days in the middle of winter) if there is a long peak power period.  As an example, if everyone in your flat has an early morning shower and uses all the hot water.  If the ripple control turns the power off to the HWC at 7am and it stays off for 3 hours before being turned on, then it takes another couple of hours to heat the water in the HWC, then there will be no hot water until lunch time.  To avoid this try not to use all of your hot water at once by staggering showers or have shorter showers.


If you have any hot water issues that mean by mid-afternoon the HWC has not re-heated then please get in contact with us.  This could be either a failure of the element, the thermostat, or in some cases the Ripple Control Unit can have an issue.

Gas Hot Water

If your flat has large 45kg gas bottles then your water is heated with an instantaneous gas water heater.  When you turn the hot tap on, cold water passes through the water heater and the burning gas rapidly heats the water as it passes through the gas water heater.


Advantages:  You never run out of hot water.  You don’t pay for having hot water stored in a large cylinder (you only pay for heating water when you actually use it).


Disadvantages:  If you use a lot of hot water (eg long showers) you will use a lot of gas which can make it more expensive than electric hot water.

What do we have to do if we have gas hot water?


If your house has two 45kg gas bottles then your water is heated by gas.  You will need to open an account with a gas bottle supplier.  They will deliver two full gas bottles to the property.  It is your responsibility to contact your gas bottle supplier for new full bottles when they become empty and to pay for all gas used.  When you receive your invoice for the first delivered bottles send us a copy and we will then reimburse the annual rental cost of the bottles directly to you.  When you leave the property remember to contact your supplier to cancel your contract and have the bottles collected.


How do the Gas Bottles Work?

There should ALWAYS be TWO 45kg gas bottles.  One will be a primary bottle which is used first.  If you are using a lot of gas at once then the gas will be used up from the primary bottle and it will take time for the liquid petroleum in that bottle to boil to more gas.  While this is happening the gas from the secondary bottle is used so you won’t run out of gas.  So both bottles are open at all times but the gas will come from the primary bottle first, so it will become empty first.

Once you see that the indicator arrow has turned red it means that the primary bottle is empty and needs to be replaced.  DO NOT TURN THE VALVE.  Gas will automatically come from the secondary bottle.  Just contact your supplier and order another bottle.


When the new bottle is delivered the delivery person can see which bottle is empty because the indicator is pointing to the empty bottle.  They will swap the bottle over and then swap the valve over to turn the partly used secondary bottle into the primary bottle (which will make the new full bottle the new secondary bottle).  This valve swap will happen by the supplier every time an empty bottle is replaced.  If you don’t order a new bottle as soon as the indicator turns red then you may empty the secondary bottle before a new bottle is delivered so keep an eye on the indicator.

It is EXTREMELY IMPORTANT that you DO NOT TURN THE VALVE yourselves.  Swapping valves can cause increased pressure in the valve and in the gas heater and can cause hundreds of dollars in repairs.



How much gas should we go through?


It depends on how much hot water you use.  If there are lots of you all having long showers you could go through a bottle in a couple of weeks.  If you are more economical you may get 4 – 6 weeks out of a bottle.  The more people in the flat the quicker you will go through the gas.  Also in winter the incoming water temperature is colder and people tend to have longer showers, so you will probably use more gas in winter.

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