Heating Options in Newcastle

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Re: Heating Options in Newcastle

Postby Quokka2 » Sat Jan 11, 2014 4:36 pm

Kombinations wrote:Our problem really at the moment is a lack of hot water (80L; I haven't looked what size would be recommended or a family of (nearly) 5 yet) - so if we can get the temperature higher, or more storage that would solve our problem.

Our family of 4 lived off an 80L element HWS until the kids left school; one of them had waist-length hair so she used quite a bit, and her Mum has always enjoyed a fairly long shower. We might have staggered our showers a bit but didn't make any drastic lifestyle changes and never ran out, to my recollection. If you run it off peak at night and solar boost during the day your running costs should be pretty low and you won't have long to wait for a recharge.

We are in SW WA which has a similar latitude and climate to Newcastle. I seem to recall our Summer-Winter HWS use was around 8-12 kW-hr a day; if that equated to 3650kW-hr a year of which half was solar and half was off peak, annual running cost @ 10c/unit would be $182.50. A heat pump is going to use a third as much power (ie up to 4kW-hr/day) for the same amount of hot water, which may cost you more if you can't do it all on off peak tariffs. For the difference in capital outlay it just doesn't stack up.
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Re: Heating Options in Newcastle

Postby Kombinations » Sat Jan 11, 2014 5:01 pm

[Moderator removed quoting of entire previous posting]



Interesting, but good to know. We have had problems for the last few winters since moving in to our house with running out of hot water. It's fine in summer. Maybe since the thermostat has been turned up it might be a bit better. My wife isn't keen of to have another winter of carefully rationed hot water. I'll still have more of a look into adding solar. Actually I just realised that you were the one who suggested this in the first place. I might have more of a look around here and then pick you brains via pm. Thanks for the offer (back on p.1).
Last edited by Gordon-Loomberah on Sat Jan 11, 2014 9:05 pm, edited 1 time in total.
Reason: removed excessive quoting
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Re: Heating Options in Newcastle

Postby Smurf1976 » Sat Jan 11, 2014 6:43 pm

I'll just add that your current 80 Litre hot water system is most likely able to be fitted with different size elements. Certainly the Rheem, Dux and Vulcan units are.

Fitting a bigger element will re-heat the tank quickly and give you more hot water. It will also add to your power bills of course if you increase hot water consumption as a result. But it could be a "quick fix" option.

The biggest single phase element for these is 6 kW, installation being a job for an electrician who will also need to check that the wiring can handle the additional load.

Other element sizes are 1.2, 1.8, 2.4, 3.0 (uncommon), 3.6 and 4.8 kW.

For a family of 4, a 4.8 kW element in an 80 Litre tank should be sufficient assuming it's on continuous tariff (not off-peak). It also just happens to be the case that the existing wiring will usually support this load too.
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Re: Heating Options in Newcastle

Postby Warpspeed » Sat Jan 11, 2014 7:50 pm

I don't know the electricity supply regulations up in NSW, but in Victoria you can have a changeover switch fitted to your power board to run a HWS either on off peak power at night, or be constantly powered on the full day tariff.

The idea is you leave it switched to off peak most of the time, but under anticipated very high demand, it can be switched to heat during the day.
For instance, for a very few hours when the washing machine is in particularly heavy use.
This may be a possible solution for you, or maybe not.
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Re: Heating Options in Newcastle

Postby Kombinations » Sat Jan 11, 2014 8:07 pm

It is off peak, so we don't get it reheated until the next day. I guess a call to AGL wouldn't hurt so I know when the peak/off peak times are. I seem to remember seeing off peak 1 and off peak 2 somewhere at some stage. Does one have longer hours than the other? Again, AGL would easily answer that question. I realise that replacing a perfectly good HWS with a heat pump unit doesn't make sense financially in the short term, but I'd rather do than than have it heating continuously and pay the extra/higher rates.

Actually the option of switching it over to heat continuously of a night (7-9pm or so) during winter might work. Or maybe we should just shower at 2am so it reheats by then 8-). I guess the short term costs of getting this type of switch put in vs upgrading to a heat pump HWS and lower ongoing costs would be interesting to look into. Are heat pump HWS's normally run on off peak?
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Re: Heating Options in Newcastle

Postby bpratt » Sat Jan 11, 2014 9:03 pm

Smurf1976 wrote:The biggest single phase element for these is 6 kW, installation being a job for an electrician who will also need to check that the wiring can handle the additional load.

Other element sizes are 1.2, 1.8, 2.4, 3.0 (uncommon), 3.6 and 4.8 kW.

For a family of 4, a 4.8 kW element in an 80 Litre tank should be sufficient assuming it's on continuous tariff (not off-peak). It also just happens to be the case that the existing wiring will usually support this load too.


Not necessarily, plenty of older houses have 1 or 1.5mm TPS cable running to hot water systems, that generally have a 1.2 or 1.8 kW elements.

A 80l tank to my way of thinking would not be big enough to take a solar heating system on it, unless all the showering was to be done during sunny days, as the thermostat would be kicking in almost as soon as you turn the hot tap on. :(
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Re: Heating Options in Newcastle

Postby Smurf1976 » Sat Jan 11, 2014 9:54 pm

bpratt wrote:Not necessarily, plenty of older houses have 1 or 1.5mm TPS cable running to hot water systems, that generally have a 1.2 or 1.8 kW elements.

Won't argue with that (I'm a licensed electrician by the way) but if it's a more modern house then typically it would be 2.5mm to the hot water system.

That said, whoever wired my house (not me) for some reason ran 1.5mm to the 3.6kW hot water and 4mm to the 3.5kW space heater. Go figure.....

Anyway, and 80 Litre HWS on off-peak is virtually guaranteed to run cold. Even with 1 person in the house you could run out quite easily. 10 minute shower (40 - 60 litres) then a load of washing. Gone.

80 Litre tank really needs to be on continuous tariff if it's supplying normal household usage. Costs quite a bit to run it that way but at least you'd have hot water. I wouldn't even think of putting one on off-peak unless it was just supplying a sink in a workplace or something like that or was a second HWS in the house just supplying the laundry or kitchen.

For the OP, if it's on off-peak night only (Off Peak 1 in NSW) and you are doing OK in Summer then just switching it to Off Peak 2 would probably fix the issue. Cost a bit more but won't send you broke.

As for heat pumps, decent ones will run fine on off-peak (manufacturers generally recommend Off Peak 2) but the dodgy ones need continuous tariff and still struggle to work. Mine (Siddons) is on Tariff 61 here in Tas - that's off-peak on 8pm - 6am and 2pm - 4:30pm each day switched by a time switch (there's no remote controlled system for off-peak here) so it's the exact same times each day. Never had an issue with it and during Summer it usually only runs during the afternoon.

I did the math on ambient temperature versus the available tariffs and concluded that overall efficiency of the heat pump on either continuous supply or off-peak with afternoon boost (Tariff 61 in Tas, Tariff 33 in Qld, Off Peak 2 in NSW) makes no significant difference so you might as well use the cheaper option which is off-peak. Running it at night only (T62 in Tas, T31 in Qld, Off Peak 1 in NSW) would increase consumption significantly however and the difference in price between T61 and T62 down here is small such that even though T62 is a bit cheaper, it would actually end up costing more due to the reduced efficiency at lower temperatures. Hence it's on T61.

Changeover switch - not sure of the laws in NSW but such a device is illegal here in Tas. If it's connected to off-peak then it's connected to off-peak - strictly no changing it over to continuous supply when the off-peak isn't on. Not sure about NSW though, it might be legal there?

But as I said previously, be wary of ducks and avoid being reamed so far as heat pumps are concerned. Lots of horror stories with those although they do make decent standard electric HWS. Not sure about their gas or solar systems so no comment on those.
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Re: Heating Options in Newcastle

Postby Warpspeed » Sun Jan 12, 2014 7:45 am

Lets think about this.
One calorie of energy will heat 1cc of water 1 degree Celsius.
One Kilowatt = 859,845 calories per hour.

80 litre tank = 80,000cc
One kilowatt should add 10.748 degrees per hour to your storage.
Fairly common heating element sizes are 1.2, 2.4, and 3.6 kW

Even the smallest 1.2 kW element, if run overnight would fully heat a stone cold 80L HWS in the time available.
But it would have pretty lousy heat recovery if powered up during the day and under constant hot water draw off.

Fitting a more powerful heating element is not going to help if running overnight on off peak.
But it should make a big difference to the recovery time on day tariff, if you decide to go that way.
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Re: Heating Options in Newcastle

Postby bpratt » Sun Jan 12, 2014 9:52 am

Smurf1976 wrote:
bpratt wrote:Not necessarily, plenty of older houses have 1 or 1.5mm TPS cable running to hot water systems, that generally have a 1.2 or 1.8 kW elements.

Won't argue with that (I'm a licensed electrician by the way) but if it's a more modern house then typically it would be 2.5mm to the hot water system.

That said, whoever wired my house (not me) for some reason ran 1.5mm to the 3.6kW hot water and 4mm to the 3.5kW space heater. Go figure.....

Anyway, and 80 Litre HWS on off-peak is virtually guaranteed to run cold. Even with 1 person in the house you could run out quite easily. 10 minute shower (40 - 60 litres) then a load of washing. Gone.


I sort of guessed you meant the more modern houses, but thought I'd add it in for those with the older houses, who might be thinking their sparky was trying to take them for a ride and charge extra for no reason.

Might have been the same sparky we had years ago who thought underground power only had to be out of sight, i.e. 6 inches down, to be 'safe' and 'legal'. doh !!!

80 litres of hot water isn't going to go far for anyone. Filling a kettle up and washing the dishes would take a fair chunk out of it.


On the solar hotwater side of things, I was down at Reece plumbing who told me about Thermann evac tube systems, which are supposedly Apricus rebadge solely for Reece.
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Re: Heating Options in Newcastle

Postby Smurf1976 » Sun Jan 12, 2014 12:20 pm

Warpspeed wrote:Fitting a more powerful heating element is not going to help if running overnight on off peak. But it should make a big difference to the recovery time on day tariff, if you decide to go that way.

+1

I was assuming in my original post that it was already on a continuous electricity supply as it's never going to work properly on off-peak given the tank size. I'm actually quite amazed that the OP has put up with it thus far.

You'd be looking at a 250 - 400 litre tank for off-peak (night only) depending on how many people etc. Similar sizing for solar or heat pump.
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