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Hinko

273 posts

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  #3246582 9-Jun-2024 18:29
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raytaylor:

 

.......I am on the contact free 9-midnight plan.   

 

I have the hot water cylinder on a timer because the local ripple control turns it on too early in the evening so I delay it until 9pm with a timer.  ............

 

But anyhow, i dont get what powerswitch has to do with ripple control. 

 

 

Thank for your interesting post Ray. I think the experience is useful to confirm the theory while being respectful of other posters.

 

There's been some recent doubt expressed about how much energy is lost when a tank is not heated, you confirm the some is lost over time, thank you.

 

I also considered the same Contact plan. Our house is not as friendly to your implementation, at least at this time. Not sure I'd get two (or three?!) night stores approved. One can focus everything on using power during the free period as you have no doubt done well, but what if Contact decides to withdraw the plan? No doubt part of the answer lies in you are set up with timers so can exploit other free / time of use power bands. I looked at your spreadsheet but there was insufficient labeling and seemingly much too much replication of data to make any useful comparisons. How much do you end up paying each month? How do you measure your in tank hot water temperatures?

 

Powerswitch fails to assess or distinguish the cost of the available load control scenarios. For example Powerswitch would not tell me I would be better to change from CN19 to NO8 or NB10 or drop load control (or install load control) which might save significant power and be the most efficient plan. 




  #3246584 9-Jun-2024 18:32
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There's been some recent doubt expressed about how much energy is lost when a tank is not heated, you confirm the some is lost over time, thank you.

 

It confirms nothing of the sort, only that the ripple turns the cylinder on before OP moves to night/free rate. 


Hinko

273 posts

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  #3246585 9-Jun-2024 18:34
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Ummm what is this then?

 

raytaylor:

 

It looses about 1kwh of heat between midnight and 6am but now its hot enough so that it can loose 3.5kwh from midnight to 9pm and still be above 60 degrees. 

 




  #3246590 9-Jun-2024 18:56
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Ah, I didn't see the full post, only the bit you quoted which doesn't include that section.

 

Losing 1kWh in 6 hours (quarter of a day) indicates that the tank significantly violates the requirements of NZS4305:1996, which doesn't seem to have been amended. Obviously, tanks older than that (it sounds like it might have been enforced in 2002) are around, but increasingly uncommon. Double check pipe lagging and consider a cylinder wrap. 

 

That sets maximum loss limits, and appears to be cited in the Building Code and publicly available:

 

 

It's noted that some non-compliant cylinders appear to be being sold, so this is something to watch out for: https://www.building.govt.nz/about-building-performance/all-news-and-updates/considering-a-new-hot-water-cylinder-check-it-is-compliant

 

However, note that tanks losing energy was never under debate. What's debatable is whether they lose more energy when heated continuously. 

 

Heat loss is generally proportional to the temperature differential. That is, a tank in a 15C ambient with 65C water (50C differential) will lose a certain amount of heat. The same tank at the same ambient with 55C water (40C diff) will still lose 80% as much heat.

 

 

 

If one does the maths based on a 'sawtooth' wave of rapid recovery and slow cooling, they'll find that the average temperature differential is halfway between the two: 45C, or 90% of the heat loss occurring from maintaining a hot tank 24/7.

 

 

 

This means that allowing your tank to fall to 55C before heating it back to 65C (and most tanks will not cool this much on their own in one day) results in only a 10% savings, and that 10% only on the parasitic loss portion, not the actual draw-off load, which is the bulk of HWC consumption. 

 

 

 

In addition, note that @raytaylor raised the setpoint of their tank to compensate for the unpowered periods, which will increase total energy loss through the insulation. 


raytaylor
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  #3246697 9-Jun-2024 21:25
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Answering the last few posts.... 

 

The hot water cylinder is a 180L 3kw manufactured September-2000 
Not sure how that affects legal requirements for heat loss. 

 

At 9pm the timer switches on and its usually finished heating by 10.30 

 

I also did an initial test when my flatmates were not home for a weekend. 

 

After a day of consuming zero hot water, I turned the thermostat back down to 60 degrees and it didnt turn on at 9pm - i had to run some water to get it to switch on. 
Edit: Post above raises a good point - the width of the thermostat control could be 5 degrees either side of the set point - they are not necessarily accurate. 

 

 

 

We renovated the bathroom and took the opportunity while the wall was open to put a temperature probe on the shower input which controls the bathroom extraction fan. This is about 3 metres away from the hot water cylinder.  

 


What I spend on electricity is probably irrelevant because my living situation and flatmates consumption habits will be different, as well as the location and local lines company being different to yours. But its approx $170 a month. Previously it used to be $220-$230 a month. 

 

Contact could drop the plan however it would just mean switching to a different provider and adjusting timers accordingly. The next best plan would be the Z energy 3am-6am free power plan however it would cost me a bit more for the heat pump running for a couple of hours in the evening in winter. 
I suspect that most households are only shifting 20% of their electricity in the free period so the plan is probably working very well for contact - so much that they have even offered alternative options such as the free weekend options and i suspect they might be behind the Z Energy free 3am-6am plan.    

 

For me, electricity has never been cheaper. 





Ray Taylor

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Spreadsheet for Comparing Electricity Plans Here


raytaylor
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  #3246708 9-Jun-2024 21:41
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Interesting Development.... 

 

Occasionally we are not home and dont use any hot water in a 24 hour period  
So just now i have gone through to check the historic stats from the wifi timer on the hot water cylinder. 

 

The absolute minimum daily electricity consumption is ~1.75kwh   

 

So it might be loosing much less than i thought   

 


Also interesting it seems i have found a few days over the last 4 weeks where unison has not turned on the ripple control at all - the cylinder stayed off for two days. 
Notice in the May/June graphs that whenever there is a period of no ripple controlled supply to the wifi timer, the day when electricity does return, it consumed a boat load of electricity to reheat.   

 


Also interesting is i haven't noticed any cold water when having a shower over those days. 
I know it took about 3-4 days of no power for the hot water from the cylinder to become noticeably cooler after the cyclone last year. I just checked with my parents next door who are heavy users of hot water and they said they did recently notice it cool down a few times.
Its been something noticed napier-wide so i suspect unison has still got repair work to do at the GXP to get the ripple control working again properly.     

 

https://imgur.com/a/hc8Gpqo  

 

 





Ray Taylor

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Spreadsheet for Comparing Electricity Plans Here


Hinko

273 posts

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  #3246709 9-Jun-2024 21:58
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raytaylor:

 

The absolute minimum daily electricity consumption is ~1.75kwh   

 

So it might be loosing much less than i thought   

 

 

The particular point I was making is that when you are home and keep taking hot water without the power on as you are doing you will save more because the perpetual power load to keep the cylinder to the set temp does not keep the meter running. That is I bet if you turn your timer on for 24 hours you will spent quite a bit more on hot water power. As you point out this is just the baseline losses when you take no hot water form the tank.


 
 
 

Trade NZ and US shares and funds with Sharesies (affiliate link).
  #3246710 9-Jun-2024 22:01
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And I calculated them above; I expect it's only about 10% of the parasitic load that would be saved. It's only worthwhile if you're going to leave the tank off for several days; long enough for it to cool down to near room temperature.


Hinko

273 posts

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  #3246718 9-Jun-2024 22:09
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raytaylor:

 

Also interesting it seems i have found a few days over the last 4 weeks where unison has not turned on the ripple control at all - the cylinder stayed off for two days. 

 

I noticed our ripple control was failing to turn off on some days, confirmed from downloading the HHR data. We have a separate meter for our hot water so it was well recorded in the half hourly meter reading data. Other ICP's were also having the same problem which points to a problem with the Wellington Electricity Lines Company Ripple Network. Their communications are somewhat wobbly but generally they deny it is their network that's been the problem. It was this that got me interested in the subject as there was no reliable evidence there were any failures within my property. Wellington Electricity say they are looking at ripple signal logging to clarify the issue but the scant details are leaving it unclear how much commitment over what time frame is in place. 

 

Did you find any days where they "forgot" to turn it off at all? 


  #3246721 9-Jun-2024 22:12
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As noted previously, leaving ripple control on 24/7 is entirely acceptable and indeed what the lines company aims for if there are no constraints. Orion notes that all summer long, all HW load is on 24/7. Your continued attempts to assert that lines companies are somehow engaged in fraud by not turning HWCs off are dull.

 

 

 

HWCs not turning on due to ripple signals is a problem that lines companies have on occasion.


Hinko

273 posts

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  #3246724 9-Jun-2024 22:19
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SomeoneSomewhere:

 

Your continued attempts to assert that lines companies are somehow engaged in fraud by not turning HWCs off are dull.

 

 

Engaged in Fraud? Let me be clear. I have not intended to say Lines Companies are engaged in fraud. nor do I consider I have said that. Careful reading of what is stated helps the forum.

 

However I have invited people to share actual data. 

 

Correct me if my recollection is wrong, but you don't have separately metered hot water so your comments are limited to your very well informed speculation rather than actual half hourly metered data under various circumstances. 


Hinko

273 posts

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  #3246725 9-Jun-2024 22:23
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SomeoneSomewhere:

 

HWCs not turning on due to ripple signals is a problem that lines companies have on occasion.

 

 

Ummm so faults where the signal chain fails to turn on is possible, but the reverse, the failure to turn off (the implication in this context) is not possible?

 

Convince me it can only fail one way.

 

But do you have appropriate meter reading data that would be required?


raytaylor
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  #3246726 9-Jun-2024 22:29
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I cant remember where exactly i read it but I understood that ripple controlled devices must fail to off or fail to offpeak mode if its a meter. The reason being that its not illegal to undercharge a consumer but it is illegal to overcharge them. 

 

I also guess my monitoring only shows if hot water is switched on by ripple between 9pm-midnight.   

 

I wouldnt know if they had it switched on during the day or early hours of the morning as my monitoring wouldnt show that. Its possible i just missed an "on" window because of my self-imposed 9pm-midnight restriction. 





Ray Taylor

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Spreadsheet for Comparing Electricity Plans Here


  #3246730 9-Jun-2024 22:51
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Engaged in Fraud? Let me be clear. I have not intended to say Lines Companies are engaged in fraud. nor do I consider I have said that. Careful reading of what is stated helps the forum.

 

 

 

Correct me if my recollection is wrong, but you don't have separately metered hot water so your comments are limited to your very well informed speculation rather than actual half hourly metered data under various circumstances.

 

These posts where you talk about a 'cash cow' and 'excessively profiting' are pretty close to alleging fraud, given that they are a regulated monopoly where those are effectively forbidden.

 

 

 

We have a PLC counting both running minutes and cycles per day, using a current switch rather than a check meter. I also did fairly substantial investigation into the underlying physics (which are not complicated) when considering how to set up the controls, given it has a temperature sensor to allow closed-loop control, not just a dumb time switch. Unfortunately, it's not networked, so getting data out is non-trivial. 

 

Ummm so faults where the signal chain fails to turn on is possible, but the reverse, the failure to turn off (the implication in this context) is not possible?

 

 

 

Convince me it can only fail one way.

 

Easy: it being on 24/7 is not a fault. WELL states that "The supply can be controlled at any time for a maximum of five hours in any 24 hour period." Zero hours is less than five hours, so that's not a fault. 

 

Orion is the same, even stating that "Control periods are restricted to only occur between 1 May and 31 August each year." In other words, turning your HWC off at any point from September through April is a fault

 

In addition, consider the ripple charts you previously posted for WELL. Note that they do not have a specific time that the CN19 signals are turned off... but "an automatic ON signal is sent at 01.00 each morning to capture all ripple control receivers (relays) that may have failed to turn back on." Again, failing to turn off means that perhaps the lines company has to shed more load elsewhere or pay Transpower higher charges. Failing to turn on is a customer experience issue that requires immediate action and must be defended against.

 

Many modern computerised ripple relays can even be programmed to act in specific ways if they don't receive signals for too long: 

 

Outstanding features are the seven-day time switch for easing transmitter load and the learning function for autonomous switching operation in case of transmitter outage.

 

 

 

There is no situation where a CN19 hot water system being turned on constitutes a 'fault'.


Hinko

273 posts

Ultimate Geek


  #3246731 9-Jun-2024 22:56
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raytaylor:

 

I cant remember where exactly i read it but I understood that ripple controlled devices must fail to off or fail to offpeak mode if its a meter. The reason being that its not illegal to undercharge a consumer but it is illegal to overcharge them. 

 

 

The helpful Orion Ripple Signal Guide at https://www.oriongroup.co.nz/assets/Be-prepared/NW702602.pdf refers to 

 

Failsafe
Turn on after 20 hours of no signals on programmed channel (ie no master and no direct signal observed)
This caters for a ripple injector failure, or a situation where an area of our network is operating on a back-up generator. We will send periodic off signals if we need the load to remain off

 

 

Seems ON is the preferred mode and is not considered a failure in this context, even though a failure to turn the relays off is in my opinion a different type of failure resulting in power being billed to the customer during a period the customer had not agreed to pay. Could it be the same for your lines company?


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