Is there any way to stop my HWS from chewing grid power overnight? We have a 2-3yr old Rheem 400L tank - far in excess of the needs of 2A2C in the evening - primarily powered by solar (Catchpower relay installed), but it keeps reheating itself at odd hours. That seems unnecessary given the size of the tank, I'd think it would hold enough hot water long enough to do us until daylight hours.
Hot Water System Timer
Ham Dragon on 08/05/2023 - 22:14
Last edited 08/05/2023 - 22:14
Last edited 08/05/2023 - 22:14
Comments
The Catchpower diverts power from the PV system to the HWS circuit if it's pulling current, before it sends excess power into the grid, and in the absence of solar energy (cloudy or night) the HWS is heated by grid power.
I'm not sure, I assume the thermostat inside controls the heating element & that it pulls power when it wants to heat up. There is no external thermostat on the model that I have installed.
They're usually set to 70C?
How’s it wired up? Is it on off peak? Sounds like it’s an off peak unit that has a solar boost. So if it’s not hot enough during off peak it’ll heat off the grid. This should be obvious on your bill, it’ll show off peak or hot water or similar as a separate item.
This is one reason I haven’t put a solar ‘diverter’ in for our hot water. We use the majority of hot water at night, so it’ll use off peak to heat overnight and be hot all day and not require any significant extra.
It's not, we have a single power rate (about 19.5c/kWh) plus peak surchage of a few cents/kWh during certain hours, there's no Tariff 33.
As I mentioned (and this might not be possible!) I figured it was large, modern & insulated enough to hold hot water until the morning.
It’ll hold the heat for a while, just how long depends on a range of factors.
If you’ve got it set to 70, drop it a few degrees.
Alternatively, youd need to get a smart timer out on the circuit. You don’t want to block it from working in case the sun doesn’t shine enough, but you also want it to not heat to 70 when 60 is sufficient and the sun is coming up in a few hours.
It's situated indoors (internal laundry). I could try turning the circuit off at 5pm when the sun goes down and waiting to see how hot it is in the morning, but I suppose I had in mind some sort of programmable controller that would act under certain conditions ie do not heat between 6p & 6a unless temp is below 50 etc.
@Ham Dragon: First step is to drop the thermostat to 60 and see how it goes. Then investigate timers etc.
So you get up to poop at 4am, you then wash your hands with cold water?
it's got a 400L tank
The rate at which the water in the tank cools down depends on several factors, including the starting temperature of the water, the ambient temperature, the insulation of the tank, and the size of the tank. However, assuming that the initial temperature of the water in the tank is around 60°C, and the tank is well-insulated, the water temperature in a 400L tank would likely drop to around 45-50°C after six hours in 6°C outside temperature assuming no water was drawn from it and replaces with cold water from the main supply.
It's important to remember that this is just an estimate, and the actual temperature drop could vary depending on various factors. It's also important to ensure that the tank is well-insulated to prevent heat loss and improve energy efficiency.
It's situated inside the laundry, which is fully enclosed & usually doesn't get below 20 degrees.
Turn off the switch at night.
Just adjust the thermostat to 60° - the minimum required for safe hot water. It will still likely come on at night but for not as long.
Simple, but effective! Thanks mate.
Be wary of going below 60°: hot water tanks are required by Queensland law to store water at 60°C or more to reduce the risk of Legionella multiplying in the hot water system and plumbing.
Cheers for the insight, I'll have a go at setting it just above, say 62.
Agreed with the above. Change to 60 degrees. Is the timer working correctly? As when it switches on and off at the programmed times? I had one that was burnt out so it was running 24/7
It doesn't have a timer, it's thermostat controlled, I want to know if a timer will help reduce energy consumption overnight.
Problem with a timer is that if you want it to heat, it should be done outside peak hours. So you need to set it to heat when power is cheap, but that also usually means early hours of the morning where the water will have cooled the most because the sun hasn’t been any use since sundown.
If you have solar panels for electricity, you can get a timer at the switch board so that it only heats during the day. I've done this at my place, so the hot water system only heats up between 10am and 2pm.
Have you ever needed it to heat outside those hours? Cloudy days? Extra hot water usage?
No, on cloudy days it still gets heated but just uses the grid. I do have a large tank 315L.
Thanks for the reply. I’d want mine to use the grid on off peak times only. That’d be cheaper.
Catch power green? Hold in solar only button until the LED flashes then it will only heat hot water on solar.
Otherwise I think Catch power relay can be programmed in the app so it won’t turn on hot water unless it’s producing.
I probably should read the manual…the installers didn't do a great job of explaining things. Thanks for that.
IIRC you can hit the boost button if it's not hot enough, which should be a good workaround.
Catch Power make great products. It’ll be able to do what you need.
My one is like the one in the video:
https://www.homeandenergy.com.au/hot-water-timer-set-up/Looks like you can get digital ones too now:
https://www.schnap.com.au/timers/2-pole-digital-timer.html?g…You'll need to get an electrician to install it.
The consensus across all states and territories is storage minimum 60° and delivery maximum 50° via thermostatic mixing valve. Legionella grows rapidly at 20-45°. If your sparky didn't raise this it may be that only plumbers are across it? Overall the death rate from Legionellosis is usually within the range of 5–10%.
The thermostatic mixing valve is to make sure you don't get burnt when you use your tap, it mixes hot water and cold to decrease the temperature before it reaches your hot water tap. It doesn't determine the temperature in your hot water tank as the mixing happens after the hot water leaves your tank.
The thermostat is what controls the temperature of the hot water in the tank, it is set between 60 and 70 degrees. These have to be legally over a certain temperature to prevent bugs etc in your tank. They are normally already made so you can't turn them down below 60…
Having a timer is no different to what used to happen with control loads… With control loads your hot water system would get heated up at night when the electrical grid had less demand. With a timer your just setting the period for when it gets heated to daytime so that it uses your solar power.
@Rafski: You're heating for 4 hours in advance of peak evening usage. Tariff 31 (>250L) supplies 8 hours minimum between 22:00 and 07:00. Tariff 33 for smaller systems supplies 18 hours minimum.
Need more details because thisis ambigousAssuming you have an electric hot water tank connected to both a solar system and controlled load circuit:Q1. If it's a cloudy day, how does your water get heated during the day time when the controlled load circuit is not active?Q2. If it's a sunny day, how does your solar system know when to stop heating the water? Do you have an external thermostat with a set temperature limit?Q3. Your Rheem has an internal thermostat. Is the temperature set different to the one in Q2?