Browse Forums Eco Living 1 Aug 28, 2009 1:12 pm I think there may have been a thread about this before, but I can't find it so here goes again. Do you leave the booster on all the time, or just turn it on when the weather is overcast and the water is getting cold? The electrician said leave it on, and the plumber said turn it off! Now we're confused. Does anyone know who's right please? Re: Solar hot water boost 2Aug 28, 2009 3:31 pm Laine I think there may have been a thread about this before, but I can't find it so here goes again. Do you leave the booster on all the time, or just turn it on when the weather is overcast and the water is getting cold? The electrician said leave it on, and the plumber said turn it off! Now we're confused. Does anyone know who's right please? Like most answers in life, it depends...... I presume you are only boosting on off-peak rates? I would choose to do this first to save money if not energy. There is no problem turning off the booster any time of the year as long as you are prepared to have a cold shower. For most of winter it not really worth trying to scrap a few kWh of savings in the hope that a nice sunny day will be enough for your hot water needs. In summer, you can be pretty confident that a day's worth of sun is going to give you a tank full of hot water. Having the booster off is unlikely to be a risky manoeuvre. That leaves the shoulder seasons. It pretty much depends on how much of the tank your household is using during the day and how much sunshine you are getting. You might be able to get away with switching the booster off on each side of summer. Re: Solar hot water boost 3Aug 28, 2009 3:38 pm dymonite is correct , it depends mostly on the behaviour of the household. What size system do you have? Remembering that any booster is still only going to boost half the tank's capacity. This is because boosting the whole tank could create an ongoing pattern where it uses the water during the day, and only boosts over night, which is pointless and basically a normal Elec system. Boosting only half the tank means that system still has room for Solar gain. So, if you've got the booster off, and only running it over night, your still only going to get 165 lt of hot water from a 315lt tank. Are you actually running out of hot water? Or are you just concerned whether the booster should be on? ~W~ Building our forever home - Lilium Estate Clyde - Land due May 2019 Built our first home - Pakenham - 2011 Re: Solar hot water boost 4Aug 28, 2009 4:25 pm My only experience with a boosted system is when we lived in a rental in Gosnells and the solarhart tank was leaking water! We generally put the booster on a few hours before we were planning to have showers etc (basically so the electricity bill didn't go through the roof). So maybe you could start with that? But then again we used to bath the kid late in the arvo and have nightly showers ourselves (rather than in the morning) so I guess like others have said it really depends on your household. Re: Solar hot water boost 5Aug 28, 2009 5:50 pm We are now living with an electric boosted solar system. I get up quite early ( anytime from 5-6.30 am) and so during winter when it's been very overcast i get up, switch on the booster and about an hour later have a shower. Hubby turns the booster off at around 8am. we find this is enough for us but we do our clothes washing with cold water not hot. Re: Solar hot water boost 6Aug 29, 2009 10:18 am kexkez I get up quite early ( anytime from 5-6.30 am) and so during winter when it's been very overcast i get up, switch on the booster and about an hour later have a shower. Hubby turns the booster off at around 8am. I wonder if a timer wouldn't be a good idea. Chris My father rode a camel, I drive a car, my son flies in a jetliner, his son will ride a camel.Saudi saying Re: Solar hot water boost 7Aug 31, 2009 9:18 am Thanks for the replies. The rental we're in has just had a solar system installed and we really notice the difference in water temperature, apparently they're set at 55 degrees?, so we're a little worried about having it in our new home [moving in next weekend YAY!!!]. I'll need to find out about the size of the tank, but there are only two of us except when we have guests - neither of us showers in the mornings usually, we're both night people , but I do love a big hot bubble bath in winter. My query was just about the best way to manage this, for both economy and efficiency. Re: Solar hot water boost 8Aug 31, 2009 9:32 am We have our heat pump (HWS) timed to start after 9pm and not to come on after 6am. Mind you it has a bigish tank 365L so it last for quite a while... Just now there are only the 3 of us, ...though miss 17 has discovered the joys of having a nice hot shower HWS is also a wet back when the fire is going (not lately) onc_artisan Where you are coming from is where you are going to... Re: Solar hot water boost 9Aug 31, 2009 4:37 pm While we're on the subject of boosted solar HWS I've been wondering about the number of panels required. The manufacture shows recommends either 1 or 2 panels for a 300 litre tank. Would an extra panel heat the water quicker or heat water in poorer conditions ie overcast. Has anyone had experience with a 1 panel gas boost connected to a 300ltr tank serving 2 adults 2 kids? Re: Solar hot water boost 10Aug 31, 2009 4:59 pm 55deg, ours was the same and since I like pretty hot showers (and baths) I found that I didn't need to use the cold tap at all, and I wasn't overly impressed with that (it was hot enough and would do but still!). Anyway the system wasn't installed correctly in the first place by the plumber (well the solar part of it) so when the people came to fix it we got the to turn the water temp up (I think it's on 65deg) and I find it much better now, I need to use a bit of cold water! They said if it was turned up much more than that we'd end up using too much gas. Ours is a solar gas boosted system, so the solar heats the water in the tank, and similar to an instant gas system the gas will boost the (hopefully heated) water out of the tank to the correct temperature (if necessary) before it goes out to the house . I think it's a great system, when there isn't enough solar gain it's just like an instant gas system... .no booster to switch on and off it's all automatic, and I have noticed that if the water tank is even just luke warm on the cloudy days, we still use less gas then if it's stone cold (like when the solar part wasn't working at all). When or if we move from here I would be pretty happy to get a similar sort of system again. It's funny, having that leaking electric boosted solar heart in the rental house just really left a bad impression on me, partially the reason we went for the split system with the tank on the ground (270L) and the solar collectors on the roof. Re: Solar hot water boost 11Aug 31, 2009 11:35 pm mudmap The manufacture shows recommends either 1 or 2 panels for a 300 litre tank. Would an extra panel heat the water quicker or heat water in poorer conditions ie overcast. You could size a system based on winter insolation but then your heating capacity becomes redundant beyond this part of the year. By summer the system is three times bigger than you need and the water will boil. Think of the average amount of insolation you get throughout different times of the year. Daily winter insolation is typically one third that of summer insolation. This is related both to the shorter days and the greater frequency of cloud cover. Therefore, at the most you can only heat one third of the hot water in winter that you could achieve in summer. This is further compromised by the lower ambient air temperatures which make the collector work less efficiently (heat loss to the surrounding air). Evacuated tube are more resistant to this (the collector is better insulated with 'double glazing'). But this might might only give you an extra 30L of hot water (a 3 minute shower). The most cost effective strategy is to size a system based mainly on household usage and summer insolation. Other factors include cold water input temperature, target temperature and ambient air temperature. When average over the year this typically results in 50-75% of your annual hot water being heated by the sun for RECS zone 3 and 4. The only place where you are reaching 90% heating is in places like Darwin where the insolation only changes 25% throughout the year. Re: Solar hot water boost 12Aug 31, 2009 11:40 pm Pebble and I have noticed that if the water tank is even just luke warm on the cloudy days, we still use less gas then if it's stone cold (like when the solar part wasn't working at all). Even that little bit helps. You need to raise the temperature of the water 40 degrees - from 15 to 55. If you bring it up another 10 degrees with the solar pre-heater then that it is 1/4 less gas you need to use to heat the water. But, if you hook it up to a heat pump then the effects multiply because the COP increases as the input and output temperature difference decreases. Re: Solar hot water boost 13Mar 18, 2010 11:07 pm Before you turn that booster off, consider this: A hot water service with a storage tank for use in Australia, by law must now be designed to heat all the water in the tank to at least 60C at least once every 24hrs, to kill bacteria. That is what the booster is for. What time of day the booster should come on depends on when you use the most water. The optimum time of operation would be after the sun has provided whatever it can, so if the sun didn't get the tank up to 60C then, the booster will. It doesn't matter whether or not its economical, its a health issue. I applaud you all for at least getting some solar benefit happening. Following these guidelines, what most find is that the electricity bill will go up. I've been selling solar hot water systems for 7 years, and what I've discovered is this; your average solar will produce about 160Lt – 180Lt of 60C (or hotter) per day, under ideal conditions. Thats enough free SAFE hot water for 2-3 people. As the ideal conditions deteriorate, the tank won't reach temperature without the booster. It may be hot enough to shower in with no added cold, but by now you could be showering in bacteria. A well designed heat pump will always heat the water to 60C then switch off. NO SAFETY ISSUES!. While its running, it will convert 1kw of electricity into 3-6kw of heat energy. The electric booster at best is 1-1. Now the bottom line! Anywhere south of Brisbane, over 12months, for 4 or more persons in a household, a "proper" heat pump will use less electricity than a solar with its booster left on to keep you SAFE. The further south you go the bigger the difference. I stress "proper" heat pump because there are some really bad ones out there that give heat pumps a bad name. The booster will only come on if the tank doesn't reach SAFE temperature, so work around that, but don't leave it off! All of this only applies to water heated to above 30C and then stored, your cold water (usually 5C-15C) is bacterially SAFE. Various studies show that not only must the water be heated to +55C, but it needs to be held there for at least 3 mins to be effective. (I worry about instantaneous GAS boosters on solars with storage tanks ?) PLEASE DO SOME RESEARCH BEFORE YOU TURN IT OFF - TO SAVE A LITTLE MONEY Re: Solar hot water boost 14Mar 18, 2010 11:48 pm Solarman does make an important point regarding Legionella. There is always the potential for significant exposure although there have been no reported cases of contracting Legionnaire's disease from hot water services. However, even non-solar storage tanks are subject to thermal stratification meaning that not all the water is held at the kill temperature for Legionella. As you draw off hot water, cold water re-enters the tank. Depending on how quickly you consume or when the next boosting cycle occurs, there is always the chance for bacteria to proliferate. In summer, you are generally guaranteed that the tank will be fully heated through in the tank. Heat pumps typically are generally more cost-effective to run in the higher temperate latitudes where there is less solar insolation. However, in the past their capital cost made them less attractive. I am not sure their comparative cost nowadays (given a similar capacity system as solar one). But if you have a large solar system or are a particularly frugal consumer you could considerably reduce additional energy to meet your hot water needs. Finally from a practical point of view of I have tried boost and no boost during summer and the difference is 1kWh vs 0kWh energy used e.g 22c/day. 1kW hr is about enough to bring the temperature of the a 300L tank from 58 to 60 degrees. Generally in summer the tank is going to be way over 60 degrees. Combined with the tempering mixing valve, you are in fact using a much smaller proportion of hot water anyway so you are really left with a reasonable amount of hot water at the end of the day ready to be reheated by the sun the next day. I have tracked my hot water energy use since May last year and correlated it with our insolation and daily temperatures. Here in the Adelaide Hills I could safely switch off the booster mid November to mid February. At a push I could extend it 2-4 weeks either side. Re: Solar hot water boost 15Mar 19, 2010 12:26 am If instantaneous electric hot water is more efficient than using a traditional hot water tank, as heat is lost through the walls of the tank while the water is waiting to be used (... so I guess the solar water tank would lose heat as well), .... is it better to use solar panels to feed the power to the grid, then use the money gained from the solar panels to pay for instantaneous gas hot water when you need it? Mech Eng Re: Solar hot water boost 16Mar 19, 2010 8:55 am This is the energy loss by a HWS storage tank. HWS efficiency It is about 15%/24 hours. However, note that PV is only around 15% efficient at converting solar energy into electrical energy. Solar HWS vary between 40% (worse) to 80% (best) at turning solar energy into thermal energy. In other words a 300L solar HWS provides as much energy in kWh as a 1.5 kW PV system (3500-3800 kWh/year) Re: Solar hot water boost 18Mar 19, 2010 10:37 pm dymonite69 Solarman does make an important point regarding Legionella. There is always the potential for significant exposure although there have been no reported cases of contracting Legionnaire's disease from hot water services. However, even non-solar storage tanks are subject to thermal stratification meaning that not all the water is held at the kill temperature for Legionella. As you draw off hot water, cold water re-enters the tank. Depending on how quickly you consume or when the next boosting cycle occurs, there is always the chance for bacteria to proliferate. In summer, you are generally guaranteed that the tank will be fully heated through in the tank. Heat pumps typically are generally more cost-effective to run in the higher temperate latitudes where there is less solar insolation. However, in the past their capital cost made them less attractive. I am not sure their comparative cost nowadays (given a similar capacity system as solar one). But if you have a large solar system or are a particularly frugal consumer you could considerably reduce additional energy to meet your hot water needs. Finally from a practical point of view of I have tried boost and no boost during summer and the difference is 1kWh vs 0kWh energy used e.g 22c/day. 1kW hr is about enough to bring the temperature of the a 300L tank from 58 to 60 degrees. Generally in summer the tank is going to be way over 60 degrees. Combined with the tempering mixing valve, you are in fact using a much smaller proportion of hot water anyway so you are really left with a reasonable amount of hot water at the end of the day ready to be reheated by the sun the next day. I have tracked my hot water energy use since May last year and correlated it with our insolation and daily temperatures. Here in the Adelaide Hills I could safely switch off the booster mid November to mid February. At a push I could extend it 2-4 weeks either side. Re: Solar hot water boost 19Mar 19, 2010 10:39 pm Thanks Dymonite, you have pretty much confirmed what I said, for 3months of the year your solar can produce far more hot water than you can use – people actually use far less hot water in summer. Your booster will be required for the other 9 months, especially in the middle of winter when the demand for hot water is highest, and your solar provides the least. If you have 3 or more people in your house your booster will use more electricity in those 9 months than one of our heat pumps would use over 12 months. For a more thorough explanation have a look at See http://www.skylineenergy.com.au/our solution.php We use the same technology for hydronic heating systems - much more suitable than solar Re: Solar hot water boost 20Mar 19, 2010 10:42 pm dymonite69 This is the energy loss by a HWS storage tank. HWS efficiency It is about 15%/24 hours. However, note that PV is only around 15% efficient at converting solar energy into electrical energy. Solar HWS vary between 40% (worse) to 80% (best) at turning solar energy into thermal energy. In other words a 300L solar HWS provides as much energy in kWh as a 1.5 kW PV system (3500-3800 kWh/year) That figure of 15% loss is very high . . . ours rate at about 5% the sun master is the solar heating to "warm" the water in the tank the S26 is your hot water system which will heat the water (25 degrees?) so with both turned on you… 2 14047 I want to build a decking to the drawn shape outlined in black. The problem is how close can I build to the gas hot water unit? Will I be able to build around it and be… 0 20230 DIY, Home Maintenance & Repair Hi, I've got a brand new (2nd hand) Bosch Hydropower 16H tankless hot water heater. Since it was installed I have noticed it leaks a lot. I took the cover off and it looks… 0 24147 |