# Forum Home Renovation Solar Electrical Systems  Solar Hot Water

## chalkyt

Hi All, 
Not sure if this is the right forum but I am sure that all of the experts will be drawn to the problem like moths to a flame. 
We live "out in the country". When we bought the place a few years ago it came with a fairly new two star Rheem Quick Recovery storage HWS. It does the job but gobbles up the LPG. I am spending up to $1000 a year on gas using 45Kg bottles which have to be delivered to me, so I started to look at Solar systems. Problem is, everyone wants to sell me a new tank as well as the panel. 
As we can have overnight lows down to -5 in winter, the system needs to be frost resistant. My scratchings around on the internet indicate that an evacuated tube system is the go. The roof is north facing and pitched at 30 degrees so it doesn't stay cold for long once the sun comes up. 
So, the question is, can the panel and assorted bits be fitted to an existing system, how do you do it and what are the tricks and traps. 
It seems that it would save $1000 bucks or so if I could use the existing tank. 
Over to you, and thanks in advance.

----------


## jago

My plumber advised me not to put any HWS on LPG as it burns too much as you're saying. Natural yes LPG NO because of the BTU differences. 
I wanted to do similar but they would not warranty the system if I used a tank (couple of years old), as it was not  matched to their system. I am sure technical people can give more reasons for and against.

----------


## Smurf

Main reason for using a new tank is that doing so is a requirement in order to get the government rebate for going solar. You don't get it if you simply add solar panels to an existing tank. 
So getting a complete new system is likely to be the cheaper option. Then you could just sell the existing gas water heater and get a few $ for it. 
As for running costs, LPG is pretty expensive stuff compared to natural gas or off-peak electricity. Not the most economical way to heat water.

----------


## SilentButDeadly

Chalky.....know your pain.  Been there done that.  Your selection issue is compounded by living in a frost area so a solar HWS will have to be specified to cope. 
You can retrofit.  We didn't because our LPG powered HWS was toast.  The new LPG boosted solar unit uses between one and two 45kg bottle per annum (also the stove).  It's a Rheem Loline. 
Suggest you head to a website entitled www.runonsun.com.au as they do a retrofit kit for well under $2K plus fitting. 
Failing that there is a buyers guide to solar and heat pump HWS in the latest Renew magazine from the ATA....it'll be at the local newsagent next week or head to Renew Magazine

----------


## chalkyt

Thanks for the response from everyone so far. I have checked out Runonsun. It looks pretty interesting and not outrageously expensive. Looks like time to put all the extra information into the brain computer and turn the handle. Gee I thought it was all going to be very simple.

----------


## Bloss

As SBD says - retrofitting is the go and with an LPG tank I don't think you are eligible for a solar rebate anyway. I have done a couple of these DIY with then my plumber coming over to do a check before I actually turned anything on. There are a few eBay suppliers including the Runonsun and they mostly supply tubes as a kit for the roof as well as the adaptor and temp sensor/control unit for the solar system and the pump for the solar system too along with instructions. This is within the capability of a competent DIY but of course the plumbing and electrical work needs to be done by licensed tradies. 
A couple of things to watch out for - you are in Jindabyne so very cold climate. That means evacuated tubes and the big ones - so 58mm diameter 1800mm long and for your location at least 30 of them. Ideally a 400L tank too - or bigger - this is because you want to have a good backup solar heated store during winter especially. Remember this is a thermal system not photovoltaic so although you need sun it collecting heat from the infra-red range not light (PV converts photons in the low to mid blue ranges to electricity and in fact is made much less efficient by heat). That means that solar HWS generally works well in a much wider range of days than PV. 
Also you should insulate all pipe work well and as you should with any HW tank you should add more insulation to it too. There are very few tanks that when touched are not warmer than the air around them, especially at the top and at night and in winter - that is simply wasted energy that you have paid for! Anticon blankets are good, but even just batts with a wrapping of sisalation type foil (or even just a cheap tarp) taped up using reflective foil adhesive tape will give improved performance and save energy. 
If you go solar then it is also important not to forget a simple fact - heating occurs in daylight hours so you should make sure that you have the tank at its coldest at the beginning of the day. The practical impact of that is that you should do your large HW uses in the morning as much as you can - so showers, washing, dishwashing use etc in the early morning so that the water can be heated susing solar energy. If you use most water in the evening or night then your booster (gas or electric) will come on and quickly heat the tank and keep it hot all night - and the solar system will not heat it anymore during the day. That costs you money and defeats the point of going solar. No need to be a solar HWS nazi - just try to do the right timings mostly, if you occasionally need to have an evening shower or have guests etc then just use it as you need to, but good habits will save money and energy. 
Ideally you should have a well-insulated solar storage tank that will allow water to heated to and be kept at 80 degrees or even 85. Then the outlets have a tempering valve so that the water is no more than 50 degrees at the tap outlets. This too means you get better performance from your solar HWS as the hotter water will take longer to drop below a usable temperature. This sort of setup is common overseas, but not in Australia - yet. Likewise the better solar HWS overseas use a storage tank with water at between 90-95 and that water is recirculated, often through a hydronic heating system, and hot water for domestic use is created via a single or a series of efficient heat exchangers. That principal is the same as instantaneous gas hot water systems - only the water being used is heated and only for the time it is needed. In this case the heat source becomes a tank of HW that is being sustained at the right temperature by a solar system in place of a fossil fuel like gas (or electricity from coal). There are some available in Australia such as the German Rotex http://rotex-solar-hot-water-hydronic-heating.com.au/ but very expensive.

----------


## watson

Moving the thread to theSolar Forum

----------

