16 April 2009

Solar Hot Water?

| semaj
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I’m currently in the market for a new hot water systems and given the rebates currently available am seriously thinking about solar.

I was after some advice from fellow Canberrans as to whether or not this is a good idea, and any recommendations for brands, suppliers and installers.

Can anyone else out there in riot-land who has done this share their stories, both good and bad?

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Assuming you have an existing electric mains HWS and it is on the sunny side of the house you should consider a Dux Airoheat 258 litre unit. These attract RECS as they are heat pump technology.They instal like a breeze and connect to existing electricty and water where the existing HWS is – even use the same slab. The Dux now has a “cold climate chip” which works perfectly in Canberra. These units are incredibilly cheap to run – mine is 70% cheaper than the old off-peak HWS I had. Unsure of current price but they sure are competitive with the cost of running a solar system with electric mains boost and they don’t look as ugly nor do they create leak contingencies with extra plumbing needed for solar as they use the existing piping with same pressure etc.

I bought a Hills Endless Solar system for a new house that’s less than 6 months old. The system was a 30 tube system and a 315L electric off-peak boosted tank. The tubes are on a north facing roof and the tank is close to all water outlets (except the kitchen, described later). I have the tubes raised to achieve maximum winter performance (which was probably overkill but the wife really likes to have hot water at the end of the day and a previous flat-panel system sometimes failed to provide this). The house is in South Australia but this is the only site I’ve found with a non “testimonial” review of a the system so I’d like to add my opinion here for anyone else searching on hot water systems.

This is my first winter with the unit. Through summer the unit worked fantastically and only once needed the booster on (when we have several days of heavy clouds come over). Since ANZAC day we have had the summer break and cooler and cloudier weather has come over. The tank now fails quite often (average of at least once a week) to provide enough hot water in the tank by 7pm for my wife to half-fill a bath. The water can be warm or even tepid. The performance tends to be unpredictable too. Today was sunny with very mild cloud cover and a maximum of 18C and we only had warm water in the tank. Sunday started quite cool and was heavy overcast all day except for a few hours in the afternoon and we had hot water. As both my wife and myself are at work during the day we are not consuming hot water.

I had installed a solar hot water at my previous house (a Chromagen split-system to replace an electric only heater that had failed). We had similar conditions there to this system. This is a shame as I’d spent considerable time looking for an improved solar hot water system to use when building the new house. I’m checking with other installers to make sure the system has been set up correctly. I know the booster works as I always have a hot shower in the morning.

As mentioned earlier the kitchen is a special case. The tap is the furthest from the hot water unit. To make sure hot water was available instantly at the tap I have a pump installed under the tap. It brings hot water from the tank to the pump and then returns it to the tank. This only runs when the water drops below a certain temperature, and then only on a timer. I’ve also insulated all of the copper pipes in the system to minimize heat loss. This shouldn’t affect the hot water system at all but is something different to normal setups. Turning the pump off for the day doesn’t seem to affect if the tank goes cold or not in the afternoon.

I have no problems with water pressure either. I don’t have an override booster but this would seem to be the best solution to my problem (get home from work, find the water is only warm, flick on the booster and the wife can have a nice hot bath and I don’t hear any complaints about it).

We bought a Hills Endless Solar from Enviro-Friendly in Phillip a couple of months ago.

On the whole we’re very happy with what they’ve done .. except .. we didn’t get a pre-installation site inspection (I think they were very busy) so we had to compromise on the siting of the tank. Make sure they come out before install date to make sure there is somewhere to put the tank. We had an old system inside, and this was installed in our carport. There are also a fair number of pipes in and out of the system, so if it is an outside install you might want to ask about where the pipes will go. I’m going to have to retrofit some colorbond flashing to cover up the pipework.

We decided not to go for the instantaneous gas booster hooked inline, but instead went for electric in-tank boosting. There were a few reasons for this (but I’d like to hear from someone with the gas booster who might be able to comment)

1. Cost. It was going to add alot to add the gas booster (the tank comes with an electric element in it anyway).

2. The evacuated tube systems are very efficient and boosting was going to be largely unnecessary (they assured us of this and other people I know with similar systems said the same thing).

3. I was worried about the cold/hot water effect with inline gas boosting. My inlaws have conventional on-demand gas (no solar) and with low pressure on their water-saving shower head the water constantly cycles between hot and cold as there isn’t sufficient flow through the unit and it has to shut off the booster. I was worried that putting pre-heated water into an on-demand gas booster would only make this situation worse (though granted the difference between “hot” and “cold” would not be as great as the solar heated water would at least be lukewarm).

They installed an override switch for the electric booster in our laundry so we can have it off most of the time and only turn it on when we need it. So far we haven’t needed to turn it on.

I would recommend an evacuated tube system for Canberra. They have superior freeze protection to flat plate systems (they don’t have any water in the manifold when it is cold, so there is nothing to freeze, expand and break the system). Evacuated tubes are used in places where it gets very very cold (think snow). Evacuated tubes are also more efficient when there is a greater temperature gradient between the outside and the water temperature your are trying to heat to. My system was producing hot water yesterday at 8am when the outside temperature was below 10degC. If you were buying a hot water sysrtem for Sydney or down the coast flat plate might actually be more efficient than evacuated tube, but in Canberra you will produce hot water for more of the year and in colder temperatures than with a flat plate.

We have no problem with water pressure.

If you go for a panel based solar hot water system, you will be less then impressed. Evacuated tubes (Hills Solar) with ground based tank and booster are the only way to go in terms of efficiency and efficacy. It will cost you more to install, but you will be happy.

solartec renewables

Sorry – I don’t know how ours works – gravity or not…ours is the ACTEW version, and under warranty for 10 years, which is great.

You can have a super hot shower though.

I’ve had solar systems in 3 houses in Canberra and never had panels freeze.

aa said :

Did you have a solar panel on the roof and the tank seperate or one of those tank and solar panels in one that they put on the roof? There’s a big difference between the two.

Combined solar panel + tank on the roof.

Not sure about specific details of the equipement, since we were only renting.
It was new though, the house was only 1 year old when we moved in during ’06.

I am currently debating a quote from Fieldforce in Philip. Pretty good deal with the rebates, but I have to factor in the added cost of moving my hot water tank for space considerations.

I read a consumer voice article on the Canberra Times that talked about warranty issues with panels freezing. Fieldforce tells me that their panels don’t freeze, though – the water keeps moving, apparently.

If you have a small house, you can also think about heat pump technology.

sepi said :

We have solar hot water and I couldn’t be happier. They systems have improved a lot in the last 5-10 years. Our water is really hot and we don’t use the booster except coming into winter.

The boosters now come with a timer, so you can set the booster to come on at 6.30AM if you expect 5 people to have a shower.

Hot water used during sunny hours is basically free, so hot washing can be done all weekend.

sepi, does the hot water system you use provide any power to drive the pump to the shower, or is it a gravity system?

We have solar hot water and I couldn’t be happier. They systems have improved a lot in the last 5-10 years. Our water is really hot and we don’t use the booster except coming into winter.

The boosters now come with a timer, so you can set the booster to come on at 6.30AM if you expect 5 people to have a shower.

Hot water used during sunny hours is basically free, so hot washing can be done all weekend.

Have a solahart with Electric boost. I think it is a ???XII and was supposed to be good for a household of 8-10 people.

Use the boost for probably 10 days a year over the last 7 years.

Runs out occasionally when wife fills up spa bath for a long soak but otherwise ok.

Low pressure is not really a problem, just change the shower head or get an adjustable jet show head.

In summary: done the job happily and can happily recommend them for a family of 4 -6.

Did you have a solar panel on the roof and the tank seperate or one of those tank and solar panels in one that they put on the roof? There’s a big difference between the two.

peterh said :

we had solar, then went to an infinity gas system. saves on gas, as it only heats the water when you need it, not to keep a tank hot…

In theory the system I had used the best of both worlds, but it seemed like we used the gas booster almost every time we used the hot water anyway!

we had solar, then went to an infinity gas system. saves on gas, as it only heats the water when you need it, not to keep a tank hot…

Had solar hot water for 3 years in my last house and it was combined with an instant gas booster for when the solar was out of juice or too many people were having showers.

The system was ok, it saved money on the gas bills.
The one thing that stood out the most was the low water pressure from the system though.
I like hard showers and wasting tons of water as fast as possible, and I just couldn’t do it using the solar hot water… 🙁

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