Mar 1, 2014: Pumps and Solar Hot Water: decisions, Decision, DECISIONS!

I’ve often said that there must be a million decisions made in the building of even the smallest, simplest home. Some are small and quick like deciding where each screw is placed in a sheet of plywood. Others are big and tricky like deciding what sort of floor, wall or roof system you’re going to use, or what sort of windows to buy. This last week has been a week of fairly significant and difficult decision making (or not making, as the case may be).

Solar Hot Water: I originally had in mind an evacuated tube split solar hot water system from Apricus Australia. In a split system the panels are on the roof but the tank is either on the ground outside or, in our case, in the storage attic above the bathroom. But this was complicated by a number of factors. First I was told that the available storage tanks wouldn’t fit in the available attic space. Then I had a bloke from Dux tell me that flat plate panels are not only more durable than evacuated tubes but are also more efficient, even in low-light conditions. This was the first time I’d ever heard that flat plates performed better than evacuated tubes so I asked him to send me more information. The document he sent is Dux advertising that makes lofty claims but doesn’t provide any information to back it up (click here to view the pdf). This is completely contradicted by the following Wikipedia page which accurately states that it is very “difficult for purchasers and engineers to make informed decisions.” I’m waiting for the Dux guy to get back to me with more information. Meanwhile Paul from Tempco in Bowral told me that after installing hundreds of solar hot water systems in this area he is now recommending that people put in a heat pump water heater and solar PV panels instead. So we haven’t made any decision yet but we’re looking at two main options. One is back to the Apricus Evacuated Tube solar system because Paul informed me that they now make a smaller (160lt) tank that will fit into the attic space that we have. The other is a split Air-source Heat Pump water heater from Sanden Australia. This systems looks pretty promising too and is the only “split” heat pump water heater I’ve seen (i.e. the compressor that usually sits on top of the tank is a separate unit so it can be outside and the tank can be inside). It claims to be super-energy-efficient, very quiet, and also has the option of a 160lt tank which would fit in the attic. I’m waiting for more information and costing for both of these possibilities but leaning towards the solar because it’s quieter and has fewer moving parts.

Evacuated tube solar panel (click on image to visit Apricus's website)

Evacuated tube solar panel (click on image to visit Apricus’s website)

Split air-source heat pump water heater system (click on image to visit Sanden's website)

Split air-source heat pump water heater system (click on image to visit Sanden’s website)

Rainwater Pump: After lengthy research and discussions with a number of technical advisors we did manage to make a decision and order the pump for the rainwater tank. The main factors that we were considering were reliability, noise and what sort of switching device. This is an elegant little device that allows us to use tank water whenever we have it and automatically switches the entire system over to town water when the tank gets low. Click here if you’d like to read more details about this exciting decision but to sum it up we settled on a CNP-CHLF2-30 external centrifugal multi-stage pump with a Bianco “Rainsaver” switch from Southwell Irrigation who have provided reliable equipment and service to my parents and their Kangaloon property for many years. They also gave us a very nice discount so the final cost for both the pump and the Rainsaver was $852, more than we had budgeted but I feel confident that this is the right equipment for our needs.

Other things I’ve been researching and trying to decide on this week are exhaust fans for the bathroom and kitchen, ceiling fans, light fixtures, plumbing fixtures, door hardware, and exactly how to make our surface-mounted electrical system. More about these fun things soon.

3 comments to Mar 1, 2014: Pumps and Solar Hot Water: decisions, Decision, DECISIONS!

  • Jason

    I have jus ordered a siddons splitsystem heat pump hot water systemspent hours reading up on evac tube and heat pumps and decided on the heat pump and a 4kw pv system

    • admin

      Hi Jason, thanks for visiting the Greeny Flat website and sorry about the slow response. I’ve been away on an extended trip and just got back. Regarding the hot water decision, it was a real toss up for us and I think the split heat pump systems are an excellent option. We settled on an Apricus evac tube solar system and it seems to be performing well enough. What I don’t like about it is that there is no monitoring system that allows me to know how much hot water is in the tank or what the temperature of the water is. So I don’t know when I need to run the booster until we run out of hot water (which has only happened once after a few days of cloudy, cold weather). I also don’t know when it’s necessary to run the booster to sterilise the water in the tank. I’ve read various opinions about this but it seems that it is necessary for the whole tank full of water to be heated to at least 60degC at least once a week in order to kill any possible Legionaire’s Disease. But I have no way of knowing if the solar system has been able to do that by itself without the booster so I’m running the booster once a week anyway. Now that I’m back from my trip I intend to press Apricus to come up with a better monitoring and control system. How are you liking your split system? Andy.

  • David

    Flat plate collectors are single glazed. Evacuated tube collectors are double glazed. Each layer of glass reduces the total sun that can be utilised. So flat plates can technically perform better in ‘some’ situations.

    That is probably the technical basis of the Dux marketing brochure. But it leaves many questions unanswered including whether this has any practical advantage to the house occupants.

    Comparing evacuated tubes to fluorescent tubes is technically correct (they are both glass tubes) but otherwise ‘confusing’. Evacuated tubes are very much stronger than fragile fluorescent tubes. Both types of systems are engineered to survive harsh weather conditions so ‘more prone to breakage’ is disengenious and unquantified.

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