Hi nimble

You are definitely right. Plumbers Forum is designed for Tradesmen to interact and share knowledge but also a place for the public to turn to for advice. No one is trying to prevent you from becoming wiser (I beleive the cold war is over), there is only a concern about the nature of the job. And honestly I can understand Thunderheads criticism due to this fact.

Your hot water cylinder.  Who designed it and who built it? Because you state it was custom made, a HWC must comply to G12 and engineers specifications also 2712 Standard code in NZ. The element and thermostat must be at a height specified by the code to suit application, Tank must have a biosafe etc.. These are only a few things you need to be aware of. Im sure you know these things already but there are only a hand full of tank manufacturers in NZ that custom make these tanks to the standard.  

No there are no disadvantages with low pressure. In fact you save water, your tank lives longer and being open vented no issues with valves and maintenance. Correctly installed its also safer then mains. Combination Wetback / Solar makes it cheap to run. I personally have one and I love it.
There is more concern in the state the Cylinder is installed, being horizontal (or @ 20 deg) your layers of heat (stratification) are much closer to each other then they would be being vertical hence less efficient, other nuisances such as hot/cold water patches could occur when showering, so even more important make sure you have a diffuser on your returns.

All your Solar / Wetback and cold come in through one end, I assume the thermostat is also on that side, that's where there is a downside of having everything open , when your showering you will introduce cold water into the tank and your probe / thermostat could get a wrong reading and end up switching on your element even though there is enough hot water in the tank available.

another thing you need to be aware of is filtration. Being on tank water means a lot of debris will get pumped into the tank. This will damage your wetback (usually steel heat exchanger) and your solar panels.  Also looking at the angle of your HWC most of it will end up slugging in the bottom corner of the tank, not really good.

My personal favourite is a Mains Pressure tank for Domestic supply, two coils, one for Solar and another designed for wetback. Wetback connected as low pressure. Glycol on both indirect wetback and Solar installations. It's more efficient and I protect my panels and wetback long term.  The water will also taste better  Merto Wetbacks is what I recommend my clients.

Hope this helps. Once your finished please let us know how efficient the system is. I'm very keen to find out.

Regards Plumber

Not a problem nimble,

Paid $1200 to a local importer of solar panels. He designed it and had it manufactured in the south Island.
Our low ceiling height would only allow for much smaller vertical tank.   I really wanted at least 200L i thought  it makes sense
that with a large insulated tank I can store more energy for cloudy days in the summer or warmer days in the winter.

Ok, im guessing it was SH in the south Island. I hope so anyway they are reliable. The bigger the better, your right.

I think this is marked on the Diagram as  pocket probe?? port located at the end with most the feeds.
Is it possible o have a longer probe thermometer...would this make a difference?

The pocket probe is not the thermostat. The probe controls the solar heating system and the solar heating controler then controls the element. Every HWC is also manufactored with an additional thermostat and Bio Safe.

The diagram doesn't show actual angle my  tank. It's much more than 20 deg i will measure tomorrow.
I'm hoping controlling the power supply with a timer will give me some control over when the element can operate. Is this a practical approach?

Not the Ideal solution but that will work to an extent.

I have looked a a few things that will hopefully help. Tipper on end of spouting to catch sediment. Wire along the pitch of my roof to annoy birds.
I'm unsure on this piece of advice?? Limestone in the bottom of my main tank to neutralise acid rain and extend the life of my tank??
Ultimately  would I want some kind of micro particle filter? These are expensive!!! Is there any more simple or cheaper alternatives??? Some kind inline filter that can be cleaned changed manually? How much do filter systems cost?

Have a look at your foot valve in the tank that should have a strainer with at least 50 microns.  All the above mentioned will help but you will still need a 10 - 20 micron strainer on your pump outlet. Cant think of the manufacturer at the moment but there is an outfit in Albany Auckland that does them in a cartridge form. They are not expansive and work well on pumps. Best ask your local merchant. If I can remember the name I will post it here.  cost somewhere between $150 - $250 by memory, its been a while.

This does concern me but i guess this can happen to a vertical system too over a long period of time. It's my understanding that this system is relatively safe as it is vented under  low pressure in a relatively strong cylinder.
As i have explained i will be having this installed  by a professional.......  i also like the metro wetbacks they seem very good value. I only have 1.7 Hectares (not 2) so i beleive unless my wood burner has an oven too i will be limited to by the environmental laws as to which fireplace i am allowed Is there any way around this it seems unfair since the fireplace will be multi purpose and i am planting a sustainable wood source.
I am planning to plant and already cutting down Eucalytus.  I beleive properly dried this is a nice source of fuel.

Once your water is filtered properly there should be less concern, I would still flush it out once a year or so depending on water quality.  Yes  "environmental laws" we love them don't we? I think I will leave it at that.

Will try to post the name soon.

Plumber

Hey Plumber

I got a reply from who i bought the cylinder from. It was manufactured by Superheat and the thermostat is located as per the diagram. Does this make a difference??

Found those details:

Hydroflow DistributorsHydroflow Distributors
221 Bush Road Auckland 0632 - (09) 415 5585
Open Weekdays 8am-5pm

The product I used a few years back is IF25RD comes with different microns as a cartridge.

Hope this helps

Plumber

Always our pleasure nimble and all the best..