It was a hot day today (36 decrees C), and has been quite warm for the last few days. At about 1pm I noticed that the hot water service was boiling.
Normally on a hot day it boils/gurgles a little bit, maybe overflows about half a litre, and that happens throughout the day every 20 mins or so. And thats OK. Thats what its supposed to do – its an open vented system.
Well, today it just continued to boil, like a kettle, non stop. I didnt think that was too good, so the only way I could think to cool it down was to cover the solar evacuated tubes. So I got up on the roof with a canvas tarp, and covered up the tubes. Problem solved.
So, I am thinking that might be a regular occurrence, particularly when we have built the house and are not drawing much water (ie heat energy) from the hot water tank.
Today we installed the solar hot water evacuated tubes. The hot water service is already installed, so I have just been waiting till my plumber can come and do the tubes and commission the unit.
The tubes are 1.8m long, and there are 30 of them.
One end goes into a manifold where the water from the tank runs through, and the other end just goes into a plastic mounting boot.
Plastic boot end
Manifold end
Each tube is like a thermos flask – its a double walled glass cylinder, and between the two glass walls is a near complete vacuum. Inside the cylinder runs a copper tube that has glycol inside it. The tube heats up from the sun, transfers the heat to the copper and thus the glycol. The glycol gets hottest at the top of the copper tube (the bit that goes into the manifold). Water flows through the manifold, and the very hot copper tip transfers the heat to the passing water.
The copper tube
Manifold and frame on the roof
Manifold, showing the openings the tubes go into
The water circulates from the hot water tank (which in my case is up inside the roof), through the manifold, and back into the tank. The circulation operates by thermosyphon – there is no electric pump required. Cold water is drawn from the tank from an outlet that is low on the tank, the manifold inlet is higher than this tank outlet, the manifold is on a slight incline, and the water returns to the tank on an inlet that is above the height of the top of the manifold.
When installing the tubes into the manifold, heat transfer paste is smeared onto the copper ends so that there is good thermal conductivity between the copper of the tube and the copper of the manifold.
Note: keep the tubes covered when they are sitting in the box ready for installation, else the copper ends will get too hot (from the sun striking the glass) to handle and apply the paste.
The manifold has rubber gaskets to ‘seal’ around the glass tube. These gaskets proved to be a real pain in the arse – we could not slide the tube into the manifold without pushing the gaskets off their seating. So, we ditched the gaskets – they were proving to be of limited value anyway. Probably really only used to stop a bit of moisture/rain from entering the manifold, but I don’t really think that would matter much anyway.
Once all the tubes were installed, and the manifold pipes penetrating the roof were insulated and lagged with tape (to protect the insulation from birds and UV), we could fill the tank and test wait for sunshine to heat things up.
Basically the thermosyphon would work or it wouldn’t. If it didn’t, then the backup was to install a small circulating pump. We may install a pump regardless, because of frost. On a cold night we dont want the manifold water freezing, and bursting pipes, so keeping it circulating every half hour for a few minutes would solve that.
This weekend we took delivery of the water pump, and installed it. Finally we can have functioning garden taps, just as the rainy season starts !
The pump I am using is made by Davey. Its a 1.8kw single phase model. I am also installing a 60 litre Grundfos pressure tank so that the pump does not cycle every time a tap is turned on. The pump will be connected directly to the 50mm ring main pipe, and will service all plumbing on the property (garden, house and workshop). Both water tanks will supply the pump.
Here is the pump an pressure tank:
This is where the pump is going, And here are all the fittings I need to link it all up:
I had just enough room to mount it on a corner of the tank slab, but had to cut away some of the concrete to get the correct angle on the 50mm inlet pipe.
There was a number of times I had to get out the heat gun and soften up the 50mm blueline pipe to get the bend out of it that is caused by it sitting in a roll for so long. Its a real pain in the butt to work with because of this bend.
It took me all day to connect it all up. It was a nervous moment turning it on, but it went OK. I ran around opening garden taps and sprinkler heads to let out the air.
I have to say, it pushed out HEAPS of water. The impact sprinklers shoot for about 15 meters.
Well, the day has finally come to install the water tanks. It was put of for several weeks because they Dave from Rural Tanks in Seymour got a very bas case of flu that took him out for more than a week.
Di’s father Sam offered to help, so I arrived at his house at 7am this morning and we trundled up to Trentham. Dave arrived at about 9:30am with his truck and two huge tanks.
There was no way he was game to drive onto the block, for fear of getting bogged, so he parked at the front, and we rolled the tanks off the truck and up to the back of the block. This actually proved much easier than I expected. Luckily for us, a perfectly flat block worked in our favour. Each tank weight about 300kgs, but they are easy to roll.
We laid out the melthoid on the concrete slabs to stop condensation seeping up through the concrete and rusting the tanks, then we simply rolled the tanks up to the slabs and tipped them over. Very easy when you have someone who has done it hundreds of times (Dave).
Sam laying out the methodSam cleaning mud off the tanks.
All in all it went very easily. The two tanks only took about an hour and a half to install.
The installed tanks.
When we were rolling them along, one of the lids poped out of its seam for about 1200mm. Dave said this is normal, and he just used a few tools to pop it back in and crimp up the seam.
At about 12:30, a water tank arrived to pump in 16000 litres of water. Again, he didnt drive onto the block, but I had forwarned him to bring 60m of hose. No probs. He just pumped from the start of the block. 8000 litres into each tank.
Dave said that a gal tank will last muck longer if it is full with water. So we need to get some more delivered. The whole reason for getting the tanks now is so that we can fill the ponds. We cant put the pond liner in without water – as you spread out the liner, you need water to hold it in place so you can stretch out all the wrinkles.
