Today I only did a little bit of practical work. The lower pressure side for the water tanks is finished. I now started looking at the routing of the pressure lines, specifically the hot water supply lines. The cold is trivial and I have already placed the drinking water lines. For the drinking water I have only 3 connection points and for the fresh and hot water I have 5 and 4 respectively. This is not really a complex installation. The tanks with all the valves and connections have been more laborious.
The main aspect of the hot water supply is the hot water circulation pipe with the circulation pump and it’s control. I also have been looking at cold water diverters, the replacement technology for existing installations where hot water circulation would not be possible. I won’t save anything on the contrary, I would have to connect the diverter hose for all outlets anyway and have to put the water somewhere. I mean this is really an improvised solution lacking a good system.
The general argument against hot water circulation is energy use for the pump and heat loss in the pipes. This is only true when one runs the system permanently, but who in their right mind would do that when he has to pay high energy cost. With decent building standards the hot water pipes are well insulated and will limit heat loss. When you use solar for your hot water as well as the circulation pump all this becomes a mute point. The water is hot enough and the pump is driven by a solar cell, so what is the point of not using such a system. Cost for pipes and labour. Most houses are built as cheap as possible and there would be no room for such convenience.
When you are lacking water it hurts when you have to wait a minute until the shower gets warm and try to recycle the water for another purpose. We are used to that since 20 years with limited water capacity in our rain water tanks. I still don’t get over the archaic plumbing in our house.
Now doing the same in my van would be a crime in my eyes. When you have a chance you do it right, like we did in the first house we built in Australia.
I have hot water solar panels, also have a solar circulation pump for the glycol through the solar panels and I could use a solar driven pump for hot water circulation but I will not do that. I do not intend to circulate the hot water all the time even if it is free. One of the reasons is that I do not want to keep all lines under pressure all the time especially not when we are driving over rough roads.
The answer is an on demand circulation system. Each hot water outlet has a control unit with a push button and a light. When the button is pushed the circulation pump will push the hot water through the pipe until a temperature sensor at that outlet signalises sufficient water temperature. The intent is around 70 degrees. This would be too hot for normal household use but we run thermostatic mixers, which means one can pre select the temperature and it will be mixed correctly every time one opens the lever. This is true for all outlets with hot water connection.
The control unit for the circulation pump can also be triggered from the central system when a use profile is activated which includes hot water.
Using thermostatic mixers is a better solution than reducing the temperature at the hot water system because the temperature regulation is more precise and stable at the outlet, and at times we want really hot water anyway. The solar panels will push the water temperature to 80 degrees easy.
All the hot water supply lines will be done in copper with compression fittings. I will install this in the next couple of days.