19.01-19
SolaStat-Plus Plumbing Issues.
Disclaimer.
For full information on compliance and safety standards for solar hot water systems the appropriate local
standards must be referred to. All plumbing to be carried out by qualified plumbers only.
We provide the following information as a guideline only to help obtain the greatest efficiency from the
system. Any information supplied here is based on feedback to us by experienced solar hot water
professionals and in no way represents a complete guide to plumbing such a system, as we are not plumbers
and do not represent ourselves as such. Best plumbing practices must be used in all instances.
Introduction.
Any solar hot water system involves professional level plumbing and water much hotter than would normally
be seen in standard domestic hot water systems. For this reason Instrumentation Control Manufacturing
Ltd recommends any installation is carried out by a registered and qualified plumber. All parts including the
pump must be rated for the elevated temperatures found in solar hot water systems.
Solar Hot Water Specifics.
1. Tempering valve.
There is a huge amount of energy radiated by the sun. It is not uncommon for the water from the solar
collector to exceed 100C (under pressure).
Therefore it is vital a tempering or ‘mixing’ valve is fitted so the domestic supply from the tank does not burn
the end users. The tempering valve must be installed to best plumbing practices. The tempering valve must
be rated to handle these elevated temperatures.
2. Non return valve.
Hot water rises and cold water falls. If the solar collector is colder than the tank, such as during the night,
the hot water from the tank can self thermosiphon up to the collector. The collector now radiates the heat to
the cool night air and the water descends back down to the tank. To stop this loss of hot water at night or
during cloudy skies there has to be a one way or ‘non return’ valve fitted.
The failure of this non return valve is a common problem with solar hot water systems. The orientation of
the valve as per manufacturer’s instructions is critical. Also the valve sometimes will not close when swarf
or other debris get caught in the valve seat.
3. Pressure relief valves.
Solar hot water systems can run much hotter than standard domestic hot water systems. Hotter water
expands more and needs high quality pressure relief valves to avoid possible catastrophic rupturing
somewhere in the system, probably the tank.
Qualified plumbers using best industry practice must decide on adequate pressure relief valves, the number
and placement of them.
4. Air Relief Valves.
It is important that air relief valves are fitted (especially in a low pressure system) to the highest point of both
the feed to and the return from the solar water collectors. Otherwise air locks can occur within the piping
etc., and not just the pump. (An air lock in the system will increase the head that the pump is working
against and for some installations this is too much and the water ceases to circulate. For systems where air
locks occur, the pump may need to be set to a higher speed or a higher head pump installed).
5. Cavitation.
A pump is used to circulate the water between the tank and the collector.
If the pressure at the inlet or impellor of the pump falls below the vapour pressure of the liquid being
pumped, cavitation will occur. Cavitation in a pump is more likely to occur as the temperature of the water
rises and/or the pressure of the water decreases.
Bubbles form when the water is sucked into the pumps impellor and collapse again as small implosions
when the water is ejected out of the impellor which can be so rapid that a rumbling/cracking noise is
produced (it sounds like stones passing through the pump) and there can be damage to the impellor and
other sensitive components as well as a drop in water volume moved.
To Next Page
Loading...