General Maintenance Issues

Although nominally "low maintenance" the following notes relate to interventions required at this installation. Simpler panels may be more reliable and therefore cheaper to maintain.

Problems with the electric blinds

Since there are no moving parts in a "traditional" solar panel there are fewer things to fail; for the curtained HFC-2 panels each contains a PTFE coated roller blind deployed by means of a 12V DC motor housed within the panel casing and activated by the solar controller module.

There has been a tendency for the electronic blinds located under the glass panel cover to jam when opening or closing. The problem may be more apparent if the blinds are operated when higher temperatures are already present, since the leading edge of the blind comprising an alloy strip may expand increasing the likelihood of the blind roller becoming stuck.

To reduce the chances of the blinds not opening or closing correctly the runners along which the blinds deploy can be coated with a high temperature lubricant such as a ceramic grease.

Another approach that seems to work well is to file the corners of the alloy leading edge, adjacent to the roller, so that the sharp edges do not dig into the runners.

Both the above actions require the panel covers to be removed and this activity also requires safe access to the panels, which in this installation means erection of scaffolding which increases the cost of maintenance.

As the blinds are operated only very infrequently the risk of the blinds sticking may not be apparent. A more frequent test of the curtain action is therefore advisable so that any problems can be remedied ahead of actual need.

Notes on removing panel covers

Panel covers consist of toughened glass in an alloy frame. The frame is riveted to the casing which holds the evacuated tubes and curtain mechanism. The rivets are hidden under alloy strips which fit tightly into a retaining channel forming a border around the frame. These strips need to be prised away from the frame to access the rivets and the best way to do this seems to be to use a fine tip screwdriver to peel back a corner of the stripping, then as a gap is created move gradually along the length of the strip until a large enough section is detached that will allow the remainder to be pulled free. The rivets can be removed easily, drilling them out with a 3mm drill bit. A cordless drill is best for this operation. once all rivets are removed the panel cover can be gently lifted away from the tube casing. Replacing the panel covers is the reverse procedure. New rivets will need to be set and the frame trim strips can be tapped back into the alloy retaining slots using a soft-head hammer.

The strips fit very precisely so care needs to be taking to make sure the mitres in the corners are set as accurately as possible when re-fitting the covers.

12V Wiring Replacement

The low voltage circuitry to operate the curtains was originally installed with unshielded twin core cable and plastic connector block junction boxes for attaching the panel blind motor leads to the 12V controller supply.

These boxes were not IP rated. As this was low voltage and the cabling seemed fairly protected under the lee of the panels this did not seem to be an issue. However the extremes of temperature and general exposure to the outdoors took their toll. The circuitry continued to function but UV damage caused the plastic to become very brittle and the boxes cracked exposing the connection blocks.

In view of this, all the 12V circuitry was replaced with heavy duty sleeved twin core cable placed inside flexible plastic ducting to give further protection from the elements. The junction boxes were replaced with IP66 rated plastic boxes and zip-tied in place. The replacement items are much better suited to the conditions and no further remedial work is anticipated to this part of the installation.

Bird damage to tubing insulation

The panels are connected to the pump station and hot water tank by stainless steel hoses covered with high temperature resistant EPDM insulation. Where this lagging was left exposed externally it became the target of magpies and crows, possibly for nesting material. In places the stainless steel tubing was stripped bare! Heat losses to this damage were probably small but obviously the intention is to keep any heat losses to a minimum.

The insulation was replaced and inverted lengths of plastic guttering were strapped over the exposed insulation with stainless steel zip-ties. The expectation is that the zip ties will hold the protective guttering in place even in high winds and will prevent further attacks by birds.