Specifications
Problem
Cause
Solution
Poor Solar Heating 
Contribution (Compared 
to previous output at 
same time of year)
Increased hot water demand
• Check if hot water demand has increased, which would 
reduce the % contribution from solar even with the same 
level of output
Poor Solar Heating 
Contribution (Compared 
to previous output at 
same time of year)
Insufficient flow rate
• Check flow gauge for proper flow rate, check pump 
operation if flow rate insufficient
• Adjust restrictor screw on flow meter
• Check heat transfer fluid pH, color and viscosity, may 
need to be flushed and replaced.
Poor Solar Heating 
Contribution (Compared 
to previous output at 
same time of year)
Partial shading of collector
• Check collector location for shading or snow build up. If  
snow buildup, ensure bottom of collector is raised off 
roof, and angle of install is at least 45
°
Poor Solar Heating 
Contribution (Compared 
to previous output at 
same time of year)
Heat loss from pipes
• Check that insulation is still in good condition with no 
exposed hot piping
Poor Solar Heating 
Contribution (Compared 
to previous output at 
same time of year)
Damage to evacuated tubes
• Check that evacuated tubes are all intact and the 
bottom is still silver
Poor Solar Heating 
Contribution (Compared 
to previous output at 
same time of year)
Heat pipes not operating
• Check that heat pipes are making good contact in 
header, and are hot at the tip
Poor Solar Heating 
Contribution (Compared 
to previous output at 
same time of year)
Scale build up in brazed plate HE 
(if BPHE used)
• Flush sediment from tank
• Back flush BPHE with vinegar (or equivalent)
• Install sieve and clean out valve before pump on BPHE 
loop.
Poor Solar Contribution 
(Compared to expected 
levels)
Thermo-siphoning
• System may be reverse thermo-siphoning at night. 
Ensure check valve after or in pump is working. May 
need to install heat trap (downward U shaped pipe) on 
return line close to tank.
Poor Solar Contribution 
(Compared to expected 
levels)
Insufficient pump run time
• For normal ON/OFF pump operation (not variable 
speed) ensure the pump is running long enough for the 
heat from the collector to return to tank - feel return line 
with hand (careful) to check. Reduce dTMin value 
slightly.
Poor Solar Contribution 
(Compared to expected 
levels)
Pump cycling too long and 
dissipating heat
• dTMin value set too low, especially if closed loop 
system (applies to ON/OFF or variable speed)
• T2 sensor too low in tank, always reading cold water. 
Move to correct location.
Poor Solar Contribution 
(Compared to expected 
levels)
Excessive tank heat losses
• Insulate both the hot and cold water pipes connected to 
the storage tank. A check valve (spring not flap) on the 
cold and hot pipe close to the tank will help reduce heat 
migration up the pipe.
• Insulate any exposed fittings and valves on the storage 
tank. DO NOT impair the operation of the PTRV.
Not enough hot water
IF ELECTRIC
Electric not heating water
• Check operation and power supply to element
• Replace element if necessary
• Check controller boost settings
Not enough hot water
IF BOILER or GAS TANKLESS
Booster not heating water
• Check gas/fuel supply
• Check operation of boiler/heater
• Check controller boost settings
Not enough hot water
Faulty tempering valve
• Check operation of tempering valve
Not enough hot water
Increased hot water demand
• Install larger capacity boiler/booster
• Revise boost settings of controller
• Install larger storage tank
Intermittent short 
batches of cold water 
when showering
Faulty tempering valve
• Check operation of tempering valve
Intermittent short 
batches of cold water 
when showering
Faulty tankless gas booster 
operation (if post gas system)
• Check operation of tankless gas booster
Apricus Solar Collector Installation & Operation Manual - USA
Copyright  2011 – Apricus Inc Doc: A7-05.4.12-PB Page 2 of 129










