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Mikesolar · 10-12-14, 08:35 AM

Controllers are almost all differential controls so they have at least 2 if not 3 thermistors (almost all the good ones are European and use a PT1000 thermister). They also have triac based variable speed control of the circ pump and are usually limited to 1A or less. Some have fixed on/off control and can take 4A but that usually limited to drainback systems. remember that in Europe 1A is 220w and here it is 120w so we are limited to the size of pump we can use for variable speed systems.

There is a reason why electronics typically have only 1 year warranties. It is still the weak link in the solar system. Lightning strikes hurt and the problems I have seen are due to the controller thinking the panel temp is hot enough to pump when it is night time out. This has been true of almost all the controllers I have seen.

If I use the PV system, the pump is light activated so cannot run at night. There are many types of pumps out there and if you can use a glycol system, a "positive displacement" pump can be used such as the Thermodynamics E-mag pump. It has a head of 100' and a suction head easily over 6'. Any of these type pumps, if kept below the top of the HX will do fine anyway.

10-12-14, 08:35 AM	#8
Mikesolar Master EcoRenovator Join Date: Aug 2012 Location: Toronto Posts: 958 Thanks: 40 Thanked 158 Times in 150 Posts	Controllers are almost all differential controls so they have at least 2 if not 3 thermistors (almost all the good ones are European and use a PT1000 thermister). They also have triac based variable speed control of the circ pump and are usually limited to 1A or less. Some have fixed on/off control and can take 4A but that usually limited to drainback systems. remember that in Europe 1A is 220w and here it is 120w so we are limited to the size of pump we can use for variable speed systems. There is a reason why electronics typically have only 1 year warranties. It is still the weak link in the solar system. Lightning strikes hurt and the problems I have seen are due to the controller thinking the panel temp is hot enough to pump when it is night time out. This has been true of almost all the controllers I have seen. If I use the PV system, the pump is light activated so cannot run at night. There are many types of pumps out there and if you can use a glycol system, a "positive displacement" pump can be used such as the Thermodynamics E-mag pump. It has a head of 100' and a suction head easily over 6'. Any of these type pumps, if kept below the top of the HX will do fine anyway. Last edited by Mikesolar; 10-12-14 at 08:51 AM..