Solar control
49
Solar control
Basic diagram:
Input
variables:
Output
variables:
Enable solar circuit
Status solar circuit
Indication of the output A
Collector temperature
= T.coll
Status MAX limit reached = cylinder limit has
been reached
Reference temperature
= T.ref
Limit temperature = T.lim
Simple description of the function:
Release of the solar pump A, if the temperature in the collector T.coll is greater by a difference than
the reference temperature T.ref, which is the (outlet) temperature of the cylinder. In addition, T.ref
must not have reached its upper limit yet.
Special features:
The system comes to a standstill when the collector exceeds the temperature of 140°C to pre-
vent damage from steam. This means that the heat medium is no longer circulated, so that
T.coll has a set upper limit (T.coll.MAX) including hysteresis.
The differential temperature does not have a hysteresis that can be adjusted and is divided in-
to a switch on and a switch of differential.
If the cylinders have bare-tube heat exchangers, the reference temperature sensor should be
screwed into the heat exchanger outlet using a t-shaped connector and an immersion sleeve
(see the section on installing sensors in the instruction manual). If the surface of the collector
is too large, the return flow temperature will increase too quickly, causing the limiter at T.ref to
switch of the system to quickly. However, T.ref also cools down quickly in the standstill medi-
um in the cold section of the cylinder. The pump will then start operating again, etc. To prevent
this "cycling" and to prevent the cylinder from overheating if good layered cylinders are used,
an
additional
optional upper limit has been defined in the module "solar control" for T.lim.
The output variable “MAX limit reached:” shows that the upper limit has been reached (status:
OFF/ON).
If no additional limit sensor T.lim is used, it suffices to indicate
User
as the "source:" in the in-
put variables.
