A.O. Smith 30 - Manual (Page 16)

Working principle of the appliance
16 Instruction manual SGS
2
gis
2.4 Protection for the
appliance
2.4.1 Introduction
The electronic controller monitors the water temperature, helps ensure the safe
use of the solar heating system, and ensures safe combustion. This takes place
using:
•
the Appliance water temperature protection
• the Gas valve
• the Fan
• the Pressure switch
• the Flame probe
2.4.2 Appliance water temperature protection
The electronic controller uses temperature sensors T
1
(7) and T
2
to monitor
several temperatures that are important for safety.
The table explains the functioning of these temperature sensors.
Temperature protection
2.4.3 Water temperature protection for the storage tank
Using temperature sensors S
2
and S
3
, the solar heating system controller
monitors several temperatures in the storage tank that are related to safety.
Temperature protection
2.4.4 Gas valve
The electronic controller opens the gas valve so that gas can be supplied to the
burner. As a safety measure, the gas valve has a double shut-off. The double
shut-off guarantees complete isolation of the appliance from the gas supply.
To help ensure smooth ignition, the gas valve opens gradually ('softlite").
Protection Description
Against frost:
- T
1
< 5°C
- T
2
< 5°C
The frost protection cuts in. The water is heated to 20°C.
For maximum water temperature:
- T
1
> 85°C
- T
2
> 85°C
The high-limit safeguard serves to prevent overheating and/or excessive
formation of scale in the appliance. If the high-limit safeguard is activated, the
heating is stopped. This causes the water in the tank to cool down. Once the
water has cooled sufficiently (T
1
< 78°C), the electronic controller resets the
appliance.
For extra safety:
- T
1
> 93°C
- T
2
> 93°C
A lockout error of the water heater controller takes place. The controller must
be manually reset before the appliance can resume operation (8.3 "Error
conditions") . The reset may only be performed if T
1
<78°C.
Protection Description
Against frost:
- S
2
, S
3
< 5°C
The frost protection cuts in. The water is heated to 20°C.
For maximum water temperature:
- S
2
, S
3
> 85°C
The high-limit safeguard serves to prevent overheating and/or excessive
formation of scale in the storage tank. If the high-limit safeguard is activated,
the heating is stopped. This causes the water in the storage tank to cool down.
Once the water has cooled sufficiently (S
3
< 78°C), the electronic controller
resets the appliance.
For extra safety:
- S
2
, S
3
> 93°C
A lockout error of the water heater controller takes place. The controller must
be manually reset before the appliance can resume operation (8.3 "Error
conditions") . The reset may only be performed if S
3
< 78°C.