System Selection Process - Marstair A2LSYSTEMATCH SMC 15 Technical Manual

1. Select Evaporator based on Duty requirement, Target cold room temperature and evaporating temperature.
(See evaporator performance tables)
2. Select Condensing unit based on Duty requirement, maximum external ambient and evaporating temperature.
(See condensing unit performance tables)
3. Calculate Expansion pipe size based on Condensing unit selection and pipe run (See pipework installation
within condensing unit section)
4. Calculate the system refrigerant charge by adding the condensing unit, evaporator and pipe run charge sizes
together.
System Refrigerant charge
MBMT
125A
125B
130B
130E
230B
230C
230E
230BE
Expansion line size
5. Calculate minimum room size acceptable based on EN 378 = refrigerant charge (kg) / (lower flammability limit
X 0.2)
6. Check whether your cold room size is bigger – If it is, that's great you can move on to the next part if not try
the following:-
a. Reducing your pipe run
b. Use 2 smaller systems instead of 1 big system.
7. Contact Marstair for a Dsear free volume assessment. This is the volume within the cold which needs to be
kept clear to ensure a flammable atmosphere will not be formed.
When installing a cold room utilising an A2L refrigerant it is important to ensure that sufficient free space is allowed
around the evaporator. The correct amount of space will ensure that, in the unlikely event of a leak occurring, a
flammable mixture is not created.
The minimum "free space" required to ensure a safe working environment has been calculated using through the
following:-
1. Formula found in BS EN 60079-10-1: 2015
2. Additional formula, to calculate the time it takes for the refrigerant to pool
3. The amount of heat energy within the material upon which the refrigerant pools
4. The time taken for the lower flammability limit of the refrigerant to be reached.
Calculations are based upon refrigerant charge sizes shown in the pre-defined systems table. If refrigerant charges are
above the values stated, the free volume requirement will be inaccurate.
This Dsear free volume information is to be passed onto the end user
4 – SYSTEM SELECTION PROCESS
Evaporator Base Charge
0.084
0.112
0.14
0.294
0.294
0.378
0.56
0.686
Grams per m pipe run
3/8"
1/2"
5/8"
SMC Condensing unit base charge
15
20
30
40
45
50
80
90
16
30
48
40
55008432-02
0.196
0.183
0.21
0.166
0.36
0.36
0.395
0.594