What happens if suction pressure is too low?
Low suction pressure/low superheat:
Apart from refrigerant leaks causing loss of critical charge, the most common problem associated with low suction pressure is: LOW LOAD, i.e., not enough warm, moisture laden airflow across the evaporator coil.
Effect of Suction Pressure
The suction pressure (or evaporator pressure) decreases due to the frictional resistance of flow of the refrigerant. Let us consider a theoretical vapour compression cycle 1-2-3-4 when the suction pressure decreases from ps to ps′ as shown on p-h diagram in Figure 2.3.
Problems Caused By High Suction Pressure
The condenser coil may struggle to release heat stored within the refrigerant. Your AC system may still turn on, but if it has high suction pressure, it may not provide sufficient cooling power. High suction pressure can lower the cooling power of your AC system.
Adding refrigerant decreases leaving evaporator superheat by increasing system pressure and increasing the flow of refrigerant through the evaporator. The suction line saturation temperature will go up and the spread between suction saturation temperature and suction line temperature will decrease.
Suction pressure should be kept at less than 200 mmHg in adults. It should be set at 80 mmHg to 120 mmHg in neonates.  The catheter size used for suction should be less than 50% of the internal diameter of the endotracheal tube.
A TXV being restricted will cause the evaporator, compressor, and condenser to be starved of refrigerant. This will cause low suction pressures, high superheats, low amp draws, and low head pressures.
Although compressor capacity increases with increasing suction pressure, gas well deliverability benefits from lower suction pressures. The ability of a well to flow gas increases with a decrease in flowing bottom-hole pressure, which can be directly influenced by compressor suction pressure.
As suction pressure decreases (NPSHA reduced), incipient bubbles grow and eventually vapor lock the pump inlet (see Figure 4). The value of this NPSHA, at which a pump losses 3 percent TDH in excess of vapor pressure, is called net positive suction head required (NPSHR).
Greater Current Draw. The greater rate of gas molecule generation in the evaporator of an overcharged refrigeration system would mean that the specific volume of the refrigerant in the suction line will be low.
Refrigerant overcharging can also result in liquid refrigerant running too far into the evaporator coil, leading to a too-low suction side pressure and a reduction in cooling capacity.
Why is compressor suction pressure so low?
Compressor suction pressure is too low or liquid returns, what should be done? 1) If refrigerant filled is insufficient, please add refrigerant. 2) If indoor temperature is set too low, please set it higher. 3) If filters are clogged with dirt, please replace the filters.
With R-410A, the same unit will operate under the same conditions with a suction pressure of 118 psi and a discharge pressure of 400 psi, as shown in Figure 1 on the next page.
Turning the adjustment stem clockwise will only increase spring pressure causing a higher superheat. Turning the adjustment stem counterclockwise will decrease spring pressure reducing superheat.
Low intermittent suction is usually ordered. Low range on the suction device is from 0 to 80 mmHg. Starting between 40-60 mmHg is recommended. The suction level should not exceed 80 mmHg.
When a suction cup is sealed against a surface and air is squeezed out of the cup, a low pressure region is created inside the suction area. It's actually the atmospheric pressure OUTSIDE the cup, pressing down on the low pressure area INSIDE the cup, that creates the suction.
A plugged TXV will underfeed the evaporator and produce symptoms that include the evaporator operating under a vacuum or very low pressure. A plugged valve will not respond to a superheat decrease or will suddenly open up if superheat is adjusted downwards.
Not enough air flow OR too much air flow can cause problems with the system. When there is not enough air flow through the evaporator or a restriction in the air flow, the Suction pressure is below normal because the refrigerant flowing through the evaporator picks up less heat than normal resulting in lower pressures.
A high suction level is effective to help you drain the breast of as much milk as possible, but this must be done without causing pain to yourself. Find your own personal Maximum Comfort Vacuum level and pump away!
If you're buying a personal grade breast pump, look for a maximum breast pump suction level of 250 – 300 mmHg. The majority of personal grade electric breast pumps on the market fall within this range. If the vacuum strength tops out at below 250 mmHg, it could mean a weaker motor.
Putting in the incorrect amount of oil, putting in the wrong type of oil, and oil contamination can all cause the pump to not reach full vacuum. For this reason, you must check the oil regularly to ensure that it is not only clean, but also properly filled.
Does higher suction get more milk?
Many moms assume that having a pump with a higher suction strength will automatically mean that they will be able to pump more milk, but in fact, pumping at too high of a setting can actually inhibit your milk production.
If there is not sufficient drop for the TXV to operate properly, liquid will back up in the condenser. This will cause the suction pressure and liquid pressure to be lower than normal, the total and evaporator superheat higher than normal, and normal to high condenser subcooling will be present.
The most common reason behind a reciprocating compressor's inability to reach sufficient pressure is a defective reed valve — which can exhaust air out from the air inlet on single stage models or, through the intercooler safety valve in the case of a defective reed valve on a two-stage piston compressor instead of ...
Any under-sizing (which is a restriction) or other type of restriction in these vital conduits that affects the flow of this refrigerant/oil vapor mixture can cause a multitude of problems from diminished capacity, refrigerant system blockages due to oil concentration even outright failure.