Flow Regulation — Flow regulation can be accom- plished by two methods. Most water control valves have a flow adjustment built into the valve. By measuring the pressure drop through the unit heat exchanger, the flow rate can be deter- mined. See Table 26. Adjust the water control valve until the flow of 1.5 to 2 gpm is achieved. Since the pressure constantly varies, two pressure gages may be needed in some applications.
An alternative method is to install a flow control device. These devices are typically an orifice of plastic material de- signed to allow a specified flow rate that are mounted on the outlet of the water control valve. Occasionally these valves produce a velocity noise that can be reduced by applying some back pressure. To accomplish this, slightly close the leaving isolation valve of the well water setup.
WARNING
To avoid possible injury or death due to electrical shock, open the power supply disconnect switch and secure it in an open position before flushing system.
Flushing — Once the piping is complete, units require final purging and loop charging. A flush cart pump of at least 1.5 hp is needed to achieve adequate flow velocity in the loop to purge air and dirt particles from the loop. Flush the loop in both directions with a high volume of water at a high velocity. Fol- low the steps below to properly flush the loop:
1.Verify power is off.
2.Fill loop with water from hose through flush cart before using flush cart pump to ensure an even fill. Do not allow the water level in the flush cart tank to drop below the pump inlet line to prevent air from filling the line.
3.Maintain a fluid level in the tank above the return tee to avoid air entering back into the fluid.
4.Shutting off the return valve that connects into the flush cart reservoir will allow 50 psig surges to help purge air pockets. This maintains the pump at 50 psig.
5.To purge, keep the pump at 50 psig until maximum pumping pressure is reached.
6.Open the return valve to send a pressure surge through the loop to purge any air pockets in the piping system.
7.A noticeable drop in fluid level will be seen in the flush cart tank. This is the only indication of air in the loop.
NOTE: If air is purged from the system while using a 10 in. PVC flush tank, the level drop will only be 1 to 2 in. since liquids are incompressible. If the level drops more than this, flushing should continue since air is still being compressed in the loop. If level is less than 1 to 2 in., reverse the flow.
8.Repeat this procedure until all air is purged.
9.Restore power.
Antifreeze may be added before, during or after the flushing process. However, depending on when it is added in the process, it can be wasted. Refer to the Antifreeze section for more detail.
Loop static pressure will fluctuate with the seasons. Pres- sures will be higher in the winter months than during the warmer months. This fluctuation is normal and should be con- sidered when charging the system initially. Run the unit in either heating or cooling for several minutes to condition the loop to a homogenous temperature.
When complete, perform a final flush and pressurize the loop to a static pressure of 40 to 50 psig for winter months or 15 to 20 psig for summer months.
After pressurization, be sure to remove the plug from the end of the loop pump motor(s) to allow trapped air to be discharged and to ensure the motor housing has been flooded. Be sure the loop flow center provides adequate flow through
the unit by checking pressure drop across the heat exchanger. Compare the results to the data in Table 26.
Table 26 — Coaxial Water Pressure Drop
50PC UNIT | | | | PRESSURE DROP, psi (kPa) | |
SIZE | gpm | L/s | 30 F | 50 F | 70 F | 90 F |
| | | (-1 C) | (10 C) | (21 C)) | (32 C) |
| 0.75 | 0.05 | 0.5 | (3.7) | 0.3 | (2.3) | 0.2 | (1.6) | 0.2 | (1.6) |
006 | 1.1 | 0.07 | 0.8 | (5.3) | 0.5 | (3.5) | 0.4 | (2.7) | 0.3 | (2.2) |
| 1.5 | 0.09 | 1.3 | (8.8) | 0.9 | (6.1) | 0.7 | (4.8) | 0.6 | (4.0) |
| 1.1 | 0.07 | 1.3 | (9.0) | 0.6 | (4.4) | 0.4 | (2.8) | 0.3 | (1.9) |
009 | 1.8 | 0.11 | 2.1 | (14.1) | 1.4 | (9.4) | 1.1 | (7.4) | 0.9 | (6.2) |
| 2.3 | 0.14 | 3.5 | (24.3) | 2.6 | (17.9) | 2.1 | (14.7) | 1.8 | (12.7) |
| 1.5 | 0.09 | 1.9 | (12.8) | 1.1 | (7.6) | 0.8 | (5.3) | 0.6 | (4.1) |
012 | 2.3 | 0.15 | 3.6 | (25.0) | 2.6 | (17.8) | 2.1 | (14.3) | 1.8 | (12.1) |
| 3.0 | 0.19 | 6.7 | (46.1) | 5.0 | (34.3) | 4.1 | (28.3) | 3.6 | (24.5) |
| 1.9 | 0.12 | 1.0 | (6.9) | 0.6 | (4.4) | 0.5 | (3.4) | 0.4 | (2.8) |
015 | 2.8 | 0.18 | 1.8 | (12.4) | 1.4 | (9.3) | 1.1 | (7.6) | 1.0 | (6.9) |
| 3.8 | 0.24 | 3.3 | (22.7) | 2.5 | (17.5) | 2.1 | (14.7) | 1.9 | (13.1) |
| 2.3 | 0.14 | 2.1 | (14.5) | 1.4 | (9.9) | 1.1 | (7.6) | 0.9 | (6.2) |
018 | 3.4 | 0.21 | 3.4 | (23.4) | 2.6 | (17.6) | 2.1 | (14.7) | 1.8 | (12.4) |
| 4.5 | 0.28 | 5.9 | (40.6) | 4.6 | (31.5) | 3.9 | (26.9) | 3.4 | (23.4) |
| 3.0 | 0.19 | 2.2 | (15.2) | 1.7 | (11.6) | 1.4 | (9.6) | 1.2 | (8.3) |
024 | 4.5 | 0.28 | 4.0 | (27.6) | 3.2 | (22.2) | 2.8 | (19.3) | 2.5 | (17.2) |
| 6.0 | 0.38 | 7.2 | (49.6) | 5.9 | (40.6) | 5.2 | (35.8) | 4.7 | (32.4) |
| 3.8 | 0.24 | 1.3 | (9.0) | 0.9 | (6.1) | 0.7 | (4.8) | 0.6 | (4.1) |
030 | 5.6 | 0.35 | 2.3 | (15.8) | 1.8 | (12.5) | 1.5 | (10.3) | 1.4 | (9.6) |
| 7.5 | 0.47 | 4.2 | (28.9) | 3.4 | (23.2) | 2.9 | (20.0) | 2.6 | (17.9) |
| 4.5 | 0.28 | 1.8 | (12.4) | 1.4 | (9.6) | 1.2 | (8.3) | 1.0 | (6.9) |
036 | 6.8 | 0.43 | 3.1 | (21.4) | 2.4 | (16.8) | 2.1 | (14.7) | 1.9 | (13.1) |
| 9.0 | 0.57 | 5.4 | (37.2) | 4.4 | (30.0) | 3.8 | (26.2) | 3.4 | (23.4) |
| 5.3 | 0.33 | 2.3 | (15.8) | 1.8 | (12.1) | 1.5 | (10.3) | 1.3 | (9.0) |
042 | 7.9 | 0.50 | 4.3 | (29.6) | 3.5 | (24.2) | 3.1 | (26.4) | 2.8 | (19.3) |
| 10.5 | 0.66 | 7.9 | (54.4) | 6.5 | (44.8) | 5.7 | (39.3) | 5.2 | (35.8) |
| 6.0 | 0.38 | 1.8 | (12.4) | 1.5 | (10.1) | 1.3 | (9.0) | 1.2 | (8.3) |
048 | 9.0 | 0.57 | 3.4 | (23.4) | 3.0 | (20.4) | 2.7 | (18.6) | 2.6 | (17.9) |
| 12.0 | 0.76 | 6.2 | (42.7) | 5.5 | (37.9) | 5.1 | (35.1) | 4.8 | (35.1) |
| 7.5 | 0.47 | 3.4 | (23.4) | 2.8 | (19.2) | 2.4 | (16.5) | 2.2 | (15.2) |
060 | 11.3 | 0.71 | 6.8 | (46.9) | 5.9 | (40.8) | 5.4 | (37.2) | 5.0 | (34.5) |
| 15.0 | 0.95 | 12.6 (86.8) | 11.1(76.8) | 10.3(71.0) | 9.6 | (66.1) |
Antifreeze — In areas where entering loop temperatures drop below 40 F or where piping will be routed through areas subject to freezing, antifreeze is needed.
Alcohols and glycols are commonly used as antifreeze agents. Freeze protection should be maintained to 15 F below the lowest expected entering loop temperature. For example, if the lowest expected entering loop temperature is 30 F, the leaving loop temperature would be 22 to 25 F. Therefore, the freeze protection should be at 15 F (30 F – 15 F = 15 F).
IMPORTANT: All alcohols should be pre-mixed and pumped from a reservoir outside of the building or introduced under water level to prevent fuming.
Calculate the total volume of fluid in the piping system. See Table 27. Use the percentage by volume in Table 28 to determine the amount of antifreeze to use. Antifreeze concen- tration should be checked from a well mixed sample using a hydrometer to measure specific gravity.
FREEZE PROTECTION SELECTION — The 30 F FP1 factory setting (water) should be used to avoid freeze damage to the unit.
Once antifreeze is selected, the JW3 jumper (FP1) should be clipped on the control to select the low temperature (anti- freeze 13 F) set point to avoid nuisance faults.
Cooling Tower/Boiler Systems — These systems typ- ically use a common loop temperature maintained at 60 to 90 F. Carrier recommends using a closed circuit evaporative cooling tower with a secondary heat exchanger between the tower and
