Manual

28
Table 4 — Air and Water Limits
NOTES:
1. Minimum air and water conditions can only be used at nominal flow rates.
2. 50PEC units may have up to two values at maximum or minimum with all
other parameters at normal conditions.
3. Operating limits shown are for start-up, not continuous operation. It is
assumed that such a start-up is for the purpose of bringing the space to
desired occupancy temperature.
3. System Water pH: Verify system water is slightly alkaline
(pH = 7.5 to 8.5). Proper pH promotes the longevity of
the hoses and heat exchangers. See Table 5.
4. Closed-Type Cooling Tower (Open Tower with Heat Ex-
changer): Check equipment for proper temperature set
points and operation.
5. Balanced Water Flow Rate to Heat Pump: Record the
inlet and outlet water temperatures as each heat pump
unit is started. This check will eliminate nuisance unit
tripouts resulting from water velocities that are either too
low or too high; it can also prevent erosive water flow
rates.
6. Standby Pump: Verify the standby pump is properly in-
stalled and in operating condition.
Table 5 — Water Quality Guidelines
LEGEND
*Heat exchanger materials considered are copper, cupronickel, 304 SS
(stainless steel), 316 SS, titanium.
†Closed recirculating system is identified by a closed pressurized piping
system.
**Recirculating open wells should observe the open recirculating design
considerations.
††If the concentration of these corrosives exceeds the maximum allow-
able level, then the potential for serious corrosion problems exists.
Sulfides in the water quickly oxidize when exposed to air, requiring that
no agitation occur as the sample is taken. Unless tested immediately
at the site, the sample will require stabilization with a few drops of one
Molar zinc acetate solution, allowing accurate sulfide determination up
to 24 hours after sampling. A low pH and high alkalinity cause system
problems, even when both values are within ranges shown. The term
pH refers to the acidity, basicity, or neutrality of the water supply.
Below 7.0, the water is considered to be acidic. Above 7.0, water is
considered to be basic. Neutral water contains a pH of 7.0.
To convert ppm to grains per gallon, divide by 17. Hardness in mg/l is
equivalent to ppm.
50PEC UNIT COOLING (C) HEATING (C)
Min Ambient Air 10.0 10.0
Rated Ambient Air 26.7 21.1
Max Ambient Air 37.8 29.4
Min Entering Air 10.0 10.0
Rated Entering Air, dry bulb/wet bulb 26.7/19.4 21.1
Max Entering Air, dry bulb/wet bulb 37.8/28.3 26.7
Min Entering Water –1.1 –6.7
Normal Entering Water 29.4 21.1
Max Entering Water 43.3 32.2
CONDITION
HX
MATERIAL*
CLOSED
RECIRCULATING†
OPEN LOOP AND RECIRCULATING WELL**
Scaling Potential — Primary Measurement
Above the given limits, scaling is likely to occur. Scaling indexes should be calculated using the limits below.
pH/Calcium
Hardness Method
All N/A pH < 7.5 and Ca Hardness, <100 ppm
Index Limits for Probable Scaling Situations (Operation outside these limits is not recommended.)
Scaling indexes should be calculated at 150 F for direct use and HWG applications, and at 90 F for indirect HX use. A monitoring plan should be
implemented.
Ryznar Stability Index
All N/A
6.0 - 7.5
If >7.5 minimize steel pipe use.
Langelier Saturation Index
All N/A
–0.5 to +0.5
If <–0.5 minimize steel pipe use.
Based upon 150 F HWG and direct well, 85 F indirect well HX.
Iron Fouling
Iron Fe
2+
(Ferrous)
(Bacterial Iron Potential)
All N/A
<0.2 ppm (Ferrous)
If Fe
2+
(ferrous) >0.2 ppm with pH 6 - 8, O
2
<5 ppm check for iron bacteria.
Iron Fouling
All N/A
<0.5 ppm of Oxygen
Above this level deposition will occur.
Corrosion Prevention††
pH
All
6 - 8.5
Monitor/treat as needed.
6 - 8.5
Minimize steel pipe below 7 and no open tanks with pH <8.
Hydrogen Sulfide (H
2
S)
All N/A
<0.5 ppm
At H
2
S>0.2 ppm, avoid use of copper and cupronickel piping of HXs.
Rotten egg smell appears at 0.5 ppm level.
Copper alloy (bronze or brass) cast components are okay to <0.5 ppm.
Ammonia Ion as Hydroxide,
Chloride, Nitrate and Sulfate
Compounds
All N/A
<0.5 ppm
Maximum Chloride Levels Maximum allowable at maximum water temperature.
50 F (10 C) 75 F (24 C) 100 F (38 C)
Copper N/A
<20 ppm NR NR
Cupronickel N/A <150 ppm NR NR
304 SS N/A <400 ppm <250 ppm <150 ppm
316 SS N/A <1000 ppm <550 ppm <375 ppm
Titanium N/A >1000 ppm >550 ppm >375 ppm
Erosion and Clogging
Particulate Size and Erosion
All
<10 ppm of particles and a
maximum velocity of 6 fps.
Filtered for maximum
800 micron size.
<10 ppm (<1 ppm “sandfree” for reinjection) of particles and a maximum
velocity of 6 fps. Filtered for maximum 800 micron size. Any particulate that
is not removed can potentially clog components.
Brackish
All N/A
Use cupronickel heat exchanger when concentrations of calcium or sodium
chloride are greater than 125 ppm are present. (Seawater is approximately
25,000 ppm.)
HWG — Hot Water Generator
HX — Heat Exchanger
N/A — Design Limits Not Applicable Considering Recirculating
Potable Water
NR — Application Not Recommended
SS — Stainless Steel