tekmar 156 Difference Setpoint Control - Manual (Page 5)

5 of 12 © 2010 D 156 - 06/10
Using ΔT•hours to Calculate Heat Transfer
Note: BTU = British Thermal Unit, lbm = Pound Mass, USGal = US gallon
To estimate the total amount of heat the system has transferred from the heat source to the storage tank use the equation:
Total Heat Transferred =
Flow Rate
X
ΔT•hours
X
K
= _____________ BTU
Where:
Flow Rate is that produced by the pump in US Gallons per minute
ΔT•hours is the temperature difference between the source and storage multiplied by the amount of time heat transfer is
taking place (time the pump runs). This variable is calculated for you by the control since the ΔT is not constant.
K is a constant calculated by multiplying the fluid property specific heat (BTU/lbm°F) by density (lbm/USGal) by 60 (min/
hr). For example, water has a specific heat of 1 BTU/lbm°F and a density of 8.33 lbm/USGal. Therefore the value of K
in this case is 1 x 8.33 x 60 = 500.
The value of K depends on the percent volume of glycol added to the heat transfer fluid. Select an appropriate K
value from table 1.
•
•
•
Ethylene Glycol Solution Propylene Glycol Solution
% by Volume Freezing Point K @ 120°F (49°C) % by Weight Freezing Point K @ 120°F (49°C)
0 32°F (0°C) 493 0 32 (0°C) 493
10 23°F (-5°C) 482 10 26 (-3°C) 492
20 14°F (-10°C) 472 20 18 (-8°C) 489
30 2°F (-17°C) 460 30 7 (-14°C) 477
40 -13°F (-25°C) 446 40 -8 (-22°C) 466
50 -36°F (-38°C) 429 50 -29 (-34°C) 446
60 -70°F (-57°C) 411 60 -55 (-48°C) 425
Table 1: K values at 120°F (49°C) for different heat transfer solutions based on % glycol. K increases with temperature.
Improper installation and operation of this control could
result in damage to the equipment and possibly even
personal injury. It is your responsibility to ensure that this
control is safely installed according to all applicable codes and standards. This electronic control is not intended
for use as a primary limit control. Other controls that are
intended and certified as safety limits must be placed into
the control circuit.
Caution
Installation
Step One — Getting Ready
Check the contents of this package. If any of the contents
listed are missing or damaged, please contact your
wholesaler or tekmar sales representative for assistance.
Type 156 includes: One Difference Setpoint Control 156, One
Solar Sensor 085, One Universal Sensor 071, Data Brochures
D 156, D 085, D 070, D 001, Application Brochure A 156.
Note: Carefully read the details of the Sequence of
Operation to ensure that you have chosen the proper
control for your application.
Temperature Monitoring
The 156 will monitor the minimum and maximum Source
and Storage temperatures. These items are available
in the Default menu and may be reset by pressing and
holding the ▲ and ▼ buttons simultaneously for 1 second. ‘Clr’ (clear) will then be displayed followed by the value being
reset to the current sensor temperature. Use this feature to
determine system performance or for troubleshooting.