tekmar 654 Snow Melting Control Installation - Manual (Page 35)

35 of 44 © 2013 654_D - 06/13
Mixing Operation
The Application Mode can be set to Mix when a mixing valve
or a mixing injection pump is installed to regulate the supply
water temperature to the snow melting system. The boiler or
heat plant can be either dedicated or non-dedicated to the
snow melting system. The mixing device position or speed is
controlled by an analog 0-10 V (dc) or a 4-20 mA signal so that
the supply temperature maintains the Mix Target temperature.
The control calculates a Mix Target based upon the Slab
Target which in turn is based upon the measured outdoor
temperature and the Melt, Idle or Storm temperature setting.
The Mix Maximum setting limits the upper temperature of the
Mix Target. The Mix Target is shown in the View menu.
Boiler protection is only available when the snow melting control
is connected to a tN4 System Control. The tN4 System Control
provides the outdoor temperature to the snow melting control
using tekmarNet(R) communication. See Boiler Operation
section regarding recommended tN4 System Controls. The
mixing device provides boiler return protection to the boiler
inlet by closing the valve when the boiler return temperature
falls below the Boiler Minimum setting. Boiler return protection
requires the installation of a boiler return sensor 082 on the
inlet to the boiler and the Outdoor/Boiler Return Sensor setting
must be set to Boiler Return.
Mixing Valve and Actuator Motor ---------------- ----------------
The 654 provides a 0-10 V (dc) signal to operate an actuator
motor for mixing using a 3 or 4-way mixing valve.
Recommended Mixing Injection Pumps --------- ---------
The control provides a 0-10 V (dc) or 4-20 mA signal to operate
a mixing device. In large commercial applications, a Variable
Frequency Drive (VFD) that can accept a 0-10 V (dc) or 4-20
mA can be used to vary the speed of the mixing injection
pump. For residential and smaller commercial applications,
specialized wet rotor, split-capacitor pumps that accept a 0-10
V (dc) signal are available from Grundfos and Taco. See Essay
E021 for piping information. The recommended models are
listed in the table below.
Taco Grundfos
Flow Rate
GPM
Turns open
of the Globe
Valve
Nominal Pipe
Diameter
003-VV 007-VV 0010-VV 0012-VV UP 15-42
F/VS
UP 26-64
F/VS
1.5 - 2.0 20 1/2" X X
2 100 1/2" X
3.0 - 4.5 100 1/2" X X
4 - 5.5 100 3/4" X
7.5 - 8.5 100 3/4" X X
12 - 13 100 1" X X
19 - 21 100 1-1/4" X X
31 - 32 100 1-1/2" X
39 - 42 100 2" X
Required Taco 00-VV control settings:
DIP Switch DIP Switch Position Description
1 ON Operates using a linear output characteristic
2 OFF Automatic operation
3 OFF Operates using a 0-10 V (dc) signal
Required Grundfos VS control settings:
DIP Switch DIP Switch Position Description
A OFF Operates using a V (dc) signal
B OFF Operates using 0-10 V (dc) range
C ON Minimum speed is off
D ON Speed control external