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Sla
Electro-Stat
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 Important item for hydronics under-floor heating
 Slab stat assures optimum radiant floor heating & comfort
QUESTION:
95º
90º
How well can an air sensing thermostat
designed to control this . . .
85º
79º
100º
74º
110º
68º
63º
59º
60º
60º
correctly control a radiant floor system
design to operate like this?
65º
81º
65º
81º
65º
81º
ANSWER:
It can, but not very well. An air sensing thermostat is designed to control your heating system based upon
air temperature (forced air). Radiation becomes heat when it is absorbed by an object, meaning in a radiant
in-floor heating application air is not heated, only objects. Thus an air sensing thermostat used in a radiant
in-floor heating system may cause you to “lose control” of your heating system.
One common example of how an air thermostat, used with an in-floor radiant heating system, can cause you
to “lose control” of your system is Solar Gain.
During the daytime hours, solar energy from the sun can satisfy your air sensing thermostat causing the boiler
to remain off. With the boiler off, no heat is generated or transferred to the slab, causing the slab to lose the
heat energy it needs to heat your building (or objects within) a few hours later. When solar energy is gone
(sun goes down) the thermostat will then require heat signaling “heat call” to the boiler. Since the air stat
has been satisfied all day, the boiler would have to start from square one and reheat the mass (which can take
several days) meaning your boiler will be on non-stop trying to catch up. This is not efficient.
Images Courtesy of Uponor Wirsbo
The principle of radiant heat or energy is a temperature differential between the floor’s surface and the objects.
The goal is to keep this temperature differential very small and the floor temperature constant. Then when
solar heat energy (or any other internal heat energy) raises the temperature of the objects or the internal air it
can only go up to the point where it becomes closer and closer to the floor surface temperature. If the floor
surface temperature is constant, comfort and stability is achieved. If the floor temperature bounces all over
the place (air sensing thermostat), comfort is lost and energy efficiency is lost.
Another example is ETS (thermal storage) designed installations where the water tubes or coils are in a sand
bed. You must use a slab stat to prevent large temperature swings or temperature overshoots.
WHAT IS THE SOLUTION?
A thermostat that uses a sensor installed within the slab to control a boiler is the solution. Our slab thermostat
includes these unique features.
#
DEVICE
CONTROL
RELAY
ES-24-BR
• Accurate temperature control
*
50#"
'.$
• Small, flexible sensor
4%34
2
"
!
7
7
*
• Sensor field extendable up to 25-feet
+
$%,
42
• Green/red light, on or off
7
2%$ ",+ 7(4
4%-03%.3/2
• Wide temperature range, 40° F to 92° F
7
7
",+
7(4
6!#
#
24V
• Direct connection to Electro-Boiler or
Electro Zone Controllers
120/240
• 24-volt system, requires 3 wires
7
2
TYPICAL CONTROL WIRING (24V)
ART-146 1.0
Electro Industries also manufactures line voltage slab sensing thermostats.
ES-120-BR, ES-240-BR
J2
LINE
UPCB5507
• Accurate temperature control
J3
GND
TEST
• Sensor field extendable up to 25-feet
J1
NEUT
• Small, flexible sensor
1U
1DEL
W6
• Green/red light, on or off
W7
RED BLK WHT
TEMP. SENSOR
• Can be wired for 240V or 120V
• 25-amp contact
L1
W8
W9
LINE
L2
LOAD
WHITE
BLK/WHT
BLK/RED
• Wide temperature range, 40° F to 92° F
BLACK
RED/WHT
TYPICAL CONTROL WIRING (120V)
ART-147 1.0
Monticello, Minnesota
800.922.4138
www.electromn.com
1/4/2008
BL004