Understanding Operation Concept; 5 Reset Ratio/Outdoor Reset - heat-timer Mini-Extension Installation And Operations

Sequencing modulating control for hydronic heating systems
Hide thumbs Also See for Mini-Extension:
Table of Contents

Advertisement

UNDERSTANDING OPERATION CONCEPT

The Mini-MOD has multiple operating modes that satisfy most hydronic systems. It can
change the System Set Point based on outdoor temperature (Outdoor Reset) or it can modulate
its stages to achieve an adjustable fixed Set Point.
In Outdoor Reset, the Mini-MOD controls a hot water heating system to provide a building with
comfortable and even heat levels. The Mini-MOD varies the temperature of the circulating
heating water in response to changes in the outdoor temperature. The heating water temperature
is controlled through the modulation of stages.
The Mini-MOD also controls the system circulating pump with an adjustable Outdoor Cutoff.
When the outdoor temperature is above Outdoor Cutoff, the pump is off and no heating water is
circulated through the system. When the outdoor temperature drops below the Outdoor Cutoff,
the system pump relay is activated and the heating water circulates through the system. The
temperature of the heating water is controlled by the Reset Ratio, Water Offset, and changes
with Outdoor temperature.
RESET RATIO/OUTDOOR RESET
When a building is being heated, heat escapes through the walls, doors, and windows to
the colder outside air. The colder the outside temperature, the more heat escapes. If you
can input heat into the building at the same rate that it is lost out of the building, then
the building temperatures will remain constant. The Reset Ratio is an adjustment that
lets you achieve this equilibrium between heat input and heat loss.
The starting point for most systems is the 1.00 (OD):1.00 (SYS) (Outdoor Temperature
: Heating Water Temperature) ratio. This means that for every degree the outdoor
temperature drops, the temperature of the heating water will increase one degree. The
starting point of the curves is adjustable, but comes factory selected at 70
Temp. and 100
F Water Temp. For example with a 1.00 (OD):1.00 (SYS) ratio, if the
°
outdoor temperature is 50
°
point of 70
F. Therefore, the heating water temperature will increase 20
°
Each building has different heat loss characteristics. A very well insulated building will
not lose much heat to the outside air, and may need a Reset Ratio of 2.00 (OD):1.00
(SYS) (Outdoor:Water). This means the outdoor temperature would have to drop
2 degrees to increase the water temperature 1 degree. On the other hand, a poorly
insulated building with insufficient radiation may need a Reset Ratio of 1.00 (OD):2.00
(SYS). This means that for each degree the outdoor temperature dropped the water
temperature will increase 2 degrees. The Mini-MOD has a full range of Reset Ratios to
match any buildings heat loss characteristics.
A heating curve that relies not only on Outdoor temperature but also on type of radiation
will improve heat comfort. The following are suggested initial settings for different
types of radiation based on average building insulation and heat loss. The contractor
can fine tune these adjustments based on the specific building need.
Type of Radiation in Building
Radiators (Steel & Cast Iron)
Baseboard (Finned copper tube& Cast Iron)
Radiant (High Mass/Concrete)
Radiant (Low Mass/Joists)
Fan Coils & Air Handlers
F, this means the temperature has fallen 20
1.00 (OD) : 1.00 (SYS)
1.00 (OD) : 1.00 (SYS)
4.00 (OD) : 1.00 (SYS)
2.00 (OD) : 1.00 (SYS)
1.00 (OD) : 1.00 (SYS)
Mini-MOD & Mini-Extension Installation Manual
F Outdoor
°
from the starting
°
to 120
°
Reset Ratio
Offset
0˚F
0˚F
-10˚F
-10˚F
20˚F
220
210
200
190
180
170
160
150
140
130
120
110
100
70
60
Outdoor Temperature (in °F)
Reset Ratio Curves
F.
°
WARNING
When controlling a non condensing
boiler directly without the use of a
mixing valve, minimum boiler water
temperature must be set to boiler
manufacturer specifications. In that
case, system temperature must not go
below such temperature.
1:4
1:3
1:2
1:1.5
1:1.25
1:1
1.25:1
1.5:1
2:1
3:1
4:1
50
30
0
-10
40
20
10
-20
1:4
1:1
130
120
110
4:1
100
70
60
50
40
Outdoor Temperature
1:4
1:1
110
100
90
-20 Offset
4:1
80
70
60
50
40
Outdoor Temperature
1:4
1:1
150
140
130
4:1
120
90
+20 Offset
100
70
60
50
40
Outdoor Temperature
5

Advertisement

Table of Contents
loading
Need help?

Need help?

Do you have a question about the Mini-Extension and is the answer not in the manual?

Questions and answers

This manual is also suitable for:

Mini-mod

Table of Contents