much better and start up a lot easier if you take this
fresh approach of pumping away. It’s good to question
habit and tradition from time to time.
Some examples are illustrated:
Below is an example of pumping away with circulator
on the supply side, which is the preferred method. The
circulator can however be placed on the return and
still allow for pumping away from point of no pressure
change.
Control Systems
As we go over different controls, all of them will fall into
some category of what part of the system they function
in or control. This is an example of some that in particular
are used in hydronic systems in particular. The
listing includes controls also used on forced warm air so
that we may have some point of reference.
1. Primary Controls (loads)
A. Is the control that is being controlled by the thermostat
or controller.
B. Require power for their operation in:
(1) Gas Valves
(2) Relays
(3) Zone Valves
(4) Zone Dampers
(5) Flue Dampers
2. Operators (operate primary controls) (switches)
A. Thermostat
B. Aquastat
C. Pressuretrol
3. Secondary Controls
A. Pressuretrol (2 lbs off .5 lb on (steam) (hot water
and steam)
B. Low water cut off
C. High limit (warm air) (200°F)
D. High limit (hot water)
E. Low limit
F. Fan Control Normally Open (Closes on a
temperature rise)
G. Reverse acting control (pump aquastat, circulator
control)
4. Loads
A. Relay coil
B. Motors
C. Transformers (primary load) (secondary
source)
When it comes to setting temperatures
for forced hot water conventional systems,
the Incorporation by Reference (IBR)
handbook suggest settings follow.
Settings for different systems
STEAM: Pressuretrol: 2 lbs. off–.5 lb. on
(on normal household jobs)
VAPOR: Vaporstat: 8 oz. off–2 oz. on (unless
engineer gives different setting)
FORCED WARM AIR: Combination fan
and limit control
Limit: 200°
Fan on: 125°
Fan off: 110°
(if separate controls, set accordingly)
GRAVITY WARM AIR: Airstat Limit
control: 250°
GRAVITY HOT WATER: Aquastat Limit
control: 140°–150°
FORCED HOT WATER: High Limit control: 185°
(for radiators)
200° (for convectors)
210°–215° (baseboard radiation)
Low limit control: 150°
Circulator control: 120°–125°
(If there is a combination control with low limit and
reverse on the same setting, set the low limit to
150°and the differential to 25°).
AUXILLARY LIMITS
STEAM: Pressuretrol: 2 lbs off–.5 lb on.
Auxiliary pressuretrol:14 lbs off–
(set cut in to nine and differential to five) 9 lbs on.
HOT WATER: High limit 180°
Auxiliary high limit 220°
Thanks to Dan Holohan for the information on pumping
away. Contact him at heatinghelp.com.
ICM/November/December 2017 21