Though a single stage system may perform adequately in many installations, the use of a two-stage system offers the ultimate in pin-point regulation. Two stage regulation can result in a more profitable LP-Gas operation for the dealer resulting from less maintenance and fewer installation call backs.
Two Stage Regulation
Two Stage Regulation has these advantages:
Uniform Appliance Pressures - The installation of a two-stage system -- one high pressure regulator at the container to compensate for varied inlet pressures, and one low pressure regulator at the building to supply a constant delivery pressure to the appliances -- helps ensure maximum efficiency and trouble free operation year round. It is important to note that while pressure at the appliances can vary up to 4 inches w.c. using single stage systems, two stage systems keep pressure variations within 1 inch w.c..
Reduced Freeze-ups/Service Calls - Regulator freeze-up occurs when moisture in the gas condenses and freezes on cold surfaces of the regulator nozzle. The nozzle becomes chilled when high pressure gas expands across it into the regulator body. This chilling action is more severe in single stage systems as gas expands from tank pressure to 11" w.c. through a single regulator nozzle.
Two-stage systems can greatly reduce the possibility of freeze-ups and resulting service calls as the expansion of gas from tank pressure to 11" w.c. is divided into two steps, with less chilling effect at each regulator. In addition, after the gas exits the first stage regulator and enters the first-stage transmission line, it picks up heat from the line, further reducing the possibility of second stage freeze-up.
Economy of Installation - In a single-stage system, transmission line piping between the container and the appliances must be large enough to accommodate the required volume of gas at 11" w.c.. In contrast, the line between the first and second-stage regulators in two-stage systems can be much smaller as it delivers gas at 10 psig to the second stage regulator. Often the savings in piping cost will pay for the second regulator.
In localities where winter temperatures
are
extremely low, attention should
be given
to the setting of the first-stage
regulator
to avoid the possibility of propane
vapors condensing into liquid in the
line downstream
of the first-stage regulator.
For instance
if temperatures reach as low
as -20°F, the
first-stage regulator should
not be set higher
than 10 psig. If temperatures
reach as low
as -35°F, the setting of the
first-stage
regulator should not be higher
than 5 psig.
As an additional benefit, single-stage
systems
can be easily convened to two-stage
systems
using existing supply lines when
they prove
inadequate to meet added loads.
Allowance for Future Appliances - A high degree of flexibility is offered in
new installations of two-stage
systems. Appliances
can be added later to the present
load --
provided the high pressure regulator
can
handle the increase -- by the
addition of
a second low pressure regulator.
Since appliances
can be regulated independently,
demands from
other parts of the installation
will not
affect their individual performances.
Pigtails
If you are replacing an old regulator,
remember
to replace the copper pigtail.
The old pigtail
may contain corrosion which can
restrict
flow. In addition, corrosion
may flake off
and wedge between the regulator
orifice and
seat disc preventing proper lock-up
at zero
flow.
Regulator Vents/Installation
The elements, such as freezing
rain, sleet,
snow, ice, mud, or debris, can
obstruct the
vent and prevent the regulator
from operating
properly. This can result in
high pressure
gas at the appliances resulting
in an explosion
or fire.
Regulator vents must be clear
and fully open
at all times. Regulators installed
in accordance
with NFPA #58 will meet these
requirements.
In general, regulators should
be installed
with the vent facing down and
under a protective
cover. Screened vents must be
checked to
see that the screen is in place
at all times.
If the vent is clogged or screen
missing,
cleaning of the vent and screen
replacement
is necessary. If there is evidence
of foreign
material inside the vent, the
regulator should
be replaced.
In applications where the regulator
employs
a vent discharge tube, be sure
it is installed
with the outlet down and protected
with a
screen or suppressor. See Rego's
Products
Safety Warning WB -- I for important
warning
information on regulators.
Suppressors
Suppressors can be helpful when
second stage
regulators with standard vents
are piped
away. Frequently the "impedance"
of the vent piping will induce
a pulsation
in the regulated pressure. A
suppressor installed
on the vent or vent piping helps
prevent
this pulsation. They also help
protect against
the accumulation of snow, ice,
insects and
foreign material in the vent
opening. They
must be installed with the outlet
facing
down.
NOTE:.
It is not recommended suppressors
be used
in conjunction with large vent.
regulators
Indoor Installation of Regulators
Regulators installed inside a
building must
have the bonnet vent piped away.
To maintain
the large vent capacity relief
feature of
the regulator, no smaller pipe
than 3/4"
NPT should be utilized.
To pipe away, remove the vent
screen from
the LV4403B bonnet vent and install
3/4"
pipe into the bonnet vent threads
and pipe
to the outside of building. Install
vent
protection on the outlet of the
pipe away
vent line. To utilize the vent
screen and
retainer supplied with the regulator,
use
a 3/4" NPT 90° elbow. Insert
screen
into 3/4" F.NPT outlet of
elbow. Thread
retainer into outlet at least
1 turn. Install
the elbow with vent screen pointing
down.
The vent line must be installed
in a manner
to prevent the entry of water,
insects, or
foreign material that could cause
blockage.
The discharge opening must be
at least 3
feet from any opening below it.
NOTE: Do not use regulators with
over 5 PSIG
inlet pressure indoors. Follow
all local
codes and standards as well as
NFPA 54 and
58 or the B149 Installation code.
Selecting LP-Gas Regulators
| Type of System | Maximum Connected Load (BTU/hr) | Suggested Regulator |
| Integral Twin Stage | 180.000** 525,000** |
LV404B23 LV404B4 Series |
| Automatic Changeover | 180,000** 500,00** |
7523B23 7523B23M |
| First-Stage System First Stage High Pressure |
500,00*** 2,500,00*** |
2032TR LV4403SR / TR Series |
| Two-Stage System Second Stage Low Pressure |
935,000* | LV4403B Series |
| Two-Stage System Second Stage Low Pressure |
1,400,000* | LV5503B Series |
* Maximum load based on 10 psi inlet, 9" W.C. Delivery Pressure
** Maximum load based on 25 psi inlet, 9" W.C. Delivery Pressure
***Maximum load based on 25 psi inlet, with Delivery Pressure 20% lower than rating
Underground Installations
On underground installations the vent tube opening must be above the maximum water table and kept free from water, insects, and foreign material.
NOTE: If the water mark on the dome of an underground tank is above the regulator vent tube end or regulator vent opening, the regulator should be replaced and the situation corrected.
Notes:
- Grade ground downward and away around housing dome. This prevents water collecting and running into or standing around dome
- End of regulator vent tube located at top of housing dome cover
- Regulator adjustment closure cap must be tight
Reading a Regulator Performance Chart
Refer to the manufacturer' s capacity chart for the size and type regulator which fits your particular application. Check the performance of this regulator with your actual load at the inlet pressure corresponding to your lowest winter temperatures (as shown in the section - Vapour Pressures of LP-Gases).
Example for a Two Stage System
Selecting the First Stage Regulator
- Assume a load of 500,000 BTU' s per hour.
- Assume a minimum delivery pressure of 9 5 psig.
- Assume a minimum tank pressure of 15 psig.
- For these conditions, refer to chart for the LV4403TR Series, First Stage Regulator, shown below.
- Find the line on the chart corresponding to the lowest anticipated winter tank pressure (note that each performance line corresponds to and is marked with a different inlet pressure in PSI).
- Draw a vertical line upward from the point of assumed load (500,000 BTU's per hour) to intersect with the line corresponding to the lowest tank pressure.
- Read horizontally from the intersection of these lines to the delivery pressure at the left side of the chart. In this example the delivery pressure will be 9.7 psig. Since the delivery pressure will be 9.7 psig at the maximum load conditions and lowest anticipated tank pressure. The regulator will be sized properly for the demand.
Selecting the Second Stage Regulator
- Assume load of 250,000 BTU's per hour.
- Assume a minimum delivery pressure of 10" w.c.
- Assume a minimum inlet pressure of 10 psig.
- For these conditions, refer to chart for the LV4403B Series, Second Stage Regulator, shown below.
- Find the line on the chart corresponding to the anticipated inlet pressure.
- Draw a vertical line upward from the point of assumed load (250,000 BTU's per hour) to intersect with the line corresponding to the lowest inlet pressure.
- Read horizontally from the intersection of these lines to the delivery pressure at the left side of the chart. In this example the delivery pressure will read 10.6" w.c.. Since the delivery pressure will be 10.6" w.c. at the maximum load condition and lowest anticipated inlet pressure, the regulator is sized properly for the demand.
