Recommended piping and water flow – Slant/Fin Oil Hot Water User Manual
Page 3
RECOMMENDED PIPING AND WATER FLOW
Good system design addresses flow rates through boilers. It is
possible to have too little flow and too much flow. Most boiler
system designs are based on a 20˚F to 30˚F temperature rise in
the boiler when it is firing at full input.
When the flow rate is too high through a module the water flow
tends to short circuit from the return tapping to the supply tapping
of a module. When flow rate is too high the boiler efficiency may
drop and there is excess electrical consumption by the circulator.
Recommended water flows and resultant pressure drops through
Caravan modules are as follows. Flow rate is for 20 rise in water
temperature and pressure drop is determined at recommended
flow rate and includes 1-1/2” pipe that connects module to
Slant/Fin header.
7-section modules are used in LDWO-850, LDWO-1300,
LDWO-1700, LDWO-2100, LDWO-2500, LDWO-2900 and LDWO-3400.
6-section modules are used in LWO-750 and LWO-1100.
5-section modules are used in LWO-600 and LWO-900.
Operating Pressures
System static pressure should be at least 15 PSI cold in modules.
When circulators are operating the pressure in the modules
should be at least 15 PSI when the water is cold.
Optional Piping Method - Primary/Secondary
When applying oil-fired Caravan boilers to a low temperature
water system care should be taken to maintain 130˚F return water
temperature inside the Caravan boiler. One way to accomplish this
is to design the boiler using primary/secondary piping.
Slant/Fin recommends a minimum of 15˚F system water
temperature rise across modules that are firing. If the desired
temperature rise is lower than a primary/secondary arrangement
should be used, either for the whole modular boiler or using a
multiple boiler system as described below. The 15˚F minimum
temperature rise can be maintained in the modules without
affecting the system water.
1. Primary/secondary piping may be applied to a Caravan
modular boiler system as demonstrated on Figure 4. In this
type of application the modular boiler is contained within the
primary loop. However, this is still a modular boiler, if it has
no valves between the modules.
2. Primary/secondary piping may also be used on each individual
“module”, please see figure 5. In this arrangement the Caravan
is no longer a “modular” boiler, it is now a “multiple” boiler
system. In a multiple boiler system each module is actually a
standalone boiler and each boiler should be equipped with a
manual reset hi limit and low water cutoff. Certain local codes
also require a minimum distance between each boiler.
Please remember to always follow code requirements applicable
to the building that the boilers are being installed in.
Most Caravan systems are applied as a modular boiler, not as a
multiple boiler. A modular boiler system is efficient, easy to main-
tain and very dependable. When a multiple boiler is used there are
additional circulators, manual reset hi limits and low water cut-offs
to install and maintain.
Some people believe a multiple boiler system is more efficient
because water flows through only those units that are firing. They
may think water flowing through modules not firing leads to energy
loss in those modules. However, we must remember a boiler heat
exchanger is designed to absorb heat from high temperature com-
bustion and transfer it to low temperature water (certainly below
250˚F water). Boilers do not make good “convectors” and very little
heat is passed through the venting of a module not firing. Oil-fired
modules experience very low airflow through the heat exchanger
when not firing.
In most applications we recommend a step or stage controller,
that modulates system water temperature, be used on a Caravan
system. These controls ensure the number of modules firing
equals the actual demand for heat. Slant/Fin’s step controllers are
the SC-3 and SC-9 model controls. Please see the Control section
of this manual for more information on these controls.
Module
Flow Rate/
Module GPM
Pressure
Drop/Module PSI
7-section
34
0.30
6-section
30
0.30
5-section
25
0.30
3
LDWO-600-2-5
21
5
⁄
8
8
7
⁄
32
8
34
3
⁄
8
4'4"
LDWO-750-2-6
25
9
29
⁄
32
8
37
3
⁄
4
4'4"
LDWO-850-2-7
28
3
⁄
8
11
19
⁄
32
9
41
1
⁄
8
4'4"
LDWO-900-3-5
21
5
⁄
8
8
7
⁄
32
8
34
3
⁄
8
6'7"
LDWO-1100-3-6
25
9
29
⁄
32
8
37
3
⁄
4
6'7"
LDWO-1300-3-7
28
3
⁄
8
11
19
⁄
32
9
41
1
⁄
8
6'7"
LDWO-1700-4-7
28
3
⁄
8
11
19
⁄
32
9
41
1
⁄
8
8'10"
LDWO-2100-5-7
28
3
⁄
8
11
19
⁄
32
9
41
1
⁄
8
11'1"
LDWO-2500-6-7
28
3
⁄
8
11
19
⁄
32
9
41
1
⁄
8
13'4"
LDWO-2900-7-7
28
3
⁄
8
11
19
⁄
32
9
41
1
⁄
8
15'7"
LDWO-3400-8-7
28
3
⁄
8
11
19
⁄
32
9
41
1
⁄
8
17'10"
Model No.
A
B
C
D †
L *
* 27" spacing between modules.
Note: Standard boiler unit prefix is LDWO.
Figure 1. Oil Caravan dimensions and typical piping/hot water models
Design Data
Max. ASME Working Pressure:
100 psi
Power Requirements:
120 V/60 HZ,
Amp (s) per module:
For Carlin burners 6.0