Laars Mini-Therm II JVT (Sizes 50-225) - Install and Ope User Manual download pdf (Page 15)

Mini-Therm II Hydronic Boiler

Page 15

5.3 Flow Requirements

All high recovery, low volume water boilers

must have adequate flow for efficient operation. Pump

selection is critical to this goal, and pumps should be

selected to provide for system design water

temperature rise. Table 6 details temperature rise and

water flow (GPM) for the Mini-Therm boilers.

Damage from improper flow is not warranted.

Failure to insure proper water flow through the

heat exchanger of the boiler will void the Laars

warranty. Flow can be verified by measuring the

difference in water temperatures between the boiler

inlet and outlet. For example: For a JV-100

installation, the inlet water temperature is 160°F

(71°C), and the outlet temperature is 180°F (82°C) at

Normal Input Rate from the rating plate. That means

there is a 20° (11°C) temperature rise through the

boiler. According to Table 1, that would indicate a

flow rate of 8 GPM (0.5L/S). Temperature rise must

be measured with the longest (highest head) zone

calling for heat alone.

Other factors to be considered before selecting a

pump are pipe size, the number of fittings throughout

the system, smoothness of the interior surface of the

pipe, the quantity of water flowing through the pipe,

whether a glycol solution is being used, and the total

length of piping in the system. Table 7 provides

examle pump selection criteria using Type L copper

piping, one zone valve and up to eight elbows for

single zone systems. Consult the factory or a qualified

system designer if you have more fittings, different

size or type of pipe (especially in retrofit situations),

or some other unique system configuraiton not

illustrated in this manual.

Figure 7. By-pass Piping.

Balancing Valve

or optional

thermostatic union,

Laars P/N 2400-030.

(Primary/Secondary

only)

System

From

System

(Return)

Out

(Supply)

Drip

Leg

Left Side View

A full size by-pass must be installed.

Size

1/2" Pipe 3/4" Pipe 1" Pipe 1-1/4" Pipe

Pump H.P. Pump H.P. Pump H.P. Pump H.P.

1/25 1/12 1/25 1/12 1/6 1/25 1/12 1/6 1/25 1/12 1/6

50 50 99 390 680 * * * * * * *

75 * 35 160 300 460 640 * * * * *

100 * * 77 150 260 330 620 * * * *

125 * * 27 80 140 170 360 600 * * *

160 * * * 25 72 57 160 330 190 480 *

225 * * * * * * * 110 * 69 330

*A circulator and/or primary/secondary piping are required. Consult

factory.

1. Chart is based on 30°F (17°C) maximum temperature rise.

2. Calculations are based on Type L copper tubing with one

zone valve and eight elbows.

3. Typical circulating pumps:

HP=Taco 007, B&G LR-20 or

SLC-25, Grundfos UP15-42F, or equivalent.

HP=B&G LR-

12, Grundfos UP26-42F, or equivalent.

HP=B&G series

HV, Grundfos UP43-75, or equivalent.

Table 7. Maximum Suggested Circuit Length in Feet.

Size

15°F

8°C

20°F

11°C

25°F

14°C

Flow Rate Headloss Flow Rate Headloss Flow Rate Headloss

gpm

l/s

gpm

l/s

gpm

l/s

50 5.3

0.3

0.1

4.0

0.3

0.2

0.1

3.2

0.2

0.1

0.0

75 8.0

0.5

0.6

0.2

6.0

0.4

0.3

0.1

4.8

0.3

0.2

0.1

100 10.7

0.7

1.3

0.4

8.0

0.5

0.7

0.2

6.4

0.4

0.5

0.2

125 13.3

0.8

2.2

0.7

10.0

0.6

1.3

0.4

8.0

0.5

0.8

0.2

160 17.0

1.1

2.5

0.8

12.8

0.8

1.8

0.5

10.2

0.6

1.2

0.4

225 24.0

1.5

5.0

1.5

18.0

1.1

3.1

0.9

14.4

0.9

1.9

0.6

Table 6. Temperature Rise °F °C.

gpm = Water Flow in gallons per minute. l/s = Water flow in liters per second.

ft = Pressure drop (headloss) through the boiler in feet of water. m = Pressure drop (headloss) through the boiler in meters of water.

Notes: 1. Shaded area is the recommended flow and temperature rise.

2. Temperature rise and associated flow rates are based on high fire operation at the Normal Input Rate from the rating plate.

Balancing

Valve

1 2 ... 10 11 12 13 14 15 16 17 18 19 20 ... 35 36

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Laars Mini-Therm II JVT (Sizes 50-225) - Install and Ope User Manual Page 15

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