OSB 2 SERIES User Manual

OSB Series 2 Oil-Fired Steam Boilers – Boiler Manual
Part Number 550-110-772/0816 9
Figure 8 Recommended piping for parallel-ow
systems with optional reservoir pipe
Modernsteamboilersaredesignedtosteamforlesstimethan
older, larger boilers. When replacing an older steam boiler the
system condensate return time may be longer than the steaming
time. This could cause the following problems:
1. Boilers fitted with an automatic water feed could overfill.
2. Unitsttedwithonlyalowwatercutoffwouldshutdownand
cycle while waiting for condensate to return.
Following is a simple method for determining whether or not
a reservoir pipe is required to lengthen steaming time for a
residential installation:
1. Disconnectcondensatereturnlineatexistingboiler.
2. Heatboilerandallowtosteamfor10minutes.Turnoffboiler.
3. Measurelengthoftimefromwhenboilerstartedtosteamto
when condensate begins to return through condensate line.
4. Measurelengthoftimefromwhencondensatebeginstoreturn
to when it stops returning. Divide this time by 2.
5. Addtimemeasuredinstep3totimecalculatedinstep4.This
sum is the average time required for condensate to return to
the boiler.
6. Ifthistotaltimeis10minutesorless,noreservoirpipeisneeded.
If total time for condensate to return to boiler (from step 5) is
morethan10minutes,areservoirpipe(orboilerfeedsystem)is
recommended. See Table 5, this page, for suggested reservoir
pipesize.InstallasshowninFigures8and9,below.
Forlargersystems(asnotedinTable5),useaboilerfeedsystem
withacondensatetankandfeedpump.Youwillhavetoinstalla
low water cutoff/pump control on the boiler to operate the pump.
See“Lowwatercutoffs”onpage20andFigure18onpage26.
UseTable6tosizeboilerfeedsystems.(Theuseofacombination
condensate tank and float-controlled condensate return pump
is not recommended. These devices do not supply water to the
boiler on demand from the boiler, and cannot compensate for long
condensatereturntimes.)
For most residential installations a reservoir pipe may be all that
is necessary to ensure proper operation.
Condensate return
Table 6 Boiler feed system sizing
Table 5 Reservoir pipe sizing
4 Connect steam piping continued
Figure 9 Recommended piping for parallel-ow
systems with optional reservoir pipe
Boiler
model
number
Net
output
Time from initial steaming to average condensate return
(boiler steaming capacity based on 970 Btu per pound of steam)
15 minutes 20 minutes 30 minutes
Steam
MBH
gallons
Pipe
length
(feet)
gallons
Pipe
length
(feet)
gallons
Pipe
length
(feet)
OSB-3 114 1 1 2 2
Use boiler feed
system
OSB-4 144 1-1/4 1-1/4 2-1/2 2-1/4
OSB-5 174 1-1/2 1-1/2 3 2-1/2
OSB-6 210 1-3/4 1-3/4 Use boiler feed system
Designed full capacity steaming time of modern boilers is 10 minutes.
Boiler
model
number
Net
output
(pounds
steam
per
hours)
Condensate
(gallons per
hours)
Minimum condensate
receiver capacity gallons
for steaming times
(minutes) of: (note 1)
Suggested
feed pump
capacity
(GPM @
15 PSI)
(note 2)
15
min.
30
min.
45
min.
60
min.
OSB-3 118 14 4 8 13 17 0.5
OSB-4 148 18 5 11 16 21 0.6
OSB-5 179 22 6 13 19 26 0.7
OSB-6 216 26 8 16 23 31 0.8
Notes:
1. Maximum time to when condensate returns to boiler.
2. If pump exceeds capacity shown, pump can be throttled with globe or ball valve.

OSB 2 SERIES Specifications

General

Brand	OSB
Model	2 SERIES
Category	Boiler
Language	English