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Series 20 Amplifiers (A1010U shown):
Modulator-Regulator Valves
Selectrastat: selector and integral sensing
Space Temperature Selector: selection only
Space Temperature Sensor: remote sensing
DESCRIPTION
Selectra® SERIES 20 electronic gas flame modulation systems are designed primarily for commercial and light industrial space heating, as components of indirect fired units with atmospheric burners. All fuel gases are compatible.
The SERIES 20 is designed for single or multiple furnace opera-tion. It is capable of controlling up to four furnaces. It may be field installed on existing equipment or specified for new equipment installation.
The system utilizes Modulator-Regulator valves. High Fire igni-tion selection (0, 5 or 25 second) is standard on all models. A wall mounted Selectrastat senses space temperature and has an integral selector with a 60º to 85º F range. Optionally, a remote Temperature Sensor paired with a separate Temperature Selector (60º to 85º F) can be substituted for the Selectrastat.
TABLE OF CONTENTSSpecifications...................................................................1Dimensions..................................................................................2Installation of Components..........................................................3Preliminary Circuit Analysis..........................................................3Field Service Checklist.................................................................4Performance Check.......................................................................5Extended High-Fire Ignition..........................................................5Low Limit Stat...............................................................................5Wiring Diagrams............................................................................6Valve Adjustments.........................................................................7
1© 2010 Maxitrol Company, All Rights Reserved
Series 20 Installation InstructionsInstallation Instructions and field service checklist
SPECIFICATIONS
Power Requirements:Single Furnace.....24V AC, 40VA capacityMultiple Furnace.....24V AC, 100VA capacity
Temperature Control Range: 60º to 85ºF
Ambient Limits: -30º to 125ºF / -34º to 52ºC
Gases: Suitable for natural, manufactured, mixed gases, liquefied petroleum gases and LP gas-air mixtures.
Pressure Limits:
Inlet (maximum) : MR410, 510, 610.....1 psi / 69 mbar
Outlet (maximum fire)standard spring*.....3.0” to 5.0” w.c. / 7 to 12 mbarH - models..... 7.5” to 12” w.c. / 19 to 30 mbarMax. set point not to exceed 10” w.c. above min. set point
Outlet (minimum fire)standard spring*.....0.2” to 1.2” w.c. / .5 to 3 mbar(-1) spring*.....1” to 2.8” w.c. / 2.5 to 7 mbar(*other spring ranges available - Consult Maxitrol Company.)
Read these instructions carefully. Failure to follow them could result in a fire or explosion causing property damage, personal injury, or loss of life. The product must be installed and oper-ated according to all local regulations.
Service and or installation must be performed by a trained ex-perienced service technician.
Transformer secondary must not be grounded in any portion of the circuit external to a Maxitrol amplifier. If existing trans-former is grounded, a seperate isolated transformer must be used. Electrical interference may effect performance and/or damage equipment.
NOTICE
MR410 (3/8” and 1/2” pipe sizes)MR510 (1/2” and 3/4” pipe sizes)MR610 (3/4” and 1” pipe sizes)
T120 - (60º to 85º F)
TD120 - (60º to 85º F) - For use with TS120
Optional: ETD-1 enclosureEFP-1 cover plate only - no enclosure
TS120 - For use with TD120
SYSTEM COMPONENTS
A1010U
DIMENSIONS
2© 2010 Maxitrol Company, All Rights Reserved
TD120 ETD-1
T120 / TS120
A1010U
2.00
3.00
3.38
6.00
Mounting Holes
3.28
1.47
.97
1.79
2.56
4.50
4.65
1.752.25
2.62
2.62.19
Mounting Holes2- Required
2.56
4.19
4.19
10-12 x 1/2’ LG.BiINDING HD. SHEET METAL SCR. (2 REQ’D.)
1.88
1.75
1.50
3.00
Power LED
Relay LED
Valve LED
VALVE LED
The PCB “Valve” LED illuminates when the output DC voltage to the valve is approximate-ly 2 VDC or greater. It does not indicate valve positioning or whether the system is in modu-lation mode.
The Valve LED will be:
• “OFF” at maximum high fire (0VDC) and during the high fire ignition duration (if used)
• “ON” when PCB “Relay” LED is “OFF”
• “ON” or “OFF” when the “Relay” LED is “ON”
Amplifier: Slide or snap out circuit board from amplifier base. Mount base with two screws in chosen location protected from weather or contaminated atmosphere. Amplifier is ready for wir-ing when circuit board is replaced on base - protective cover need not be removed.
Selectrastat: Pull dial and cover outward. Loosen screws in ter-minal strip, tilt out and lift up. Install in area where representative space temperature is to be sensed. Wire as shown in appropriate diagram, page 6 - reassemble.
Space Temperature Sensor: Remove cover and install in area where representative space temperature is to be sensed. Wire as shown in appropriate diagram, page 6 - reassemble.
Space Temperature Selector: Install in control cabinet or other chosen location. Remove cover and wire as shown in appropri-ate diagram, page 6 - reassemble.
NOTE: For systems using up to four automatic gas valves with 0.8 amp maximum current each, a 100VA transformer will be adequate.
In the event that the automatic valve(s) current exceeds 0.8 amps, it would be advisable to wire according to the ‘Indepen-dent Power Supply’ diagram, page 6. The transformer for the modulating power - terminals 8 and 9 - should be 40VA, and the automatic valve transformer should be capable of handling re-quired loads up to 3.5 amps maximum. If exceeding 3.5 amps, it will be necessary to operate an auxiliary relay with contact rating sufficient to handle the automatic valves and any accessories.
PRELIMINARY CIRCUIT ANALYSIS
In order to diagnose the cause of problems in this system it is necessary to determine certain values. It is helpful to have an AC and DC voltmeter and an ohmmeter capable of reading 0 to 15,000 ohms. For ease in trouble shooting, it is necessary to rewire the system, replacing the discharge air sensor with a 4500 ohms, eg. 4300 ohm + 200 ohm, 1/2 watt test resistors in series.
Modulating Function Test - when temperature at Selectrastat or Sensor is 60º to 85ºF (16º to 29ºC):Connect a DC voltmeter to amplifier terminals 1 and 2. If more convenient, the meter may be attached to the MR valve termi-nals. Rotate temperature selection knob to maximum setting. The DC volts should read zero, Valve LED is “OFF”. When the temperature selector is slowly rotated to its minimum setting, the voltage should gradually increase to 20+ volts, Valve LED is “ON”. See pg. 2, “Valve LED”.
Automatic Valve Function - when temperature at Selectra-stat or Sensor is 60º to 80ºF (16º to 29ºC):Disconnect the wires at amplifier terminals 10 and 11, and con-nect an ohmmeter. Rotate temperature selector to maximum set-ting - ohmmeter should show continuity, Relay LED is “ON”. Ro-tate temperature selector to minimum setting - ohmmeter should show open circuit, Relay is “OFF”. Reconnect the wires to termi-nals 10 and 11.
Automatic Valve Function - when temperature at Selectra-stat or Sensor is less than 60ºF (16ºC) or greater than 85ºF (29ºC):Disconnect the wires at amplifier terminals 10, 11 and 3. DC modulating voltage across terminals 1 and 2 should be zero. Ohm reading across terminals 10 and 11 should be zero ohms.
Reconnect wire to terminal 3 of amplifier. Carefully connect a piece of jumper wire across the therm-istor as shown (make only temporary connec-tion). Ohm reading at terminals 10 and 11 should be infinite (open circuit). Modulating voltage at terminals 1 and 2 should be greater than 17 volts.
Reconnect wires to terminals 10 and 11. Amplifier is not faulty if the above conditions are met.
GAS TRAINS
Valve: The MR valve must be in upright position, in a horizontal run of pipe only, with pilot gas supply upstream.
If diaphragm type automatic gas valve is used with separate regulator, install MR valve downstream from diaphragm gas valve. Retain regulator in manifold and adjust 2 or 3 turns to compensate for pressure drop of MR valve.
If full combination control is used, install MR valve downstream. Adjust regula-tor in combination control 2 or 3 turns to compensate for pressure drop at MR valve.
If solenoid type automatic gas valve is used with separate regulator, replace regulator with the MR valve.
INSTALLATION OF COMPONENTS
3© 2010 Maxitrol Company, All Rights Reserved
NOTICE
Wiring Run: Control wires connecting the Selectrastat or Space Temperature Sensor must not be run close to or in-side conduit with power or ignition wires. Doing so may cause the unit to function erratically or may destroy the amplifier. If shielded wires are used, shield must be insulated and grounded at the amplifier location only. Clip R55 off of circuit board.
VALVE LED
4© 2010 Maxitrol Company, All Rights Reserved
FIEL
D S
ERVI
CE
CH
ECK
LIST
SYM
PTO
MPO
SSIB
LE C
AU
SEFI
ELD
TES
TR
EMED
YA
.A
utom
atic
con
trol
val
ve w
ill
not c
lose
des
pite
full
rang
e of
mod
ulat
ing
volta
ge a
t te
rmin
als
1 an
d 2.
1. A
utom
atic
con
trol v
alve
not
ope
ratin
g pr
oper
ly.
2. I
nsta
llatio
n w
iring
err
or.
3. A
mpl
ifier
is n
ot o
pera
ting
prop
erly.
1. R
emov
e w
ire fr
om v
alve
, if v
alve
doe
s no
t clo
se -
valv
e is
not
ope
ratin
g pr
oper
ly.
2. R
emov
e w
ire fr
om a
mpl
ifier
term
inal
10
or 1
1. If
val
ve re
mai
ns o
pen,
che
ck fo
r mis
wiri
ng.
3. I
f AC
vol
tage
will
not
dro
p to
zer
o at
term
inal
s 8
and
11 -
whe
n D
C v
olta
ge a
t ter
min
als
1
and
2 is
abo
ve 2
0 V
DC
- am
plifi
er is
faul
ty. I
f spa
ce te
mpe
ratu
re is
less
than
60º
or
g
reat
er th
an 8
5ºF
(<16
º or >
29º
C),
see
Pre
limin
ary
Circ
uit A
naly
sis,
pag
e 3.
1. R
epla
ce a
utom
atic
con
trol v
alve
.
2. C
orre
ct w
iring
.
3. R
epla
ce a
mpl
ifier
.
B.
Aut
omat
ic c
ontr
ol v
alve
w
on’t
open
des
pite
full
rang
e of
mod
ulat
ing
volta
ge a
t te
rmin
als
1 an
d 2.
4. A
utom
atic
con
trol v
alve
not
ope
ratin
g pr
oper
ly.
5. O
pen
wire
to a
utom
atic
val
ve.
6. A
mpl
ifier
is n
ot o
pera
ting
prop
erly.
4. R
ead
volta
ge a
cros
s va
lve
term
inal
s. If
24
VAC
, val
ve is
not
ope
ratin
g pr
oper
ly.
5. R
ead
volta
ge a
cros
s te
rmin
als
8 an
d 11
on
ampl
ifier
. If 2
4 VA
C, c
heck
for o
pen
circ
uit t
o
a
utom
atic
val
ve. I
f spa
ce te
mpe
ratu
re is
less
than
60º
or g
reat
er th
an 8
5ºF
(<16
º or
>
29ºC
), se
e P
relim
inar
y C
ircui
t Ana
lysi
s, p
age
3.
6. I
f AC
vol
tage
read
ing
rem
ains
zer
o - w
hen
DC
vol
tage
at t
erm
inal
s 1
and
2 is
bel
ow 1
4
V D
C -
ampl
ifier
is fa
ulty
. If s
pace
tem
pera
ture
is le
ss th
an 6
0º o
r gre
ater
than
85º
F (<
16º
>
29º
C),
see
Pre
limin
ary
Circ
uit A
naly
sis,
pag
e 3.
4. R
epla
ce a
utom
atic
con
trol v
alve
.
5. C
orre
ct w
iring
6. R
epla
ce a
mpl
ifier
.
C.
No
gas
flow
.7.
Mal
func
tioni
ng p
ower
sup
ply.
8. M
R v
alve
inst
alle
d ba
ckw
ards
.
7. R
ead
volta
ge a
t am
plifi
er te
rmin
als
8 an
d 11
(24
VAC
).
8. A
rrow
s on
MR
val
ve s
houl
d po
int i
n th
e di
rect
ion
of g
as fl
ow.
7. P
ower
sup
ply
mus
t be
24 V
AC
.
8. I
nsta
ll pr
oper
ly.
D.
Con
tinuo
us h
igh
fire.
9. O
pen
circ
uit i
n se
nsin
g an
d se
tting
ci
rcui
t.9.
Dis
conn
ect a
nd m
easu
re a
cros
s w
ires
conn
ecte
d to
am
plifi
er te
rmin
als
3 an
d 4
(A10
10U
mod
els)
. Sho
uld
read
bet
wee
n 8,
000
to 1
2,00
0 oh
ms.
9. I
f abo
ve 1
2,00
0 oh
ms,
che
ck c
ircui
t for
ope
n or
loo
se w
ires.
E.C
ontin
uous
hig
h fir
e bu
t au
tom
atic
val
ve c
ycle
s.10
. O
pen
circ
uit i
n w
iring
to M
R v
alve
.
11.
Plu
nger
jam
med
or i
nsta
lled
upsi
de
dow
n.
12.
MR
val
ve n
ot o
pera
ting
prop
erly.
10.
Che
ck w
iring
for d
efec
ts.
11. E
xam
ine.
Plu
nger
sho
uld
be s
moo
th a
nd c
lean
and
ope
rate
free
ly in
sol
enoi
d sl
eeve
.
M
ust b
e in
stal
led
as s
how
n in
“Val
ve A
djus
tmen
ts” p
g. 7
, “M
/MR
Val
ve D
iagr
am”.
12.
Mea
sure
vol
tage
acr
oss
MR
val
ve.
10.
Rep
ace
wiri
ng if
nec
essa
ry.
11.
Cle
an p
lung
er if
nec
essa
ry.
12.
If m
odul
atin
g vo
ltage
s ar
e ob
tain
ed b
ut n
o ga
s
m
odul
atio
n, M
R v
alve
is fa
ulty
. Rep
lace
if n
eces
sary
.
F.Fu
rnac
e w
on’t
activ
ate
due
to c
onst
ant h
igh
mod
ulat
ing
volta
ge. (
abov
e 17
V D
C)
13.
Sho
rt ci
rcui
t in
sens
ing
and
setti
ng
circ
uit.
13. D
isco
nnec
t and
mea
sure
acr
oss
wire
s co
nnec
ted
to a
mpl
ifier
term
inal
s 3
and
4
(A
1010
U m
odel
s). S
houl
d re
ad b
etw
een
8,00
0 an
d 12
,000
ohm
s.13
. If
belo
w 8
,000
ohm
s, c
heck
circ
uit f
or s
horts
or
mis
wiri
ng.
G.
Con
tinuo
us lo
w o
r med
ium
fir
e, b
ut a
utom
atic
val
ve
cycl
es c
orre
ctly
.
14.
Hea
t loa
d re
quire
s lo
w fi
re o
nly.
15.
Plu
nger
and
/or m
axim
um s
prin
g
m
issi
ng.
16.
Jam
med
plu
nger
.
17.
Oth
er v
alve
pro
blem
s.
18.
Inad
equa
te s
uppl
y pr
essu
re.
14 I
ncre
ase
tem
pera
ture
set
ting
10 d
egre
es.
15.
Che
ck fo
r par
ts (s
ee “V
alve
Adj
ustm
ents
” pg.
7, “
M/M
R V
alve
Dia
gram
”).
16.
Exa
min
e. P
lung
er s
houl
d be
sm
ooth
and
cle
an a
nd o
pera
te fr
eely
in s
olen
oid
slee
ve.
Mus
t be
inst
alle
d as
sho
wn
in “V
alve
Adj
ustm
ents
” pg.
7, “
M/M
R V
alve
Dia
gram
”. 17
. R
emov
e w
ire fr
om M
R v
alve
.
18.
Rem
ove
sprin
g 5
from
MR
val
ve (s
ee “V
alve
Adj
ustm
ents
” pg.
7, “
M/M
R V
alve
D
iagr
am”)
pus
h do
wn
on p
lung
er. I
nsuf
ficie
nt m
anifo
ld p
ress
ure
with
furn
ace
oper
atin
g
in
dica
tes
supp
ly is
too
low
.
14.
If he
ater
goe
s to
hig
h fir
e, s
yste
m is
wor
king
c
orre
ctly.
15.
Inst
all c
orre
ct p
arts
.
16.
Cle
an p
lung
er if
nec
essa
ry.
17.
If M
R v
alve
rem
ains
on
low
fire
, val
ve is
not
o
pera
ting
prop
erly.
Che
ck it
em 1
9 be
low
, the
n
re
plac
e va
lve
if ne
cess
ary.
18.
Che
ck fo
r obs
truct
ion
in g
as p
ipe
ahea
d of
con
trols
.
I
ncre
ase
gas
pres
sure
if p
ossi
ble.
H.
Inco
rrec
t dis
char
ge a
ir te
mpe
ratu
re.
19.
Cal
ibra
tion
19.
Che
ck s
eal o
n ca
libra
tion
pote
ntio
met
er.
19.
Rec
alib
rate
per
“Tem
pera
ture
Cal
ibra
tion”
p
roce
dure
.
I.Er
ratic
or s
ever
ely
puls
atin
g fla
me.
20.
Dirt
y or
stic
king
plu
nger
.
21.
Inte
rmitt
ent s
horti
ng in
wiri
ng.
22.
Am
plifi
er n
ot o
pera
ting
prop
erly.
20.
Exa
min
e. P
lung
er s
houl
d be
sm
ooth
and
cle
an a
nd o
pera
te fr
eely
in s
olen
oid
slee
ve.
Mus
t be
inst
alle
d as
sho
wn
in “V
alve
Adj
ustm
ents
” pg.
7, “
M/M
R V
alve
Dia
gram
”.
21.
Insp
ect w
iring
.
22.
Obs
erve
DC
vol
tage
acr
oss
ampl
ifier
term
inal
s 1
and
2.
20.
Cle
an p
lung
er if
nec
essa
ry.
21.
Cor
rect
wiri
ng.
22.
If er
ratic
or p
ulsa
ting
DC
vol
tage
is o
bser
ved
and
wiri
ng s
how
s no
def
ects
, rep
lace
am
plifi
er. I
f
e
rrat
ic o
r pul
satin
g vo
ltage
con
tinue
s, c
onta
ct
Max
itrol
Com
pany
.
*Con
trol
circ
uits
ext
erna
l to
the
Serie
s 20
can
cau
se b
urne
r mal
func
tion.
Alw
ays
chec
k m
anua
l val
ve to
be
cert
ain
gas
is o
n, a
nd c
heck
lim
it co
ntro
ls fo
r nor
mal
ope
ratio
n.
With the modulator-regulator valve installed as instructed (volt-ages are approximate)...
Low Fire is above 14 volts DC.Manifold pressure can be adjusted as follows: Standard spring 0.2” to 1.2” w.c. (.5 to 3 mbar), MR*10B10L-1 spring 1” to 2.8” w.c. (2.5 to 7 mbar).
High Fire is obtained at zero volts DC.Use manufacturer’s pressure specifications when available. Maxitrol standard factory settings are 0.5” w.c. (1.25 mbar) mini-mum and 3.5” w.c. (8.75 mbar) maximum. H-1 models 1.75” w.c. (4.35 mbar) minimum and 11” w.c. (27 mbar) maximum.
At Selectrastat/Temperature Selector:
1) Set below room temperature and slowly increase setting until furnace begins operating. Furnace should ignite and remain on low fire. If high fire ignition is being used the furnace will ignite at high fire for the set duration or either 5 or 25 sec-onds (see Extended High Fire Ignition below), then modu-late to low fire. At low fire (manifold pressure about 0.5” w.c. [1.25 mbar]), a reading of approximately 14 or more volts DC should be obtained.
2) Rotate 3º higher.
3) Furnace should now be at high fire, manifold pressure about 3.5” w.c. (8.75 mbar). Less than 2 volts DC should read across Modulator-Regulator valve terminals. Rotate slowly to a lower setting. Furnace should modulate to low fire, with voltage at modulator approximately 15-17 volts, internal relay will trip and solenoid automatic control valve (s) will close.
If the preceding readings are obtained, proceed with Furnace Adjustments. If the preceding readings are not obtained:
4) Recheck wiring to ensure system is consistent with appropri-ate wiring diagram.
5) Check power source for 24 volts, Power LED is “ON”.
6) Some automatic control valves require as much as 20 sec-onds to open. In this case, check fro 24VAC output at auto-matic valve terminals, Relay LED is “ON”.
Furnace Adjustments:
For space heating, first calculate heat loss. If reduction of furnace input is indicated, consult furnace manufacturer about changing to smaller orifices. Do not try to reduce by pressure adjustment or throttling the gas supply.
An oversized furnace input is easily identified, particularly dur-ing cold weather. If outdoor temperature is low and the system cycles on and off instead of maintaining a low input, the furnace is oversized. Consult furnace manufacturer.
PERFORMANCE CHECK
LOW LIMIT STAT
When fresh outside air is introduced and the space being heated is up to temperature, the furnace will shut off. If the recirculated air should be too cool, temper it by wiring a duct-stat, as shown.
5© 2010 Maxitrol Company, All Rights Reserved
High Fire Ignition
Low Limit Duct Stat
Note: Terminals 10 & 11 MAX LOAD is 3.5 Amps.
LOW LIMIT DUCT STAT(not furnished by Maxitrol)
J1
J1
J2
TIMER DISABLE
5 Seconds
25 Seconds
STARTTIME
STARTTIME
The high fire start duration is field selectable. Amplifier will hold MR valve in the High Fire position for the set duration.
High-Fire duration of 0 seconds, 5 seconds, 25 seconds. (Times are approximate).
A1010
8
9
10
11
12
EXTENDED HIGH-FIRE IGNITION
0 Seconds
Common Power Supply
SINGLE FURNACE OPERATION
24V-40VA
GASVALVE
A1010U
MR VALVE
T120
A1010U
24V-40VA
24V-40VA
GASVALVE
A1010U
TD120
TS120
MR VALVES 4 MAX.
24V-100VA
A1010U GAS VALVES (4 MAX.) 3.5 AMPS MAX
A1010U
TD120
TS120
A1010U
24V-100VA24V-100VA
GAS VALVES (4 MAX.) 3.5 AMPS MAX
6© 2010 Maxitrol Company, All Rights Reserved
A1010U
Common Power Supply
Independent Power Supply
Remote Temperature Sensor with Separate Selector
MULTIPLE FURNACE OPERATION
Wired in Parallel
Remote Temperature Sensor with Separate Selector Independent Power Supply
R55 Removed. *
R55 Removed. *
R55 Removed*
These wiring diagrams are for Series 20 space air sensing systems only. The R55 (Zero ohm Jumper) MUST be Clipped off of circuit board (located near terminals 5 & 7, outside of cover.)
(MR valves and automatic gas valves wired in parallel as shown)
* R55 IS A ZERO OHM JUMPER
8
8
VALVE ADJUSTMENTS
(See bulletin MMR_MT_EN for additional M/MR valve information)
NOTE: High Fire Adjustment should be checked whenever Low Fire Adjustment is changed.
Low Fire Adjustments:
A) Remove Cover (2)
B) Remove maximum adjusting screw (4), spring (5), and plunger (8). A small magnet is useful for this purpose.
C) Using minimum adjusting screw (9), set manifold pres-sure to furnace manufacturer’s specifications.
D) Replace plunger, spring retainer, spring and maximum adjusting screw in proper order.
E) Perform High Fire adjustment.
High Fire Adjustments:
A) Disconnect wire from amplifier terminal 3, remove cover plate (2).
B) Using maximum adjustment screw (4), set manifold pres-sure to furnace manufacturer’s specifications.
C) Reconnect wire to amplifier Terminal 3.
D) Replace cover plate (2) on Modulator-Regulator valve and reconnect wire to amplifier terminal 3.
1
10
9
8
7
6
23
4
5
M/MR Valve Diagram
Top Housing
Cover Plate
Seal Gasket
Maximum Adjustment Screw
Maximum Adjustment Spring
Solenoid
Minimum Adjustment Spring
Plunger
Minimum Adjustment Screw
Minimum Adjustment Screw Stop
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
7© 2010 Maxitrol Company, All Rights Reserved
The plunger is a precision part. Handle carefully to avoid marring or picking up grease and dirt. Do not lubricate.
NOTICE
8Maxitrol Company23555 Telegraph Rd., PO Box 2230Southfield, MI 48037-2230
SEL20_MI_EN_04.2010
www.maxitrol.com© 2010 Maxitrol Company
All Rights Reserved
