Bryant Q674, T874 SETTINGS

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

11 60-2485—8

8. Move the HEAT and COOL levers to the maximum tem-

perature desired.

9. Slide the stop brackets until one rests a

ainst the HEAT

lever and the other a

ainst the COOL lever.

10. Firml

hten the mountin

screw.

11. If the HEAT and COOL levers are to be locked in place

at a specific temperature, use the two insulated head

screws supplied instead of the two ad

ustable lever stop

brackets.

CAUTION

Equipment Damage Hazard.

not

use standard screws that provide metal-to-

metal contact with the stop brackets. Short circuit and

potential e

uipment dama

e can result.

Mount Thermostat

1. Remove the thermostat cover b

pullin

the bottom

e of the cover awa

from the base until it snaps free

of the cover clip.

NOTE: The cover is hin

ed at the top and must be removed

pullin

up at the bottom.

2. Carefull

remove and discard the pol

rene packin

insert that protects the mercur

switches durin

ship-

ment.

3. If LED indication

(

EM.HT., CHECK, etc.

)

is to be used

with the Q674 Subbase, install the preprinted insert

under the thermostat setpoint scale. To install, push

both thermostat setpoint levers to the far ends of the

thermostat. Use index fin

er to

entl

pull out the plastic

setpoint scale about 1/4 in.

(

6 mm

)

. Position the desired

preprinted insert in the space above the LED li

hts.

Reposition setpoint levers.

4. Turn over the thermostat base and note the sprin

fin-

ers that en

e the subbase contacts. Make sure the

sprin

fin

ers are

not

bent flat, preventin

proper elec-

trical contact with the subbase.

5. Set the heat anticipator indicator

(

)

to the respective

current settin

of each sta

e. See Set The Heat Antici-

pator section.

6. If the thermostat provides optional lockin

cover assem-

, start the Allen lockin

screws in the cover with the

wrench provided. See Fi

. 10.

7. Note the two tabs alon

the top inside ed

e of the ther-

mostat base. The tabs fit into correspondin

slots on top

of the subbase. Mount the thermostat on the subbase.

8. Ali

n the two captive mountin

screws in the thermostat

base with the posts on the subbase. Ti

hten both

screws.

Do not overtighten screws

or dama

e to sub-

base posts can result.

Fig. 10. Installation of locking cover assembly.

SETTINGS

CAUTION

Equipment Damage Hazard.

On s

stems usin

as valve, never appl

umper

across the valve coil terminals, even temporaril

. This

can burn out thermostat heat anticipator

(

)

Set the Heat Anticipator

Move the indicator to match the primar

control current draw.

When usin

a T874 Thermostat with two sta

es of heatin

set each heat anticipator to match its respective primar

control current draw. If

ou cannot find the current ratin

the primar

control, or if further ad

ustment is necessar

, see

NOTE and use the followin

procedure to determine the

current draw of each sta

The current draw of each heatin

sta

e must be measured

with the thermostat removed and power on to the heatin

stem.

1. Connect an ac ammeter of appropriate ran

e between

the heatin

terminals of the subbase:

a. Sta

e 1—between W1 and RH or R;

b. Sta

e 2—between W2 and RH or R

c. Sta

e 3—between W3 and RH or R.

2. Move the s

stem switch to HEAT or AUTO.

3. After one minute, read the ammeter and record the

readin

a. Sta

e 1—__________A;

b. Sta

e 2—__________A;

c. Sta

e 3—__________A.

NOTE: If e

uipment c

cles too fast, set the indicator to a

her current ratin

, but not more than one-half divi-

sion at a time, and recheck the c

cle rate. Most con-

ventional two-sta

e heatin

uipment is desi

ned

to operate at three c

cles per hour per sta

e, and

one-sta

e heatin

uipment at six c

cles per hour,

at 50 percent load conditions. When usin

the T874

Thermostat in heat pump s

stems, set the heat

ALLEN

RETAINING

SCREWS (2)

M956