RT-SVX35H-EN 99
Service & Maintenance
Table 34. Control settings and time delays
Control Description Elec. Designation Contacts Open Contacts Closed
Combustion Airflow Switch
(Gas Heat Only)
4S25 see Note 1 0.1 - 0.25" wc rise in press diff
High Limit Cutout
(Gas Heat Only)
4S26 250 + 15°F 210°F
Supply Airflow Switch
(Gas Heat Only)
4S38 0.03 - 0.12" wc 0.15 + 0.05" wc rise in press diff
Disch High Limit
(Electric Heat Only)
4S27 133 + 5°F 110 + 5°F
Linear High Limit
(Electric Heat Only)
4S33
185 + 10°F (std./cULus)
165 F + 10°F (cULus)
145°F (std./cULus)
125°F (cULus)
Freezestat
(Hydronic Heat Only)
4S12 (N.O.) Auto Reset 40°F
Gas Heat Units
Prepurge Timer:
Fenwall 4DL5 N.C. - timed to close 60 seconds
Honeywell 4U18 internal timing function 60 seconds
Sequencing Time Delay Relay 4DL6 N.C. - timed to close 60 seconds + 20%
Note: The combustion airflow switch (4S25) differential is 0.02" - 0.08" wc.
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