Robertshaw SP735 Ignition Control

Re: Burners Cycling Off

The SP735 is a spark ignition controller. Once 24VAC is received on "TH" and "TR (Common)", the control will start an ignition sequence by powering the pilot valve "PV" while sparking through the on-board ignition transformer "IGN".

When the board senses flame through the "SENS" terminal, it powers the main gas valve "MV".

The gas valve will stay energized until 24VAC is removed from "TH" or flame signal is lost.

Possible Causes (From Most to Least Likely):

1. Losing power from the thermostat
2. Safety Trip
   • Pressure Switch
   • Limit Switch
3. Loss of pilot flame signal
   • Dirty sensor
   • Clogged pilot orfice
   • Low gas pressure

CHECKOUT

1. Check for Power at Controller
   • Check for 24VAC between "TH" and "TR".
   • Monitor voltage as equipment operates.
     • Power drops out when burners kick-off = Thermostat or Safety
     • Power present when burners kick-off = Loss of Flame Signal