Two stage gas valve

keith123

I’ve used the Tekmar steam outdoor reset control before with much success.

I’m now learning about how 2-stage gas valves are meant to lower the fire once the pickup factor is satisfied.

I’m asking what Honeywell model is good to use either spark or standing? Residential Weil- Mclain or Peerless.

Also, what tells the gas valve when to downfire?

Thanks !!

EdTheHeaterMan

Usually a second pressure control. Full high flame on start up, then once the pressure reaches 3/4 of the high limit pressure, the operating limit (second pressure control) will reduce the firing rate to low flame. If low flame can't keep up, the pressure will drop and high flame will re-engage. Once the room thermostat is satisfied the flame is terminated.
A second idea is a 2 stage thermostat. The thermostat will need to be after the limits (sequence of operation logic) and stage one will go to low flame on the gas valve. Then as the room temperature drops stage 2 will kick into high flame. (This may not be the best for cold start up)

mroberts5

Interested too.