Henry1
04-25-2007, 10:34 PM
Our new Thermo Pride OC2-56D downflow oil furnace has been shortcycling since the dealer installed it --and the new return air system--in February. I have shown pictures of the installation elsewhere on this site. The general consensus of members on this site was that our return air system was not giving the furnace enough return air.
The fan and limit control (PN 350124) is the only part listed in the manual for this UL (Underwriter's Laboratory) approved furnace. The helix of the fan and limit control is about a foot long and kept tripping out at 250 F limit. So anytime we needed to warm up the house, it took at least six burner on-off cycles to satisfy wall thermostat demand.
The installer got another fan and limit control with an eight inch reach. I notice that the furnace does not shortcycle anymore, but that furnace temperatures stay around 200F as indicated on the dial of the shorter fan and limit control.
The installer told me that the factory sent him the shorter fan and limit control so our shortcycling problem would go away. But it looks to me that the part might not be measuring temperatures in the area where the furnace was supposed to have it's temperatures sensed.
I made it clear to the installer and the installer's factory representative that I considered his fix to be a "band aid" approach that did not address a return air system that was poorly designed according to other HVAC professionals who have seen our installation.
Is this a standard industry fix? I told my installer that we have to have more return air and not a shorter limit switch that senses temperatures in a cooler part of the furnace.
I do not see that this UL-certified furnace allows any other part other than the 11 inch long probe to be used.
What other problems could this create?
The fan and limit control (PN 350124) is the only part listed in the manual for this UL (Underwriter's Laboratory) approved furnace. The helix of the fan and limit control is about a foot long and kept tripping out at 250 F limit. So anytime we needed to warm up the house, it took at least six burner on-off cycles to satisfy wall thermostat demand.
The installer got another fan and limit control with an eight inch reach. I notice that the furnace does not shortcycle anymore, but that furnace temperatures stay around 200F as indicated on the dial of the shorter fan and limit control.
The installer told me that the factory sent him the shorter fan and limit control so our shortcycling problem would go away. But it looks to me that the part might not be measuring temperatures in the area where the furnace was supposed to have it's temperatures sensed.
I made it clear to the installer and the installer's factory representative that I considered his fix to be a "band aid" approach that did not address a return air system that was poorly designed according to other HVAC professionals who have seen our installation.
Is this a standard industry fix? I told my installer that we have to have more return air and not a shorter limit switch that senses temperatures in a cooler part of the furnace.
I do not see that this UL-certified furnace allows any other part other than the 11 inch long probe to be used.
What other problems could this create?