Sounds like a blockage in the exaust or a fan bearing may be chattering somewhat slowing the air flow. I had a similar problem a month ago. Its a dirty job but I havn't seen the problem since. Martin -----Original Message----- From: Ed Popielarski [mailto:[log in to unmask]] Sent: Wednesday, August 06, 2003 7:28 AM To: [log in to unmask] Subject: [TN] Temp stability in Zone 3 Hi everyone, I ran into an issue that has me scratching my head (no, it's not fleas!) My customer is having temp stability problems in Zone 3 of a BTU VIP70 reflow oven no gas. Below are the setpoints of each zone in deg C: Z1T: 140 Z1B: 140 Z2T: 140 Z2B: 140 Z3T: 140 Z3B: 140 Z4T: 180 Z4B: 180 Z5T: 230 Z5B: 230 All zones are holding +/- 1 deg C EXCEPT Z3T which after setpoint is reached, climbs very slowly (about 5 deg C/hour) and Z3B at half that rate. Once this 5 deg deviation is reached, the system alarms (as it should). I have confirmed the solid state relays are not "leaking" (swapped them with good zone), the computer is setting the duty cycle of these at 0% (once setpoint has been reached) , this has been confirmed electrically, and there are no ground faults in the heaters, convection fans are running. BTU has offered the customer little, if any advice. My theory is that "stray energy" from Z4 and possibly Z5 are heating Z3 which, possibly due to inadequate ventilation, cannot cool. I was hoping someone in the forum might have experienced a similar issue and would share that experience. I haven't measured the exhaust flow rate yet, as I didn't want to chase a "ghost", but it IS running. It's not often I get stumped (Steve G. can attest to that!) but this one really has me baffled. Regards, Ed Popielarski QTA Machine 27291 Jardines Mission Viejo, Ca. 92692 Phone:949-581-6601 Fax: 949-581-2448 Cel: 949-337-2578 WWW.QTA.NET <http://www.QTA.NET> --------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 -----------------------------------------------------