JCI/Lennox hiccup

[Jason Grossman]

I have a building with 12 Lennox RTUs with the lennox controls package DDC board in them. They also have, factory installed ,UNTs that do the actual temp control and the Lennox board only sees a tstat input that determines what the unit should be doing.
My problem is that I get periodic faults on the lennox board that indicates that the unit saw a simultaneous call for heating and cooling. The unit locks out and needs to be manually reset.
Anyone seen this or know what in JCI is causing the heat and cool
BOs to close at some point.

Thanks Jason

[chrisc]

I would recommend rewriting the Lennox OEM RTU program that is written for the UNT controller. That program typically covers all Lennox RTU configurations but I've seen problems with it. I'll typically use a MA Single Path or 100% OA program depending upon the economizer sequence that is being used. Remember you may have to remap points to the front end, I've had at least a dozen jobs typical to yours in the last 2 years. The Lennox factory wiring is a nightmare and their wiring diagrams are worse. Good Luck.

[mtnwrench]

I have the same problem on one of my buildings. I have tried downloading new configs like stated above. Doesnt help. For some dumb reason, at odd times this happens. There is no way in hell that the UNT is sending out heat and cool commands at the same time. The problem must be in the Lennox board but it doesnt happen enough to justify spending much time on it.

[Jason Grossman]

Thanks for the replies. I have rewritten the UNT programs and it didn't seem to help. I really like the lennox rtus but I could do without the microprocessor controlled by another microprocessor. The wiring and setup for these units is a nightmare. Too many dipswithces.

[twisted pair]

That is a common complaint with JCI to many dip****s. Look at IndyBlue. Need I say more.

[chrisc]

It seems as though your problem is more with the Lennox board then it is the UNT. The Lennox board has more setup then just dip switches you have to access control parameters with the keypad. Good Luck they do suck!!

[cleancondenser]

If you can get me a model number I may be able to help

We had this problem with both

the LCA and LGC units

In one case it was two faulty sensors ,Outdoor and Humidity

It is definetly the Lennox end

[rolo]

this is a johnsun problem they want the guy to buy a york

[redfive]

I have 15 RTUs (LGA) , all with UNTs hooked to Metasys. when I do my summer check or winter checks for cooling and heating, They would lock out if I swopped between cooling call and heating call to fast on Metasys. The lennox neededs a slight delay. Also its how the lennox is set up. If you dont tell it to let the unt run the whole show, you get a conflict. Specialy when it comes time for dehumidification. The unt will call for cooling and heating at the same time to do this. Best way is to check your pid loop in hvac pro and deadbands to spread the calls out a little bit, if they are not already. The lennnox its self is not the prob. if it is giving full control to the unt. Johnson likes to run the show, but most units these day can do it all by themselves, they only need a cooling or heating call. So if you are dehumidifying, its best to let the lennox control it and limit the unt to cooling and heating only. The LGAs are realy smart, and a joy to work on. Iv had no probs with them.

REDFIVE