blower?

sspeedster37

I have a commercial 4 ton, rooftop, Carrier unit that the blower motor will only operate when I jump R and G on the Test termnals. When I jump out R and Y, the compressor and condensor fan operate, but no blower fan. I know when you jump out R and Y that the unit should operate as if the it was cooling and all components should work. Any ideas? If it helps the model number is 48tje006-501ga and the Blower fan is 208/230/ 3phase. Its an existing unit that had been running so the installation shouldn't be an issue. Thanks for any ideas or suggestions

mechanicalDvr

I don't know of any unit that will bring on the fan if you jump out R-Y, that will just bring on a cooling relay, the t-stat subbase is were you get the signal for the fan relay (ie; when the stat makes r-y the r-g is also made). In the controls of the unit itself the fan and cooling relays are isolated from each other they need to be energized by a "jumper" on the customer side of the terminal strip.

sspeedster37

Thank you. I have done alot of installs and air balance, but only a little service. Its a reconditioned space so I was just trying to make sure the unit was operating. Maybe since I have always jumped it out at the tstat thats the reason why the fan always came on. Thanks for the response and I will re-install the tstat and everything should work

mechanicalDvr

Anytime.