Teco US TR20 - Manual (Page 6)

Unscrew and remove ring nut over UV port.
Remove plug and o-ring from ring nut.
Place o-ring over the top of the quartz sleeve and push down
approximately 3/4 inch to 1 inch onto the quartz sleeve.
Insert quartz sleeve into heat exchanger until o-ring seats
into outlet lip. If you encounter resistance while inserting
the quartz sleeve, gently turn sleeve and apply very slight
force.
Step 3
Installing The Quartz Sleeve