2 furnace units attached

[Jon mackay]

Has anyone heard of attaching 2 furnaces together and using them in sequence?

Found the blower compartment sides removed and the furnaces are both activated for heating and cooling. I was thinking that this might throw off the air balance with the 2 blowers both on at once or some other issue. Seemed strange to me.

Small commercial aplication.

[neal lewis]

Some manufacturer installation manuals have instructions on how to "twin" the furnaces.

[Michael Thomas]

Usually there is an OEM or after-market "twinning controller" installed, for example"

[Markus Keller]

'Twinning' 'was' a common method for oversized homes. Ruud and Rheem furnace boards had, and may still have, terminals specifically for twinning so the boards respond properly to the stat. You should see significantly larger ducts in a twinning configuration. If not recommend full evaluation.