Furnace blower to assist wood furnace

[NaturalCauses]

I have an old (1981) Woodchuck 526 add-on furnace to supplement my heating oil furnace. The Woodchuck is hooked into the ducts in parallel to the oil burner, coming before it as airflow goes. The blower fan on the Woodchuck isn't powerful enough to circulate air through the entire house (1200 sq ft ranch). The two registers on the main floor closest to the furnace have noticeable airflow when the blower is on, but the ones with longer duct runs (bedrooms) don't have noticeable flow.
I thought about turning on the blower fan for the furnace manually to assist with pushing air through the system to the outer rooms, but am concerned that it could have a negative affect on the blower fan in the Woodchuck. Could the change in pressure within the system, particularly the cold air return, put a higher load on the blower and shorten it's life/cause it to burn up?

 

[brenndatomu]

The Woodchuck is hooked into the ducts in parallel to the oil burner, coming before it as airflow goes.

Can you draw this out? If it comes in ahead of the main furnace then that would be a series install.
Depending on the details of your setup, using the main blower may dilute the warm air with cold air too much to do any good. I'd just throttle the registers closest the furnace to force air down to the other end.
Need more details though...
Oh, and welcome to Hearth!

 

[NaturalCauses]

I'll get some pictures and a diagram added when I get home tonight. I didn't even think about the heat being diluted with the cold air. There are dampers in all the ducts that can be closed, maybe I'll try and partially restrict the airflow to those 2 registers.

 

[begreen]

The pressure difference to the stove should be negligible if the heating system is balanced. You want to be careful restricting or damping down too many registers or blocking a return. This can cause the blower to race and can lead to premature burnout. If the ductwork is unsealed and uninsulated it is likely too cool down the air too much. Hot air furnace ductwork can be quite lossy which used to be ok when oil was cheap and 140-160F air is being moved. You might not notice a 10-20º drop because the room is still getting warmed up. But when there is a 10-20º drop and you are moving say 80º room air, the air at far points of the system can come out too cool.