Hot Air Bleeding System Not Working Properly

New problem, or old problem?

The suction unit would be the easiest/cheapest solution. If it works.

Otherwise re-pipe.

I can't judge if it new or old because we are in the 1st startup of the furnace.
You can consider it as an inherent problem maybe :)

Hint:
For the suction unit suggestion: The suction unit will not be continuously running. It will only work when bleeding valve opens (Hot Air Temp. > 450 ° C).
I mean that the cost will not be high as it's running continuously.

i dont know what i'm talking about - but is your valve (location+function correct)

fig. follows:

Sorry ci139, I didn't understand what you mean

that makes 2 of us (****i never designed any air systems) but :: if your hot air preffers a route to furnances instead of temperature control shaft (or was it to bleed the cool air in) - whatever the case i cannot evision your diagram providing a fast responce in eigher case - unless you set a blender hot off replaced by the amount of cool air - as i said - i donno what i'm talking****

in other words if you decrease your hot air pressure behind the bleed it's original temperature remains only the amount of heat transferred to furnances per unit time decreases - so your furnaces have likely "tremendous" heat capacitance the only way to tell the temperature will go down is to predict such by airflow temperature + (plus) "supply" flow speed - (minus) losses in furnance = indirectly (predictively) - if your sensor is in suply tract the only way to "set" it's reading (fast) is to beed in additional cooler air ((1-ce again i don't like to "advise" something i don't have no practical experience in))

trivia:[p/]

<*>. the designers of your heaters must know the required test procedures and their order incase of any malfunction

(1) incase you test with no load (no heat loss) in furnances test with it

(2) if your input airflow is too hot (for a valve to operate normally) adjust it

(3) if you have a sensor(/?controller)-network problem (reffer to <*>)

NB! - i just improvise here without any knowledge related to your design nor metallurgy proceses in general - you have to think yourself - good luck!

ok, thanks ci139 for your comments