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Long story short. We were called to look at this ladies residential system
It was a hydronic air handler with a HRV.
But what I noticed is there is only 3 vents going in/out of the unit
The fresh air,exhaust,and return from the house are there but they are just using the blower to push the new mixed air straight into the supply. Is that doable or should it be vented into the return?
Because when you open the door there a lot of pressure.
Thanks

Sorry it's a life breath and I can't remember the model number off the top of my head L4Y-p16 I want to say is the end of it.
Also it has a general aire 1042 humidifier with the stat mounted in the mechanical room. Her main thermostat doesn't control humidity....  I would say a steam humidifier would be better in that application(better period)  because the air passing over the pad isn't that warm no?
As well as a thermostat to control it all
HRV is hooked through bathroom fans
This lady is totally unhappy with what she got from this other company.

Is this a combo air handler with a built in HRV?

If it's a standalone HRV, most manufacturers allow a return/return or a supply/return connection.  I find most people that use the supply/return connection forget to install an elbow inside the supply plenum, otherwise the supply airflow will overcome the "fresh air to building" airflow.  I'm not a big fan of dedicated, or in your case a central draw point configuration.  Bathroom exhaust fans are far more effective than the HRV in my opinion.  I will always use a return/return hookup for any HRV installation, whether it is a simplified or central draw point configuration.

Our Building Code Article 9.32.3.11(3) states,

Quote(3) Where a heat recovery ventilator is connected to a forced air heating system, the supply side of the ventilator shall be directly connected to the return air side of the forced air heating system.

I'm not sure if this code would apply to a combo air handler / HRV system.  I assume they are designed and approved to offer a supply/return configuration.

The hydronic system should have 130F - 140F water feeding the heating coil, which should be enough heat to evaporate the cold water on the humidifier pad and give you humidity.  The humidistat should be mounted on the return air duct, at least 12" above the bypass or humidifer, to provide accurate humidity throughout the house.

Yeah it's built into the air handler.
But I called Life breath techs and they agree it should be going into the return