Replacement Commercial Air Conditioners

[sailoday280]

We are replacing a roof top Air Conditioner. The 12 story high rise bldg is 35 yrs old and was designed to have pressurized corridors/hallways.
Presently, due to age, etc, the bldg is not pressurized.
The engr wrote a spec for the replacement AC. He use desig conditions of inlet air to evaporator:
CFM , DB and WB and pressure drop inH20 based on conditions of 35 yrs ago.
I maintain that since bldg is not presently pressurized, the vendors will be giving us a machine that will not perform correctly.
And
1--engr should have recommended using DB/WB based on present data such as from ASHRAE, etc?
2--engr should have estimated available dp and cfm for flow to evaporator or recommended testing for avilable dp and cfm?
I'd appreciate your responses/
Regards

 

[EnergyProfessional]

What is the engineer's scope of work that yo pay for? 1:1 replacement or new design? You get what you pay for...

i would be concerned with his approach as it may not meet current code. check with your JHA if you need to meet current code or are grandfathered in.

If he really only copies the old design 1:1, why do you need an engineer and not just a copy machine?

 

[317069]

Why your building is not pressurized now?
You need a pressurized building either 35 years ago, now, or in future.
Did you compare weather tables of 35 years ago and current days to say he is using DB/WB of 35 years ago.

 

[urgross]

They didn't have mean coincidental wet bulb or dry bulb publication 35 years ago; techmology has improved since then.

 

[sailoday280]

To all
Sorry the bldg is approx 29 yrs old.
Added info:
The spec calls for the 40 Ton AC unit to be either Trane or Carrier. Vendors have replied only with price.
We don't know the mfgr.
With wrong Design CFM and evaporatr air flow dp, how will performance be effected?
Thanks
Sailoday

 

[317069]

he said [engr should have recommended using DB/WB based on present data such as from ASHRAE, etc]
what does mean DB/WB here, hope not energy efficiency