recovery Wheel Calculations

[mmotlak1]

I want to make a manual calculations for air to air energy recovery unit. I have the amount of exhaust air and supply air.
how to make this calculations according to ASHRAE standard 90.1 2007 requirements.

 

[EnergyProfessional]

You'll need sensible and latent efficiency. May be hard to get the actual data, since manufacturers only provide that for soem points. With different lowrates, and imbalanced exhaust and intake this all changes. If you have these data, you also can enter them in Trace etc. but again, you need to find that out for the specific condition.

A nominal 2000 cfm ERV can operate at 1000 cfm in and 1600 cfm out, with 2000 cfm balanced etc.

I think what you really want is go to the manufacturer's website and use their tools. I'd think nowadays all manufacturers have soem doftware to calcaulte that at any condition.

 

[cdxx139]

Greenheck's CAPS software program does a nice job and spits out what your looking for in easy to read format.

knowledge is power

 

[mmotlak1]

Thanks guys for reply, my problem is, I submit a project to the authority to take approval in the design, the recovery wheel system was selected based on the manufacturer software. but the authority engineer requiring the manual calculations for this. the data i have the fresh air and exhaust air quantity and the minimum effectiveness 70% according to the regulations.

 

[EnergyProfessional]

does he also require mnaual Load calculations done with an abacus and drawings done with paper and pensil?

 

[317069]

Talk to his boss. ask manufacturer,

 

[EnergyProfessional]

I run into the problem that I enter lighting W/ft² on the schedule (actually Revit does it automatically) and also show what code requires. Typically I'm 30% below code, so I'm golden. But AHJ requires to enter the data into that darn Comcheck software (where there is not actual verification, I can entirely make up numbers and no one would notice).

Same for insulation. I see the buildings that never anywhere meet code. But according to Comcheck it ia all good and they get approval.

I think it is time AHJ is required to actually have some engineering knowledge and use computers....

 

[chicopee]

By recovery wheel system, I believe that the Ljunstrom rotary regenerative air heater may fit you classification. Such air heaters have a small foot print and are very efficient. While I have no manufacturer's data, you may want to contact distributors for technical literature about the performance of such air heater. I concur with 317069 about contacting the manufacturer of your unit since such manufacturer will have published data.

 

[cry22]

See ASHRAE systems and equipment handbook - air to air energy recovery, you will find the formulas.

The reviewer probably has a good reason to suspect your design, and I must say he is right, cause rightly so, you do not know, you did not do any calculations and yet you are signing and stamping in your permit application.
You cannot rely on a vendor numbers, you have to check and verify the vendor numbers.

I can think of one reason:
One of your air sides temperatures (exhaust side) may be below the freezing point in winter, which will freeze your wheel and he wants to see that it is safe to operate your wheel or provide heat trace or some type of control.

 

[EnergyProfessional]

cry22: But if JHA doesn't trust the calculation of manufacturer software, how does JHA trust the efficiency numbers provided by manufacturer? All the calculations the engineer would do, are based on those. So either way we need to trust the manufacturer. I'd think their number are ARI or some othe standard certified.

It's like using boier efficiency... i use manufacturer numbers and don't do my own tests.