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ben's plumbing 11-09-2012 04:21 PM

who cares...
 
to manual j or not.......Installing a home hvac system isn't merely a matter of calling a technician and having them perform an installation over the course of an afternoon as some think.There are a number of regulations in place to ensure that all residential hvac systems are properly sized. many may wonder why these regulations are so strict and require such exact calculations. The truth is these benefit the homeowner as much as the environment.If to big it can lead to a number of problems.Reduction of comfort and moisture control can be issues with oversized hvac systems ,as can energy waste.It can also increase installation cost.As far as regulating bodies,the acca require that anyone installing an hvac system submit a compliant load calculation that follows the manual j format...its the indusrty standard that is sumitted to inspectors for approval BEFORE installing a hvac system.......when deciding to have a hvac system installed its important to go with a company that will ensure accurate calculations for proper size of equiptment this will save the customer money.

Doc Holliday 11-09-2012 04:27 PM

It is certainly not required on a changeout of an existing system. You can do like for like all day long.

ben's plumbing 11-09-2012 04:33 PM

Quote:

Originally Posted by Doc Holliday (Post 1048271)
It is certainly not required on a changeout of an existing system. You can do like for like all day long.

yes you can but if its sized wrong ...remember 2 wrongs don't make a right...

Doc Holliday 11-09-2012 04:47 PM

That's why you talk to the customer, find out comfort levels and run times to get a feel for if there needs to be a load calc performed. Or if the system is grossly over or undersized for the conditioned space. If oversized then there would be moisture and mildew evidence, if undersized the system runs far too long, struggles to get to set point.

In my 12 years the only load calcs that have been done were for new construction.

Technow 11-09-2012 05:11 PM

All of my estimates include manual j and manual d, coupled with the HO interview. Its pretty obvious after you do the d and J why they have a complaint..

And it was always obvious why.....Back in the 90's when I went to my first company the super duper lead guy showed me how he determined how many outlets to put in a room....."UH...this room needs 2 outlets"...and I said: but the load calculation says it needs 300 cfm and the 4x12's have enough quiet flow and throw for 100 cfm? he said "I have been doin this for 15 years....etc. etc..:thumbup1:

beenthere 11-09-2012 08:56 PM

Quote:

Originally Posted by Doc Holliday (Post 1048271)
It is certainly not required on a changeout of an existing system. You can do like for like all day long.

Most people/customers will think their unit is sized right because it gets the temp down to X degrees and they are comfortable at that temp. Little do they know that the next size smaller, or even 1 ton smaller will cool their house down to almost the same temp, but lower the humidity by 5 to 10% and make them feel just as comfortable at a 2 degree warmer indoor temp, and cost a lot less to run/use.

carmon 11-09-2012 09:07 PM

beating the dead horse again...... i do not use manual j and probably never will.... and I will get over it......:eek::eek:

JJboy 11-09-2012 09:09 PM

Quote:

Originally Posted by carmon (Post 1048482)
beating the dead horse again...... i do not use manual j and probably never will.... and I will get over it......:eek::eek:

Do you use micron gauge or just 25 minutes?

carmon 11-09-2012 09:13 PM

micron gauge.... always


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