sizing -- J needed?

[restar]

I am about to replace my 2.5 ton carrier unit. Spec is a new
infinity carrier unit, price is reasonable based on other estimates for
a new condenser, inside coil / lines and install. Probably be at 14.5
as the new furnace is not being replaced. Old unit was a '99 410 unit,
he estimated 10 seer. Living in Minnesota, probably on 1/4 of the days
in the summer.

After I gave him the upper level square footage, the HVAC guy started talking 'we know your house size type -- its a standard split level -- no need to do a standard J calc on my laptop.

This was based he said that I don't use continually during the summer, so
quicker cooling would be an advantage over lower humidity with a 2 ton
unit.

How much do customer use patterns / preference go into selecting the
tonnage for a unit. That is, is there some fudge as to a 2 or 2.5 unit, or
should I demand to go strictly by the J report?

Thanks -- you expertise is greatly appreciate!

[hcong]

Have him do a calculation before undersizing your unit. He might end up with a 2 ton... so then his assumptions are backed up by science .

Also, oversizing your unit is not good, but undersizing your unit is also just as bad. It shortens your unit's life and if you can only hold 80 F, then you might not be comfortable.

Not all standard split levels are the same. Even houses of the same model and in the same tract have different orientations and sun exposures. Usually many of the older units are oversized but a little due diligence is never a bad thing.

[BaldLoonie]

What's the point of spending the big bucks on an Infinity only to cripple it with the old furnace?

[udarrell]

In MN with long cold winters, I'd get a Home Energy Efficiency Audit & do what I could to reduce winter heat-loss. Then U can have the Manual j performed.

That will save utility costs the year-round.

Depending on the amount of airflow (1200-CFM or more) required for heating, you may need to up-size the tonnage of the indoor coil above the condenser's if the J then calls for 2-Ton.

I'll leave your other questions for others to respond to.

[hvacmike85]

In MN with long cold winters, I'd get a Home Energy Efficiency Audit & do what I could to reduce winter heat-loss. Then U can have the Manual j performed.

That will save utility costs the year-round.

Depending on the amount of airflow (1200-CFM or more) required for heating, you may need to up-size the tonnage of the indoor coil above the condenser's if the J then calls for 2-Ton.

I'll leave your other questions for others to respond to.

Im not sure what upsizing the coil deos for heating plz inform me???

[udarrell]

Im not sure what upsizing the coil does for heating plz inform me???

Well, if your A/C would only need a 2-Ton indoor coil it's top airflow rating is 900-CFM, if heating required 1200 to 1300-CFM you would need a 3-Ton evaporator coil, for that 2-Ton condenser, to flow that CFM Volume; comprehend...

[hvacmike85]

Well, if your A/C would only need a 2-Ton indoor coil it's top airflow rating is 900-CFM, if heating required 1200 to 1300-CFM you would need a 3-Ton evaporator coil, for that 2-Ton condenser, to flow that CFM Volume; comprehend...

Oh ya I got ya here in indiana winters and summers are about equal so I've never had to do that, I've heard upsizing the coil can help dehumidify faster/better but I dont have facts to prove it, seems to work on a few I did. maybe that was for an orifice though?