HVAC Question - Another One

[Tripp11]

Here's the quick and dirty:

New system put into our house in 2014 - 85% furnace and 16 SEER AC unit - Bryant

Routine, annual checks performed by the installer for the first 3 years, and I have performed them these last 2 years

Every summer, I don't feel the system is really running like it should and our house just never really seems as cool as it should - install company always just said it's really hot out and the system checks fine

A few days ago, the fan speed on the AC unit is running like at 30% of what it should run and I think a capacitor is out - we call and have them come out

Service tech says it is indeed the capacitor and replaces and then leaves - doesn't check anything else

My dad ran his own HVAC company 25 years ago, so I know a little about systems

My supply temp is 65 degrees steady and my return air temp is 75 degrees steady - shouldn't this temp swing be more than 10 degrees? It seems to me if it's not more than 10 degrees, the system isn't working right and I'm wasting a boat load of energy with a system trying to work harder than it should.

Our thermostat is been set to 72 since the capacitor has been replaced at 5 today, and the thermo inside temp reading is 77 and it really hasn't budged since the guy left.

So, my main question is: Should the swing in temp between the supply air and return air be more than 10 degrees? I'm thinking it should be 15-20 degrees, no?

Second question: What else might be wrong with it? I'm going to have to tell this company what is wrong with it before they fix it - I hope not, but feel that way.

Thanks!

 

[ChristianPatriot]

Yeah if you have to tell the company what’s wrong....find a different company.

Yes “typical” systems have around a 15-20 degree delta across the evaporator. 75-ish return should equal 55-ish supply. Sounds refrigerant related to me. First thing is to make sure the whole system is clean. Condenser. Evaporator. Air filter. Once that’s done you start looking at your superheat and subcooling and go from there.

 

[Tripp11]

Yeah if you have to tell the company what’s wrong....find a different company.

Yes “typical” systems have around a 15-20 degree delta across the evaporator. 75-ish return should equal 55-ish supply. Sounds refrigerant related to me. First thing is to make sure the whole system is clean. Condenser. Evaporator. Air filter. Once that’s done you start looking at your superheat and subcooling and go from there.

It's one of the "big box" HVAC companies - <slams head on table>. They sold my wife on 10 years free parts and labor, and then tonight, the guy tried to tell me he had to charge me labor - I told him he can try, but I won't pay it. He didn't try.

So, the 10 degree delta is weak. Thought so. The past summers they just always explained that away by telling me it's been a really hot summer. Duh.

Condenser coil, evaporator coil and air filter are all clean. I serviced them myself at the beginning of the summer - and I change the filter every 2 months.

Crappy service drives me insane. Thanks CP.

 

[ChristianPatriot]

Yes 10 degrees is weak, even in 90+ heat.

If you get a chance tomorrow, there are two lines coming out of the outside unit. The big one should be cold and sweating, the little one should be warm, not hot.

 

[scott delaney]

a 20*delta T is about perfect. have you hoses off the condenser coil and checked your filter? both will make you system run like this

 

[Tripp11]

Yes 10 degrees is weak, even in 90+ heat.

If you get a chance tomorrow, there are two lines coming out of the outside unit. The big one should be cold and sweating, the little one should be warm, not hot.

Big one is cold and sweating outside by the AC unit. Hard to tell temp of little one outside, but inside (our furnace is in our garage) the little one is fairly hot. Definitely more than warm.

I've called the "big box" again and hopefully they will send someone who will spend some time diagnosing the issue some more. I'm now thinking we might have been just burning money the last 4-5 summers as I remember this 9-10 degree delta change present back then.

Thanks for all the help, CP.

 

[Tripp11]

a 20*delta T is about perfect. have you hoses off the condenser coil and checked your filter? both will make you system run like this

Yep. Every spring/summer, I clean the condenser coil and the evaporator coil before we start the AC cooling season. And our filter is replaced every 2 months.

 

[churchmouse]

OK.......people listen closely.....the warranty aint freaking free. You pay for that. More than you know. And most (not all but) companys will try and skirt the issues on problem units. If they luck out and you never call that is another chunk of money they put in their pockets. You should never have to call them if they do the job right. Yes there are turds that make it into the field and need to be addressed. Sounds like OP might have one of those.

If the lines are at temp (SH/SC) as in warm to the touch and sweating/cool you might be a half ton short. Hard to say over the interwebs and guys, 20*s delta is too much. 15* is the sweet spot. 20 is indicative of other issues. Especially on a 16 seer unit like the OP has. The TXV is not going to let the unit run the evap that cold. Not on R-410 anyway. R-22 on an Oriface metering device might but that is not optimum either. A steady 60* discharge will cool/de-humidify any house if the unit is sized properly. When mine drops below 60*s it is time to change out the filter.

OP, I dropped you a PM and hope you find the issues.