Any HVAC techs in the house?

[General Lee]

I just had a new AC/Heat pump installed last week. The company has been out twice since the install. First time was because a factory defect in the indoor coil. That was replaced and all seemed fine. Had them out today because my split temps were falling compared to last night when the new coil was installed. All their readings are testing within spec so I'm gonna let it ride for the time being.

Here is next dilemma, the unit is short cycling especially in the evening. Outdoor temps have cooled (its about 70* outside right now) house T-stat is set at 74. The AC is coming on and reaching set temp 4- 5 min and shutting off. 5 min being off, AC comes back on. On for 5 off for 5. All evening long. I got two other digital thermometers reading 73. House T-stat shows 74. I finally turned off the AC for now because I'm tired of hearing it.

The T-stat is a Honeywell 8000 programmable. Anything I can check before I bug the HVAC company again?

 

[sailfast]

I just had a new AC/Heat pump installed last week. The company has been out twice since the install. First time was because a factory defect in the indoor coil. That was replaced and all seemed fine. Had them out today because my split temps were falling compared to last night when the new coil was installed. All their readings are testing within spec so I'm gonna let it ride for the time being.

Here is next dilemma, the unit is short cycling especially in the evening. Outdoor temps have cooled (its about 70* outside right now) house T-stat is set at 74. The AC is coming on and reaching set temp 4- 5 min and shutting off. 5 min being off, AC comes back on. On for 5 off for 5. All evening long. I got two other digital thermometers reading 73. House T-stat shows 74. I finally turned off the AC for now because I'm tired of hearing it.

The T-stat is a Honeywell 8000 programmable. Anything I can check before I bug the HVAC company again?

How big is the house and unit?
Load calculations?

 

[General Lee]

Well after some reading I found out about cycles per hour (CPH) and my T-stat CPH can be changed. It's currently set to 5. 3 seems to be the common setting. I wonder if it has any adverse affects on my system changing it to 3 cycles per hour.

Sailfast - approx. 2,000 sq. foot. Don't know what you mean by Load calculations.

 

[lexluther]

Sail is asking the Sq ft of the house and the size of the unit.

 

[lexluther]

Usually the unit size is in tons, I bet you have 5 or 6...

 

[CADplans]

Sailfast - approx. 2,000 sq. foot. Don't know what you mean by Load calculations.

If the AC unit is too big,, it can "cool" the thermostat too quickly.
In other words,, if the load calculations call for 3 tons, and they sold you a 4 ton unit,,, this would happen.
The main purpose of an AC is to remove the humidity. The AC ultimately reduces the temperature, also.

The major negative with an over-sized unit is that it does not run long enough to reduce the humidity.
A cool, dry house is comfortable,, a cool, humid house feels "clammy",,, or "sticky" or whatever.

 

[lexluther]

Actually a cool dry house is unhealthy...contributes to alergy and other sinus problems. The system should be designed to maintain a healthy clean air in the home. Find an installer who thinks more in terms of 1 ton per thousand Sq ft rather than the traditional "wisdom" of 1 ton per 500 Sq ft and knows that healthy air has the proper humidity level which is much higher than you might expect.

 

[Raspy]

Well after some reading I found out about cycles per hour (CPH) and my T-stat CPH can be changed. It's currently set to 5. 3 seems to be the common setting. I wonder if it has any adverse affects on my system changing it to 3 cycles per hour.

Definitely change your duty cycle setting and see if that moves you in the right direction. Second thing, is the thermostat too close to the unit where it is actually blowing on it?

 

[General Lee]

Ok, The unit is a 3.5 ton with a 4 ton indoor coil. 14 SEER. The specs for the 3.5 ton unit were 1900 -2400 sq. foot. They didn't do any Manual J calculations and account for numbers of windows and doors. Just took square footage measurements. The old unit was a 3.5 ton as well.

Raspy - I did change the duty cycle to 3. For the last couple hours, it has ran 3 times within the hour. It is possible the T-stat could be picking up some vent air.

 

[Raspy]

If the old unit that was the same size, worked well when it was still working, then your problem is in the control of it. Load calcs aren't going to tell you much here. Was the thermostat moved? I'd say to reduce your cycles per hour to the minimum and see if it begins to overshoot. If not you should be fine, that is unless it's blowing on the t-stat. But it really sounds like it is working OK, it's just annoying to hear it running. I get that and agree.