Steven,

A basic inspectors tool for all the reasons you stated. It's also good for those ducts way up high in the ceiling. I always check every duct or baseboard in a home for heat. Like you said some don't always work.

James,

I never dreamed how handy it would be when I first got it. It is great for all things warm or cold. It is useful, in the summer, for determining just how hot an attic is too. I put it right up there with a moisture meter, a basic means of testing circuit polarity and wiring and a rot probe. As you say, it is basic to essential for doing a thorough job.

Boy Steve, that 125 degree reading is sure high.  The rest of the system must be closed off.  All registers should read the same in a properly balanced system, and that reading is normally in the 85 degree range.  Your are absolutely right about how handy the laser thermometer is.  I won't go into a 150 degree attic.  I also use it at the electric panel, looking for hot spots

Yes,

Although we inspectors do not check the balancing of the heating or A/C system, as that is exhaustive, when I find something like this 58 vs 125 I will mention it. Usually there is a need for service of the furnace anyway so I call for the HVAC pro to make necessary adjustments at that time. Also, often the duct closest to the furnace will be quite a bit warmer than others far away.

David,

I believe it is physical impossibility for all registers to read the same temperature. Close would be fine. As Steve said the closer to the furnace the warmer the temperature. This would be especially true with older uninsulated duct work.

For those reading this, who are not inspectors, the whole thing of balancing ducts, and why it is exhaustive, has to do with people who live in homes adjusting heat supply registers. Someone finds a room they like too hang out in most of the time and opens the register, and closes one elsewhere. Then someone else in the house, like the kid, gets too hot at night and turns off all ducts in his or her roomf. These changes affect the different registers and unbalance the system compared to how it was put in. However, another factor is that sometimes flex ducts have come loose or been crushed below. Or metal ducts have come loose. As James says, insulation on ducts is a factor too. As and inspector, I check ducts for warm air but do not adjust the air flow. If I did, I might irritate the resident who spent lots of time messing up the balancing of the system! I picked up these simple tips at a consumer hot to do it yourself site. Some of this is beyond the capabilities of the average user.

http://www.allabouthome.com/tips/mechanical/forced_warm_air_heat.html

Balancing the Heat

• If some rooms are too hot or cold, try adjusting the dampers in the registers and, if your system has them, the dampers in the warm-air ducts.
• Leaving the thermostat at one setting, let the system run for 3 hours to stabilize the temperatures. Open the dampers wide in the coldest rooms. Then adjust the dampers room by room until temperatures are balanced. Wait half an hour after each adjustment before rechecking or readjusting.
• Speeding up the blower may help heat chronically cold rooms. Adjust the motor pulley of a belt-driven blower or, for a direct-drive blower, change the electrical connections (see owner's manual).