Originally Posted By: jpeck
This post was automatically imported from our archived forum.
I’ll stir the mix even more.
When even take TD readings?
The TD will tell you absolutely NOTHING *UNLESS* the coil is clean, the filter is clean, there are no restrictions in the air to and through the coil, including the supply duct downstream, and there is no leakage from the cabinet upstream of the coil.
That means, unless you find everything clean and sealed, taking TD readings is meaningless.
Now if all is well, a TD may give the a/c tech clues on where to start trouble shooting the system, but, how many air handlers do we find which are clean, have clean filters, and are properly sealed, not leaking air? Not many, if any. That means that before you measure the TD, look at the air handler unit. If it is not one of the 'all is well' ones, don't bother taking a TD, it will only give a false reading. The system, based on you observations, are screaming out for service and repair by a qualified and licensed a/c service contractor. Taking a TD will not tell you anything reliable, and if you take one, the agent may try to use it to shoot down your other findings.
HI: The filter was clogged, the coil was clogged, the TD was -18 degrees.
Agent: TD was -18 degrees? Why that is right where it should be, there is nothing wrong with that system.