My A/C installer just installed my new heat pump system using duct board to make the transition from the air handler to the plenum. I noticed heating elements just inside the top of the air handler. These are maybe 4" - 6" from the fiberglass ductboard. Is there any danger of fire when the heat coils are energized? Does ductboard burn? He sealed the inside corners with duct sealer. This is a caulking that looks like tile mastic.
The air handler is Rheem RBHK.
He should have installed a sheet metal sleeve on the indoor unit, but I have seen a lot of units installed without the sleeve, and I have never seen the ductboard damaged by heat that way. If you hold a torch flame to the ductboard, you will burn a hole in it, but the fusible links & temperature limits will hold the heater temperatures to about 180 degrees up to about 250=BA maximum. Using duct mastic was a good thing. The heater element should be 6" from the ductboard, but he has that covered.
Stretch
OK, good. Another question... He left the DIP switches in the factory settings, so the system blows much harder than the old one did. I have heard that these systems should be quiet. Should I reset the switches to reduce the blower speed or just live with it.
Stretch
Tocapet,
Dip switch settings depend on what size outdoor unit you have. I measure air flow with a highly accurate device called a flow hood. HALF of the systems that I measure have 200 CFM per ton OR LESS!! The systems SHOULD have about 400 CFM per ton! Probably your old system, like most systems, had too little air flow. Now you are getting close to what you should have. If the grilles are noisy, you can have him install more streamlined grilles with wider spacings between the fins, they will be quieter. Remember, AIR Conditioning begins with AIR!
By the way, for the best cooling season humidity control, the dip switches should be set to ENHANCED mode. (Unless you live in the desert.)
Stretch
From looking at the installation manual, he didn't set the system up for
2-stage operation. The thermostat has 2-stage heat, 2-stage cool capability, but he set it up for single-stage. English is not his first language, although he did the rest of the installation very professionally. I'm thinking of re-doing the wiring for 2-stage operation.
This is Turtle.
I don't like Duct board but it will not burn very easily. I use it to put between the wall and my copper fittings and not burn the wall. Still don't like it.
TURTLE
Is the outdoor unit single stage or 2 stage? A normal heat pump is one stage. The thermostat would be wired for 1 stage cool. The first stage heat will be the compressor. The second stage heat will be the auxiliary strip heat - usually W or W2 on the thermostat. There is no second stage cool. If you have a 2 stage heat pump outdoor unit, you have two stages of cooling, but usually only two stages of heating just like before. The third stage of heat, high speed compressor operation in heat mode, is controlled by the outdoor unit due to outdoor temperature. Be careful fooling around with the thermostat. You could fry the control system in a way that is not covered by warranty. If you think you have a 2 stage outdoor unit, have the contractor come back and set it up properly. Heat pump thermostats are not DIY stuff.
Stretch
I was referring to the air handler stages. You said the DIP switches should be set for enhanced mode. The air handler has dual-stage fan capability. The condensing unit is single-stage. I have the wiring diagrams.
Air handler = Rheem RHBK 24J145HD 3-ton Condenser = Rheem Classic RPPB 036JAZ 3-ton.
In reviewing the wiring diagram the installer used, it appears that he did set it up correctly for 2-stage heat. IE: 1st-stage heat pump, 2nd-stage electric backup heat. (W1 and W2) So, the only thing I am now concerned with is the DIP switch settings. Do you have any information? As it is now, the A/C comes on full blast and then when it cycles off, the blower drops to a lower speed for the last 90 seconds.
By the way, I am near Dallas, Texas.
I am not a Rheem dealer, so I do not know their settings, but that is not enhanced mode. You are in a high humidity area, so it should be on enhanced mode. In enhanced mode it will start at 50% for about a minute, then go to 80% air flow for about 8 more minutes, then go to
100% till the thermostat satisfies. Then it will drop to 50% for about a minute, then shut off. The installer should be able to do that for you. By starting at low air flow, the indoor coil gets colder right off the bat, and takes more moisture out, especially in mild weather with short run times.Stretch
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