XL19i 3 Ton Heat Pump Variable Speed 3.5 ton Air Handler Trane Residential Zoning 6 Zones
by Jim Harvey
SW Colorado passive solar three-level 2700 sf house. No heat required on sunny days (3/4 of winter). Vast south facing glass does require AC until Thanksgiving, but it's very inexpensive with moderate outdoor temps in fall.
The alternative to AC in the fall is solar shades, which would cost $7k-$10k installed. So far we've found AC to be simpler and cheaper. My wife loves temps 75 to 80 (cooling set points are 78 because humidity is nonexistent), so I'm in shorts at home much of the year. On cloudy winter days heating set points are 70 to 72.
Zoning keeps temps within 1 degree of set point for all zones. Unless we have guests, we only condition 3 of the 6 zones (1350 sf). Ductwork allows either Bypass (never used, because everyone agrees this is a less than ideal approach), Trane Relief (also never used because it results in temps overshooting set points), or Dump into normally unconditioned Sun Room and/or Basement Hallway. The latter works well. We also have ducted returns from every room except kitchen and baths.
Of the three who made appointments, one never showed, one told us nobody wants or needs zoning, and the third made a good impression and a week later gave us quotes for 3 and 4 ton XL19i systems.
We had done our own load calculation showing 30kbtu cooling load and 48kbtu heat load. He didn't choose the XL19i. Instead, we asked for it because our research showed we would be using far less than full capacity for much of the year. We chose the 3 ton system despite the heating load of 48kbtu, because half of that load was for our sun room which we rarely condition, and on sunny days that room is plenty warm regardless of heating load. We're happy to heat it on the occasional cloudy day when we want it at 70.
Despite our dangling large $ in their eyes, the contractor refused to consider installing ductwork. (We had used a wood stove for cloudy winter days for 25 years, and had electric baseboard heat as backup.)
So we obtained Manual D and other associated publications and designed the ductwork with requirements that: (1) ducts are slightly oversized for zoning, (2) each room other than kitchen and baths has a ducted return, (3) options for bypass, relief and dumping excess air are all available, (4) manual balancing dampers are installed at all branches to allow for fine tuning after installation, and (5) ducts were well sealed throughout with all metal/flex junctions joined by steel hose clamps rather than break-prone plastic ties.
We installed the ductwork as time allowed over the next six months. Since I had wired the whole house myself when it was built, I ran all electric work for the system according to locally applicable codes in a few days.
We had our contractor make up supply and return plenums according to our drawings. They refused to install turning vanes at the 180 degree turn where the return plenum ran under and up into the air handler, despite Manual D guidelines showing significant improvement.
The contractor had never before sold or installed a heat pump, because "Everyone knows they don't work in Colorado." He sold us the "matched 3 ton air handler" for our 3 ton heat pump. After the line set was connected and a vacuum pulled they switched the system on and added refrigerant for the line length.
After they left we found that the system first stage turned itself off after twenty minutes every time well before set point was reached. When the second stage ran it turned off after two minutes every time. The contractor refused to come out to check on the problem. He told us our filter was probably clogged, even though we had a Trane electronic air filter with only a few days use.
We had another contractor come out, and they put gauges on the system. It was apparently turning off on high pressure or temperature limit switches, because pressures were rising to almost 450 psi on the R22 system.
We posted the equipment model numbers on the HVAC-Talk forum, and in less than an hour we were provided with a link to a Trane internal dealer memo emphasizing that our 3 ton heat pump, unlike the AC only 3 ton XL19i, required the 3 1/2 ton air handler rather than the 3 ton unit we had been sold. The contractor who had sold us the system refused to speak to us or take the wrong air handler back. He also by implication refused to reimburse us for the $1,500 cost of the correct air handler.
When we tried to get a contractor to install the correct air handler, we found that none would speak to us.
I obtained training and licensing appropriate to handling refrigerant and installing the air handler. Once we installed the correct air handler, the second stage worked flawlessly, but the first stage did not. The first stage compressor had a damaged suction valve due to the severe and repeated overheating caused by several days of twenty minutes at a time excess pressure, and the failure of the contractor to verify performance.
We replaced the compressor at our cost of about $1,000. Added to the cost of $1,500 for the correct air handler, we had to spend $2,500 out of pocket to obtain a functioning system. Without the aid of caring processionals on the HVAC-Talk forum, we might never have known what was wrong.
Get AT LEAST 10 REFERRALS FOR EVERY CONTRACTOR YOU'RE CONSIDERING. Investigate every referral. Obtain in writing ahead of time whether using existing ductwork, even when competently homeowner installed, voids anyone's warranty.