An under-performing furnace. The fix...
From the day we picked up our new KZ Spree TT almost 2 years ago, the furnace had trouble keeping the interior warm in cold weather. Once it got below 40F, it just wasn't quite warm enough and the furnace would run almost non-stop overnight when the outside temp. dropped. Was cold in the bedroom and needed extra covers. Took it to the dealer who said it was the sail switch and they installed a new one. No improvement. The factory whacked a big hole in the subfloor for the ducting about 10"x10". I could feel the draft coming up from below and could see the ground below around a hole for the propane line. With the hole being right next to the furnace, I was guessing that some of the return air was coming up from the underbelly space and cold outside air was being re-circed instead of mostly interior air. As well, for the 2014 Spree 262RKS model, the factory ran a 4" duct under the subfloor and over about 5' to an outlet in the kitchen area. The duct was non-insulated and it sat on top of the coroplast which had no insulation so the duct was sitting right on top of a cold surface.
I decided to seal up the hole in the subfloor and to insulate the duct. Pic #1 shows the hole in the floor. Pic #2 shows the 4" flexible semi-rigid aluminum ducting I used alongside the original factory flexible ducting (like a dryer exhaust hose) about 8' long. I used commercial type duct insulation wrap about 1" thick along with aluminum foil duct tape as shown in pic #3. Pic #4 shows the original ducting to the kitchen wall grill and pic #5 shows the new ducting and how it connects to the grill. Pic #6 is the finished product beside the furnace. It was a bear to measure and fit the plywood to accomodate the ducts & PEX and the fact that the cuts for the square were wavy didn't help. I sealed up any cracks and gaps with expanding foam.
Getting the new duct under the floor and from the furnace over to the grill on the back of the opposite dinette seat was a real bear to put it mildly. Turn out there is an open web joist with about a 3" gap between the upper and lower flanges (chords). The original flex duct had to have been partially collapsed thus restricting air flow. To get the new duct in there along with the 1" insulation wrap, I had to ovalize it. Not a problem but it was a very tight squeeze. My forearm is only about 18" long to fingers and I could not quite reach the duct as it got pushed through and a quick job turned into a couple of hours. I used a right angle grill adapter designed for 4" duct going into a 2x4 wall that has oval end on it.
While in there, I also changed the 2" ducting to the bedroom to 4" because the bedroom was always colder than elsewhere. The last pic shows what all the wiring was originally like from the factory beside the furnace. I've now done many hours of tidying up the wiring and modifying/fixing the ducting & floor opening.
When all done, all I can say is WOW. What an unbelievable improvement. Instead of taking hours to get comfortably warm, it's now more like minutes. Warm air now comes blasting into the kitchen and same with the bedroom. I installed a new grill in the bedroom that has a damper so can control the heat output as needed. While I had an open can of spray foam, I also sealed up any other holes through the floor (under kitchen sink for ex.) and assume that has helped also.
BTW, when the dealer "fixed" the furnace, they either pushed or stomped on the furnace and caved in the top. Had to pull it back together and put in some screws to hold it together. I sealed things up with some aluminum tape as can be seen in the pic. (Lesson is, don't let the dealer touch anything if you value what you own.) Of course, wouldn't it be nice if the factory did a much better job to start with... Pffft.
If replying to this, please try to avoid quoting and posting all the pics to reduce the number of pages that could result.
I decided to seal up the hole in the subfloor and to insulate the duct. Pic #1 shows the hole in the floor. Pic #2 shows the 4" flexible semi-rigid aluminum ducting I used alongside the original factory flexible ducting (like a dryer exhaust hose) about 8' long. I used commercial type duct insulation wrap about 1" thick along with aluminum foil duct tape as shown in pic #3. Pic #4 shows the original ducting to the kitchen wall grill and pic #5 shows the new ducting and how it connects to the grill. Pic #6 is the finished product beside the furnace. It was a bear to measure and fit the plywood to accomodate the ducts & PEX and the fact that the cuts for the square were wavy didn't help. I sealed up any cracks and gaps with expanding foam.
Getting the new duct under the floor and from the furnace over to the grill on the back of the opposite dinette seat was a real bear to put it mildly. Turn out there is an open web joist with about a 3" gap between the upper and lower flanges (chords). The original flex duct had to have been partially collapsed thus restricting air flow. To get the new duct in there along with the 1" insulation wrap, I had to ovalize it. Not a problem but it was a very tight squeeze. My forearm is only about 18" long to fingers and I could not quite reach the duct as it got pushed through and a quick job turned into a couple of hours. I used a right angle grill adapter designed for 4" duct going into a 2x4 wall that has oval end on it.
While in there, I also changed the 2" ducting to the bedroom to 4" because the bedroom was always colder than elsewhere. The last pic shows what all the wiring was originally like from the factory beside the furnace. I've now done many hours of tidying up the wiring and modifying/fixing the ducting & floor opening.
When all done, all I can say is WOW. What an unbelievable improvement. Instead of taking hours to get comfortably warm, it's now more like minutes. Warm air now comes blasting into the kitchen and same with the bedroom. I installed a new grill in the bedroom that has a damper so can control the heat output as needed. While I had an open can of spray foam, I also sealed up any other holes through the floor (under kitchen sink for ex.) and assume that has helped also.
BTW, when the dealer "fixed" the furnace, they either pushed or stomped on the furnace and caved in the top. Had to pull it back together and put in some screws to hold it together. I sealed things up with some aluminum tape as can be seen in the pic. (Lesson is, don't let the dealer touch anything if you value what you own.) Of course, wouldn't it be nice if the factory did a much better job to start with... Pffft.
If replying to this, please try to avoid quoting and posting all the pics to reduce the number of pages that could result.
