heat pump heating/cooling questions.

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Old 02-14-15, 12:15 PM
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heat pump heating/cooling questions.

Hello,

My name is Kevin, I have a new house in central florida, with r38 insulation in the roof, and r13 (I do believe, maybe r15 in the walls) reflective tin roof and cement board aka hardy-board siding with dual payne, vinyl frame windows. I have a 2 ton heat pump, carrier brand.. the air handler model number is fx4dnfo25. my home is around 1200 square feet I have disabled the electric heat.
When I moved in the house it was june, the beginning of the hottest part of the year. im custom to living in much larger house, requiring the unit to run much longer to cool it down, giving you the nice dry feeling with long run times. In this house, it was constantly click click click... click with the thermostat, 10 minute cycles. only off for around 10 minutes. The a/c guy replaced the thermostat and says it is working correctly. its good to have many cycles to maintain. but I know starting and stopping is bad for the unit.. and my wallet. when we are at the tail end of summer, its worse because it doesn't have to run very long to satisy the thermostat. I don't think the house is as dry as it could be with a longer run cycle.
I can fix it by putting the air on 72 or something in the summer, but the problem comes back as soon as it gets to 72... it only runs 10-12 ..MAYBE 15 minutes to maintain.. thus the humidity comes back. I know they are more efficient when they run longer. The fan speed was on medium. it was 1,2,3,4,5... 4 is for electric heat. it was on 2 ( medium) I placed it on 1, and it got a little better. On the stat, The cph was on 5, I put it on 2...are the above two actions ok?
I have a what some call a shotgun house..aka long and narrow house. with a long hallway from front to back. the return is is the back half of the hallway, and the thermostat right above it. there are 6 doors that air pours out of in the hallway right to the air return, this being said, I feel the air or heat doesn't run long enough to push all of the air from the front of the house to the back, would moving the stat farther up the hallway closer to front help?
For example, when I run the heat lately, I have the heat set to 74... I notice when I get up and set the heat to 76 before my shower, the heat comes on, and shortly after, it says its 71 or 72 in the house a few minutes after heat has been running.. I wonder if its finally pushing the cold air from the front of the house down the hallway. By the way I disabled electric heat to save $$$, and to try and lengthen run times. I suppose my questions are.. 1. Are my assumptions in regards to the stat location? 2.) Shouldn't my run times be longer? 3.) What can I do?..4.) always kinda thought I needed a ton & 1/2 unit..?. Sorry that was so long winded, just trying to give you all the info I can.

Thanks in advance.

Kevin
 

Last edited by Kevin Dixon; 02-14-15 at 01:48 PM.
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Old 02-15-15, 03:44 PM
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From you description of what's going on, it sounds like you need a return at the other end. I'd like to know how uniform the temperature is around the house. With the short cycling, it does sound like the equipment might be somewhat oversized but without doing a load calculation (manual J), I wouldn't want to say for sure.
 
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Old 02-15-15, 06:03 PM
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Grady,

Thanks for your response, It is several degrees cooler up front when the heat is on, and on the flipside, several degrees warmer when the air is on in the front of the house. I have a partitioning wall that seperates the kitchen/dining room from the living room, heat seems to get stuck under that as well. I was considering cutting into the partition wall and adding something similar to a " barometric vent" to help the air get out from above that wall and back to the return. Im no expert, but I feel all of this could be avoided by longer run times.
My air handler is in the laundry room, and a return is ducted out the bottom straight thru the wall into the hall. It would be a little more tricky to add a return considering I don't have a true " return duct". But I know it could be done.
If this hasn't overloaded you enough, I am in the process of plumbing the hose for propane, as of right now for stove, tankless water heater, with dreams of a furnace. My last house had one and I love that 130 degree air that pours out in the winter. Seeing as my system is still new, can I just swap out the air handler and continue to use my existing heat pump for an outdoor unit? Any ideas/concerns? Do you know of one that is compatible with my carrier heat pump model 25hcb324a300, or maybe any suggestions? Im kinda thinking a 98% eff. furnace wouldn't be worth the money here... Any thoughts?

Thanks in advance.

Kevin
 
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Old 02-15-15, 06:29 PM
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Something you could do with a furnace is to add a fossil fuel kit. With that you could still use the heat pump if you so desired & when cooler weather hit or you switched to "emergency heat" you could use the LP.

I don't see why any furnace upon which you could mount the indoor coil wouldn't work.

As far as opening a way for air to move, you could cut out the dry wall between studs & put a return grill on both sides of the wall. I do suggest this be done both high & low. Obviously, a true return system would be better but also a lot more expensive.
 
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Old 02-15-15, 06:34 PM
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I love that 130 degree air that pours out in the winter.
Do you really need that much heat in central Florida ?

A 98% furnace would be overkill there. You'd need to be able to remove the evaporator coil from your existing air handler and install it into your new furnace.
 
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Old 02-15-15, 06:36 PM
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Ok,

So it seems we are on the same page. That's what I was referring to doing, barometric vent/return grille on each side. That's what I was referring to. What do I put in between them in the wall to give it a straight shout from grill to grill?
I have one of those above every interior door in the house, they have some sort of metal duct just so no hot attic air gets in.
my last house just had a furnace, no heat pump. Im sure they sell a/c coil/furnace combo units that are compatible for my system. Would it be a good idea to go to a/h that has an a-frame coil? or maybe one that has smaller coil.. or would that flood the evap with still having the 2 ton heat pump?
 
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Old 02-15-15, 07:17 PM
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well.. no... what I meant in that sentence about the 98% furnace was that it is overkill.... my old house had a small 80% furnace and it worked great....don't need a huge one for florida....Plus... it fits my "off the grid" agenda....as far as I know... the tankless gas water heater, stove, and furnace.. are all more efficient than there electric counterparts.. correct? I had never thought about doing that.. maybe that's what my old house did.. it was there when I moved in... I guess your saying since the a/c lines are there already.. just pack it in there? right?
 
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Old 02-17-15, 02:19 PM
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Hey grady, back to our discussion on my unit being to big... is this something I should bring up to the builder? not sure how much he will want to swap out my unit... but its worth a try right? days like today when its in the low 80's or high 70's and very humid... its only running less than 10 minutes at a time.... and coming back on less than ten minutes later.ithe fan speed was on 2 (medium) I put it on 1 (low) to slow down the cycles.. but it says the cfm rating at that selection is 631 cfm's...is that enough ?? I thought I remember hearing something about 400 cfm per ton... if a manual j says it needs a 1.5 ton..cant you leave the 2 ton a/h in there and replace the outdoor unit? at one of my old rentals, I remember them installing a new system with the a/h being set half a ton bigger for "efficiency" I think.... and out of curiosity ...I was reading in the manual.. and it has optional 208 or 230v operation... whats that all about? its set on 230...
 
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Old 02-17-15, 04:00 PM
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You can probably leave the 2 ton coil but may have to change the expansion valve or piston.

Six hundred thirty one cfm is not enough for 2 tons. Your memory of 400/ton is correct. Some equipment will tolerate as little as 350/ton but that's about the minimum.

Almost all equipment today will operate on either 208 or 230 volts & it nearly all comes set-up for 230. Sometimes you may have to change a fan speed or something else simple for 208.

High end equipment is far better for dehumidification than is single stage stuff. The equipment has no way to know what the humidity is. It just operates on the thermostat (temperature).
 
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