New install questions

[cjay]

I recently had a trane system installed and have a few questions.

XL14i Heat Pump
XV90 Variable speed motor 90% efficient gas furnace.
High Efficiency coil
VisionPro 8000 Thermostat.


Roughly what temperature should I expect to be getting out of the heat registers with only the heat pump running?
I'm getting at best 82 to 84 degrees (86 degree a few feet past the output side of the coil.)with an indoor temp 0f 64 and an outside temp of around 44.


When the company rep came out for the estimate he recommended a horizontal furnace because he said there wasn't enough vertical room for the gas furnace and the coil. (It's installed in a stand up crawl space) The installer positioned the furnace vertically made a 90 degree elbow and installed the coil horizontally. Is that acceptable practice?


Is there a way to figure out what the balance point is? One company did a calculation and came up with 33.
The installer set it to 40. That seems a little high to me by what I've been reading. Since gas is currently considerably more expensive than electric I'd like to set it as low as possible.

You much leakage thru the duct system is acceptable? I think the work on this install was clearly inadequate by anyones standards but am wondering what I should expect. I also ordered a cleaneffects filter which isn't currently available and plan on having them repair the ductwork when that is installed. They added a 2nd return and did a fair amount of work tying the system into the original ducting.
The transition from the furnace to the coil is the worst of it. There are gaps in three places with about as much air escaping as you would expect from a small room fan. The ductwork running from the coil to the original duct has a hole in each corner of all the seams that is big enough to easily blow out a match. I haven't checked out the return side yet. Should the seams on both the return air and the output side be taped or somehow sealed? If the sheetmetal work is done properly should it seal on its own?

I'm a bit disappointed at this point. Considering the quality of the duct work makes me wonder about the quality of the rest of the install. System charged improperly etc.

thanks in advance,
cjay

[aircooled53]

Balance point is ok,for Texas.
If the unit runs for approximately 15-20 minutes,supply temps should be between 90-120..Without heat strips.

Ductwork needs to be sealed/now; don't wait or they may forget to do it.All seams need to be sealed,filter rack,plenums,returns,supplys and coil area..NO Gaps..

Your trying to make air changes in the conditioned space not the closet..Make sure the return is sealed well..

1st.year warranty issues..all

[hyper_racing]

There should be no duct leakage. You are paying to heat your house, not the crawl space. They should seal up all the seams. When all is sealed up, you want be pulling in the cold air through the return leaks which will make the register temps go up a little. Depending on your area, maybe set the secondary heat to come in at about 32 or so.

[cjay]

aircooled53, thanks for the prompt reply.

I probably should have noted that I live in western washington if that makes a difference on the balance point setting.

As far as the heat pump output temp is concerned what do you think would be causing the low output temp. I've let the inside temp drop to 62 so I could turn it up and have the system run for a long time. It never gets higher than 84.

One other question I had. Whats the difference between aux heat and emergence heat. Wouldn,t they both be the gas furnace on my system?

thanks

[jeffshvac]

it almost sounds like your duct system qualifies for the wall of shame.send pics.

[cjay]

jeffshvac

Heres a few pics one that shows the hole in the corner of the duct and and two others one showing the 1/8 to 3/16 inch gap between the furnace and duct and the other between the coil and duct.

While doing some research here and other places it sounds like there is a fair amount of animosity from the pros about homeowners trying to go the cheap route and getting what they paid for. I'd say this is understandable and does happen but in my case and I would bet in a lot of others that is not the case. Of the four companies I recieved quotes from two quoted a gas furnace and two an air handler. Of the two that quoted the gas furnace option the bids were exactly the same to the dollar and were both reputable well established companies as far as I could tell. I chose the one that spent the most time on the initial visit measure the room size, window size etc. While I'd say that the fact that you all spend your spare time on these forums pretty much proves that you take pride in your work. There are many out there that don't even if you are paying a fair price.

http://img62.imageshack.us/img62/6684/oldtonew0pn.jpg
http://img62.imageshack.us/img62/5083/furnace1fj.jpg
http://img58.imageshack.us/img58/8179/coil5ov.jpg

[dan sw fl]

Originally posted by aircooled53
Balance point is ok, for Texas.

If the unit runs for approximately 15-20 minutes,supply temps should be between 90-120..Without heat strips.


I don't know how _aircooled53_ determines his expected temperature for a XL14i heat pump with the heat strips Off.

Basics: Q = CFM * Dt * 1.08
i.e. 3-ton = 1,200 CFM

Q = 1,200 * 20 * 1.08 = 25,920 BTUh
at 35'F outside temperature
.......

XL14i ..
2TWX4036 / TWE040 ( or 4TWX4036A/ 4TEE3F040)
Ratings

47'F 33,400 BTUh COP 3.56
35'F 25,960 BTUh COP 2.84
17'F 21,000 BTUh COP 2.48

Expected temperature difference
from return aair to supply air at the air handler
26'F rise at 47'F outside air temp
20'F rise at 35'F
17'F rise at 17'F

64'F room temp + 20'F = 84'F Supply Air

Set point should probably be close 32'F.
However, a load analysis must performed to determine the heat loss for your specific residence.

OR set balance point to 32'F and
see how unit performs when the outdoor temp is 33'F.

[Edited by dan sw fl on 01-30-2006 at 03:23 AM]

[wyounger]

Thanks Dan!

You saved me a bunch of typing. At these conditions it's fairly normal for the heat pump to produce 20 degree temperature *rise*. Supply temperature depends on return temperature.

As for the balance point, you can just keep setting it lower and lower until you find the point at which it gets too low. You'll know when that happens by noticing that the system can't keep up using the heat pump at a certain temperature. However with this type of dual fuel system, you specify a fixed changeover point, and if you set that exactly at the balance point, you will have basically zero recovery capacity when you're at or just above that temperature. That's OK if you're not going to use temperature setbacks during the winter, but it will drive you crazy otherwise.

Example: Assume the actual balance point is 32 degrees, and you set the changeover temp in the thermostat at 32. If you set back the thermostat while you're away or asleep, and it's 34 outside when it comes time to heat the place back up again, the thermostat will only be allowed to use the heat pump. But at that condition, the heat pump would take hours to heat the house up again; it's really only enough to maintain temperature under those weather conditions. If you set the thermostat's crossover temperature to 40, you'll get to use the furnace and warm up promptly. But in doing so, you'll also end up using the furnace to maintain temperature in the 32-39 degree range when the heat pump could actually do the job alone.

My answer (which I readily admit is only a good solution in the sun belt) is to set the thermostat's changeover temperature aggressively, so it uses the heat pump all it can, and then to use basically no setbacks at all during the winter. By not using setbacks, you never ask the heat pump to do something that it can't do in a reasonable amount of time. The efficiency lost by keeping the house warmer during those hours is made up by the (cost) efficiency gain of making more use the heat pump and less of the furnace. During the spring and fall, when it's not so cold outside and the heat pump can do a better job of recovering after a setback, then you can use setbacks more traditionally and not worry about the heat pump catching up in a reasonable amount of time.

In colder areas, where it's likely that you'll spend a lot of the winter below the balance point, then it's much more complicated to optimize a strategy for setting back (or not setting back) a dual fuel system. That question is worth a whole thread, though.

[md master]

I have this very same system and I've set the balance point at 25*. Stays very comfortable.

I also had little verticle room so I installed the furnace verticle with a 90* el with turn vanes into a cased "a" coil horizontal. Works well.

[aircooled53]

Originally posted by dan sw fl

Originally posted by aircooled53
Balance point is ok, for Texas.

If the unit runs for approximately 15-20 minutes,supply temps should be between 90-120..Without heat strips.


I don't know how _aircooled53_ determines his expected temperature for a XL14i heat pump with the heat strips Off.

Basics: Q = CFM * Dt * 1.08
i.e. 3-ton = 1,200 CFM

Q = 1,200 * 20 * 1.08 = 25,920 BTUh
at 35'F outside temperature
.......

XL14i ..
2TWX4036 / TWE040 ( or 4TWX4036A/ 4TEE3F040)
Ratings

47'F 33,400 BTUh COP 3.56
35'F 25,960 BTUh COP 2.84
17'F 21,000 BTUh COP 2.48

Expected temperature difference
from return aair to supply air at the air handler
26'F rise at 47'F outside air temp
20'F rise at 35'F
17'F rise at 17'F

64'F room temp + 20'F = 84'F Supply Air

Set point should probably be close 32'F.
However, a load analysis must performed to determine the heat loss for your specific residence.

OR set balance point to 32'F and
see how unit performs when the outdoor temp is 33'F.

[Edited by dan sw fl on 01-30-2006 at 03:23 AM]

64' rise at 44'=90' Learn how to add..But your right and I should have add a little better myself before giving an answer.. If you noticed I stated for Texas not Washington, maybe he should have a capacity check done to find out just what the system is producing..

Way to go Dan!! Make me look bad..LOL

[seatonheating]

Have the installer come back and use duct mastic on all joints! Make sure that if he wrapped any duct that he removes it and gets those joints too. While they are out, you may want to think about getting your entire duct system sealed(resealed) to ensure that the heat you are paying for is being used in your house. Also, double check the insulation on any undconditioned ductwork. Code is R-8 ( 3 inch ). BTW, no electronic air cleaner? With this system you don't want to skimp on your filter.
Good Luck

[cjay]

md master

What do you mean by "turn vanes" ? Is it some sort of special ducting? What he used was just a square cornered piece with a bit of a bevel on the outside corner. Inside is square. That he made up.

[cjay]

seasonheating

I ordered the trane cleaneffects but they said it wasn't available yet. I'm hoping to get the duct work sealed properly when they come out to install the air cleaner. Hopefully it'll be as good as it's supposed to be.

[dan sw fl]

Originally posted by cjay
What do you mean by "turn vanes" ?
Is it some sort of special ducting?

Turnign vane is an internal air foil ( deflector or guide, if you will).

For example,

http://www.ductmate.co.uk/turnvane-assembly.html

[cjay]

Is the turning vane assembly in the el something I should expect to be part of the installation? Also, is clear silicon an acceptable way to seal the seams in ductwork?

[Freezeking2000]

i use silicon all the time.