Confirming Specs

[staze]

Hey All,

Just wanted to start out by saying, this forum is great. Wonderful reading, and lots of knowledge. Thanks!

Okay, so, background. I live in the Pacific Northwest (Lower Willamette Valley to be specific), and live in a house built in 1978, 1400 sq. ft., with *gasp* ceiling heat. For those that don't know, ceiling heat was mostly a PNW creation (due to low power costs) that best resembles floor radiant heat, only backward. There are electrical wires embedded in plaster in the ceiling, and when called for, they heat up, and warm the objects in the room. This mainly means you end up with a warm head, and cold feet.

I purchased the house a year ago, and forced air was one of the first major upgrades on my list... ceiling heat sucks (even with our cheap power). After going to the Home and Garden show recently, I talked to a few HVAC installers, and arranged for appointments. All recommended heat pumps for some of the same reasons ceiling heat was popular here (cheap electricity). Also, since we're a temperate climate, heat pumps are generally pretty efficient here.

First guy came out, was very nice, took some measurements, and was very open to our ideas. The big problem being that we don't have any ducting, and we're a split level, so getting the trunks between one level and another are a bit of a challenge (upstairs will have ceiling registers, downstairs will have floor registers). He did not do a Manual J on site, but said he would mail us a quote and a load calc the following week. Total time on site, about an hour.

Second contractor came (from probably the best known name in town), took detailed measurements, did a manual J on site, showed us heating load, cooling load, and gave us 3 quotes for 3 different compressor/AH setups. The main reason for 3 options was because we freaked a bit when we saw the costs he was giving us. The options were:

1. 2.5 ton XL15i (4TWX5030B1) with a VS air handler (4TEE3F39A1).
2. 2.5 ton XL14i (2TWX5030B1) with the same handler.
3. 2.5 ton XR13 (don't have the model numbers). This one was basically the "you said you wanted to save some money up front," option.

All 3 would include the TCONT802 stat, etc.

We got a call back from the first contractor, who said he was going to mail us the quote, etc. Turns out they install Amana and Goodman (same company), and I've heard less than stellar things about their products. The second contractor obviously uses Trane.

So, after doing some reading here, and elsewhere online, I signed the paperwork today to get the XL15i. It looks like the most efficient, and it does have R410, where the XL14i is R22. While I know R22 will be made until 2030, we here in Oregon are a bit of "green freaks" and I like the idea of a lower impact refrigerant. And ultimately, the cost difference between the XL14i and the XL15i, after tax credits, and the $400 rebate Trane has right now on the XL15i, the difference was all of about $500 (plus or minus a few hundred... I'm trying to be as non-specific as possible to avoid any implication of "prices").

So basically, I'm just curious if I'm crazy here, or if there's anything I'm missing. It's a lot of money that's going into this (thankfully the local utility is paying for about half of the cost with a 0% interest 5 year loan). I have never heard anything bad about the contractor I'm going with, and that includes their commercial side doing the HVAC at my office, and my boss using them for his home install.

Thanks very much, again, great site. feel free to ask questions... the contractor is very good about responding to email, so anything I don't know off hand is easy enough to get.

-Staze

[beenthere]

Isn't your area more of a heat concern then a cooling concern.
You should find the different BTU output of the 13, 14i, and 15i.
The one that provides the higher heat output at the lower temps would be the better for heating applications.
The one that brings on the aux heat the least, would be the better choice.

[tigerdunes]

staze

a very good system.

Here are the performance numbers from the CEE HVAC directory.

1382160 Active OEM XL15I WEATHERTRON TRANE 4TWX5030A1 4TEE3F39A1 30000 13.00 15.75 30000 9.00 18000

nothing shabby about these numbers.

What are you doing about an air cleaner cabinet? How many returns for the ductwork system? You will need at least one for each level.

Your area/climate is relatively mild. I would not use a Trane stat if dehumidification in the summer is important-the Honeywell VP IAQ is superior.

What size aux heat strip? I would think a 5KW would be adequate, no more than a 7KW.

IMO
:)

[staze]

Isn't your area more of a heat concern then a cooling concern.
You should find the different BTU output of the 13, 14i, and 15i.
The one that provides the higher heat output at the lower temps would be the better for heating applications.
The one that brings on the aux heat the least, would be the better choice.

We do have more cooling that heating days.

http://www.cityrating.com/cityweather.asp?city=Eugene

But, being temperate, we don't get a lot of sub freezing, or more than a few 100+ degree days (or even 90+ degree days).

Looking at the specs provided by the installer...

The XR13 has a HSPF of 8.5, and the 14i and 15i are both 9.0. So then the advantage becomes cooling, with the 15i getting a higher SEER and EER.

-Staze

[staze]

staze

a very good system.

Here are the performance numbers from the CEE HVAC directory.

1382160 Active OEM XL15I WEATHERTRON TRANE 4TWX5030A1 4TEE3F39A1 30000 13.00 15.75 30000 9.00 18000

nothing shabby about these numbers.

What are you doing about an air cleaner cabinet? How many returns for the ductwork system? You will need at least one for each level.

Your area/climate is relatively mild. I would not use a Trane stat if dehumidification in the summer is important-the Honeywell VP IAQ is superior.

What size aux heat strip? I would think a 5KW would be adequate, no more than a 7KW.

IMO
:)

The filter is probably going to be an in-return filter. Because the AH is being put in the attic, I don't really want to climb up there and replace a media filter every 3-6 months (opening the return will be much easier). At some point in the future, I might switch to the CleanEffects, but the cost is prohibitive at this point, and still not worth it after the $200 Trane Rebate (we don't have any filter now... so something is still better than nothing).

Humidity in the summer isn't an issue. We don't get balmy like the east coast, or south, or Hawaii even. It generally stays pretty comfortable, humidity wise (there are always freak "wow, it's muggy!" but that usually is only when it's 80-90F out, and the humidity hits all of 60% or something).

They're actually putting in a 10kw strip. The heat and cooling load on the house, if I recall correctly (don't have the manual j with me), were about 27000btu, or so. The difference between the two was like, 600 btu or something small like that. The installer also seemed to think BTU output for the strip was about 3.14btu per W... dyslexia I guess, because it's 3.414btu per W, or output would be 341400... which yeah, is a bit high. But, the system should be able to under power it, yes? Just because it's 10kW doesn't mean it always uses that much (that would be kinda dumb if it always runs at full power).

Thanks!

[BaldLoonie]

Personally I'd upgrade to the Vision Pro IAQ stat, it's the CONT9xx something in Trane talk if they have it yet. Then ask that dehumidify on demand be used and Comfort R be turned off. That way you get full airflow in dry weather and the control automatically slows the blower for extra dehumidifaction in humid weather.

Trane heat pumps have tended to be "light" on heating, where the heating capacity was lower than the cooling capacity. Especially true on dual fuel setups. But the new 4TWX5 series has changed that to where you get more heating capacity from the unit. Something to consider or look at in the ratings as you compare.

PS: Remember that 85° and 60% RH outside means dewpoint of 70° which is rather steamy! You'd like the dehumidify on demand feature in that weather and full airflow when not humid

[h20 stove]

10KW strips will put out 34,140 btus at full output, which is not too high for your heat load

[staze]

Personally I'd upgrade to the Vision Pro IAQ stat, it's the CONT9xx something in Trane talk if they have it yet. Then ask that dehumidify on demand be used and Comfort R be turned off. That way you get full airflow in dry weather and the control automatically slows the blower for extra dehumidifaction in humid weather.

Trane heat pumps have tended to be "light" on heating, where the heating capacity was lower than the cooling capacity. Especially true on dual fuel setups. But the new 4TWX5 series has changed that to where you get more heating capacity from the unit. Something to consider or look at in the ratings as you compare.

Okay, so turn off Comfort-R? Isn't that what has the blower on at 30% or so all the time? That was one of the big points they were talking about is having the blower on at low speed all the time to keep air moving.

I really don't want to dehumidify so much... I don't really ever recall having a humidity problem in the house. If I've seen anything on this forum, it's been people saying the IAQ is great, and to get it (because of it's humidity control)... but I have yet to see anyone say that that lives in the PNW, where we don't really get humid days.

And yeah, the XL15i is indeed a 4TWX5 series (or, at least, the one I'm looking at)...

[BaldLoonie]

Comfort R is a slow ramp up of the blower in cooling mode for extra dehumidification. It has to be turned on by the installers, I'd guess most don't bother but it is a nice feature. But in this day of controls like the IAQ that can do more, my house is better without this feature. Now in low humidity the blower starts on full blow which has helped cool distant rooms. Only in times of humidity do I slow it down.

You can still run the blower constantly which is 50% of normal cooling speed. I do this except in humid weather when it tends to make the house humid by evaporating the water off the coil in the off cycle.

[staze]

Comfort R is a slow ramp up of the blower in cooling mode for extra dehumidification. It has to be turned on by the installers, I'd guess most don't bother but it is a nice feature. But in this day of controls like the IAQ that can do more, my house is better without this feature. Now in low humidity the blower starts on full blow which has helped cool distant rooms. Only in times of humidity do I slow it down.

You can still run the blower constantly which is 50% of normal cooling speed. I do this except in humid weather when it tends to make the house humid by evaporating the water off the coil in the off cycle.

Ah, okay. Yeah, now I remember... the whole supercooling of the coil... if I recall correctly, it's a couple switches on the air handler. *shrugs*. I'll ask about other stats... but I'm fairly content with the TCONT802...

[beenthere]

Ah, okay. Yeah, now I remember... the whole supercooling of the coil... if I recall correctly, it's a couple switches on the air handler. *shrugs*. I'll ask about other stats... but I'm fairly content with the TCONT802...
Only because you haven't experienenced the IAQ's abilities.

[staze]

Only because you haven't experienenced the IAQ's abilities.

wow, that's subjective.

I still fail to see how the IAQ would be beneficial in the PNW when we don't have humidity problems, or anything like that. Right now, I have ceiling heat... which is horrible, and I keep my house at about 62-65 in the winter because it's so bad.

What really, does the IAQ give me, that would be worthwhile?

[nashobasales]

Not to nit pick but the option 2 should be a 2TWX4030, if it is indeed XL14i. The model listed is the XL15i with R22.

[staze]

Not to nit pick but the option 2 should be a 2TWX4030, if it is indeed XL14i. The model listed is the XL15i with R22.

Oops... Probably a transcription error on my part, or on the contractors part. It should be the 2.5 Ton, XL14i with R22.

[nashobasales]

Oops... Probably a transcription error on my part, or on the contractors part. It should be the 2.5 Ton, XL14i with R22.

Just wanted to make sure you knew, that was all.;)

[staze]

So, here's a question...

Someone mentioned that the 4TWX5 series was better at heating. Does that mean that there is more of a difference between the R22 and R410 XL15i besides refrigerant?

[staze]

To answer a previous question... only 1 return. The house is a split level, but you enter on one level, and go up 6 steps to the hallway that heads to the bedrooms, which is where the return will go (the hallway ceiling). So really, the house is more like a single level than a 2 level house.

Everything still seem reasonable?

[dash]

The IAQ stat,can better dehumidify your home in mild or damp weather ,when the cooling doesn't run enough to keep the humidity below 50%.

[staze]

The IAQ stat,can better dehumidify your home in mild or damp weather ,when the cooling doesn't run enough to keep the humidity below 50%.

Not sure that's an issue here in the PNW... it's rare that we get very high humidity when it's not raining, and I don't know that I've ever had a humidity problem in the house now, and that's with no forced air.

So yeah... not sure if it's worth the extra (not even sure if the contractor has the IAQ as an option... waiting for a response to my email anyway (or will ask when they come out for the measure-up).

Thanks!

[dash]

I don't know your climate,but the city data you posted shows some high humidity.



No one is talking humidity problems,just improved indoor comfort,with dehumidification controls.


Plus internal cooking,showers,etc. add to the indoor humidity,the choice is yours.

[staze]

I don't know your climate,but the city data you posted shows some high humidity.



No one is talking humidity problems,just improved indoor comfort,with dehumidification controls.


Plus internal cooking,showers,etc. add to the indoor humidity,the choice is yours.

Indeed. I will see what the installer says, and probably go mainly from the price, since I don't ever feel the need to dehumidify the house (I have several plants in the house that are not going to like the change to forced air... further lowering the humidity might just make them even angrier).

I'll post back after the measure-up.

Thanks!

[staze]

So, measure-in happened today. 6 day job (last day sounds like it's mostly balancing, measurements, etc).

The response about the Trane 9x series tstat, or the IAQ, was mainly that we don't have humidity problems here in the PNW, so it's not really worth it. They mainly install the 9x's in existing systems that only have 4-wire runs to the tstat, and the tstat then talks to the base over that, and the base talks to the unit over 7-wire.

The price difference is about $100, sounds like. Not sure it's worth that... but I'm still going to think about it.

Anyone honestly think it would be worth it, when humidity isn't really an issue. Can you tell the tstat to keep humidity within a certain range on the 9x/IAQ? I have a lot of plants, and I'd prefer not to over-dry the house... though, the installer said that shouldn't be an issue.

I guess the question then, if I go for the 9x, is, would I then have them leave comfort-R off?

Thanks!

[beenthere]

Not familar with the Trane to know evrything it can or can't do.

A few things the IAQ can do.
Slow VS blower
Cool to dehumidify
Control humidifier
Control fresh air damper, or ERV/HRV
Lock out strip heaters ( requires OD sensor )
Independant CPH settings for each stage of heat

[staze]

Not familar with the Trane to know evrything it can or can't do.

A few things the IAQ can do.
Slow VS blower
Cool to dehumidify
Control humidifier
Control fresh air damper, or ERV/HRV
Lock out strip heaters ( requires OD sensor )
Independant CPH settings for each stage of heat

From what I know of the Trane, it locks out the strip heater at 40F. The 900 series, or the IAQ, sounds like it can do lower than that.

I know the installer talked about the VS blower running at 30% most of the time... but that may be the blower itself doing that, instead of the tstat. And Comfort-R does do the supercool to dehumidify, but since the 802 doesn't have a humidistat, it sounds like it's arbitrary.

beenthere, thank you very much for this... it's the first time I've actually seen what it's capable of. Could you explain the last point? And maybe how it has more control over the VS blower than the VS blower defaults?

Anyone have any opinions on the balance point of a heat pump (where it becomes less/equally effective to use for heat than say, a strip heater)?

My community utility has no rules as far as strip heater lockouts... the neighboring utility mandates that they have to be locked out above 35F instead of this installers default, of 40F (and the Trane 800 series ability of 40). Though, that would require an outdoor sensor... which the installer hasn't mentioned. Think I'll email tomorrow about that...

Thanks!

[beenthere]

CPH. Stands for cycles per hour.

You can set the strip heaters CPH to cycle on and off a lot so that the heat pump runs longer at colder OD temps. Or set the CPH so that they don't cycle much, this will cause them to stay on so the stat is satisfied, and both the strips, and HP shut off.

EG: First stage heat compressor 3CPH, second stage heat compressor 4CPH, first stage aux 2, second stage aux 3.

With the IAQ, you can set the HP to run 400 CFM per ton in cooling. Then if the Humidity does rise, the IAQ will slow the blower down. That way, on hotter days, you have the higher sensible cooling ability of 400 CFM per ton, and on lower temp days, you still have the slower blower speed if the humidity starts to rise. ( sort of the best of both worlds ).

[staze]

I kind of follow. I mean, I guess the question would be if it's worth the extra money to get the 900 series, which is based off the IAQ in my house, in the Pacific NW (I've noticed most people on this forum seem to hail from the other side of the Rockies).

Are there any negatives to the IAQ systems? While I'm an IT professional, I don't claim to know a whole lot about HVAC (which is why I'm here). Is the documentation for the IAQ fairly clear? Is this all something I could do myself, or would I be asking the installer to set all this stuff up? Will the IAQ based system save me any money in the long run?

Basically, it sounds like the people on these forums think the IAQ is the best thing since sliced bread, but I don't want to get something if it's going to make my life more difficult, or not really give me anything tangible. And the problem with tangible is that I'm not going to be able to have the 800, and then compare it's features with the 900, and see which works best for the cost/money.

*sigh*

Any other info you might have would be great.

Thanks.

[beenthere]

The installer set is easy. So yes you could change settings on the IAQ if you wanted or needed to.

If the 900 can't slow the blower, then the IAQ could save you a small amount in the summer, by not having to enable comfort r.
Don't know if the 900 lets you set independant CPH. But the IAQ letting you do that, allows you to feel better about your system. As far as if you prefer it to shut off, or cycle a lot.

[staze]

The installer set is easy. So yes you could change settings on the IAQ if you wanted or needed to.

If the 900 can't slow the blower, then the IAQ could save you a small amount in the summer, by not having to enable comfort r.
Don't know if the 900 lets you set independant CPH. But the IAQ letting you do that, allows you to feel better about your system. As far as if you prefer it to shut off, or cycle a lot.

Okay, changed the tstat to the Trane XL900. According to everything I've seen online, this is the exact same thing as the Honeywell IAQ, just branded "Trane".

So, cool. Install starts tomorrow... Supposed to take 6 days in all. Will post back when I can actually turn the system on. =P YAY! Forced air!!! No more ceiling heat!

[staze]

Well, install is done. They finished a day ahead of schedule. System so far works great... amazing how nice it is to have central air (and therefore central air filtration). The outdoor unit is a bit louder than I thought it would be, but the indoor AH is basically silent. They put the outdoor unit on a preformed pad (on gravel) and then rubber "feet" on the corners to reduce vibration. Anyone have any suggestions on further reducing the noise (other than putting egg crate on the exterior house wall closest to it?) =)

I in fact got the Honeywell IAQ, since apparently the Trane rebranded XL900 is like, $40 more, and all you get is "Trane" written on it. Dumb.

So far so good... I went through after the installer set up the IAQ and tweaked it a bit... he had the CPH for the HP set to 9, which obviously seems a bit high. I set it back to 3 since that seems to be the recommendation here on the site.

I would be very curious for any recommendations on settings for the tstat. I'd be more than happy to post here with what I have things set to... right now, I don't have the tstat doing humidity control, but the humidity is stable at about 36% ± 1%. I'm keeping the house at 68F during the wake-leave, and return-sleep, and 66F from leave-return, and sleep-wake, since HPs tend not to do large recoveries well.

The system does seem to run fairly often when it's holding temp, but I couldn't find anywhere in the tstat settings to adjust the swing sensitivity, and since the tstat doesn't show 1/10th of a degree, I have no idea how much of a drop it's recovering from. I do know that when it drops to 66F, the house takes at least 1-2 hours to come down those 2 degrees.

The only other question is, the tstat is set to lockout the Aux heat at >35F... does that mean the Aux heat will NEVER come on above that temp, or does that mean it will only come on when there is a huge/slow recovery? Does anyone know those "thresholds"?

Thanks everyone! Great site.

[beenthere]

Won't come on above that temp, except for defrost.

Its in the installer manual the different settings you can have for aux lock out.
It will take a while for the stat to learn the house. Then you should notice less cycles since you said you reset it to 3 CPH.

[staze]

excellent! yeah, I notice it's cycling less, and getting better about figuring out recovery times.

Now if I can only teach myself how to read the electrical meter right... I swear between yesterday and today it ran backward. =P

[staze]

So as a final comment, system works great. Haven't tried the AC yet obviously, but at this point, I was averaging 54kwh/day last month (ceiling heat), and this month since the new system was installed, I'm averaging 30-35kwh/day (heat pump). And that's with keeping the house at 68 or so, rather than the 62 I was keeping it with ceiling heat.

Thanks everyone for the advice. Now I'll just be paying off the system for several years. =) Go home ownership!

[squirrel71477]

Staze thats good to hear.

[bc3141]

I'm glad your system seems to be working out. I'm just curious, what was it about the ceiling heat that you didn't like, just the cost, or were there comfort issues? I'm interested because I just retrofitted a couple of rooms with hydronic radiant ceiling and so far I'm very pleased with it. Maybe the way it's controlled makes a difference, or perhaps the ceiling height?




So as a final comment, system works great. Haven't tried the AC yet obviously, but at this point, I was averaging 54kwh/day last month (ceiling heat), and this month since the new system was installed, I'm averaging 30-35kwh/day (heat pump). And that's with keeping the house at 68 or so, rather than the 62 I was keeping it with ceiling heat.

Thanks everyone for the advice. Now I'll just be paying off the system for several years. =) Go home ownership!

[tigerdunes]

Well, install is done. They finished a day ahead of schedule. System so far works great... amazing how nice it is to have central air (and therefore central air filtration). The outdoor unit is a bit louder than I thought it would be, but the indoor AH is basically silent. They put the outdoor unit on a preformed pad (on gravel) and then rubber "feet" on the corners to reduce vibration. Anyone have any suggestions on further reducing the noise (other than putting egg crate on the exterior house wall closest to it?) =)

I in fact got the Honeywell IAQ, since apparently the Trane rebranded XL900 is like, $40 more, and all you get is "Trane" written on it. Dumb.

So far so good... I went through after the installer set up the IAQ and tweaked it a bit... he had the CPH for the HP set to 9, which obviously seems a bit high. I set it back to 3 since that seems to be the recommendation here on the site.

I would be very curious for any recommendations on settings for the tstat. I'd be more than happy to post here with what I have things set to... right now, I don't have the tstat doing humidity control, but the humidity is stable at about 36% ± 1%. I'm keeping the house at 68F during the wake-leave, and return-sleep, and 66F from leave-return, and sleep-wake, since HPs tend not to do large recoveries well.

The system does seem to run fairly often when it's holding temp, but I couldn't find anywhere in the tstat settings to adjust the swing sensitivity, and since the tstat doesn't show 1/10th of a degree, I have no idea how much of a drop it's recovering from. I do know that when it drops to 66F, the house takes at least 1-2 hours to come down those 2 degrees.

The only other question is, the tstat is set to lockout the Aux heat at >35F... does that mean the Aux heat will NEVER come on above that temp, or does that mean it will only come on when there is a huge/slow recovery? Does anyone know those "thresholds"?

Thanks everyone! Great site.

Staze

perhaps I overlooked it but what did you finally purchase?

mdl and size of condenser and air handler?
what size heat strip?

just wondering...

TD
:)

[beenthere]

Biggest complaints I hear about electric radiant ceiling heat, is the cost.
Only people that I hear say it doesn't keep them warm, is the ones that keep the temp set low to save money.

[staze]

Cost cost cost. Electric ceiling heat is just really friggin' costly. Like I said, keeping the house at 62 ran me $80/month in electric (and that's with my area having about the cheapest electricity in the nation, at $.0463/KWh). And basically, your head was warm, but your feet were cold, and the floor was cold, etc. If I were going to do radiant, I'd do floors in the kitchen, and bathrooms (tiled areas).

The other real problem with electric ceiling heat is that you really can't do anything to your ceiling infrastructure. Install a fan, put in can lights, etc, because you risk breaking a wire for the heat, and killing the entire zone. The only good thing about ceiling heat is it was zonal, but it really wasn't worth it.

As for what I got, I got:

XL15i, 4TWX5030B1 with the 4TEE3F39A1 air handler. The Aux strip is a 10KW, and the tstat is the Honeywell IAQ. I opted to not get the CleanEffects for several reasons, mainly the cost... and a few sites that said a well maintained media filter will do just fine in keeping down allergens. The filter is in the return, and is 20x20x4 (not the Honeywell sizing).

The installer did a great job, and because they couldn't do the trunk from the attic to the crawl space (the AH is in the attic in the upper part of the house, so the trunk is just to feed the ducting in the crawlspace in the lower part of the house) how they initially thought, they did it another way (using more ducting) and didn't charge any more.

Please feel free to ask anything else. The duct testing and such is this friday. A 3rd party is coming to do a blower door test, and a blower duct test (I think that's what they called it) to make sure everything qualifies for the state tax credits, and the 0% interest loan I'm getting through my utility company.

[tigerdunes]

staze

a very good system with very good performance numbers.

1382160 Active OEM XL15I WEATHERTRON TRANE 4TWX5030A1 4TEE3F39A1 30000 13.00 15.75 30000 9.00 18000 *

There should be a Trane rebate on this system.

If I have any question, it would be the size of your heat strip-I think a 10 KW is too large and a 7.5 KW would be a better choice for your area/climate.

IMO
:)

*numbers from the CEE HP directory...

[staze]

staze

a very good system with very good performance numbers.

1382160 Active OEM XL15I WEATHERTRON TRANE 4TWX5030A1 4TEE3F39A1 30000 13.00 15.75 30000 9.00 18000 *

There should be a Trane rebate on this system.

If I have any question, it would be the size of your heat strip-I think a 10 KW is too large and a 7.5 KW would be a better choice for your area/climate.

IMO
:)

*numbers from the CEE HP directory...

There is a $400 rebate on the system... which I really should mail in tonight. =P

7.5KW would provide 23565btus (7500W x 3.142btu/w)... the heatload on my house is about 27000... so 10KW is actually more appropriate. I did ask, and they thought it was about right since you can't get a 9KW strip... and in case the HP does go out, I'd rather not have a 60F house in the winter while waiting for a repair. =P

Yeah, I'm very happy about the system. I also should qualify for about $740 in State tax credits... which after all is said on done, the XL15i ends up costing just a couple hundred more than the 14i, and I get a more efficient system. =)

[tigerdunes]

staze

just to remind you that you will receive 18 KBTUs at 17 deg outside temp.

There are different approaches on sizing of heat strips.

1.to size for the full heating BTUs required for your area/climate(like you have)

2.size the heat strip for your area/climate heating loss that includes the 18 KBTUs plus any supplemental required

3.install several heat strips that are staged and based on demand at different outside temps (like two 5 KWs that are wired to be staged)

perhaps some HP experts on this forum have other ideas on this subject.

Good LucK on your new system!
:)

[staze]

The strip should run at partial power when it doesn't need full on... 10KW is it's max power, to my knowledge.

I mainly only expect to need it largely if the HP dies... meaning I'd need all 10KW to keep my house heated until the repair on the HP is done.

I'm not sure about the math (I really don't want to sit and figure it out), but a 10KW strip is going to produce hotter air than than a 7.5KW strip... meaning it will bring the house up to temp faster at higher energy use than a 7.5KW will using less energy.

Say, a 10KW strip produces about 31400 BTUs/hour. So, my whole house at 27000 BTU load, would be heated in some set amount of time (we can't say time because we don't know starting temp, and end temp). A 7.5KW strip would produce ~23600 BTUs/hour.... meaning it would take 25% longer to heat the house than the 10KW strip, all the while using 7.5KW (and that's assuming my house wasn't losing heat while the 7.5KW strip was trying to heat). Maybe I'm completely wrong on my logic... but undersized sounds like it would use more power in the long run than correctly sized. But, I'm also not figuring in it being used as a second stage heat.

Also, it is EXTREMELY rare to get down to 17F in the Willamette Valley. We might have hit that once this year, and this year was especially cold for parts of the winter. Normal lows aren't much below freezing, and that's only at night.

Thanks, I will and have been enjoying it!

[beenthere]

Personally.
I prefer to have enough strip heat to heat the house at design temp. And if the strip stepping means the heat kit is over sized, by 2 or 3 KW, so be it. Nothing worse then a customer having to shiver for 2 to 4 days untill a new refrigerant part comes in.