Looking for air handler recommendations

[KCA]

Hi all,

I'm in the process of switching out an old electric furnance and A/C unit with a heat pump. The electric furnance is 24kW (80k BTU) and the A/C unit is a 3 ton (I believe it might be a Bryant, but I don't see a badge on it). The A/C unit is 15 years old and works fine, but as you can imagine, the electric furnance is hard on the wallet.

I have already done a Manual J and I come up with ~28k BTU cooling and about 68k BTU heating. They must have done a Manual J when they put in the 3 ton unit as it was probably the perfect size as I have added insulation to attic and basement since then. I could probably go 2.5 ton on the heat pump, but the 3 ton cooling has served us well, so that is what I would like to stick with.

I was considering going with a 4 ton 2-stage unit. Set it up so that only the low stage (3 ton) is used in the summer and both stages could be used for heating, if needed. An HVAC tech has already verified that I have enough supply/return to support a 3.5 or 4 ton unit.

My main issue is with regards to the air handler. The current electric furnace has the intake on the side and the "A" coil sitting on top of the furnance. Most new air handlers seem to put the "A" coil on the bottom and blower on top. This is a basement install, so I would have to add a box under the air handler for return air. The issue that I have is with height.

Right now, floor to canvas flex connector is 66". I can get to 70" if I get rid of the flex connector. The supply plenum can't really be moved since it is already up to the joists. The modular blower/cased coils that I have checked (Goodman, York, etc.) are in the 57"-60" range. This only gives me about 10" to work with for the RA box. Some 1-piece air handlers are shorter, but I am not sure what would be best for this situation.

It doesn't matter if the air handler is communicating or not. I probably won't be able to use that feature since I have a Bryant 2-zone system. I am looking for leads on a good air handler that is maybe a little shorter or even better would be one that would allow side return air.

Sorry for the long post.

[beenthere]

A 4 ton 2 stage scroll system will be 2.8 to 3.2 tons in first stage. And may not be able to remove enough moisture in summer even running only in first stage. Making your house humid that you end up turning the thermostat lower to be as comfortable as you are with your current 3 ton. And using as much or more electric to keep you comfortable.

Unless that tech did a static pressure test on your duct system. He can't know if its sized big enough for your current 3 ton, let alone a 3.5 or 4 ton. So you might want to have that done. So you don't end up like m any do. And have a very loud and uncomfortable system.

[jimj]

A 4 ton 2 stage scroll system will be 2.8 to 3.2 tons in first stage. And may not be able to remove enough moisture in summer even running only in first stage. Making your house humid that you end up turning the thermostat lower to be as comfortable as you are with your current 3 ton. And using as much or more electric to keep you comfortable.

Unless that tech did a static pressure test on your duct system. He can't know if its sized big enough for your current 3 ton, let alone a 3.5 or 4 ton. So you might want to have that done. So you don't end up like m any do. And have a very loud and uncomfortable system.

:ditto::ditto:

And I will add that for sure you do not want to be over sizing with zoning.

[grizzzlle]

I was thinking on trying the same thing with using s 2 stage pump for the same reason (needing the additional heating capability). The idea was recomended to me by two companies that have given me quotes for installs at my house. It will be interesting to see resposes to your question.

[KCA]

Thanks, guys.

beenthere: I wonder why you might say that the 1st stage on a 4 ton system will be less effective at removing humidity than the current 3 ton? The units that I have been looking at are right at 3 ton nominal on the 1st stage (+/- a bit depending on temperature). I was planning on using a variable speed air handler compared to the multi-speed motor that is in there now (set for high for AC and med-high for heat).

The tech didn't measure static. He simply used a ductolator. I agree that static should be checked to see what the ducts can really support. The zoning does add some additional challenges. I do know that this controller will crack open the other zone if you start exceeding the setpoint for the plenum temperature. I don't recall if it has any logic like that for cooling, but if I did go bigger (or even same size with 2-stage), I would try set something up so that the 2nd stage would be locked out unless both zones were calling.

Anyway, many of the 3 ton handlers seem to be about the same size physically as the 4 ton. The cased coils might be a little shorter, so it could work.

So, option 1 would be say 3 ton (1 or 2 stage) + variable speed air handler

option 2 would be a 4 ton, 2 stage + variable speed air handler assuming that the ducts can support the flow.

Either way, I need a quality VS air handler that will be under 60" in height (50" would be better)...or I need something with a side return air setup, but I only seem to see that in gas furnances.

[Kevin O'Neill]

Hi all,

I'm in the process of switching out an old electric furnance and A/C unit with a heat pump. The electric furnance is 24kW (80k BTU) and the A/C unit is a 3 ton (I believe it might be a Bryant, but I don't see a badge on it). The A/C unit is 15 years old and works fine, but as you can imagine, the electric furnance is hard on the wallet.

I have already done a Manual J and I come up with ~28k BTU cooling and about 68k BTU heating. They must have done a Manual J when they put in the 3 ton unit as it was probably the perfect size as I have added insulation to attic and basement since then. I could probably go 2.5 ton on the heat pump, but the 3 ton cooling has served us well, so that is what I would like to stick with.

I was considering going with a 4 ton 2-stage unit. Set it up so that only the low stage (3 ton) is used in the summer and both stages could be used for heating, if needed. An HVAC tech has already verified that I have enough supply/return to support a 3.5 or 4 ton unit.

My main issue is with regards to the air handler. The current electric furnace has the intake on the side and the "A" coil sitting on top of the furnance. Most new air handlers seem to put the "A" coil on the bottom and blower on top. This is a basement install, so I would have to add a box under the air handler for return air. The issue that I have is with height.

Right now, floor to canvas flex connector is 66". I can get to 70" if I get rid of the flex connector. The supply plenum can't really be moved since it is already up to the joists. The modular blower/cased coils that I have checked (Goodman, York, etc.) are in the 57"-60" range. This only gives me about 10" to work with for the RA box. Some 1-piece air handlers are shorter, but I am not sure what would be best for this situation.

It doesn't matter if the air handler is communicating or not. I probably won't be able to use that feature since I have a Bryant 2-zone system. I am looking for leads on a good air handler that is maybe a little shorter or even better would be one that would allow side return air.

Sorry for the long post.

Since 3 ton has been adequate, why not go with a 3 ton 2 stage heat pump. It will run in low stage most of the time. And you will get better dehumidification.

[seatonheating]

Since 3 ton has been adequate, why not go with a 3 ton 2 stage heat pump. It will run in low stage most of the time. And you will get better dehumidification.

X2

[beenthere]

Thanks, guys.

beenthere: I wonder why you might say that the 1st stage on a 4 ton system will be less effective at removing humidity than the current 3 ton? The units that I have been looking at are right at 3 ton nominal on the 1st stage (+/- a bit depending on temperature). I was planning on using a variable speed air handler compared to the multi-speed motor that is in there now (set for high for AC and med-high for heat).

3 ton plus or minus is 2.8 to 3.2. Many 2 stage have less moisture removal ability in first stage then older units do at full capacity. So the new unit running at 2.8 to 3.2 tons, won't remove as much moisture per hour, and your home won't feel as comfortable at the same temp.

Your old system could have a SHR(sensible heat ratio) of .7, and a new 4 ton 2 stage could be at .78, or even .84 in first stage(the indoor coil won't be as cold). While there are ways to compensate for this. Those ways are for units sized to the cooling load. Not units that are oversize for the cooling load. And can't compensate for the over sizing.



The tech didn't measure static. He simply used a ductolator. I agree that static should be checked to see what the ducts can really support. The zoning does add some additional challenges. I do know that this controller will crack open the other zone if you start exceeding the setpoint for the plenum temperature. I don't recall if it has any logic like that for cooling, but if I did go bigger (or even same size with 2-stage), I would try set something up so that the 2nd stage would be locked out unless both zones were calling.




Duculator can NOT tell you if the duct work is sized right for your current 3 ton, let alone a 4 ton. Without knowing the length of the duct work in TEL.

Need to have the static checked on both ducts, and know how much air is being moved at that static.

If your current 3 ton is only moving 1050 CFM and is working against a .75" static, then if a 3.5 single stage, or 4 ton 2 stage tried to move 1400 CFM through that same duct work. It would have to work against a 1.33" static. At that static, a VS ECM motor is using alot more electric then your current multi speed PSC motor uses.


Going to a 4 ton 2 stage at 1400 CFM, will only give you about 8,000 BTUs more heat at 17° outdoor temp, over a 3 ton 2 stage at 1200 CFM. Coupled with the duct work alterations that you would need done. It would be a long time before that 4 ton could break even with a 3 ton 2 stage on energy savings.

[tigerdunes]

KCA

what is your location?

I will assume nat gas service is not available to your home. correct?

IMO

[KCA]

Central VA. Unfortunately, no gas to the house. It is available at the street and I did consider going gas as I do like the warm heat (like I get with the electric furnace). However, electricity is below average here ~$0.08 per kwh or less (this is just the generation portion of the bill) and gas is higher than average here the last time I checked. Also, since nothing else is on gas, I would be stuck paying the service charge for all those months where I am not using gas at all. They make the cost to disconnect and reconnect service high enough so that people won't just have the gas shutoff when they are not using it. I think that the service charge is ~$15/month. Then there is running the vent, getting combustion air, etc. I know that our neighbors have a heat pump and gas furnace and they switch over to the gas when the temperature falls below freezing. They are older folks and like it toasty, so the combo probably works well for them. I'll go back and run the numbers for gas and see what I come up with. The problem is that the price of gas tends to be much more volatile than electric, so it is hard to figure out what the future price difference might be.

beenthere: Thanks. That is just what I needed to know on the SHR. I'm an engineer, so when someone says that 3 tons of this doesn't equal 3 tons of that, I like to know why. Based on the manual J, it appears that about 5k BTU of the ~29k BTU total is latent. I thought that it might have been higher since is it somewhat humid here in the summer (102 grains of moisture) and it is an older house, so there is more infiltration than on a newer home (I have been sealing up the leaks, though).

I agree that the only way to really know the duct capacity is to measure. Things like TEL can get you in the ballpark, but there is nothing like measurement to know what the true capacity is. I do know that the static is probably high when only one zone is calling as you can hear the difference when standing next to the air handler. I'll have to measure the static and air flow and see what we get.

It does appear that I can probably save enough height going with a 3 ton coil/blower to give enough room for a decent sized RA box under the unit.

Thanks.

[KCA]

I did a couple quick and dirty measurements over the weekend. I put together a simple u-tube manometer just to get an idea of what the current static is.

With the blower on med-high, I get the following dP:

- Zone 1: 1/4" (0.25)
- Zone 2: 5/16" (0.3125)
- Zone 1 + Zone 2: 3/16" (0.1875)

I also estimated air flow by looking at the dT across the furnace. The zone control system has a temperature sensor in the supply plenum, so I can see what the output temperature is. With 1 zone calling, I get a temperature rise of ~52 F and both zones calling gives a rise of ~45F.

Now, if the furnance is putting out the rated BTUs (24kW or 80,000BTU), this means that there is something like 1400-1600 SCFM flowing, depending on how many zones are calling. This doesn't really seem to be correct. A couple things might be going on here:

1. an element or sequencer is dead, so only 3 out of the 4 elements (6kW each) are actually working. We had a dead sequencer last year (the 1st in the series) and wouldn't kick the heat on when the basement was cold. That one was replaced, but there are others in there that are older. If an element/sequencer was dead, then my numbers would line up better with a 3 ton blower (~1050-1200 CFM).

2. The plenum temperature hadn't reached a steady value, but it appeared to be stable.

3. It is actually flowing this amount as the blower been replaced at some point (43 year old furnance), and maybe someone installed a larger blower?

Anyway, I'll see if I can get someone to come measure the static/airflow in a more accurate fasion and have the elements checked out to make sure that all of them are working.

More than likely, I'll just stick with a two-stage 3-ton unit, but I still want to see what the real static/CFM is beforehand so I know for sure that the ducts will support the flow properly.

Any brand recommendations? I know that everyone seems to like their own thing, but any suggestions would be helpful. I know that getting a good install is the main thing. Mostly, I have been looking at the specs for Goodman/Amana, Rheem/Ruud, and a bit from York (Affinity series). I'm looking for a SEER in the 16-18 range, HSPF in the 9.0-10.0 range. The SEER is less important as our A/C is pretty cheap to run even with our current unit (~10 SEER, I think). I'm open to other brands too. The ones that I listed are just some of the easier ones to find detailed specs on and I haven't looked close enough at other brands to narrow down a model.

Thanks.

[beenthere]

Did you measure both supply and return static, or just supply static?

[KCA]

That is the total dP. One end of the tube stuck in just before the filter and the other end stuck into the A/C coil area (A/C is placed on top of the electric furnance). I tried removing the return end of the manometer to see what just the static was, but the difference was too small to notice. So, it looks like the resistance of the return is small compared to the supply. It doesn't surprise me much as the returns are short in distance and fairly large (I have a central return type of setup).

[beshvac]

Hi all,

I'm in the process of switching out an old electric furnance and A/C unit with a heat pump. The electric furnance is 24kW (80k BTU) and the A/C unit is a 3 ton (I believe it might be a Bryant, but I don't see a badge on it). The A/C unit is 15 years old and works fine, but as you can imagine, the electric furnance is hard on the wallet.

I have already done a Manual J and I come up with ~28k BTU cooling and about 68k BTU heating. They must have done a Manual J when they put in the 3 ton unit as it was probably the perfect size as I have added insulation to attic and basement since then. I could probably go 2.5 ton on the heat pump, but the 3 ton cooling has served us well, so that is what I would like to stick with.

I was considering going with a 4 ton 2-stage unit. Set it up so that only the low stage (3 ton) is used in the summer and both stages could be used for heating, if needed. An HVAC tech has already verified that I have enough supply/return to support a 3.5 or 4 ton unit.

My main issue is with regards to the air handler. The current electric furnace has the intake on the side and the "A" coil sitting on top of the furnance. Most new air handlers seem to put the "A" coil on the bottom and blower on top. This is a basement install, so I would have to add a box under the air handler for return air. The issue that I have is with height.

Right now, floor to canvas flex connector is 66". I can get to 70" if I get rid of the flex connector. The supply plenum can't really be moved since it is already up to the joists. The modular blower/cased coils that I have checked (Goodman, York, etc.) are in the 57"-60" range. This only gives me about 10" to work with for the RA box. Some 1-piece air handlers are shorter, but I am not sure what would be best for this situation.

It doesn't matter if the air handler is communicating or not. I probably won't be able to use that feature since I have a Bryant 2-zone system. I am looking for leads on a good air handler that is maybe a little shorter or even better would be one that would allow side return air.

Sorry for the long post.

Carrier/Bryant's Variable speed airhandler is 53 1/2" tall.

10" tall is borderline at 3tons if assume 200 sqin of opening to the bottom of the airhandler

[KCA]

Thanks.

I also see that York makes a 1-piece variable speed (AVG, Affinity) that is about 52" tall for 3 ton and 57" for 4/5 ton . The Goodman/Amana 1-piece is about 53.25" (variable speed, but non-communicating).

My current return (after the return plenum) is 24x12. This goes into a RA drop with a 20x25 filter. I agree that dropping down to 10" wouldn't be too good. If I go with one of the 1-piece handlers listed and drop the canvas connector, the box could be 15"-16.75" tall.

It looks like Rheem/Ruud has one even shorter with the 3 ton handler being around 42.5", but the 4 ton is around 55.5".

[Keith73]

Since capacity has been well covered in this conversation, have you considered horizontally mounting the unit or is it in a closet like space?

[seatonheating]

You can also do a modular air handler and locate the coil in the return drop??


Like this:



http://i821.photobucket.com/albums/zz140/adorkablejosh/heightissues.jpg

[KCA]

Keith: It is in a somewhat large closet in the basement. I don't think that I have the space to do horizontal and would require lots of changes to the ductwork since it is currently setup for a vertical install. Thank for the idea, though!

seaton: That's a pretty good idea. I didn't really think of that. That might be a good solution.

BTW: Do you guys typically use pre-fabbed RA boxes or are they typically made to order? I haven't had experience with these, so just wondering what to expect.

Thanks!

[seatonheating]

Keith: It is in a somewhat large closet in the basement. I don't think that I have the space to do horizontal and would require lots of changes to the ductwork since it is currently setup for a vertical install. Thank for the idea, though!

seaton: That's a pretty good idea. I didn't really think of that. That might be a good solution.

BTW: Do you guys typically use pre-fabbed RA boxes or are they typically made to order? I haven't had experience with these, so just wondering what to expect.

Thanks!


Depends on the job. In your instance I like to use something like this:

http://electronicaircleaners.com/447380-002.aspx

[KCA]

I did see that style while looking at filter options. That might be a good option especially if I go with a thicker filter. The current setup has a 1" filter between the RA drop and the furnance side. There wouldn't really be room to add a 4-5" filter there without adding some offsets or similar.

Thanks for all the help so far. I do appreciate it. I like to figure things out and get the details before going forward. Most of the info geared towards homeowners (product brochures) just glosses over the features. Usually two people relaxing on the couch or playing with their dog and telling me how this system is quiet and comfortable. I like details/specs. If you say it is quiet, tell be how many dB it is rated at and at what conditions. :)

[KCA]

Double checked that all elements were working. The furnance originally came with four 6kW elements. At some point, it looks like three of them were replaced with 5kw units. The top three were pulling ~21A each and the bottom was ~24A. Loaded voltage = 237.5.

So, basically, ~21kW of heat. Temperature rise of about 45F (65F-->110F) with both zones calling works out to around 1450CFM or so. The actual flow might be a little more or a little less depending on the measurement uncertainty of the temperature, but should be pretty close to the actual value.

Based on this and the measured static, it looks like it will support 4 tons. I figure that at 1600 CFM, the static should be under 0.25" with both zones calling. If the static ends up being a bit too high for some reason or if there is too much duct noise, the blower speed can be lowered a bit.

So, I can probably support the 4 tons, but I will have to decide that if I really want/need the 4 tons. 3 tons would be cheaper, better summer performance, and some of the 3 ton AHU tend to be smaller than the 4 ton units. Also, the system is on zones and zone 2 is hardly used (bedrooms, only heated/cooled when needed). Because of this, I couldn't even use the 2nd stage much because I don't think that 1 zone would take the full amount of air from a 4 ton unit without a bunch of duct noise and possibly a high static pressure (I figure 0.5"-0.6" based on my numbers, but with measurement uncertainty plus a dirty filter, it could be higher).

Based on my needs, probably the 2-stage, 3 ton unit w/ 15kW of aux/emergency strips should do the job.

[beenthere]

That is the total dP. One end of the tube stuck in just before the filter and the other end stuck into the A/C coil area (A/C is placed on top of the electric furnance). I tried removing the return end of the manometer to see what just the static was, but the difference was too small to notice. So, it looks like the resistance of the return is small compared to the supply. It doesn't surprise me much as the returns are short in distance and fairly large (I have a central return type of setup).

Is just before the filter, between the filter and blower? Thats were it should be put.

Was the other end under the coil, or in the air flow after the coil. Should have been between the coil and furnace.

[KCA]

I put the one end just before the filter as that was the easiest spot for it. I can repeat with it after. There's just a cheap fiberglass job in there now, so I don't think it will change much. The filter is right against the furnance side with no duct in between. I'll see if I can find a place to stick it where it will be after the filter.

On the other end, I tried near the center of the A-coil (where the lineset connects) and also repeated the test going in through the drain line for the coil so it would be in the stream before the coil. That is about the best I could do as the coil sits right on the furnace. The results were the same as far as I could tell. There would be some difference if I had a more precise way to measure it, though.

[KCA]

Just took another measurement with the end placed after the filter. After the filter adds something under 1/16" to the previous numbers (I would guess about 0.05"). The filter is fairly dirty as the basement has been under reno and been working with drywall

[beenthere]

Your supply static reading is false. The static reading has to be taken between the coil and furnace. The areas you read in are all after the coil, so you don't know what supply static the furnace is working against.

Between the filter and furnace is "before" the air filter(for future reference).

Next, are you just looking at the water movement of one side of the manometer, or are you adding the movement of both sides. You must add both sides together. So if it moved 1/4" on one side, it moved 1/4" on the other side, and equals 1/2" of static.

[KCA]

I am taking the supply static before the coil. I put the tube through the condensate drain and pushed it under the A-coil, so it is between the furnace and the coil.

When I said "before" the filter, it is before in terms of the direction of airflow. I repeated with the tube inserted between the filter and the furnance. I also verified the filter dP by then placing 1 tube before the filter and one tube after the filter to see the loss.

I am looking at the net movement (difference between the two sides). That is what matters. Like you side, if the one side moves down say 1/8" and the other up 1/8", you get a total of 1/4".

[beenthere]

Most coils, you can't get a tube/probe to go under it to get to the inlet side of the coil.

[KCA]

I think that I've decided to go with the York 8T Affinity (3 ton) with the AVG air handler (52"). This system has a good SEER and HSPF, will fit the space, and I know the ductwork will support it. This 3 ton unit can pull more BTUs at 17F (and at a higher COP) than many lower units, so the difference between the BTUs of this at 17F and a lower model/brand 4 ton unit at the same temperature is not much.

Even if the ductwork would support 4 ton of flow, most of the 4 ton air handlers would just be too tall for the space. In addition, since it is a zoned systems and normally only 1 zone would be calling, there would been almost no time where I could use the full 4 tons as 1 zone wouldn't carry the flow without having too much noise.

The upfront cost between 3 and 4 tons isn't much, but I think that overall, the 3 ton will be better. At any rate, this will save a ton of money in the winter (get rid of the electric furnance) and should save a few bucks in the summer too compared to the current 10 SEER system.

Thanks for the input. I'll take some pics once it is all installed.

Kent

[leander311]

Sounds like a great choice and good point about low-temp performance. That should make up for the added cost over a "lesser" unit... What SEER is your selection vs. the 10 SEER you have now? Oh yah, and did you say what part of the country you're in? I'm curious... We had some rolling blackouts here in DFW during the 5-day cold snap last week. I kept scratching my head as to why we'd have such a terrible electric demand, when it occured to me a few million tstats had probably just kicked over from HP to backup strip heat!

[KCA]

The Yorkie has a SEER of about 17.5 with this combination. The AC part isn't a big deal as our current bills aren't that bad in the summer. We keep it around 78F and mainly just use the AC to maintain the indoor humidty. The winter is the big one as we are currently electric furnace only (no heat pump, no gas). That thing really makes the meter move. Even being very conservative on the temperature, heat off at night, heat off for much of the day, it is real easy to blow through 3300kwh per month or more. In fact, the 1st January after we moved in (before adding more insulation), the usage was over 4000kwh. If we kept it nice and toasty 24/7, I bet the usage would be 7000kwh or higher.

In our house, there is a separate panel just for the furnace (150A breaker). When the inspector was looking over the house when we moved in, he thought that it probably went to a subpanel, but it was just for the furnace. :)

Our neighbors used to live in Ohio. The house had strip heat when they moved in and the previous winter had seen useage of 10,000kwh per month!. Electricy was much cheaper back then, but they quickly switched to gas before another winter came around.

We live in central VA. The winters aren't too bad. The design temperature for this area is 16F. High temps in the winter are often 30s or 40s.

It doesn't appear that our utility has any rebates going away froim the furnace, but I would think they would love to get that thing off the grid.

Although, it would have been a bit better to get the heat pump last year (better tax credits), I was originally thinking of waiting since the current AC still worked and a new heat pump is fairly expensive. However, with tax returns, a bonus at work, and mild weather coming, it is a good time to make the switch. I believe the current AC coil leaks anyway since a tech had to add 3.5 lbs of R-22 last year as the indoor coil was freezing up (before he came, I verified clean filter/coil). I don't think that he actually repaired any leaks (I wasn't home, so I don't know for sure)..so it would probably need to be recharged/repaired this summer anyway.

I debated other systems. In fact, I spent a couple weeks digging into the specs/dimensions or various units. This should be a good system and will fit the space. The 4 ton would be slightly cheaper to run in the winter, but I could only use the 2nd stage when both zones are calling, and that isn't often. Usually, we only heat/cool the zone we are in, so it isn't often when both are running.

I just have to work through if I want to add anything to it (better filtration, humidification, etc.). I do have to break up some concrete and put down a new pad. The current concrete is cracked and has settled by a couple inches.

[leander311]

4k kwh in January, and dedicated 150a panel...wow...

Yes, on top of the energy, the yearly top-off of R22 would not have been cheap going forward.

Lots of good filtration options out there. Thick pleated filter like an Aprilaire 2200 seems to be the consensus favorite around this site... Keep us updated!

[KCA]

Will do. :)

If I can get someone out this week to remove the R-22, I'll disconnect the old line set and move the condensing unit so that I can break up the old pad and work on putting together a new one.

Electrical is something that will have to be figured out too. The current furnace is fed using SE cable (aluminum) from the 150A disconnect. Seems like all the manufactures now want only copper conductors, so either new copper conductors will have to be run back to the disconnect (and the disconnect will have to be replaced as it has to protect the wires and running copper wires that can support 150A is expensive and not needed). Option 2 would be to use the SE cable to feed a new panel and use that panel to feed the air handler, etc. Option 2 might not fly as subpanels are typically ran off the main panel and require 4 conductors (2 hot, 1 neutral, and 1 ground), SE cable has only 3 (two hots and a bare jacket of wires (used as a neutral)).

I have been redoing everything in the basement, but I have left the drywall off in the areas where wiring/linesets will need to be replaced. Once that is done, I can finish the drywall and move forward.

[leander311]

Interesting point on the SE service. If your new furnace does not have any 120V loads, I don't think you necessarily need to pull new wire or install a subpanel, as the 3rd conductor will not normally carry current and thus serve as your "grounding" or "safety" conductor. A non-fusible disconnect would allow you to get those aluminum conductors terminated and from there run copper to your equipment.

Or if you truly wanted a dedicated sub-panel for possible future use, and for marginal added cost, you could run in parallel to your existing SE a 4th conductor, with which you'd tie the ground bus at the subpanel to the ground bus at your main panel... and if the subpanel will go in at a detached building, you'll need to add a separate ground rod, bonded to said subpanel. I went thru this scenario in detail when a practicing EE PE came down to Austin to help me put in my 60A subpanel for my detached workshop. Of course, consult your AHJ if you really want to be 100% certain.