Home HVAC Advice Needed

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Either your figures are wrong, or your house was built without insulation or something crazy. 10 tons for a 2,300 sq ft house is completely insane. I'm in a 2,400 square foot house in MD and we have 3.5 tons AC, totally adequate. 80,000 BTU (~6.5 "tons") furnace which runs 95% of the time in the low stage of 52,000 BTU.

jeff
Could the requirements for a heat pump be different? The backup heat is electric booster coils. No furnace.

House is a well built in 2000. The two units were installed around 2015 or 2016.
 

The Critic

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I know a little about HVAC.

Here's what I would do (and have done in your situation)-

Install a single, "mini-split" multi-port heat pump condensing unit and two indoor ducted, multi-position air handling units inside. One for downstairs, one for upstairs. The most idiotic thing to come about in the last 25 years is the use of zone damper systems in residential construction where a single system serves multiple floors. They simply do not work. To equate that to your line of work, Mr. Critic - that is the same as putting 4 different wheels and tires on a single vehicle because the owner wants to drive over turf/pasture (wide turf tractor wheel/tire), go rock crawling (18" x 12" wide wheel with a 35" x 12.50 x 18 Patagonia tire; run highway speeds daily (20" x 9" wheel with Michelin LTX M/S tire) and an 18" steelie with a snow tire because the owner goes to the mountains on the weekends in January/February.

What kind of sense does that make? About the same as a single unit serving two-three floors.....


My suggestion - sounds like you need a 4-ton multi-port condensing unit and two indoor units, probably a 3 and a 2-ton. Brand? Daikin.

Your climate will support a heat pump very well. I suspect your power bill will reduce enough to pay the PREMIUM this system will cost over the same old chit that the contractors are suggesting to replace the existing.

Feel free to PM me if needed.



Edited.....



HOLY CRAP at those electric rates..... BTW, you won't need gas with my suggestion...


Also, I wrote a song about all this-

Will send you a PM this week.

In summary, the temperature differences between the first/second floor are an area of improvement, but isn't a "critical issue" in my book.

Heat pump's are out of the equation due to the electricity rates.
 
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Just to add some context to the conversation:

Gas bill from the coldest month of last winter:

View attachment 104653
Base electricity rates:

View attachment 104654
At those gas rates maybe it wouldn't be crazy to buy a high efficiency furnace...would be interesting to calculate a break-even point for an 80% vs a 95% or so. That bill is quite a bit higher than my largest one last winter living in the great white north...over $2.00 per therm is crazy.
 
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I think @EA82 and @CDX825 are HVAC professionals - any thoughts?

Thank you.
Without seeing it I can only speculate whats going on. Being a two story house you will always have a difference in temperature between floors. But it also seems like you have a duct work issue which is very common in residential hvac. Is it a lack of supply air or a lack of return air? I'm betting return air. You really need a return in every room in the house except the bathroom on the second floor. All your heat in the summer ends up on the second floor so anything you can do to pull it out and condition it helps a lot. I also like to see high wall mounted returns on the second floor because you pull the heat off the ceiling that way. Also helps to pull the heat off the second floor in the winter and push it back down to the first floor. They had mentioned you have a return at the top of your stairs. I don't see a problem with that and actually prefer to see a big return either there or in the hallway to catch any heat rising from the first floor. Supply air could also be an issue especially being that they have to run farther on the second floor. You can sometimes get more air flow to the second floor by just adjusting the dampers on the individual runs if they have them. Close ones down on the first floor just a tad that get really good flow and it helps push it to the rest.

As far as equipment goes I would go with a 95 percent efficient furnace. Single stage or even two stage with ecm blower which is standard on all of them now. Going from a 80 percent to 95 percent furnace would save you a lot on your gas bill. Also being that the new furnace would have an ecm blower motor you could run the fan all the time to keep the temperature more balanced in your house. The ecm motor doesn't use much power to just circulate the air. I would say stick with a single stage air conditioner because even a 14 seer ac is going to be way more efficient than your current unit. Generally you can go a seer or two higher in single stage if you are looking for more efficiency.
 

The Critic

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Without seeing it I can only speculate whats going on. Being a two story house you will always have a difference in temperature between floors. But it also seems like you have a duct work issue which is very common in residential hvac. Is it a lack of supply air or a lack of return air? I'm betting return air. You really need a return in every room in the house except the bathroom on the second floor. All your heat in the summer ends up on the second floor so anything you can do to pull it out and condition it helps a lot. I also like to see high wall mounted returns on the second floor because you pull the heat off the ceiling that way. Also helps to pull the heat off the second floor in the winter and push it back down to the first floor. They had mentioned you have a return at the top of your stairs. I don't see a problem with that and actually prefer to see a big return either there or in the hallway to catch any heat rising from the first floor. Supply air could also be an issue especially being that they have to run farther on the second floor. You can sometimes get more air flow to the second floor by just adjusting the dampers on the individual runs if they have them. Close ones down on the first floor just a tad that get really good flow and it helps push it to the rest.

As far as equipment goes I would go with a 95 percent efficient furnace. Single stage or even two stage with ecm blower which is standard on all of them now. Going from a 80 percent to 95 percent furnace would save you a lot on your gas bill. Also being that the new furnace would have an ecm blower motor you could run the fan all the time to keep the temperature more balanced in your house. The ecm motor doesn't use much power to just circulate the air. I would say stick with a single stage air conditioner because even a 14 seer ac is going to be way more efficient than your current unit. Generally you can go a seer or two higher in single stage if you are looking for more efficiency.
Thank you.

This is the only return in the entire house:

6D173E84-D2D0-49B9-9F23-06F1E4F123EE.jpeg

I am not sure of the duct size, but it takes a 20x25x1 filter.

I was also advised by a tech that installing a two-stage system into a home where ductwork is undersized can be extremely problematic. Supposedly this can cause insufficient airflow to the second story (presumably during the 1st stage) and also reduce the lifespan of the units. Is there any truth to this?

Lastly, if I choose to install a 2-stage a/c and 2-stage furnace (with variable blower, such as a Rheem R96V), is there any benefit to doing this if I do not install the air scoop and damper?
 
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Will send you a PM this week.

In summary, the temperature differences between the first/second floor are an area of improvement, but isn't a "critical issue" in my book.

Heat pump's are out of the equation due to the electricity rates.

The inverter-controlled compressors in mini-split heat pump systems are EXTREMELY efficient. The inverter systems are just THAT much better than the plain-old residential HVAC systems. I promise you.

I understand the electricity rates. But you're main use is in summer. 40 degrees outdoor temps in the winter are prime temps for heat pumps. Plus, you won't be spending money on natural gas to heat. Trust me, California is about to make natural gas MUCH MORE EXPENSIVE.

PM me anytime.... I am glad to help.
 
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Critic, another issue with you going with a traditional gas furnace (90%+) and air conditioner is I feel your cooling load is greater than your heating load. This means your air handler/furnace will be grossly oversized for your heating needs. You will NEVER see any benefit from the 90%+ AFUE furnace. It will short cycle and will just be too much heat for your needs.

Again, broken record, but there is where the inverter-driven mini-split style heat pumps shine. They basically operate "all day long" (continuously) and 'chase' the setpoint. This provides ultimate comfort and operates the equipment at the minimum speed needed. This sounds counter-intuitive, but is actually the opposite. Instead of cooling for 12-15 minutes and slamming off, the unit cools just enough to NOT satisfy the thermostat and just keeps running, preventing the space from absorbing heat gain from the objects/structure and then needing to bring the system on at full bore again for 12-15 minutes.
 

FZ1

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He has some valid points, but it ultimately depends on customer needs and budget. Mine is 25 years old and to me, is the equivalent of a 200K mile old car. I need reliability with minimal hassle, so I am electing to replace.


That is sorta what one contractor suggested - an air scoop to divert more air flow to the 2nd story plus a dampener door for the winter months. I'm trying to avoid a true "zone setup" since the ductwork is already a bit undersized for the house.


HVAC performance to the second floor could definitely be improved, but it is not dire enough to justify spending $20K for a second system. If I can make the existing setup a bit better for a minor additional cost, that would make more financial sense.


Temperature distribution throughout the house is currently an issue. The situation isn't dire, but if it can be improved for a small amount of money, then I will give it some serious consideration. Replacing windows is probably a $50K+ affair that I'm hoping to avoid, at least for now. For some of the systems, a 10-yr extended labor warranty is only $700 and I am hoping to be out of this house before that expires.



Original windows, hoping to avoid replacement for now. This is a very large expense. Current system does not have damper doors.

4-ton A/C unit. Supposedly real R22 was used. I paid $400 for each top-off.


All 3 quotes have included "HERS testing" and re-sealing ducts as-needed. Is this the same thing?

I do plan to improve the attic insulation at some point.
Curious as to the origin of the freon leak and cost to repair / replace the leaking part vs. new system
 
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JC1

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Critic,

Maybe you should get a thermal camera to have a look into the walls in those rooms to see if there are any major issues with the insulation etc. Even if you upgrade the HVAC those problems may still exist. Even if you don't fix those issues right away at least you know what's going on behind the walls.

I'm in process of fixing the crappy insulation in my 2 car garage. I've added extra rigid styrofoam and roxul where I could and added cellulose into the walls where no insulation existed. I already see a big difference in the temps in the bedroom above the garage.
 

The Critic

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Critic,

Maybe you should get a thermal camera to have a look into the walls in those rooms to see if there are any major issues with the insulation etc. Even if you upgrade the HVAC those problems may still exist. Even if you don't fix those issues right away at least you know what's going on behind the walls.

I'm in process of fixing the crappy insulation in my 2 car garage. I've added extra rigid styrofoam and roxul where I could and added cellulose into the walls where no insulation existed. I already see a big difference in the temps in the bedroom above the garage.
I do plan to improve the insulation, but that will be further down the road. One of the upstairs rooms resides over the garage and the heat from the garage can definitely be felt.
 
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The Critic

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Just wanted to share some bids. All of them are for 4-ton units and include HERS testing and local permits.

Contractor A:
1) Lennox ML14/ML180: $10,894
2) Rheem RA16/R95T: $12,342
3) Rheem RA17/R96V, Econet Thermostat: $15,928 (eligible for the $450 tax credit)

(Lennox combo is 14 SEER/80% eff single-stage. RA16/R95T is 16 SEER/95% eff single-stage. RA17/R96V is 16 SEER/95% eff two-stage with variable speed blower. Rheem also offers a 10-yr extended labor warranty for an extra $650.)

Contractor B (current company I use for repair):
1) American Standard Silver 16/Bryant Legacy 915S furnace: $18,040
(16 SEER single-stage a/c and 95% efficiency single-stage furnace)

Contractor C:
1) Carrier Performance 16 (24APB6)/Comfort 95 (59SC5): $11,5000 to $12,200
(16 SEER single-stage a/c and 95% efficiency single-stage furnace)

Contractor D:
1) Trane XR16/S8X2: $18,400
(16 SEER single-stage A/C and 95% efficiency two-stage furnace with ECM blower. However, this is the only quote that includes installing an air grabber "to bring more balance to the system air flow.")

Seems like there is a significant savings to go from a 80% to 95% efficiency furnance:

1655920532104.jpg
 
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FZ1

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Looks like it's the Lennox. Check out the price increase to go from 14 to 16 on the Lennox. Much cheaper to determine if the leak is fixable and the cost to do so. PS a 2 stage furnace fan should not be that much more.
 
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Natural gas is going way up in price. You'd be foolish to get an 80% furnace. Why not get a heatpump? If you need aux heating, at least get a 96% furnace.

As for the second floor, I'd put a minisplit up there to supplement the existing a/c.
 
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To me option 2 for contractor A, or contractor C seem to make the most sense, whichever equipment you like more.

But yeah I just paid $7800 to have a single 3-ton a/c added to my home, just by itself. Prices seem to be all over the place.
 
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The Option with the scoop directing air flow is the safest and the most cost efficient IMO Critic, also your new furnace will be able to move more air than the old 97 one so that in itself will make a difference.
I'm not a fan of one AC system for both floors, there always seem to be airflow and hot/cold issues.
We are currently dealing with a lot of airflow issues on brand new 3 story town houses that the builders decide to put one unit for 3 floors with inaccessible duct work.
Out of the options you gave i vote for the 16 seer carrier unit, Contractor C, the price looks reasonable also.
 
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As far as equipment goes I would go with a 95 percent efficient furnace. Single stage or even two stage with ecm blower which is standard on all of them now. Going from a 80 percent to 95 percent furnace would save you a lot on your gas bill.
I was under the impression that in warm climates with less furnace use, the payback for higher efficiency furnaces did not add up??
 
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