Z3Dreamer
Thinks s/he gets paid by the post
Thank you.
I am trying to find out if anyone has such a system and if they are happy. Somehow, I have not made it clear what the contractor is proposing.
Options for new HVAC system
- Thread starter Z3Dreamer
- Start date
Thank you.
I am trying to find out if anyone has such a system and if they are happy. Somehow, I have not made it clear what the contractor is proposing.
Music Lover
Give me a museum and I'll fill it. (Picasso) Give me a forum ...
I have a somewhat similar situation to the OP at our cabin. I'm adding a mini-split for better heating and cooling capability. A 40-year old wall AC unit is being removed but only because it's in the same place where the mini-split will be installed and because it's just slightly quieter than a jet engine at takeoff. I'll give it away or repurpose it somewhere.
But I'm leaving the existing baseboard heaters in place. They work and on cold days I can use both systems to quickly heat the cabin.
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- Oct 13, 2010
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Contractors of all types like projects where existing infrastructure isn't touched; they drop-in their package and get out quickly rather than customize to fit every odd thing they encounter with existing installations. But now the owner has two systems to operate and maintain. Contractors also tend to make more money selling the full package than just adding or replacing a component. For these reasons, the recommendation is often "Buy the Complete New System". That might make sense if you want to put the whole thing behind you as quickly as possible, but it's gonna be more expensive. If you find a tech with a truck that knows how to fix stuff, they can often get your current system perforing adequately for a fraction of the cost of the new package.
ncbill
Thinks s/he gets paid by the post
Still makes no sense...both the heat pump & central A/C would need their own separate air handler & would both be connected to the same ductwork.
Original central A/C-only unit should simply be replaced with a heat pump & new coil...new air handler will contain the backup gas furnace.
38Chevy454
Thinks s/he gets paid by the post
Maybe the confusion is the basics of operation of A/C and heat pump. In A/C mode, the compressor runs and the high pressure heated refrigerant goes through the outside unit, which is the condenser, then goes through the inside evaporator coil where it becomes low pressure cold refrigerant. The air blowing through the evaporator gets cold and distributed through your ducting. The outside condenser has hot air blowing out because it removed the heat from the compressed refrigerant.
In heat pump mode, the compressor runs and the high pressure heated refrigerant goes through the inside (now acting as condenser) coil, then goes through the condenser outside where it becomes low pressure cold refrigerant. The air blowing through the outside unit (now acting as the evaporator) gets cold. The inside coil has hot air blowing out because it removed the heat from the compressed refrigerant; and is distributed through your ducting.
So there is no such thing as having separate A/C coil inside and a heat pump condenser inside. They are one in the same piece, just depending on which way the refrigerant flows from the compressor. Heat pump mode is just switching the condenser and evaporator functions from how they are in A/C mode. You also only have one outside compressor unit.
Now when it is cold outside around freezing, give or take, the efficiency of heat pump drops because it is harder to use cold outside air to make extra cold air going through the (fuinctioining as) evaporator outside. So the supplemental heat function where you have in OP's case a natural gas fired traditional type furnace. In my case since no nat gas available, I have propane. You can also have big electric resistance coils to provide supplemental heat. But elec coils are the most costly way to heat.
Hope that helps, as I sensed there is confusion on the number of pieces in the system.
In heat pump mode, the compressor runs and the high pressure heated refrigerant goes through the inside (now acting as condenser) coil, then goes through the condenser outside where it becomes low pressure cold refrigerant. The air blowing through the outside unit (now acting as the evaporator) gets cold. The inside coil has hot air blowing out because it removed the heat from the compressed refrigerant; and is distributed through your ducting.
So there is no such thing as having separate A/C coil inside and a heat pump condenser inside. They are one in the same piece, just depending on which way the refrigerant flows from the compressor. Heat pump mode is just switching the condenser and evaporator functions from how they are in A/C mode. You also only have one outside compressor unit.
Now when it is cold outside around freezing, give or take, the efficiency of heat pump drops because it is harder to use cold outside air to make extra cold air going through the (fuinctioining as) evaporator outside. So the supplemental heat function where you have in OP's case a natural gas fired traditional type furnace. In my case since no nat gas available, I have propane. You can also have big electric resistance coils to provide supplemental heat. But elec coils are the most costly way to heat.
Hope that helps, as I sensed there is confusion on the number of pieces in the system.
FedRetired50
Recycles dryer sheets
I can tell you my actual experience with replacing 2 whole-house systems 4 years ago. I'm at 750 feet in northern MD so I'd bet my temps are similar to yours. I regularly see teens in the winter, single digits multiple times, and at least once it will hit negative single digits, once going to -10 F.
My downstairs is open-air so I ripped out the 12 SEER A/C, replaced it with a 31 SEER 12k btu mini-split HP. Kept the propane furnace for backup.
Upstairs I replaced the 12 SEER HP with a 16 SEER HP and new air handler. The contractor, a friend of mine, said that once you get above 16 SEER the added complexity means they break down more often so you never get to a break even point.
I also have a wood stove that gives me 75% of my total heating, but shoulder seasons over the last few years I've relied mostly on the heat pumps. My electric bill has *dropped* from an average of $200/mo over a 12-month period to $175. I also will use the mini to help heat up the downstairs when I get home and the fire was low. Where my upstairs unit used to run 24/7 during the hottest days, now it cycles 50/50. Same for even very cold days. Both units are rated to provide a high % of heat output even into negative digits. Both units blow *hot* air, not tepid like my old systems and every other one I've felt in the past. The mini doesn't even have a resistive backup. As for that propane backup, I've never needed it. I've used it a half-dozen times to help warm up the house when it is really cold and I've come home to a dead fire (and had the heat pumps dialed back), but it has never been a requirement. In winter I do keep it on and set below the heat pumps JIC.
My downstairs is open-air so I ripped out the 12 SEER A/C, replaced it with a 31 SEER 12k btu mini-split HP. Kept the propane furnace for backup.
Upstairs I replaced the 12 SEER HP with a 16 SEER HP and new air handler. The contractor, a friend of mine, said that once you get above 16 SEER the added complexity means they break down more often so you never get to a break even point.
I also have a wood stove that gives me 75% of my total heating, but shoulder seasons over the last few years I've relied mostly on the heat pumps. My electric bill has *dropped* from an average of $200/mo over a 12-month period to $175. I also will use the mini to help heat up the downstairs when I get home and the fire was low. Where my upstairs unit used to run 24/7 during the hottest days, now it cycles 50/50. Same for even very cold days. Both units are rated to provide a high % of heat output even into negative digits. Both units blow *hot* air, not tepid like my old systems and every other one I've felt in the past. The mini doesn't even have a resistive backup. As for that propane backup, I've never needed it. I've used it a half-dozen times to help warm up the house when it is really cold and I've come home to a dead fire (and had the heat pumps dialed back), but it has never been a requirement. In winter I do keep it on and set below the heat pumps JIC.
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Jeb-NY
Recycles dryer sheets
I can add a little to the conversation, I had your system 2 - heat pump that heats and cools with an LP furnace as backup for very cold weather. Mine was 15 years old. I asked a friend that has his own heating/AC business, in a different state so doesn't have any dollar interest, how long I should expect it to last. He said somewhere between a week and 10 years. He also said if I wanted anything other than off the shelf it was better to replace while my old system was running if I had the money, since the better units had a delay 1-6 months depending on brand and what you wanted. I had a new furnace and heat pump put in. To get the SEER 19 I wanted I had to replace the whole system. I have not went through the Summer yet but I can tell you my old system burned about 100 Gal of LP per Winter and according to the fancy thermostat that came with the system I burned about 30 gal this past Winter al the rest of the heat by heat pump. I could have went even more efficient but the extra cost would not have had a pay back in my heat zone before it needed replacing, the heating contractor said for our area above SEER 19 was strictly for bragging rights.
A few things to check. Lots of good articles on the internet. Talk to more than one contractor, I spoke to 3 and eliminated the company I had been using after they changed owners and service went way down hill. If they can't explain what you need so you understand change contractors. I had a variable speed compressor heat pump put in I believe it has 5 levels, more efficient and quieter accept in very hot or cold weather. I also got the multi speed blower fan, if it doesn't need fast it runs so slow you can't hear it and doesn't blow as much air when not needed. If your house can use a split system they are the most efficient, it would not work the way our house is setup.
By the way we live in NorthEast TN in the edge of the mountains. My system switches over to LP at around 25 degrees. Where you live and what you can afford up front verses spread out will make a difference on what system is best for you.
A few things to check. Lots of good articles on the internet. Talk to more than one contractor, I spoke to 3 and eliminated the company I had been using after they changed owners and service went way down hill. If they can't explain what you need so you understand change contractors. I had a variable speed compressor heat pump put in I believe it has 5 levels, more efficient and quieter accept in very hot or cold weather. I also got the multi speed blower fan, if it doesn't need fast it runs so slow you can't hear it and doesn't blow as much air when not needed. If your house can use a split system they are the most efficient, it would not work the way our house is setup.
By the way we live in NorthEast TN in the edge of the mountains. My system switches over to LP at around 25 degrees. Where you live and what you can afford up front verses spread out will make a difference on what system is best for you.
Retired Expat
Full time employment: Posting here.
For the renovation of our home we did mini splits throughout. Living room/great room & master bed all got heating/cooling Inverter heat pumps as they are used regularly. Guest rooms or rarely used areas just standard heat pumps. We like the individual controls and not conditioning rooms we aren’t using. As our utility offers a multi rate plan we can shut down for the 4 hours a day they charge a hefty premium for use over the low rate period.
Works great and was cheaper to install than redoing ductwork to add zones and replace all the equipment.
Works great and was cheaper to install than redoing ductwork to add zones and replace all the equipment.
Safe Harbour
Recycles dryer sheets
The latest HP's are good to -14F
My SIL in Boston just replaced an old gas furnace with a HP. The HP is good to -13F. This winter they had one of the coldest stretches in years, a few days at about -10F and we're perfectly comfortable. Also even below -13F the heat pump still runs and still heats, so reduces your auxiliary heat bill (dual fuel or electric strip), it's just that it needs a boost to keep up with temperature delta it must raise the incoming air. So thinking HP's are only good to 35˚F or even 0F is a few generations old. My SIL didn't even out in an auxiliary heat source.
Also modern variable speed HP's are more comfortable than a furnace. A furnace blasts very warm air for short times to warm the house. A modern variable speed HP runs at a slow speed continuously. So slow you don't get hit with moving air. This is a misconception by furnace proponents who say they don't like the cold feeling air from a HP. They assume a low temp blast of air like would come from a HP running short times like a furnace does (older fixed speed or multispeed HP units).
The unit they put in was a Mitsubishi. The cool thing about the Mitsubishi is that for internal units you can mix both traditional ducted units and/or add ductless (mini-split) units. Obviously it can also be only one type too.
I find it hard to understand why you would do anything other than a modern HP today. One more thought, always get three proposals for a new system. I have seen the estimates for exactly the same equipment vary by more than 30%. It will also help you decide what equipment you should really get.
My SIL in Boston just replaced an old gas furnace with a HP. The HP is good to -13F. This winter they had one of the coldest stretches in years, a few days at about -10F and we're perfectly comfortable. Also even below -13F the heat pump still runs and still heats, so reduces your auxiliary heat bill (dual fuel or electric strip), it's just that it needs a boost to keep up with temperature delta it must raise the incoming air. So thinking HP's are only good to 35˚F or even 0F is a few generations old. My SIL didn't even out in an auxiliary heat source.
Also modern variable speed HP's are more comfortable than a furnace. A furnace blasts very warm air for short times to warm the house. A modern variable speed HP runs at a slow speed continuously. So slow you don't get hit with moving air. This is a misconception by furnace proponents who say they don't like the cold feeling air from a HP. They assume a low temp blast of air like would come from a HP running short times like a furnace does (older fixed speed or multispeed HP units).
The unit they put in was a Mitsubishi. The cool thing about the Mitsubishi is that for internal units you can mix both traditional ducted units and/or add ductless (mini-split) units. Obviously it can also be only one type too.
I find it hard to understand why you would do anything other than a modern HP today. One more thought, always get three proposals for a new system. I have seen the estimates for exactly the same equipment vary by more than 30%. It will also help you decide what equipment you should really get.
Z3Dreamer
Thinks s/he gets paid by the post
OP. Sorry for the confusion but the contractor's proposal said I would have a new furnace and a new heat pump AND HE WOULD LEAVE THE EXISTING AIR CONDITIONING UNIT IN PLACE. I spoke to him and he clarified that I would ONLY HAVE A NEW FURNACE AND A NEW HEAT PUMP. HE WOULD REMOVE, NOT LEAVE THE AIR CONDITIONER.
They are good contractors but their writing skills are not the best. Young puppy...
Anyhow, the issue is do I go cheap and just replace the stuff inside the house (furnace, coil, etc.) or do I also replace the existing 14 year old air conditioner with a heat pump? We live in the NC mountains so air conditioners last a long time up here. They don't see much use.
They are good contractors but their writing skills are not the best. Young puppy...
Anyhow, the issue is do I go cheap and just replace the stuff inside the house (furnace, coil, etc.) or do I also replace the existing 14 year old air conditioner with a heat pump? We live in the NC mountains so air conditioners last a long time up here. They don't see much use.
Jeb-NY
Recycles dryer sheets
As I implied in my message a HP/AC unit is good for 15-25 years depend if you want to replace in an emergency situation or pick and chose when and with what. I figured I had the money so why wait and maybe save a little on electric and LP. If money is tight do piecemeal and hope for the best.
Z3Dreamer
Thinks s/he gets paid by the post
I agree. Have asked contractor for a proposal that only includes replacing coil and furnace. No HP/AC. Just to know the difference. And for the amount that this whole system is going to cost, I am getting a proposal from another contractor.
I am on the other side of the ridge from you at 3,850 feet. So, you know how much we use the A/C (about 2 months) and how cold it is in the winter. If it works well for you, that is one factor.
REWahoo
Give me a museum and I'll fill it. (Picasso) Give
Good to see the clarification. I could not make sense of the original proposal.
ncbill
Thinks s/he gets paid by the post
I'm pretty cheap but would replace both interior & exterior units at nearly 15 years old.
So you'd have a new heat pump outside & a new air handler w/ the gas furnace built into it inside.
What do you pay for electricity?
I know some setups in the mountains also add electric heat strips since they can get cheap TVA electricity which can be used in addition to expensive propane for auxiliary/backup heating.
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FedRetired50
Recycles dryer sheets
Agree, at 15 years old, tech has come a long way since then. Go with HP so you have the option to use it for heat, and the furnace.
What are your typical winter temps?
What are your typical winter temps?
In one of our properties I had a 20 year old Lennox 5 ton AC with a gas furnace. The indoor coil was corroding out so I bought a new 5 ton HP and matching coil. I had repaired that AC a few times (typical capacitor issue/fan motor) so I thought it was time. Probably could have just done the indoor coil. It cost me <4k for the new coil and HP, and some new install parts.
The 16 SEER HP I installed 9 years ago is showing signs of a minor issue. If I called an HVAC tech, they would evacuate the system, do a leak vacuum test, recharge and then address the real issue. OR more likely they would claim its time for a new unit. They would claim it does not hold adequate vacuum, and with the ice up, it must be low on R410A!
So, I ordered a defrost temp sensor from Supply House for $6.12 and fixed it myself. Its called trouble shooting, something techs do not want to do. They follow a protocol to be able to prove and upsell replacements. In this case, the defrost worked if I forced it with manual override, so I knew the reversing valve was working, the duct temps were spot on (not likely low on R410A), and the defrost control worked on override, but the sensor would not let it run. Also, you might have to know that these little sensors fail over time quite often.....
The 16 SEER HP I installed 9 years ago is showing signs of a minor issue. If I called an HVAC tech, they would evacuate the system, do a leak vacuum test, recharge and then address the real issue. OR more likely they would claim its time for a new unit. They would claim it does not hold adequate vacuum, and with the ice up, it must be low on R410A!
So, I ordered a defrost temp sensor from Supply House for $6.12 and fixed it myself. Its called trouble shooting, something techs do not want to do. They follow a protocol to be able to prove and upsell replacements. In this case, the defrost worked if I forced it with manual override, so I knew the reversing valve was working, the duct temps were spot on (not likely low on R410A), and the defrost control worked on override, but the sensor would not let it run. Also, you might have to know that these little sensors fail over time quite often.....
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