one large heatpump vs two smaller ones

[pendulum]

Thanks in advance. What is more electrically efficient to operate? a larger (5ton) zoned heat pump system or two (2 and 3 ton) heatpumps each providing their individual zones?

I am starting the process of getting a new heatpump for my home. The first contractor to come out suggested splitting my current unit into two units for up and down stairs rather than replacing the one unit? I wasn't expecting that, but looking at the ducting it would be easy for him to add a second unit with minimal ductwork. It would offer redundancy if there was a christmas eve/ 3am heatpump issue in the future.

The second quote recommended a 5 ton replacement and new zone system.

Would two smaller units act similar to a 2 stage unit? Two units with out a zone system or one larger system with a zone system? I would appreciate any thoughts.

[super_tech_1]

use the five ton zone system. Less maintenace. less repairs. I would also take this oppertunity to get a two stage with variable speed air handler

[beenthere]

2 smaller ones. As you said, the redundency is good to have on evenings and weekends to avoid after hours or holiday charges.

[t527ed]

smaller units are more efficient than the same model 5 ton unit.

plus side you have one working if one fails.

down side you have 2 systems to maintain.

[DanW13]

Years ago most homes or all homes did not have zoning avaiable in the homes like they do today and that's one of the main reasons a majority of 2 story homes with a large foot print would have 2 furnace's & AC units one for each floor. In today's market zoning is available to anyone who can afford to have it installed using a single funrace and AC/HP for the same size homes that 20 or 30 yrs ago would have 2 smaller units giving the home owner double the equipment to maintain, and double the cost of installing. I would suppect that as long as you have a rebutable contractor/Installer who knows zoning and runs the proper manual D,J for your home to make sure the equipment is properly sized your best bet would be to go with 1 furnace/HP for your home and zone it= less maintience,Installation cost, and I believe better control and better comfort. When everyone is up stair sleeping you can heat the bedrooms, when everyone is up and about you do not have to heat/cool that part of home the same as you do the part of the house where you do most of your living, and if you really think about it it basically have 2 systems in one with zoning.

[beenthere]

Years ago most homes or all homes did not have zoning avaiable in the homes like they do today and that's one of the main reasons a majority of 2 story homes with a large foot print would have 2 furnace's & AC units one for each floor. In today's market zoning is available to anyone who can afford to have it installed using a single funrace and AC/HP for the same size homes that 20 or 30 yrs ago would have 2 smaller units giving the home owner double the equipment to maintain, and double the cost of installing. I would suppect that as long as you have a rebutable contractor/Installer who knows zoning and runs the proper manual D,J for your home to make sure the equipment is properly sized your best bet would be to go with 1 furnace/HP for your home and zone it= less maintience,Installation cost, and I believe better control and better comfort. When everyone is up stair sleeping you can heat the bedrooms, when everyone is up and about you do not have to heat/cool that part of home the same as you do the part of the house where you do most of your living, and if you really think about it it basically have 2 systems in one with zoning.

He most likely doesn't have duct work sized for zoning.

For zoning it would be sized to handle 125% of what a single zone system is sized to. Since it wasn't zoned originall, do you really think his duct is proper sized for zoning?

Its more likely that his existing duct would work better for 2 smaller units, then a zoned single unit.

And will provide less air flow issues then using one unit. But, its up to him how much trouble he wants.

[pendulum]

He most likely doesn't have duct work sized for zoning.

For zoning it would be sized to handle 125% of what a single zone system is sized to. Since it wasn't zoned originall, do you really think his duct is proper sized for zoning?

Actually my house was originally set up for zoning with oversized ducts and returns through out. it has an old 6 zone zonex system, it has given very unreliable results for the 3 years i have owned the house, problems with Las sensor, problems navigating multiple inputs for heat/cold and anybodies guess who wins, etc. (it has been serviced multiple times)

My house has 6 16x20 inch returns (one for each zone), with a guestimate 20x20 box at each return. The air handler is in the crawl space and supplies the whole house currently and when the zone system is working, all of the house is comfortable.

The suggested second unit would tie into the current systems through upstairs/downstairs ducting returns which is ? guestimate 20x20 each and would be located in craw space.

I have seen multiple responses each way. So let me clarify.

As a hvac professional, would you want to operate two smaller systems in your house or one larger zone system (given that you could service them your self, etc)

Im assuming that if only two smaller condensor units are running it will use less electricity than one larger unit, but then again, you are running multiple airhandlers, so it may be a wash?

Thanks again.

[beenthere]

Myself.

I would prefer 2 units.

1. The redundency, so I wouldn't have to fix one in the middle of the night if one failed.
2. I wouldn't have one large unit running to do only 50% of the house or less. (even 2 stage systems are at a min of 60% capacity in first stage, so if one zone is only a 2 ton load, your still running a 3 ton capacity, if its a 5 ton unit for the whole house)
3. With 2 units, you can size much closer to the actual needs of the house. (with one unit, if the house only needs 4.5 tons, you end up with a 5 ton unit. With 2 units you can install a 2 ton and a 2.5 ton to have only 4.5 tons.)


A 2 ton and a 2.5 ton system still uses less electric then 1 5 ton unit, even allowing for the second air handler.(takes less HP to move the 1800CFM with 2 air handlers, then 2000CFM of a single 5 ton air handler.

[beachtech]

Thanks in advance. What is more electrically efficient to operate? a larger (5ton) zoned heat pump system or two (2 and 3 ton) heatpumps each providing their individual zones?

I am starting the process of getting a new heatpump for my home. The first contractor to come out suggested splitting my current unit into two units for up and down stairs rather than replacing the one unit? I wasn't expecting that, but looking at the ducting it would be easy for him to add a second unit with minimal ductwork. It would offer redundancy if there was a christmas eve/ 3am heatpump issue in the future.

The second quote recommended a 5 ton replacement and new zone system.

Would two smaller units act similar to a 2 stage unit? Two units with out a zone system or one larger system with a zone system? I would appreciate any thoughts.

two smaller systems will over all be more efficient

better tempurature control, one side of the home may not need the AC as the other will. up or down. instead of firing up that big 5ton'er utilizing a smaller 2-3ton unit that draws less power will hande the job.

and all the reasons beenthere stated! especially the part where is one breaks down you still have another to run to lol

[beachtech]

Years ago most homes or all homes did not have zoning avaiable in the homes like they do today and that's one of the main reasons a majority of 2 story homes with a large foot print would have 2 furnace's & AC units one for each floor. In today's market zoning is available to anyone who can afford to have it installed using a single funrace and AC/HP for the same size homes that 20 or 30 yrs ago would have 2 smaller units giving the home owner double the equipment to maintain, and double the cost of installing. I would suppect that as long as you have a rebutable contractor/Installer who knows zoning and runs the proper manual D,J for your home to make sure the equipment is properly sized your best bet would be to go with 1 furnace/HP for your home and zone it= less maintience,Installation cost, and I believe better control and better comfort. When everyone is up stair sleeping you can heat the bedrooms, when everyone is up and about you do not have to heat/cool that part of home the same as you do the part of the house where you do most of your living, and if you really think about it it basically have 2 systems in one with zoning.

whatever it is that you do, go do it!!!

because it is not HVAC

[DanW13]

Beech Tech,
Thanks for the idea, I never claimed to be a HVAC specialist as I was just giving my opinion as a HO !!!! If you don't like what I post please do not read and keep you thoughts to yourself, Evidently you do not read the rules of this forum !!!!

[catmanacman]

i would go with 2 systems If the upstairs and downstairs are the same footage then the downstairs will probably need less ac

[lentz]

We always recommend two units for two stories. Much better confort and a little less cost in operation. Make sure they are sized right and the duct system is sized correctly also. Two 20 X 20 is a little small for 5 tons. Need about another 100 sq. inches of filter area. Now would be a good time to seal all the joints and add insulation if nessary.

Good Luck