Advice please (mini-split vs zone for media room)?

[Reinyn]

I have a bonus room over the garage that is too hot most of the time. I have PCs as well as a video projector in the room so it has a significant extra heat load.

The main house is 1960 sq ft and the bonus room is about 440.

My current HVAC equipment is a Goodman 3 ton 16 seer dual stage heatpump and a 80% furnace with a variable speed blower. Currently there is one Honeywell 8000 t-stat on the ground floor.

The bonus room has two regular sized registers and a return.

I have spoken with two HVAC contractors and one is pushing zoning while the other is pushing mini-split. Apparently the zoning setup is relatively straightforward (one main trunk to the 1st floor and a separate trunk for the bonus room)

The zoning cost is 50% - 66% the cost of the mini-split.

I would like to save the money, but I also want something that works well. At first I was in favor of the mini-split since it would be a independent system, but now I think using my existing equipment with the zoned system might be a better way to go.

I'm just looking for a couple more expert opinions
Thanks,
-Reinyn

[SoFlaDave]

If its hot with the air conditioning now it won't be any different with a zoning system when the rest of the house is calling for cooling as well. Also, with such a huge disparity between the size of the zones (assuming 2 total zones) any time the small zone is calling for cooling you're gong to be forcing about almost 2 tons of air into a space that only needs maybe 1/2 a ton. That excess either needs to be bypassed or dumped into the other zone.

Most of us here agree that adding a zoning system to existing ducts is a crap shoot at best and the system really needs to be designed around the zoning system to function reliably.

[Reinyn]

If its hot with the air conditioning now it won't be any different with a zoning system when the rest of the house is calling for cooling as well.

Hi Dave,

Part of my problem is that the bonus room exterior gets a lot of sun relative to the rest of the house. The house is well insulated energy-star construction and the air conditioning doesn't run that often. If it is running the bonus room isn't too bad (but still not hitting the tstat number set downstairs). I can't keep it running just for the bonus room or the rest of the house gets too cold.

I definitely agree about 2 tons of AC being too much for the space. I would at least have extra registers added and then maybe dump some of the output back to the main system.

If money was not a factor I would do the mini-split. I'm waiting on a quote for a 110V mini-split system that will hopefully knock some off the price relative to the 220V system.

Thank you,
-Reinyn

[motoguy128]

The zoning is a good solution if you have good access for adding adequately sized ductwork. But, us the existing system oversized enough to handle the extra load? I assume you're in a hotter climate since you have a 80% furnace with a higher SEER heat pump. A load calculation can be done. IF you have enough capacity, then I'd go with zoning. Done right, it can even make the rest of the house more comfortable since run times will be even longer than they are now.

However, if this small room is used as a media room and will be occupied by a large number of people and if the existing system doesn't have a lot of extra capacity, then go mini split.

THe decision will mostly come down to load calculations. Keep in mind that once you add the ductwork, future repalcement costs will be lower. If you go with a 2nd system, in the future, you'll have to repalce 2 systems.

What is the occupancy of that media room?

Cna you add a 3rd zone that would seperate the bedrooms from teh bonus room and the rest of the house. IF you are marginal on capacity, a zone systme cna be undersized a little if the zones seperate rooms that are not typcially occupied at the same time. So on a hot day, in the afternoon, the bedrooms are kept warmer tha nthe rest of the house. In the evening the bedrooms are cooled off and the other areas are allowed to warm up a little.

[SoFlaDave]

Another option would be installing a thermostat with a remote sensor that can factor the average temp between the 2 rooms and run accordingly. It may still slightly over-cool the main space but it should be manageable. The Honeywell Prestige is my go too for that type of application. Pop a wireless sensor on the wall upstairs.

The difference in cost between 110 and 240 volt systems is negligible in my experience.

[Reinyn]

What is the occupancy of that media room?

The media room mostly has low occupancy. Usually it is just me on the PC, but when I have company for a movie (4 people) and run the projector it adds quite a bit of heat. I probably only average one movie per week. My thinking is that if I zoned that room I would either leave the tstat off or set to a high temperature until I was actually going to be up there.

My neighbors all have 95% furnaces with 14 seer heat pumps. I traded some furnace efficiency to get the dual stage heat pump. I live in central Washington (Tri-Cities). I also spent a bit extra for R-60 insulation. I believe I have the extra capacity in the system.

Adding a third zone is probably not a option right now. I'm not sure how the ducting to the bedrooms works. However if I went zoned for the media room maybe it would be easy to add later?

The difference in cost between 110 and 240 volt systems is negligible in my experience.

I believe I already have 110 available outside for the mini-split heatpump vs. running a new 240 circuit.

[crymtide]

Sounds like you've answered your own question, and need the mini split but don't want to bite the bullet. There are no magic pills. It is what it is.

[Reinyn]

Sounds like you've answered your own question, and need the mini split but don't want to bite the bullet. There are no magic pills. It is what it is.

Well that is how I was originally leaning, but both the contractors have told me that the zoning is very straightforward with my system. Now Motoguy has me thinking about zoning off the master suite which would be nice because it always seems colder then the rest of the house. In for a penny, in for a pound. I might be able to sell that to the wife instead of spending all this money on just "my room".

I will get the estimates on Tuesday and go from there.

I'm also struggling with buying more equpiment when I have enough capactiy for the house. I know the mini-split is more efficient, but what is the payback timeframe. Is it going to be able to save me $10 a month? 20 seer vs 16.

[motoguy128]

Do you also need to heat the space in winter? IF you have natural gas, the furnace will be cheaper under about 30F than a heat pump. So much of what you save in summer, you may give back in winter.

IF you aleady have imbalance issues and can redistribute some existing capacity, you will make the existing system more efficient. Longer run times will pull out more humidity as well.

Make sure when you add a branch, the it's done off the main plenum if possible. That way if down the road you add more or find out you need a 4 ton system, it can handle the airflow.

Finally, with zoning, the installer needs to evaluate the airflow to each zone and make sure that in low stage, the unit get enough airflow, or you'll need to add a bypass duct and a discharge air temperature sensor.

[tinknocker service tech]

zoning if done correctly is an option but you will need the proper controls that will stage the equipment and ramp the blower accordingly

adding a bypass to a v-drive motor is not a good idea and all manufactors frown on it

zoning with proper controls may well cost just as much or more then a mini split will and you will get no pay back at all

a mini split will give you full control of your operating cost and comfort as long as it is sized correctly

zone with a bypass on a v-drive will cause the controller to have problems and can also wype put the controler

do your home work before getting into a bigger problem

[Reinyn]

Hi Guys,

I really appreciate all of the advice. If the zoning system requires a bypass to work properly then I would rule it out as a option. If I zone I would add extra registers to the bonus room. I have a 10" round supply going to that room from the furnace and the contractors both thought it would be sufficient.

If I do the mini-split I would not use it for heating. Heating the bonus room is not a problem at all, lol. Most of the winter I had the dampers closed in that room and it was comfortable. If I do the mini-split my thinking is that I would add a manual damper at the furnace to close off the bonus room from the main system and leave it closed until I needed heating.

In fact I would conisder a A/C only option for that room, but I don't think it would save me much over a heat-pump.

[Chuck]

The fact is, the only way you will keep that room comfortable at all times is with the mini split.

Zoning off of the existing system might be cheaper but I can almost guarantee that you won't be happy with it for many of the reasons listed above.

The pros posting here are the best, the elite of the industry, and they could likely design a zone solution that would work. Are your contractors capable of it? Maybe, maybe not. But it is hard to screw up a mini split installation.

Cynical? Maybe, but also realistic.

And yes, go for the heat pump. Very little more money, and you will thank yourself later.

[tinknocker service tech]

Hi Guys,

I really appreciate all of the advice. If the zoning system requires a bypass to work properly then I would rule it out as a option. If I zone I would add extra registers to the bonus room. I have a 10" round supply going to that room from the furnace and the contractors both thought it would be sufficient.

If I do the mini-split I would not use it for heating. Heating the bonus room is not a problem at all, lol. Most of the winter I had the dampers closed in that room and it was comfortable. If I do the mini-split my thinking is that I would add a manual damper at the furnace to close off the bonus room from the main system and leave it closed until I needed heating.

In fact I would conisder a A/C only option for that room, but I don't think it would save me much over a heat-pump.

ok her is something you havent been inforn by your contractors
when the zone calls you are feeding a 10in supply and doesnt matter how many register you add you will be sized for about 350 to max 400 cfms depending on how long this truck is
now you ecm blower is set to deliver 1200 cfms or more so when the zone calls the ecm controler will ramp the motor trying to reach the total cfm it is set to deliver and will just keep ramping till it hits its max static pressure and at some point the controller will just wype out
it will while working make the system sound like a wind tunnel and interfere with listening to tv or have a conversation
you need a damper control that will drop the compressor to low stage and ramp the blower down to proper cfm for the supply to that room and ramp it back up to max for when both or the larger zone is calling in order for this to work properly
a bypass will just add to the problem in reverse

lennox and trane are about the only one i know that have a damper system that will do what i just said. at least that i know of

do some research before you make a costly mistake

[precision hvac]

Garage attached to home I assume.
Room over garage.
Is house 2 story also?
How are you accessing the room? From the house or through the garage?
If only access to that room is through the garage- you probably won't be able to use the existing system.

I vote mini split, especially for a media room. If you are watching movies- they are very quiet.

[Reinyn]

ok her is something you havent been inforn by your contractors
when the zone calls you are feeding a 10in supply and doesnt matter how many register you add you will be sized for about 350 to max 400 cfms depending on how long this truck is
now you ecm blower is set to deliver 1200 cfms or more so when the zone calls the ecm controler will ramp the motor trying to reach the total cfm it is set to deliver and will just keep ramping till it hits its max static pressure and at some point the controller will just wype out
it will while working make the system sound like a wind tunnel and interfere with listening to tv or have a conversation
you need a damper control that will drop the compressor to low stage and ramp the blower down to proper cfm for the supply to that room and ramp it back up to max for when both or the larger zone is calling in order for this to work properly
a bypass will just add to the problem in reverse

lennox and trane are about the only one i know that have a damper system that will do what i just said. at least that i know of

do some research before you make a costly mistake

Thank you for your input.

The zoning system would use Honeywell control boards. (Another T 8000 thermostat, and a HZ 432 zone control board). There is a Honeywell board of some sort on the furnace for what I assume is controlling the variable speed motor)

I appreciate your feedback about possible noise, since it is a media room I would like to keep it quiet.

The room is accessed through the house and it is open to the downstairs. (No door for access to the bonus room. I may add a door later).
It is over the garage and has a single window that I have covered up with the projection screen.

At this point after listening to all the feedback and hearing about the many potential problems with the zone system I am strongly leaning towards the Mini-Split.

Thank you,
-Reinyn

[Reinyn]

I know this thread has been dead for over a year, but I thought I would post a follow-up just in case the same question comes up again.

I ended up going with a mini-split system for my bonus room. Originally I asked the contractor for a Goodman branded unit to match my main Goodman system. I figured the same company could service everything then and it was a bit cheaper. They had to special order the unit and when they pulled it off the truck I saw that it was a 9K BTU cooling only unit rather then a 12K BTU heat pump that I had asked for.

I think the contractor felt bad for me, or he was just trying to get me off his back (LOL) because he offered to install for me a Mitsubishi inverter driven unit that he had at his warehouse for the same price as the Goodman. So I couldn't pass that up.

Anyway the point of the story is that it works AWESOME!!!

It is very quiet (quieter then my projector fan) and the 12K unit has no problems cooling my ~450 sqft space even with the projector and PCs running with several people in the room.

So Mini-split systems are great and it is so much better then trying to zone my main system. There is a good chunk of the year where I need cooling in the bonus room and heat in the downstairs. It is great to have a dedicated system for each area. The system is so efficient that I haven't noticed a appreciable impact on my utility bills.

[Patrick Eubanks]

This is the Ask Our Pro's forum, and only Pro members that have been vetted by the AOPC may post advise, commentary, or ask questions of the OP here.

You can find the rules for posting and qualifications here.

Further infractions may result in loss of posting privileges.

[catmanacman]

thanks for thinking of us as it is nice to hear back how the final solution worked out glad you happy