R-410A will be banned in new equipment starting January 2025, not 2023. R-410A will still be produced and available for servicing purposes after that date - although the price may be higher than today. See this article:

https://www.coolingpost.com/world-news/us-to-ban-higher-gwp-hfc-refrigerants/

Currently Daikin makes a small R-32 single zone mini split - which is only available in a few states. To my knowledge none of the manufacturers have announced anything bigger yet with R-32 or R-454B, but I would expect them to start showing up in 2024. The big problem is that as of now, many state building codes still prohibit installing units with semi flammable refrigerants over a certain charge size. Ironically, given how gung ho they have been about banning R-410A, California has been a laggard in updating their building codes to allow other refrigerants to replace it.

Why are you installing so many mini splits if you already have existing ducts? Why are you installing 6 tons of cooling?

 

Why are you installing so many mini splits if you already have existing ducts? Why are you installing 6 tons of cooling?

More than half my installations are abandoning ductwork and existing equipment and installing Mini Splits

I would think you know the answer to your own question but I could list a few good reasons if you really dont know.

 

I saw both Jan,2023 and Jan,2025 phaseout dates on the web after you pointed out this out. It appears that phaseout schedule has been pushed out by 2 years.

https://www.iaqmedics.com/article/r410a-phaseout-new-2023-efficiency-standards-in-alexandria-va

 

I debated a lot about ducted vs ductless and here are my reasons to lean towards ductless.

1. Current system has two zones. The furnace and air handler for the upper floor is in the unconditioned attic and I have no option to move these into conditioned space. Keeping air handler / duct for the new heat pump in the attic will squander away some of the efficiency gain.

2. The duct system in the attic is in bad shape. These are gray type flex duct ( 1992 vintage ) and are already crumbling. I can probably change the ducts in the attic without spending a fortune, but the same may cost much more ( and cause destruction ) for the ducts of the 1st floor that are buried in the ceiling / walls. The home is on slab foundation and there is no crawlspace. I am not sure if these gray ducts in the conditioned space have also deteriorated to the same extent as the attic ones or not and it's possible that they may not need replacement. But I keep hearing that it is recommended to replace ducts at 25-30 year span anyway. Your opinion on this will be helpful.

3. As per this presentation, the CFM requirements for the ducted heat pumps are low and the old duct system designed for the oversized furnaces / ac may not work that well. By the way, my 1992 built 3375 sq ft home in the temperate bay area has two 110000 btu 80% furnace and two 5 ton AC - one for each zone. These are way more oversized system and I am sure the ducts are also the same.

I removed your youtube link as I don’t see the relevance on a 1:36 rant about “Zero Carbon Homes” fitting in this discussion.

4. I am an empty nester and not running 3 zones out of six most of the time sounds like a good option to have for reducing energy bill.

As regards to 6 ton of cooling , it is not final yet. I am waiting to get Manual J done before finalizing it. Interestingly, I did a heat load calculation based on my past gas consumption and by following this method and it came out to be 36000 BTU / hr. Since it is so less than the current system, I am doubting if this method actually works or I made mistakes somewhere.

https://www.greenbuildingadvisor.com/article/replacing-a-furnace-or-boiler

Will appreciate your viewpoint in this regard.

 

2. The duct system in the attic is in bad shape. These are gray type flex duct ( 1992 vintage ) and are already crumbling. I can probably change the ducts in the attic without spending a fortune, but the same may cost much more ( and cause destruction ) for the ducts of the 1st floor that are buried in the ceiling / walls. The home is on slab foundation and there is no crawlspace. I am not sure if these gray ducts in the conditioned space have also deteriorated to the same extent as the attic ones or not and it's possible that they may not need replacement. But I keep hearing that it is recommended to replace ducts at 25-30 year span anyway.

You would just replace whats external to the home, or the attic. Whats in between floors is fine, dont matter if the insulation falls off, whats lost just warms the floor or ceiling.

Ducts dont need to be replaced every 25 years. But that grey goodman ductwork you speak of does.

 

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How long did it take you to come up with that answer? :grin2:

 

Running 3 zones out of 6 is NOT a good option. Reducing air flow that much will be bad for your equipment. Get separate systems for the two areas so you can set them at different temperatures.

 

My hvac system will have two outside heat pumps and don't know yet what capacity these should have. It may be in the range of 2 to 3 tons each.

One heat pump will drive two zones ( mini split heads ) on the 1500 sq ft 1st floor comprising living area, family area, kitchen and foyer. These are big with open plan and 16' vaulted ceilings. These will run all the time, albeit with lower thermostat setting in the night when 1st floor is not occupied. Switching off the heat pump system or too much of setback is not recommended , I think.

Another heat pump will drive 5 zones on the 1500 sq ft 2nd floor , comprising of master bed + bath, 3 small bed rooms and a loft. Master bed and Loft are big and will be occupied most of the time. I am not planning to put heads in two separate smaller baths having no exterior wall, as these should get conditioning from other surrounding zones. The three bedrooms are the ones, which I plan to keep switched off unless needed. The head load of these bedrooms together should be 35% of the capacity of the upper floor heat pump. I guess Mitsubishi VRF system should be able to dial down accordingly without being inefficient.

Am I right in making these assumptions ?

 

Hard to answer about your first floor ducts without knowing more. What are they made out of? What path do they take to get to the 1st floor? I find most ducts other than older flex like yours, hold up well and don't necessarily need to be replaced just because they're old.

I find 36000 to be much more believable for your heat load. It's best to confirm with a Manual J, but the gas bill calculation is quite accurate, much more accurate than a Manual J with garbage inputs. If the Manual J differs significantly from the gas bill calculation, it's important to not just dismiss the gas bill calculation out of hand, and review every input into the Manual J to make sure it's accurate.

Getting your distribution system out of the unconditioned attic, and eliminating the potential for poor duct design, are big upsides of going ductless.

The main downside to using ductless as your primary HVAC system is air distribution. Unless you have a super tight Passive House or something, you need a mini split head in each room to ensure good distribution of air and sufficient comfort comparable to a ducted system. But that many heads leads to very high installation costs compared to just replacing a furnace or air handler, and also requires oversizing the heads in each room (even the smallest available heads are oversized for most rooms). This can lead to problems with comfort and efficiency, especially when you are using multi-head units which have more limited turndown when one zone is running.

For multi-split systems, it's best to limit ductless heads to larger rooms and open plan areas, and use "mini duct" units to serve groups of 2 or 3 smaller rooms, like bedrooms. This way you still get the benefit of having lots of control zones, and turning off unused areas, but you aren't sacrificing comfort or efficiency.

 

While I would agree that the smallest 6000btu wall mount running at full capacity is to big for most rooms we install them in, They do ramp down well. I dont know the number but its likely in the 3000-4000 bedrooms we've installed 6k heads in over the last 6 years, never had a single complaint about comfort.

Installing a mini ducted does sacrifice comfort and efficiency over wall mounts, and it costs more.....For me anyways. We can do 3 wall mounts for cheaper than a mini ducted air handler.

 

If your new systems will be ductLESS then the ducts are irrelevant.

Be careful about oversizing ductless systems. They have reduced dehumidification when they ramp down to operate at lower capacity. Most average size homes don't need more than 3 tons of cooling capacity. Well sealed homes need even less.

 

If his first post about living in the Bay Area is reference to California then he has no concerns about humidity to worry about. One of the few perks we still have living here.