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Comment by avidphantasm | Hacker News Reader

This doesn’t sound any better than the efficiency of Mitsubishi/Trane “hyper heat” heat pumps, which are already on the market.

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Mitsubishi's products seem to be mini-split systems[1].

--> EDIT: Or maybe not... they seem to offer forced-air too. <--

The DOE challenge is for ducted systems. Their site[2] says:

> The Challenge is currently focused on residential, centrally ducted, electric-only HPs.

The DOE challenge also has other requirements[3] that I don't know if the Mitsubishi systems satisfy. It requires certain levels of efficiency and "grid interactivity" (meaning Energy Star "demand response"[4] where your utility can temporarily tweak your thermostat settings).

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[1] https://www.mitsubishicomfort.com/residential/new-products

[2] https://www.energy.gov/eere/buildings/cchp-technology-challe...

[3] https://www.energy.gov/sites/default/files/2021-10/bto-cchp-...

[4] https://www.energystar.gov/sites/default/files/ENERGY%20STAR...

Kind of a shame, ducted heating has a lot of issues, but is the best for retrofit I guess.

I wonder why ducted systems were part of the requirements, is it because it's just aimed at the USA and then mostly at adoptability for existing systems (which seems to be ducted mostly)? I only have anecdotal experience and no numbers to back that up, but it's the only reason I can come up with that would put such a restriction in place.

I'd say rip the ducts out and just use split systems but I imagine other people have thought about that and figured it's not the best way to go. (or at last not in the US)

Yes, because nearly every house in cold climates is ducted, and we’re trying to get people off oil heating quickly, easily, and cheaply. Popping a new heat exchanger in an existing furnace is stupid simple compared to running coolant lines to new, wall-mounted exchangers all over the house.

I think that's true, if the ducts exist already that's simplest and cheapest. If they don't mini-split type systems are. But I suspect that long term those are going to be a pain in the butt because you have a lot of failure points.

Mini splits seem to be pretty reliable. They’re very common outside of North America. Most of the leading manufacturers seem to be from Japan (Mitsubishi, Fujitsu, Daikin)

Hydronic heat distribution (baseboard and radiators) is quite common in New England.

Not in any construction in the last 50 years.

Sorry, meant to mean "in the US", since this was an American Government competition.

New England is part of the US.

Many of the Mitsubishi heat pumps work with central ducted systems just fine. I have one (replaced a central gas heat, electric AC system). It’s just a different air handler but the heat pump was the same as would have been used in a mini-split install.

When cross shopping the Mitsubishi vs Trane, the Mitsubishi was miles ahead. I didn’t even get the most cold weather efficient option (not needed for my climate).

Oh, you must be right. I was finally able to find this on Mitsubishi's site:

https://www.mitsubishicomfort.com/residential/products/ducte...

And that says it's compatible with some "hyper-heat" outdoor units. So apparently they do offer both.

How did you find a Mitsubishi installer? I like the product but couldn’t find a contractor in the Portland Oregon area.

I used Mitsubishis site to find the local “diamond” contractors (those factory trained and do enough volume). Then cross referenced vs yelp.

https://www.mitsubishicomfort.com/find-a-contractor

I see a few in Portland and several in nearby zip codes. Hopefully one can work for you. There are different tiers of “diamond” so you can compare if the difference matters to you.

One thing that’s a bit different is the air handler and outside compressor run on one circuit (mine is a 3 ton unit). So there’s a power line between the 2 units. That threw off our city inspector. But it works out nice since I now have an extra 20A breaker free :)

Thanks! Do you have the technical docs with the efficiency curves for the Mitsubishi ducted systems? I can’t find the materials amongst all the marketing.

For example this is the Carrier Infinity 24 we are considering. https://d1049ui2fjityy.cloudfront.net/userfiles/inriver/docu...

I found it in their catalog. You’ll need your model or series. After all the specs there were some efficiency/temp tables. It was under Pros (vs homeowner) -> USA -> product support -> catalog -> m and p series.

Catalog:

https://mylinkdrive.com/viewPdf?srcUrl=http://enter.mehvac.c...

pocket guide:

https://mylinkdrive.com/viewPdf?srcUrl=http://enter.mehvac.c...

For reference, here’s what we have: 36KBTU AIRHANDLER/HEATPUMP HI-STATIC M SERIES DUCTED SYSTEM INDOOR MOD# SVZ-KP36NA OUTDOOR MOD# SUZ-KA36NA2

It’s a slightly older model as we had height restrictions to work around. This prevented us from getting a newer or hyper heat model. IIRC ours had good efficiency into the 20F range which was plenty for us.

In comparison, the Trane dropped efficiency at 50F and needed heat strips at that temp (so pretty crap).

It depends on what they mean by this:

> The prototype delivers 100% heating at 5°F at double the efficiency, and 70% to 80% heating at -5°F and -10°F. DOE’s Oak Ridge National Laboratory validated the performance and efficiency of Lennox’s prototype.

Usually when people talk about efficiency of heat pumps they are comparing to electrical resistance heating (which is 100% efficient). If that's what they mean then they are saying 200% efficient at 5℉, which is not as good as Mitsubishi, which is better than 200% at 0℉.

But in the first paragraph they say:

> The U.S. Department of Energy (DOE) today announced that American heat pump manufacturer Lennox International became the first partner in the U.S. Department of Energy’s (DOE’s) Residential Cold Climate Heat Pump Technology Challenge to develop a next-generation electric heat pump that can more effectively heat homes in northern climates relative to today’s models.

It could be that they are stating efficiency compared to current heat pumps, not compared to resistance heating, in which case they would be claiming quite a bit higher efficiency than Mitsubishi, which would certainly justify calling it a breakthrough.

Another possibility is that what they could be claiming as the breakthrough is the 100% heating at 5℉ part. The Mitsubishi cold weather heat pumps start losing capacity below 23℉, falling from 100% at 23℉ to 76% at -13℉.

I don't think that would be as big a breakthrough as double the efficiency of current heat pumps, because it wouldn't make it so heat pumps are feasible in climates too cold for Mitsubishi. But it would make it so that in places you can use a heat pump you might not need as big of a heat pump with the new technology as you would need with a Mitsubishi. That could lower up front cost making converting from something else to a heat pump more feasible for many.

Domestic is the key here.

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