Efficient Use of Air-source Heat Pumps

[wwu123]

I wonder if radiant/floor heating is better than minisplits (that is, assuming the issue is just heating a certain area of the home and not cooling it).

I just put down $35k to overhaul every goddamn window in this house. Biden Money isn't going to help since the IRA encourages spreading out window replacements over a goddamn decade. Barf.

House = money pit. Uggghhhhh.

Did you already do the windows? If not, once you replace those old leaky, single pane windows, you might find you can set the thermostat lower than 74 in winter. Because old drafty windows create circulation and gradients that make your skin feel chilly.

I noticed it the most stepping out of the shower - used to feel chilly with our old windows. After we remodeled and put in new insulation and double paned windows, it feels warm getting out of the shower, even though the thermostat is still set to the same temp (68 in winter).

 

[mspohr]

Did you already do the windows? If not, once you replace those old leaky, single pane windows, you might find you can set the thermostat lower than 74 in winter. Because old drafty windows create circulation and gradients that make your skin feel chilly.

I noticed it the most stepping out of the shower - used to feel chilly with our old windows. After we remodeled and put in new insulation and double paned windows, it feels warm getting out of the shower, even though the thermostat is still set to the same temp (68 in winter).

We installed hydronic floor heating in our new house. Best heat ever! No drafts. Comfortable warm floors.
(Air source heat pump.)

 

[holeydonut]

Did you already do the windows? If not, once you replace those old leaky, single pane windows, you might find you can set the thermostat lower than 74 in winter. Because old drafty windows create circulation and gradients that make your skin feel chilly.

I noticed it the most stepping out of the shower - used to feel chilly with our old windows. After we remodeled and put in new insulation and double paned windows, it feels warm getting out of the shower, even though the thermostat is still set to the same temp (68 in winter).

No... the windows take like 3 months to make (it's like 25 windows and a big patio slider UGGGHHHHH). I even got the fancy coating and whatever to further improve the window insulation. I'm 99% sure it's not the circulation gradient though... wife is just cold all the time even sitting there with sweatshirts/jackets on. Those will be no matter what.

 

[Big Earl]

We installed hydronic floor heating in our new house. Best heat ever! No drafts. Comfortable warm floors.
(Air source heat pump.)

Daikin Altherma or something else? Does your unit have a hydronic buffer tank? My folks have an Altherma; it short cycles and has all kinds of issues due to not having any sort of buffer tank. I’m thinking of installing one myself since their installer doesn’t seem to get it.

 

[mspohr]

Daikin Altherma or something else? Does your unit have a hydronic buffer tank? My folks have an Altherma; it short cycles and has all kinds of issues due to not having any sort of buffer tank. I’m thinking of installing one myself since their installer doesn’t seem to get it.

I installed a Chiltrix CX34 myself. (No refrigerant work required since it's a sealed unit... Just PEX plumbing.)
It has a buffer tank for hydronic heating. (Also does DHW)
The hydronic floor heating uses Warmboard subflooring which works great.
This is the second Chiltrix I have installed. First was in the other house on my lot 7 years ago. Also does floor hydronic with buffer tank and DHW.

 

[STS-134]

We installed hydronic floor heating in our new house. Best heat ever! No drafts. Comfortable warm floors.
(Air source heat pump.)

What did the HVAC company do to manage two indoor coils? You'd need both a coil that heats water for your floor heating and a coil that cools air for your air conditioning. Ideally, you'd want two sets of ducts even if doing forced air, with floor supply vents and a low wall intake for heating and ceiling supply vents and a ceiling intake for cooling, so this isn't a bad setup, except for the fact that if you're only heating or cooling air, you can manage the entire system with dampers.

 

[mspohr]

What did the HVAC company do to manage two indoor coils? You'd need both a coil that heats water for your floor heating and a coil that cools air for your air conditioning. Ideally, you'd want two sets of ducts even if doing forced air, with floor supply vents and a low wall intake for heating and ceiling supply vents and a ceiling intake for cooling, so this isn't a bad setup, except for the fact that if you're only heating or cooling air, you can manage the entire system with dampers.

We don't need or have cooling in the mountains.
The whole system is heated water. Floor hydronics radiate to the air.

 

[wwhitney]

What did the HVAC company do to manage two indoor coils?

FWIW, on the Chiltrix CX-34, it supports a zone valve for switching from space heating/cooling to domestic water heating. So I assume you make the volume of the system between the outdoor unit and the zone valve small, and in the cooling season you just have a little extra inefficiency from that volume of water ping-ponging between hold and cold.

The installation manual tells you to make the volume of the space heating/cooling system at least 15 gallons, using an "extra volume" tank if necessary, to reduce short cycling. But I assume that doesn't apply to the domestic water heating configuration, as the water in the indirect tank should have a large thermal mass.

Cheers, Wayne

 

[mspohr]

FWIW, on the Chiltrix CX-34, it supports a zone valve for switching from space heating/cooling to domestic water heating. So I assume you make the volume of the system between the outdoor unit and the zone valve small, and in the cooling season you just have a little extra inefficiency from that volume of water ping-ponging between hold and cold.

The installation manual tells you to make the volume of the space heating/cooling system at least 15 gallons, using an "extra volume" tank if necessary, to reduce short cycling. But I assume that doesn't apply to the domestic water heating configuration, as the water in the indirect tank should have a large thermal mass.

Cheers, Wayne

I don't have experience with cooling but that sounds right.
We just do hydronic floor heating and DHW. There is a diverter valve to switch between the DHW tank and the hydronic buffer tank.
We have four heating zones with a manifold valve.

 

[STS-134]

We don't need or have cooling in the mountains.
The whole system is heated water. Floor hydronics radiate to the air.

I find it hard to believe that you'd never need cooling unless you're way up there in elevation (above 9000 feet or so). Even people up at Tahoe at or above lake level need cooling for a few hours in the afternoon on the hottest days of the year.

 

[mspohr]

I find it hard to believe that you'd never need cooling unless you're way up there in elevation (above 9000 feet or so). Even people up at Tahoe at or above lake level need cooling for a few hours in the afternoon on the hottest days of the year.

I've lived at Tahoe for 45 years (elevation 6500 feet) and never had cooling. Never felt the need for it. Max temps in the summer are low 80s and dry so just don't get hot.
I guess if things got really bad in the future with climate warming I could switch the system over to cooling but never felt the need.

 

[STS-134]

I've lived at Tahoe for 45 years (elevation 6500 feet) and never had cooling. Never felt the need for it. Max temps in the summer are low 80s and dry so just don't get hot.
I guess if things got really bad in the future with climate warming I could switch the system over to cooling but never felt the need.

South Lake Tahoe has definitely gotten into the low to mid 90s before and Tahoe City into the low 90s as well. Which is definitely AC required weather. I believe Truckee has been over 100 without the moderating influence of the lake next to it. Record temp recorded in Tahoe City; Heat wave to last through week

 

[mspohr]

South Lake Tahoe has definitely gotten into the low to mid 90s before and Tahoe City into the low 90s as well. Which is definitely AC required weather. I believe Truckee has been over 100 without the moderating influence of the lake next to it. Record temp recorded in Tahoe City; Heat wave to last through week

Where I live (on a ridge at 6500 ft), it just doesn't get hot enough for me to want cooling... ever.