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Heat pumps of the 1800s are becoming the technology of the future

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Re: Heat pumps of the 1800s are becoming the technology of the future

#151

Post by jimmaswell »

fifteenforty wrote: post #109

In a house I own in Melbourne, Australia, I just replaced an old gas central heating system with 3 new top of the line Daikin mini split heat pumps. The new units can heat the entire house for the same amount of electrical energy that was used to run the FAN in the old gas unit. They are crazy efficient. Ducts are dead. The Daikin Alira X is the gold-plated option and cost $8k AUD for 2x2.5kw and 1x7.1kw units includ…

> Ducts are dead.

How do you move the heated/cooled air into/around the house without ducts?

Re: Heat pumps of the 1800s are becoming the technology of the future

#152

Post by aclatuts »

code_biologist wrote: post #136
newmac wrote: post #134

Earlier quoted context omitted.

Agree, ducts are wonderful! If you don't have ducts, go ductless for sure.

Am I crazy, or are those two sentences completely contradictory?

I think he means having a duct work for the whole house for a central heat pump is good. But having a heat pump per zone is also good if you don't have ducts for the whole house. Some newer home designs separate heating and cooling from the air exchange systems so there are multiple zones of heating and cooling.

Re: Heat pumps of the 1800s are becoming the technology of the future

#153

Post by nemo44x »

kccqzy wrote: post #132
throw0101a wrote: post #118

Earlier quoted context omitted.

> Ducts are dead. Ducts are still needed to circulate air, especially if you want to remove stale air (e.g., bathrooms, kitchen) and bring in (filtered) fresh air (to bedrooms).

Not being snarky but why don't you just open the window for that? I have a CO2 detector that I believe is a reasonable proxy for stale air. When it goes above 1000 I simply open the windows. By the time I remember to close the windows the reading is almost always below 500.

Part of it is code. Make-up air systems need a duct for example. Also a lot of people like their air filtered so opening a window isn’t great for that. Also winter.

Re: Heat pumps of the 1800s are becoming the technology of the future

#154

Post by fifteenforty »

Gordonjcp wrote: post #146
fifteenforty wrote: post #112

Earlier quoted context omitted.

You have to think carefully about where you run the ducts. They can be a huge source of energy loss. 40% is the number quoted by the EPA. Most roofs in Australia still aren’t sealed. The air barrier and insulation barrier is the ceiling. The roof space itself is not insulated, so the ducts are exposed to extreme temperatures, thus destroying the efficiency. Here is just one article on it: https://newenergythinking.co…

Why wouldn't you just lay insulation on the ducts, same as you do with water pipes?

US and Australian units are different for insulation, but in my terms the insulation around the best ducts is R1.5, but good ceiling insulation is R6. 4x difference

Edit: not to mention the huge difference in surface area. Ducts can expose your conditioned air to a huge, poorly insulated surface. Bad for efficiency.

Re: Heat pumps of the 1800s are becoming the technology of the future

#155

Post by [deleted] »

teruakohatu wrote: post #111
phkahler wrote: post #35

Earlier quoted context omitted.

The fridge is heating your home, so that reduces the burden on whatever is heating your home. The coil on the back gets hot.

> The fridge is heating your home Not really, efficienty aside the heat it puts out the back is coming from inside the fridge... Which is coming from the room housing the fridge. So over the course of a day it should be neutral.

[deleted]

Re: Heat pumps of the 1800s are becoming the technology of the future

#156

Post by fifteenforty »

_benedict wrote: post #135
rootusrootus wrote: post #130

Earlier quoted context omitted.

Indeed, sounds like a problem with the fan. My 3000sf house uses 1100W for the fan, and about 4000W for the heat pump. I expect converting to mini-splits would increase, not decrease my overall power usage.

Pretty sure mini splits are significantly more efficient today, with SCOP of above 5, so that seems unlikely?

This unit runs at about 5

Re: Heat pumps of the 1800s are becoming the technology of the future

#157

Post by ComputerGuru »

mmaurizi wrote: post #81
ComputerGuru wrote: post #56

Earlier quoted context omitted.

A good chunk of the United States (and a number of other countries) uses forced air natural gas heating. If you fall into that group, you can install a "whole-house humidifier" that injects steam into the hot air plenum, distributing it around the house. This makes the air less dry (obviously) but also has the side-effect of actually reducing the need for heating because air holding moisture feels warmer than air wit…

We run our steam humidifier just fine on 120v, but we have a relatively small townhome at 1400sqft

Be careful you’re not running it independently of whether or not the furnace is actually on. 120V generally can’t evaporate enough water in the short window while the furnace is running and many techs will set it up to run at all times (with the blower but not the furnace) to compensate. This lets mildew or mold grow in your ducts.

Re: Heat pumps of the 1800s are becoming the technology of the future

#158

Post by rootusrootus »

_benedict wrote: post #135
rootusrootus wrote: post #130

Earlier quoted context omitted.

Indeed, sounds like a problem with the fan. My 3000sf house uses 1100W for the fan, and about 4000W for the heat pump. I expect converting to mini-splits would increase, not decrease my overall power usage.

Pretty sure mini splits are significantly more efficient today, with SCOP of above 5, so that seems unlikely?

I recently replaced my [central, ducted] heat pump, and the new one is rated with a 4.981 SCOP. It's fairly efficient, but not the most efficient on the market.

Re: Heat pumps of the 1800s are becoming the technology of the future

#159

Post by fifteenforty »

jimmaswell wrote: post #151
fifteenforty wrote: post #109

In a house I own in Melbourne, Australia, I just replaced an old gas central heating system with 3 new top of the line Daikin mini split heat pumps. The new units can heat the entire house for the same amount of electrical energy that was used to run the FAN in the old gas unit. They are crazy efficient. Ducts are dead. The Daikin Alira X is the gold-plated option and cost $8k AUD for 2x2.5kw and 1x7.1kw units includ…

> Ducts are dead. How do you move the heated/cooled air into/around the house without ducts?

It’s a ‘mini split’ in US lingo. There are thin, highly insulated refrigerant lines going between the outside unit and the inside unit. The inside unit exchanges heat with the air. https://www.daikin.com.au/our-product-range/split-system-air...

Re: Heat pumps of the 1800s are becoming the technology of the future

#160

Post by naijaboiler »

coffeebeqn wrote: post #108
jillesvangurp wrote: post #15

Earlier quoted context omitted.

The good news is that the process of running your fridge moves the heat from the fridge into your home, which in the winter is not such a big problem. Your fridge is just another heat pump. It's a bigger problem in the summer when you are maybe trying to cool your house using air-conditioning and your fridge adds heat to your house to keep the fridge cool. Much less desirable.

Simple- just keep the fridge doors open during the summer

actually, that makes the room warmer. Your fridge just becomes a bigger heatpump with the door open. the compressor has to work hard to cool a larger area, so therefore uses more electricity and dumps more heat out into the room.
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