this post was submitted on 22 Nov 2023
611 points (98.0% liked)
Technology
59436 readers
3913 users here now
This is a most excellent place for technology news and articles.
Our Rules
- Follow the lemmy.world rules.
- Only tech related content.
- Be excellent to each another!
- Mod approved content bots can post up to 10 articles per day.
- Threads asking for personal tech support may be deleted.
- Politics threads may be removed.
- No memes allowed as posts, OK to post as comments.
- Only approved bots from the list below, to ask if your bot can be added please contact us.
- Check for duplicates before posting, duplicates may be removed
Approved Bots
founded 1 year ago
MODERATORS
you are viewing a single comment's thread
view the rest of the comments
view the rest of the comments
First, That's Washington. Not Ohio, New York State, or the overwhelming majority of the US.
Second, the Washington rule only applies to commercial buildings and large, multi-family residences: apartment buildings. It does not apply to single-family homes. I can't find the specific criteria, but I doubt it applies to duplexes or triplexes.
Third, the rule only applies to new construction, and not renovation. You can still replace existing gas water heaters with new gas water heaters, you just can't install a gas water heater in a new, large building.
Fourth, that same rule in Washington requires heat pumps for HVAC, and prohibits gas furnaces. The situation you envision of gas furnaces and heat pump hot water is prohibited in the circumstances envisioned in that rule. The only situation where we can consider gas heat and heat pump hot water is in renovating existing buildings, where the Washington rule does not apply.
Your "Washington" rule is therefore irrelevant to your argument, and my point is perfectly relevant. The conclusion is simple: you must replace a gas furnace or resistive/radiant electric heat with an HVAC heat pump before you will save energy from a heat pump water heater during winter. During winter, whatever your heat source your furnace uses will be the heat source for your hot water. If that is gas or resistive heating, your total efficiency will drop, and every watt hour consumed by your water heater will be wasted compared to a water heater that uses the same type of heating as your furnace.
Clearly washington knows that the long-term solution to replacing gas appliances is with heat pump. Its a state that is north and was used as an example for a place that is much colder than southern states that you claimed would only make sense for heat pump water heaters to be sensible in.
Then for anyone making the switch, they should get the heat pump powered equipment when they can, be it if the water heater is replaced before the hvac unit or vice versa. Logically speaking there is not downside to having a heat pump water heater next to the gas furnace. It does not need to heat up a large volume the size of the house, only a tank of water. It is still efficient and the losses you claim are negligible or measurably not there.
Where did I supposedly make that claim?
I'll give you a hint: I didn't. All my references to northern climates were only to demonstrate that water heaters in northern climates are indoors, within the heated space of the northern home.
I never claimed that heat pump water heaters were not sensible for northern climates. My claim was that they were not sensible for winter use in gas-heated homes.
Yes, there absolutely is. The heat inside a gas-heated space is produced from burning gas. Pump heat out of that space and into water, and the temperature of the space drops. To get the temperature back up, you need to put more heat into the space. Again, the source for that heat is gas.
You're burning gas to produce heat, then pumping that heat into the water. You can make this process more efficient by moving the flames closer to the water. Get them close enough, and the flames can heat the water directly, without needing the pump.
Look, a heat pump water heater does not generate its own heat. It takes heat from a space, and puts it into water. Where the heat got into that space by gas, the water is heated with gas. Where that heat got into that space by solar, the water is heated by solar. Where the heat got into that space by robot ninjas, the water is heated by robot ninjas. The heat pump merely takes the gas-heat, wood-heat, or ninja-heat, out of the living space, and into the water. To maintain the temperature of the living space, you need to add heat: gas heat, wood heat, ninja-heat, whatever.
If the source of the heat around the water heater is provided by gas, you would be better off burning the gas inside the water heater, where it doesn't need a "pump" to push it into the water.
Another way to look at it: Furnaces located inside insulated structures, like northern furnaces located in basements, do not produce "waste" heat. The heat that doesn't come from the ducts still goes into the house.
Yet another way to look at it: would it make sense to install a traditional heat pump to draw heat out of the insulated, gas-heated, northern basement and push it into the living room?
False. To see any winter gains, the HVAC system must be switched first. All of the gains of the heat pump come from the "free" heat drawn in from the atmosphere. Until the heat pump HVAC system is installed, your heat pump water heater is a particularly inefficient gas water heater all winter long, more than erasing any gains you will achieve during the summer.
So much anger. Have a good day, I cannot read your post intellectually anymore and will not participate