What is KISS in this case? Periodic recirculation or no recirculation at all? In that setup you end up with lukewarm or cold, but not hot water and end up wasting water down the drain until the hot water comes through. Took a week or so until it became routine and now it is just a habit with the Alexa routine.
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CPUC NEM 3.0 discussion
- Thread starter jjrandorin
- Start date
I have a gas water heat. ALso have a preheat solar water setup. Never have a water hot issue. No re-circulation pump. Considered but decided was not worth money and upkeep. Yep, I was water getting it hot, but KISS..
Interesting - I've been pleased with the noise from my Rheem HPWH. It's on the other side of a wall from any living space, but can be heard, but it's not loud at all. The bathroom fan is much noisier, for example. Even right next to it, the noise level is fine.
You mean 300% Coefficient of Performance ... hopefully someone won't read your post and think a net efficiency over 100% is possible haha.
The only thing that can be over 100% effective are bollards.
but it is possible. Heat pumps can generate heat 300% over straight resistance heating
No, they're heat-pump water heaters with regular resistance heating for backup or high demand situations.
I agree with you HVAC heat pumps are the bee's knees. But you're mixing up Efficiency and COP.
COP of a Thermoelectric Cooler (TEC)
Technically, the word efficiency relates to the ratio of the amount of work one gets out of a machine to the amount of power input. In heat pumping applications, this term is rarely used because it…
thermalbook.wordpress.com
how so?I agree with you HVAC heat pumps are the bee's knees. But you're mixing up Efficiency and COP.
COP of a Thermoelectric Cooler (TEC)
Technically, the word efficiency relates to the ratio of the amount of work one gets out of a machine to the amount of power input. In heat pumping applications, this term is rarely used because it…
heat pumps are 300% to 400% efficient. Not talking COP. 400% would be in warm climates
Heat pumps require some electricity to run, but it’s a relatively small amount. Modern heat pump systems can transfer three or four times more thermal energy in the form of heat than they consume in electrical energy to do this work – and that the homeowner pays for.
Heat pumps require some electricity to run, but it’s a relatively small amount. Modern heat pump systems can transfer three or four times more thermal energy in the form of heat than they consume in electrical energy to do this work – and that the homeowner pays for.
Noise can really depend on when you got it - the current Gen 5 versions are significantly louder than the Gen 4 design - some say 2-4 times louder based on actual decibel measurements
Why are they not the same basically? That article, plus others like it, all say COP is used instead of Efficiency because the latter is often greater than 1 (100%). Intuitively I guess people think efficiency should be between 0% and 100%. But if folks like getakey are willing to talk efficiencies of 300% to 400%, aren't they the same thing. Esp since all the work/energy/heat is being used to heat the water.I agree with you HVAC heat pumps are the bee's knees. But you're mixing up Efficiency and COP.
COP of a Thermoelectric Cooler (TEC)
Technically, the word efficiency relates to the ratio of the amount of work one gets out of a machine to the amount of power input. In heat pumping applications, this term is rarely used because it…
COP != Efficiency... that's why I'm trying to say we should refer to that math everyone's using in this thread as COP instead of just keep incorrectly calling it efficiency.
"...heat pumps, air conditioners and refrigeration systems can have a coefficient of performance (COP) greater than one. However, this does not mean that they are more than 100% efficient, in other words, no heat engine can have a thermal efficiency of 100% or greater."
I get your point. I was just trying to be consistent with the efficiency of a gas furnace. It cannot be greater than 100% either, but the modern ones get darn close. Heat pumps can create more heat (move more heat) than the thermal amount of electricity consumed, i.e., the COP. My point was that a modern furnace with current cost of gas is less expensive than a heat pump with CA gas and electricity costs.COP != Efficiency... that's why I'm trying to say we should refer to that math everyone's using in this thread as COP instead of just keep incorrectly calling it efficiency.
"...heat pumps, air conditioners and refrigeration systems can have a coefficient of performance (COP) greater than one. However, this does not mean that they are more than 100% efficient, in other words, no heat engine can have a thermal efficiency of 100% or greater."
Yeah, I know what you were trying to say... I was just trying to get consistent language so people reading wouldn't start thinking COP and efficiency were the same thing.
Also an issue is that a heat pump costs a boat load more money than a gas furnace (at least, when I was getting bids/quotes). Which is why I was saying earlier in this thread that if PG&E really felt NEM "hurt" poor people from being able to afford wise energy investments, then PG&E should have put in their ridiculous proposal that a portion of the NEM 3 fixed costs fees would go into a general fund to be returned to homeowners by way of rebates for things like heat pumps, insulation, or better windows.
But of course PG&E doesn't really want to help poor homeowners, and would never consider a program to help poor people afford an efficient heat pump.
Right now unless you get a pallet of SGIP batteries or have connections with installers, it's really tough to afford the investments to go all-electric. It's easy for people to say "all electric is good" but the reality is that it's hard to pay for without subsidies.
Watch the latest YouTube from Technology Connections - he explains that Heat Pump heat from electricity made from NG is /still/ more efficient that pumping that NG to your house and burning it locally for heat.
OK, I get it. But it's stilly semantics (for this non-technical forum). What good is it to say that the Efficiency of this heat pump is say 98% in "work done" spinning this compressor, as only 2% of the energy was lost to friction - but let's ignore that other 2-3X amount of massive heat that was desirably transferred from one place to another. Let's come up with a different term, that would happen to be the same number less two zeros, if only efficiency could be greater than 100%....COP != Efficiency... that's why I'm trying to say we should refer to that math everyone's using in this thread as COP instead of just keep incorrectly calling it efficiency.
"...heat pumps, air conditioners and refrigeration systems can have a coefficient of performance (COP) greater than one. However, this does not mean that they are more than 100% efficient, in other words, no heat engine can have a thermal efficiency of 100% or greater."
Or is there a substantial difference, like 98% of energy put in winds up as motor heat dissipating in a room that doesn't need it, so one technical term subtracts 0.98 and the other does not?
I think we were just lectured the past 24 hours that we're not supposed to use the term efficient in the first case ;-)
@holeydonut, just having fun ... Actually think COP is a really easy and intuitive figure to work with to compare costs, when I've been trying to calculate whether to eventually replace the gas furnace with a heat pump.
that guy is hard to listen to for 20 minutes
Not many Heat Pumps have COP of 2.5 at cold temps which is the breakeven point compared to burning NG at home. But, my comparison was cost using my rates for NG and Electricity. It would be cheaper for me to burn NG. That said, I installed a heat pump 2 years ago because I have solar and my old gas furnace was dying, but it is only for half of my house. It is a 16 SEER heat pump. I'll have to look up the COP for heating. Since the gas was plumbed there already, I got a unit with gas as the backup. My experience with the unit is that for outside temps below 40 degrees, it has a hard time. That is not very cold. For example, on colder nights, that portion of my house can get down to 66 degrees. If I only use heat pump mode, it takes a long time to bring the temp up to 72 degrees., on the order of 4 hours. S
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