Water Heater Busted...

[IslandLizard]

Heat pump water heaters in the house REMOVE btu's from living space in winter. No one ever includes the recovery of living space btu's in the calc's for the water heaters operation. No btu consumption is free.

Excellent observation!
I was thinking about that when walking the dog last night, and again this morning.

50,000 BTUs into the hot water tank is 50,000 BTUs removed from a heated home interior. Helps the AC with cooling, but counterproductive when heating. Maybe feed outside air to the "intake" when weather isn't extremely cold, say above 30F.

 

[IslandLizard]

Hey what about something like this?

Interesting! A solid green(er) solution for the near future. Much better than an all-in-one indoor heat pump unit.

Price is kinda high ($3900) while transportation and installation may be a bit tricky. The outside piping needs freezing protection in applicable areas.

 

[rkhanso]

My son is a plumber and he's not a fan of the tankless water heaters. His experience is they're high maintenance, not cheap initially, and usually rated "optimistically" for how many faucets they can supply at the same time.
The standard-type water heater has been around for so long because they work well. Size it right, know your water hardness and do basic draining/cleaning/tuning based on that and usage.
But based on what's important to you (efficiency, size, recovery, etc) - research is your friend.

 

[twd000]

Heat pump water heaters in the house REMOVE btu's from living space in winter. No one ever includes the recovery of living space btu's in the calc's for the water heaters operation. No btu consumption is free.
I went from domestic hot water via a oil fired boiler for baseboard, to geothermal with on demand propane hot water. I am very happy.
Eric

there are two sides to that coin. Yes, the HPWH removes heat from the living space in winter, but on the flip side it cools and dehumidifies the basement during the summer. You may recoup the savings by not having to run a standalone electric dehumidifier all summer

 

[Kent88]

Interesting! A solid green(er) solution for the near future. Much better than an all-in-one indoor heat pump unit.

Price is kinda high ($3900) while transportation and installation may be a bit tricky. The outside piping needs freezing protection in applicable areas.

You should go for it.

I think LG has similar tech, thought I doubt it would be much (if any) cheaper, but I don't know if you can get it sized for just the water heater. It's supposed to replace the boiler as well, if I'm understanding this correctly. Their site has me in something of a recursive loop of links.

 

[Horseflesh]

My traditional natural gas fired 50 gal tank is on its way out so I have been studying this too.

I will probably replace it with the same kind of unit. My reasoning is that tankless and other more high efficiency units are expensive enough that payback is not a guarantee, plus the more complex units have a higher likelihood of needing a repair.

Tankless needs electricity, too. I assume a high efficiency/power vent tank does also. When we have a power outage, not having to worry about hot water is nice. (I do have a generator, but I’m not going to bother to hook it up unless the outage hits a half day or so.)

A boring 50 gal tank is the devil I know and will probably give me another 10 trouble free years.

 

[AJinJacksonville]

My traditional natural gas fired 50 gal tank is on its way out so I have been studying this too.

I will probably replace it with the same kind of unit. My reasoning is that tankless and other more high efficiency units are expensive enough that payback is not a guarantee, plus the more complex units have a higher likelihood of needing a repair.

Tankless needs electricity, too. I assume a high efficiency/power vent tank does also. When we have a power outage, not having to worry about hot water is nice. (I do have a generator, but I’m not going to bother to hook it up unless the outage hits a half day or so.)

A boring 50 gal tank is the devil I know and will probably give me another 10 trouble free years.

I wouldn't say it's the devil...haha...but it is certainly headed down that road it would appear. Luckily, we are in a spot where the power is usually not off for too long during outages. We do not have gas appliances/supply, so if the power went off for a long amount of time (ie. following a hurricane), we would run out of hot water supply from the tanked unit at some point anyway. So I do not really take that into consideration. If the power is out so long that we start stinking and need showers...we will take cold showers...haha.

We have a tanked unit installed in our attic that short-circuited and almost caught our house on fire, and have had a tanked unit that failed and pissed 50 gallons all over our wood floors (and that's with preventive maintenance).

I will definitely keep you all posted how the electric tankless works for us. It has been a thing in Europe for decades now...so I will cross my fingers. Also, for anyone considering it, the electric tankless/on-demand unit I am installing for a 2700sq house comes out to about $1000 (for the unit itself plus a pre-filter for our hard north Florida water) for the initial up-front cost. It only consumes electricity when it is providing hot water.

 

[IslandLizard]

You should go for it.

I think LG has similar tech, thought I doubt it would be much (if any) cheaper, but I don't know if you can get it sized for just the water heater. It's supposed to replace the boiler as well, if I'm understanding this correctly. Their site has me in something of a recursive loop of links.

Sadly, it's just a heat pump based domestic hot water heater with a separate storage tank.

I understand it was designed so it can be installed by a regular plumber or DIY, without hiring a refrigeration technician, but the tradeoff is risk of freezing due to using water as the transfer fluid between the (outdoor) heat pump unit and the (indoor) storage tank. That's a real limitation, IMO, except for those in the south where temps don't drop anywhere near 32F. I wonder if glycol can be used instead of water for the transfer, but didn't see it mentioned anywhere.

I think it's relatively expensive at $4k. We paid (only) twice that amount 10 years ago when we had a new whole house heat pump/AC unit installed, consisting of the outdoor compressor console, a new air handler and evaporator, accessory heating coils, including all labor and parts to hook it up to the existing duct work. Would have really been nice if it could also provide hot water, it's not that far a fetch, for the ultimate homerun.
I did pour the 4x5' concrete slab for it and laid the main wiring.

 

[Kent88]

I completely get that the price is absurd, and I was being silly there.

Although you have me confused now. The way I understood it, the SanC02 uses C02 as the heat transfer medium going between the outdoor unit and the indoor storage tank. I don't think that water is pumped from the house back outside to get warmed up and then pumped back inside to the storage tank. This tech is advertised as working down to -20°F weather in Canada, unless I am mistaken.

 

[IslandLizard]

I completely get that the price is absurd, and I was being silly there.

Although you have me confused now. The way I understood it, the SanC02 uses C02 as the heat transfer medium going between the outdoor unit and the indoor storage tank. I don't think that water is pumped from the house back outside to get warmed up and then pumped back inside to the storage tank. This tech is advertised as working down to -20°F weather in Canada, unless I am mistaken.

I hoped it was a tongue in cheek endorsement.

The liquid CO2 had me intrigued as well!
Out of curiosity, I read the installation manual up to page 17 and gave up once I realized the convolution trying to keep the water loop from freezing.

From what I gather, liquid CO2 is used in the condenser, that's why it will work down to -20F. The CO2 goes through the 1st heat exchanger inside the (outside) compressor unit, that heats a water loop (up to 50'!) to the storage tank. That water loop heats the domestic water in the storage tank through a 2nd heat exchanger.

Unless I totally misread and glycol can be used, the heat exchanger loop using water is a crazy weak link for something that's used outdoors. Terrible engineering or a sick joke?

 

[Kent88]

No, looking back over it now it does appear that it is a water loop that goes between a heat exchanger in the outdoor unit and the storage tank. Glad you pointed this out to me before I ordered this for myself .

That does seem like a weird way to set it up. Why not have the heat exchanger indoors on top of the tank and run a refrigerant that can't freeze all the way there? I guess I'd know if I was an engineer, or had an engineer explain it to me.

You probably saw the Freeze Protection bullet points. It does reference some kind of freeze protection heater. That seems strange, as the entire unit is a heater that is supposed to work effectively at temperatures as low as -20F. It should be able to sense when the outside temperature is below freezing and just run the system slowly to keep the water moving, which should keep it from freezing. I wonder if there is a backup heater in the outdoor unit for cold snaps where the temperature might be below spec?

Or perhaps -20F is just the threshold for where you'll be able to get the hot water like you want, but perhaps it can still (with an efficiency penalty) pick up heat at lower temperatures without getting the water as hot as you want, but still well above freezing.

 

[IslandLizard]

it does appear that it is a water loop that goes between a heat exchanger in the outdoor unit and the storage tank.

The only reason I can see to use water and not a real refrigerant is to prevent the involvement of an AC contractor during installation who also needs a CO2 setup. Most don't do CO2, R-410A being most common now. Liquid CO2 for refrigerant may well be an industrial niche market, I don't know, I've read/heard about it in the past.

It does reference some kind of freeze protection heater.

Oh yeah, the heat tape instructions...
I switched off at the purging of the closed water loop. Altogether this unit is not a simple installation.

I watched the AC/heating guys install my unit, only to swap the whole (outdoor) compressor unit out for another new one the very next day as the first one seemed to perform below specs.
They also do checkups (scheduled by me) and perform maintenance, they know what they're doing. It's definitely outside any DIY realm.

After 5 years of perfect use, we started to get issues that boiled down to the evaporator coil (it had developed small leaks). Although still covered under the 10-year manufacturer's warranty, it still cost us close to $1000 all in, as all the testing, dye injection, top-up refrigerant, re-installation labor, and whatnot, was not covered "unexpectedly." There was a class action lawsuit about that very evaporator issue, but never found out the skinny on how it ended. In my view that evaporator is some outsourced Chinese manufacture, costing less than $400 shipped to the local warehouse door. I still regret not driving to the hearing in Philly to give them my 25 cents of input. Then again, maybe best not to, I may have ended up in contempt and/or in jail.

 

[Kent88]

Getting off-topic, my parents-in-law only use mini-splits for AC, which works great for the spaces that the units are in, but they made some interesting decisions in placing them. Just two units, one in their bedroom and the other in the living-room/dining-room/kitchen. For those spaces it works great.

I wish they had one with the inverter, because their only other source of heat is in-floor heat that is really slow to respond when the thermostat is adjusted.