Planning to install 220 electrical outlet

One of the older documents I saw not that many years ago, indicated that source sides were labeled as 120V, while load side appliances were commonly labeled as 115V (or possibly even 110V?), with the expectation of some wiring loss in between. The included tables shows a somewhat narrow tolerance on the 120V supply side, and a wider and fully overlapping tolerance on the load side.

 

8 gauge works to 50 amps for THWN (75℃) and THHN (90℃) and similar insulations. These are single wires with single insulation layer, which must be put into conduit for protection. But in NM-B or UF insulations (60℃), multiple wires bundled together with an extra insulation layer so can be put in certain locations without conduit, 8 gauge is good for only 40 amps.

... before that 80% derating factor for continuous loads. And the wire will still be hot. If you want it to run cooler, use a heavier gauge than the minimum required.

 

It isn't horsesh!t, it is reality in numerous areas with old low-capacity infrastructure.

You seem to be confusing power with energy. They are not the same. Power is the rate at which the device pulls energy at any given moment. Your utility meter measures just total energy over time. High power pulled briefly can be the same total energy as low power pulled over a much longer time.

For an analogy, power is equivalent to how fast you blast (or dribble) water from a hose into a bucket. Energy is just the size of the bucket, not the rate at which it is filled. Your water pipe and hose diameters and lengths limit how fast (power) you can fill the bucket. The water meter measures only how much went into the bucket (energy), not how fast or slow it filled.

Your tankless system pulls all its energy at high power, just while the hot water is running, then nothing when the faucet or shower is turned off. Tanked heaters pull lower power that can't keep up with the spigots, so must take a long recovery time to catch up reheating the tank.

Both types make hot water with the same initial efficiency. But tanked heaters suffer standby losses (heat leaks) just sitting around when the water isn't flowing. Older type tanks might lose 20% in typical household patterns, or worse if the inlet and outlet pipe heat traps were missing or misconfigured. Modern tanks properly installed lose just 4% to 6%. Your tankless heater has essentially no standby loss, that is why it saves energy -- lots of savings compared to old wasteful tanks, just a little compared to the more recent, formerly (before the rules changed) Energy Star models.

For homes and neighborhoods built for small service (e.g. lots of natural gas service for heat / hot water / cooking / clothes drying, so homes had 50A to 100A service), the high power draw of tankless can cause lights to flicker when its heating element turns on and off. Homes and neighborhoods originally built without gas so that all those heating appliance had to use electric resistance, were typically built with 200A or larger service, so tankless water heat is typically less of an issue.

But now-a-days, heat pump water heaters (HPWH) absolutely slaughter every kind of electric resistance heater for efficiency, including your tankless heater:

Smart $aver - Heat Pump Water Heater - Duke Energy

My now-old Tier 2 HPWH has a Northern Climate rating to save 50% compared to my old Energy Star resistance tank, but thanks to being in a milder winter area (thus better annual heat pump performance) than the (now obsolete) Northern Climate definition, I actually save closer to 65%. (I have a separate kWh meter on the water heater circuit to measure it.) Today we have a very wide choice among Tier 4 and Tier 3 units that will do even better.

The main disadvantages of HPWHs are even longer recovery times than resistance heaters (no "endless hot water"), and less freedom of install location. Some households may want a larger tank, and really cold regions will need models with backup resistance heat for the very coldest weather. But the annual energy savings are definitely worth it.

 

If I was going tankless, I think I'd prefer a lower powered one in the kitchen and one in each bathroom so as not to abandon a bunch of hot water in the pipes. But that's a lot of work and even those can strain the capacity of some older homes' wiring.

When I was in Honduras most people had gas tankless water heaters because cooking & water heating was done with propane and tankless saved a lot of money.

 

Many modern-day heat pump water heaters have a lot of flexibility. Ours though it is a Heat Pump Water Heater has two resistance heating elements also just like a traditional water heater.

There are 4 Modes to choose from:

1. Heat Pump Mode - the unit will only use the Heat Pump to heat the water

2. Hybrid Mode - the unit will use the Heat pump as the primary source of heating but if the controller predicts it will run out of hot water then it will engage the resistive elements to keep up

3. Electric Mode - the unit only uses the resistive elements to heat water

4. Vacation Mode - the hot water heater is disabled until the homeowner selects one of the other 3 modes.

This type of flexibility has some advantages - if the heat pump function fails you get a fault but can still use the resistive elements to make hot water, you don't ever really run out of hot water if you select hybrid mode the unit will preemptively engage the resistive elements to help keep up with demand.

One disadvantage is that even though our Heat Pump Water Heater usually runs below 3 amps on maximum demand I had to run wiring/circuit to make the circuit to the heater capable of carrying the demand for the rarely used resistive heating elements.

Note: it is important I feel to have the resistive elements options on a Heat Pump Hot Water Heater. Having a Heat Pump and its associated components does add some complexity and additional failure points to the unit. Our 1st GE Geosprings Heat Pump Hot Water Heater was replaced under warranty after one year when the Heat Pump quit working (Leak in condenser). It was replaced at no cost. While waiting for the replacement unit to be delivered it was a non-event since we just switched to resistive heat function on the unit to provide us with hot water. I can tell you the increase in the electric bill was dramatic when we were on the resistive heating elements. It is truly amazing how much a Heat Pump Hot Water Heater will save a household in electricity charges. Ours is located in our basement where it dehumidifies the space as well as help cool it. We have a pit type basement with 8 foot walls, the heat migration from the earth into the basement gives the heat pump all the air heat it needs to work well.

 

While I do discourage electric tankless for most people (excepting some niches and circumstances where HPWHs don't work well) for several reasons, it must be noted that gas tankless doesn't carry the same disadvantages. The only real problem with gas tankless is the carbon-emitting gas part, not the tankless part. If one is going to use gas, then go right ahead with tankless.

I believe that most HPWHs currently available in the U.S. do have both these electric resistance elements. But there are some that don't, and more so in certain foreign markets such as Japan and Australia.

That vacation mode should also provide freeze protection, keeping a certain minimum temperature, though far below what anyone considers 'warm'.

Modern Vacation modes often allow users to set their return date. The appliance will then turn on early enough to fully reheat just before the users return. Mine is too old to have this feature, so I usually change it to use just the top resistance element to get enough hot water for brief evening showers, then return to heat pump mode to heat the rest of the tank.

BTDT when the evaporator fan motor quit, until I could replace the failed run capacitor. (This particular maker went bankrupt, making the warranty meaningless, so I was on my own.)

Traditional electric water heaters did sometimes run out of hot water, especially back when families were larger, washing machines and dishwashers consumed more water, multiple laundry loads were run back-to-back, teens took long hot showers, then Mom wanted to fill the bathtub to the rim for a relaxing soak. By then, the water is barely lukewarm, because the electric heating elements can't keep up in real time. That is why we have storage tanks in the first place, to heat most of the water well before it is needed.

And that is why the tankless installers advertise "endless hot water". You can use all the aforementioned hot water in a short time, and Mom can still have her hot relaxing soak in the tub, because the tankless system is powerful enough to keep up.

Traditional tanks have a large first-hour rating, based mostly on the tank size, then a smaller recovery rate rating, based just on the power of the electric elements. HPWHs may match that recovery rate in resistive or hybrid mode, but are slower in heat-pump-only or economy mode.

New installations do need to be aware of this, but it should be a non-issue for folks replacing a traditional electric tank. The new HPWH should not exceed the demand of the original water heater, so can simply wired to the original circuit without any electrical changes.

 

"HPWHs may match that recovery rate in resistive or hybrid mode, but are slower in heat-pump-only or economy mode."

They can do better than resistive when they are running heat pump and resistive combined.

The real downsides of heat pump water heaters are the initial cost, the complexity, their size and their free air volume requirements which preclude small utility rooms and closets. There's also an argument that they are noisy especially when used inside and inside use simply robs heat from the space heating.

 

Somebody quoted me $7,250 for an 80-gallon unit, installed. Seemed just a bit dear.

 

Well, there is the corresponding power vs. energy issue: you do need a considerably higher-diameter gas supply line to supply the giant whoosh when it runs, and a matching increased vent capacity for the combustion products. If your existing storage unit is vented through a masonry chimney, etc., with certain dimensions, that might not be adequate for the tankless. You might have to add through-wall venting, and at least at the time I looked into the possibility, that had to be with stainless steel vent pipe and likely run high three figures or more just to install the vent.

At least in towns like mine, the gas distribution is high pressure to the house, and dropped by a regulator right at the house meter. There wouldn't be any upgrade to the service line needed, as long as the regulator that's installed can handle the extra whoosh. If not, the utility can install a bigger regulator; that's cheap.

Apparently there are some towns where the gas service distribution is low-pressure without individual house regulators (that came up a few years ago in the news about the Andover, Massachusetts gas explosions). In a town like that, if the low-pressure line serving your house isn't big enough, there'd be digging involved to change that.

 

Around here at Home Depot a 80 gal A O Smith Heat Pump Hot Water Heater list for about $2690.

There are a bunch or rebates available to take advantage of when buying these units. The AO Smith site list up to $2000 in rebates depending on where you live.

In 2015 we received a federal tax credit and a $500 rebate from our Utility when we purchased ours. Ours would save us in the neighborhood of $250 to $350 each year in utility cost. At the time the 50 gallon GE GeoSpring listed at $999 from the local Lowes. When you put the credits, rebates and savings together it was considerably cheaper than a conventional water heater.

I can see where a specialized install could add considerable cost. Most especially if replacing a gas unit and new electric service would have to be run to the installation.

The only thing different for installing a Heat Pump Hot Water Heater is that it does generate a small amount of condensate so this must be taken into consideration - our goes right into the sump pump area. I guess you need to keep in mind it will be pulling in air and exhausting cooler air when you pick your location.

Some misconceptions about HPHW heaters are their size - ours was 12 inches taller than a conventional 50 gallon water heater and about 75 pounds heavier.

They can be put in an utility closet but the closet doors will have vent grill requirements.

They can be slightly noisy but newer ones will often address this with newer fan design and soft start technology. Moving air through a condenser is always going to have some noise. A garage or basement is an ideal place for a HWHP. I think your climate and housing situation would dictate the best location

Many HWHP warranties are now for 10 years, their reliability has improved a great deal.

 

In that mode, mine popped the circuit breaker several times, so I ceased using it. I don't know how many others are designed better to not do this, vs. just running a single portion at a time, switching between them as appropriate.

The first models were indeed excessively noisy, but later designs have been much quieter, in varying degrees. The Tier ratings (1-4) set minimum efficiency and maximum noise ratings for each level. Placed outside the living space, noise should be quite manageable these days.

Placement inside the home in a place where it robs heat, in a heating dominated climate, is a mis-installation that typically voids any local rebate offers. (The same might not apply to any federal tax credits.) The heat is supposed to come primarily from outside the building envelope. Intake and exhaust venting may allow such installation.

Inside placements may actually be beneficial in AC-dominated climates, getting a 2-fer in improved water heating efficiency and reduced AC load. But careful design is needed to not spoil things.

My all-electric house was built with the water heater in a kitchen closet. After water damage from an overnight failure, I vowed to avoid a repeat by eventually having it moved to the more water-tolerant garage, even before learning about HPWHs. Finally made the move several years before the replacement heater reached its expected end of life. Then a month or so later, selected and had a HPWH swapped in.

The old water heater closest was then converted to expanded pantry space, a very nice kitchen improvement.

 

Another nice alternative to multiple tankless systems is a recirculating pump at the far end of the house. It draws the water forward from the hot water line and recirculates it back through the cold line to the hot water tank. Two different models I found were a remote control where you turn it on in the morning for your showers or one that will automatically turn on at a certain time via timer. That way you're not sending two or three gallons or more down the drain just so you can get to the hot water.
.

 

Here is a link to a new product Rheem makes. A Heat Pump Water Heater made to easily replace gas, oil or propane water heaters. It runs on 120 volts and can run by plugging into a regular 120 v outlet. It is an industry first product!

Rheem Hybrid Electric Water Heater - ProTerra® Plug-in Heat Pump Water Heater with HydroBoost (120V Shared Circuit) - PROPH80 T0 RH120-M - Rheem Manufacturing Company


Brochure:
DD063F75-EEE9-477C-AD14-30247B4E3E44.pdf

 

"In that mode, mine popped the circuit breaker several times, so I ceased using it. I don't know how many others are designed better to not do this, vs. just running a single portion at a time, switching between them as appropriate."

Since 4500 watt resistive elements in water heaters operate one of the time, the typical 30 amp breaker is more than enough to run one of those resistant heaters and the much lower wattage heat pump.

 

It should work fine with the 30A breaker, but for some reason mine didn't consistently do so, and I didn't make much attempt to figure out why. A clamp-on ammeter with recording function would help diagnose the problem, but I don't have such tools.

I notice that the Rheem model linked in John431's post gives an ambient temperature range down to 'just' 37F. I also noticed that on some other models too. But I'm not aware that mine has a low temperature cutout, and do know that it does operate colder, including when the garage drops to 30F. But that cold, it occasionally runs into distress, with the unit (not the breaker) tripping out for a while with a momentary alarm beeper, before restarting. Perhaps the compressor draws excess starting current in such conditions?

There is no chance that both resistive elements are on together. 'Normal' operation has access only to the upper element. If the heat pump portion fails, the unit must be slightly re-wired to power the lower element to get a full tank in resistance backup mode. Which I did when the fan drive was broken. Without rewiring, the top element doesn't heat all that much water.

 

Doesn't that defeat his intent of saving heat energy? All that hot or warm water continually circulating in both sets of pipes will increase energy loss.

It will save water, so is useful in areas where water scarcity is top priority. But I don't see how it can save energy when that is the top priority.

 

In the case of long runs, adding another water heater wastes money; first to install (purchase, plumbing, fuel, maintenance and periodic replacement) to say nothing of the square foot cost in conditioned space especially for those of us without basements. Cost to add recircs at the primary water heater is insignificant. Especially those that use existing hot and cold lines to the remote bath. Easily controlled via wifi light switches.

But its not about cost. Its about quick access to hot water at the distant fixture. While two minutes down the drain is not a wallet buster, most don't like the wait to wash their hands. Central tankless systems are actually worse for hot water timing and often becomes a complaint when a traditional tanked heater has been replaced by a tankless. Tanked heaters maintain heat on the outgoing hot water pipes which effectively reduces wait time.

Plus retrofits of most tankless heaters require provisions for condensate management and new venting. Which is why the latest Rinnai tankless come with non-condensing and recirc capable options. Retrofits are often a bad fit for tankless in large houses.

 

Help me understand what's good about this.

It looks like it just doesn't have any resistive elements installed, so recovery would take forever, right?

I've got a direct oil heat system right now. I plan to keep it, but I want to add a HPWH and a set of valves so I can switch.

 

It looks good for warm places with small electric service capacity, in households not needing more than about 45 to 72 gallons of hot water in a 4 to 6 hour period (recovery rate is just 12 gallons per hour).

Pennsylvania is clearly NOT within its recommended zone for installation, as called out in its spec sheet:

The spec sheet does show no resistive mode. Actually, I don't use the resistive mode on my Northern Climate model either, except in the first few hours after returning from a long trip for which it was shut down.

 

The appealing part of these new offerings are no 240v service needed. You can just plug it in in any available 120 outlet that might be nearby. So, if an installation had an existing 120 outlet near there is no need to have an electrician run a 240 volt circuit which is a deal breaker for many.

The other unit in the brochure needs a dedicated 120 v circuit and boast the largest compressor in the industry giving it an outstanding recovery time and hopefully negating the need for resistive elements.

I do like the fact that our Heat Pump unit has resistive elements for backup but it is ironic - I never want to have to use them.

Each of us have unique situations for our hot water needs and the unit's environment - what seems like an innovation and opportunity for one of us might be unappealing to another situation - I understand that.

I mentioned these new type units in case a need for an electrician to run a 240 v circuit was a showstopper for someone who might have a nearby 120 v outlet near their desired installation point and wanted to get off gas, oil, or propane to take advantage of Heat Pump technology.

As the one gentleman pointed out the graph in his post indicates the desired operating temperature is above 37 degrees. A note to this might be if the installation point is in a conditioned space, it will be above this requirement. An unfinished pit type basement is an ideal spot for a Heat Pump Water Heater. In our area and many areas of the US a pit (underground) basement will stay near 50- 55 degrees even in winter.