Tankless water heater yes/no

[sarahperdue]

I'm considering a tankless water heater for the country house. I like the idea of it taking up less space.

The rest I'm not sure about. Electric vs gas? If I go with gas, I'll install it during the restoration but keep using the electric tank until we move here permanenty and get natural gas service. An all electric home is also a possibility

Thanks,
Sarah

 

[wayupnorth]

I know of several people with tankless Rinaii gas water heaters. All say they never run out of hot water but you can only have one tap open at a time. They are silent and only use gas when a faucet is turned on. Not one owner has a bad thing to say about them.

 

[circlew]

My sister and her husband are on their second tankless gas water heater. The first one was a real pain to deal with, as the faucet had to be fully open for any hot water to be made. Their present one seems to work well, with no such issues.

Don't know why someone would say only one faucet could be used at a time, unless it's a small capacity unit. My sister's doesn't have such limitations. The washateria I sometimes go to has two gas tankless units, and multiple washers can fill with hot water at once, in addition to the restroom sink.

If you decide on a tankless electric water heater, you must have a high capacity electrical system. The heaters alone require a 150 amp circuit for units large enough for a whole house. This means a minimum 400 amp service coming into the house. If you have electric space heating, it may require larger. My plumber told me he installed two electric tankless units in a rather large all-electric home, and an 800 amp service was used.

 

[DADoES]

 
Tankless water heaters, of course, heat the water instantaneously as it flows through, which calls for a L-A-R-G-E instantaneous input of energy.

Capacity ratings are based on temperature rise (lowest expected seasonal supply temperature vs. the desired output temperature) and required gallons-per-minute flow rate to handle the expected number of simultaneous usage tasks.

Gas units have burner ratings upwards of 200,000 BTU.  Electric units require upwards of a 120+ amp circuit.  The gas supply service or electrical service to the house may need upgrading to accommodate it.

"Instantaneous" refers to heating the water on-the-fly as it flows through (vs. storing a large volume of already-heated water in a tank).  It does not mean that water at 130°F will be instantly flowing from a turned-on tap that hasn't been run for 6 hours (unless a recirculation pump is involved, which partially kills the premise of tankless, LOL).  There is still several seconds delay while the gas burner ignites (or elements energize) and the heating chamber rises to-temp and the supply line is purged.  Tankless does not compensate for plumbing designs that place usage points at a distance from the water heater unless (again) a recirculation pump & path is involved, or multiple tankless units are placed strategically near the distantly-spaced usage points.

The primary benefits of tankless are 1) less physical space required vs. a tank heater and 2) endless supply of heated water which can accommodate soaking tubs and such, and may lead to increased usage when family members find they can shower for 2 hours without the water going cold.

I have an electric unit, 120 amp circuit, it varies the power draw according to the heating requirements.  There is no natural gas in this area outside town and the builder opted not to involve the infrastructure for propane.  There are two whirlpool tubs in the house (which I rarely use), which may have been a factor in the builder installing tankless vs. a large-enough tank unit to handle them.  It's in a broom closet in the laundry room.  I like that I can set any temperature between 50°F and 140°F.  I set it at 103°F as normal for showering, raising it temporarily (it auto resets after 30 mins [or 15, 45, or 60 depending on the option setting]) for other tasks ... or sometimes lower it for example for a cooler shower after yard work.

A minimum flow-rate is required to keep the unit activated so lowering the setpoint is better than attempting to moderate by turning down the hot flow.  I've run across complaints from people about showers starting hot and going cold, which can happen if the tankless setpoint is too high and the showerer (showeree?) turns the hot flow down too low which causes the unit to turn off.  The fix, counterintuitively, is to reduce the setpoint so the hot flow can be run faster.  Best performance for a discrete hot water task is to set the unit exactly at the desired temperature and run only the hot tap.

There's no physical restriction on how many hot water faucets can be turned on simultaneously.  The output temperature will be reduced if the unit's heating capacity is exceeded.  Some tankless units may have a built-in flow restriction mechanism that lessens the flow rate in an attempt to maintain the target output temperature.  I think mine is too old (18 years) to do that.

 

[mattl]

The current draw for electric is massive and the gas requirements are substantial. Make sure your utilities can support a tankless.  in your area temp rise should not be a problem, but in northern areas it can be in the winter. It also depends on how hot you like your water, me I like HOT and my gas heater is set as high as it will go, 150 ish.

 

[qsd-dan]

If you have NG to the house, that would be your best option since it's cheaper to run and has a longer life. Get a condensing unit rather than a non condensing. You'll need at least a 3/4 inch dedicated line to the unit itself, preferably 1 inch.

 

[gizmo]

Hi Sarah

 

Here is a link to my review of one of these units on productreview.com.au

The review is 11 years old, my opinion hasn't changed. The Rinnai instantaneous has been fantastic.

 

It has a strainer in the inlet to catch any muck in the water supply, we find it gets restricted every couple of years and needs to be cleaned out. It is an easy D.I.Y. task. We are on tank water, on mains it might be only every 5 years??

 

I consider that I have a pretty good knowledge of these units, including how to get the best of them, and their limitations. I'm happy to answer any further questions you may have.

 

If you buy a gas instantaneous, I'd strongly recommend Rinnai brand and get the optional temperature controller pads, say one in the kitchen and one in the bathroom, so hot water is made to the end-use temperature and you don't blend cold water in to it. This is dramatically more efficient and as a side benefit, you will find that the lower the delivery temperature, the less the flow is robbed from one outlet when someone opens a second outlet.

 

The temperature controller pads allow you to easily set it to (sorry, I'm metric) 45 degrees C for a shower and later to 55 degrees C for washing dishes. As the water is heated for use, not stored at high temperature, there is no concern about legionella bacteria, so no need for it to exceed 60 degrees C.

 

The smaller units have a lower minimum flow requirement, so a small unit is less likely to do that annoying thing of cutting out at low water flows. If you have a large home or it is important to you that it can supply multiple outlets at the same time without flow reducing, I'd fit two separate smaller units, maybe one for bathroom and one for kitchen/laundry? This would cost more of course and the plumbing would have to be modified to keep the two circuits separate. 

 

If it is just for you and partner, then a single small unit should work just fine. You may need to communicate with each other, something like "Sweetie darling, I'm about to have a shower and if you turn on another tap I will slit your throat..."

https://www.productreview.com.au/reviews/7dd45df3-3272-3347-aced-0f85a196d571

 

[sudsmaster]

Only ever lived with a tank type water heater, always gas.

 

However, apparently on this block there was a problem with the water main about 10 years ago. Sand was getting into it. And that showed up in the water heater tank. Probably made it burble more.  I got in the habit of flushing the water heater... it's probably due for another flushing. The water company fixed the leak/sand problem, apparently. The current water heater here is probably 30 years old now, might be EOL.

 

I *think* the sand/water main problem was responsible for a number of residents needing to replace their water heaters more often than otherwise might be necessary.

 

One good thing I did a few years ago was to replace the anode rod in the water heater. The old one was nearly gone.

 

[combo52]

Best water heater options

Tankless gas water heaters are best where there’s a space problem or you need a near continuous amount of hot water occasionally.

They do have a number problems the lifespan of them is still a mystery they need more maintenance they won’t work without electricity if you try to run hot water at multiple places at the same time there will be some drop off in temperature.

A tank type gas water heater is still a good choice they will work without electricity.

In a more southern location like yours a heat pump electric water heater is probably the best long-term option it’s easily as cheap to operate as a gas one and it has the added benefit of dehumidifying and cooling the area that it’s installed in.

I highly recommend the heat pump water heater. You often can get large rebates from your power company for buying them.

I would never use a pure electric water heater either tank type or instantaneous it’s just not a Sustainable choice in a planet that’s got such Serious energy issues

 

[sarahperdue]

Great info, all

John, I've never heard of a heat pump water heater. I'm a little confused--are heat pump water heaters electric? Do they require gas?

When you say pure electric are you making a distinction between electric heat pump vs pure electric?

Currently, I have an electric tank water heater--sounds like what you are describing as pure electric.

I currently don't have gas service to the house, but that might change when we become permanent residents.

Something I keep forgetting to mention is that the water is from a limestone aquifer and is very alkaline. I have problems with calcium scale in the plumbing fixtures especially when the water sits--toilets when we haven't been down in a while. As far as I can recall, washing machines seemed to last a pretty long time.

 

[DADoES]

 
Tankless water heaters should be given recurring maintenance, flushing with a descaler solution on a schedule according to how bad is the water hardness if it's not mechanically softened.  A proper installation includes bypass valves to faciliate connecting hoses and a pump for the process.

Heat pump water heaters are electric tank units with a refrigeration system attached on top to draw heat from the room air and put it into the tank ... same-but-in-reverse as a refrigerator removing heat from inside the box and putting it into the room. They also have traditional heating elements in the tank in case of compressor failure or a high-demand usage event in which the heat pump can't keep up.  A side benefit is that they cool and dehumidify the room in which they're installed, a large boon for a garage or storage room in a hot summer climate.  Some models can perhaps be connected to outdoor intake and exhaust ducts.

 

[qsd-dan]

Explanation of a heat pump water heater below. If you add a solar system in a addition to one of these units, you could achieve net zero...basically, free heated water. The heat pump end of the unit is only good to about 120F, any setting above that and the elements will kick in. These generally work best in hotter areas where the water heater is located in the garage.

 

[daveamkrayoguy]

Househuntng online, I would see at least one tankless water heater, in mostly fairly small-sized one-bathroom dwellings, and of course there seems to be a demand for them if you find them in hardware stores or big box retailers like Home Depot and Lowe's...

The demand is small, if I''d never really seen one in real life, only a few TV commercials, otherwise, with the exception of a few electric tank water heaters in such small applications where little demand for hot water is needed and electrical is a more practical option there, gas-tanked heaters are the majority...

Good luck with your research on where you wil go for your hot water, Sarah...

-- Dave

 

[mattl]

I'll second or third the recommendation for a heat pump water tank. quite efficient.  As mentioned often rebates from utilities are available.

 

[gizmo]

Yes despite giving the Rinnai instantaneous gas a big rap, I would also strongly recommend a heat pump HWS.

One of the world's first of these was Siddons Solarplus in Australia, I think 1970s?? They were very reliable.

Newer ones are super efficient, you get maybe 4500 watts of heating for every 1000 watts of power consumed. The nearest thing to magic that is real. In Australia they are always mounted outdoors, it appears in USA they are often indoors or in garages?

 

Link below is to a Sanden brand, I think Japanese?? and super-efficient with CO2 refrigerant. There is a how-it-works video, which I haven't watched. Sanden has a very good reputation here, not sure if it is available in USA.

How the Sanden Heat Pump Works – Sanden Hot Water Heat Pumps

www.sanden-hot-water.com.au

 

[gizmo]

Sarah - to answer your questions above, heat pump hot water units are fully electric. No gas.

They are super efficient, so they generally only require a small electric connection - In Australia, a standard 240 volt 10 amp, in USA I don't know if they are 110 volt 15 amp or something upgraded from there, but they won't require a huge heavy power supply.

I get the idea you like to really research before purchasing,(like me) and I would recommend you doing some homework to get your head around these heat pump units. They are amazing and a very good option.

 

[polkanut]

Go for gas!

We have a 40-gallon Ruud Power Vent model that was installed in July of 1998, and it's still going strong. Granted this is only a 2-person household, but still. We've only run out of hot water twice, and both times it was because of me. Each time I decided to do a load of laundry, run the dishwasher, and take a shower, all at the same time. Otherwise, never any problems with running out.

Power Vent | Ruud Residential Gas Water Heaters

www.ruud.com

 

[pulltostart]

Sarah,

You could contact Alabama Power and see what they have to offer in the way of rebates.  I switched from a gas water heater to electric last fall and APCO gave me the water heater for switching.  They might have an offer on a heat pump model that would better inform your decision.

 

lawrence

 

[sarahperdue]

ANYTHING

That sucks heat and humidity out of a room is a great thing in southern Alabama! This concept alone is enough to sell me on the heat pump--especially since I'm planning to install the unit in a bathroom...

Lawrence, I will definitely talk to the power company. My buddy at APCO is on my list to call anyway. After the last hurricane, the put the replacement power pole in my front yard because the oak that fell on it during the storm needed to be removed before they could replace it in its original location. I just had the oak removed.

Chris, thank you for your detailed information. I'm becoming increasingly interested in the heat pump. It sounds like an excellent option for my location.

Tim, I'm not doing gas until the house is continuously or almost continuously occupied. It's located over 30 minutes from the nearest fire department, and I worry too much about the damage careless burglars could do if they removed appliances (water and space heaters) without properly turning off the gas. I watched my great grandmother's house burn to the ground in 1978. Rational or not, I'm afraid of connected gas in an intermittently occupied residence.

Sarah