Tankless water heaters

[Splatter]

I’m remodeling my bathroom and I’m considering upgrading to a tankless water heater at the same time.

I live in southwest Montana and have a bath/shower and 2 sinks that will draw from the heater.

Some of the things that I’m wondering about are brand, output/size of the heater, wiring it in (which will probably be the hardest part for me), and any issues that you may have encountered if you’ve done this before.

My place is pretty old and I’ve been upgrading as I get the cash to do so. As it sits most of the house is wired for single phase electric and it seems that most heaters are dual phase. Is this a tough obstacle to overcome? I was also wondering about 220 vs 110.

Electrical is not my strong suit so any advice on that front is greatly appreciated.

Thanks everyone.

 

[slingerHB]

Your house is single phase electric,your voltage is 120/240 volt. Your terminology is off just a little! Most on demand water heaters are gas (natural gas/propane) they do make electric on demand but that is definitely not the most efficient or cost effective way unless you are on municipal electric which is cheaper. If it is a gas on demand then it will only require a 120v outlet to plug in. I'm no help on sizing of the unit though.

Sent from my SM-A426U using Tapatalk

 

[Esq]

You will regret using an electric on demand hot water heater. They take a lot of juice for a small output. You would be better off getting a propane unit. To size the unit you will want to know the temperature of your water during the coldest time of the year. For me, our well water is always apx. 58-degrees, but City water can be as cold as 40-degrees at times. Then look at the chart for the unit, it will show how many gallons of hot water it will deliver at whatever starting temp. For small houses, I have used the Rheem Performance Plus 7.0 GPM available at Home Depot for just under $1k. There may also be local rebates available to you.

 

[BBob]

Most all tankless manufacturers have sizing tables or recommendations regardless of gas or electric. Most are broken down by region as well. You won’t be running a whole house electric on 110 even if it’s a small home. Most electric will require two or more double pole breakers to operate so you need to make sure there is room in your panel.

 

[butcherboy]

Make sure you size it for the correct size of gas line as well.

 

[Jstumbaugh]

You want a Navien NPE240 given the climate that you’re in with the ground water temp and your demand needs. 110v outlet plug. You will have to mitigate the condensate it produces and direct vent it.

 

[BBob]

Make sure you size it for the correct size of gas line as well.

Agreed! Most homes gas lines aren’t sized large enough to run the BTU’s so you need to budget for upsizing lines. Definitely check before buying.

 

[Broomd]

You will regret using an electric on demand hot water heater. They take a lot of juice for a small output. You would be better off getting a propane unit. To size the unit you will want to know the temperature of your water during the coldest time of the year. For me, our well water is always apx. 58-degrees, but City water can be as cold as 40-degrees at times. Then look at the chart for the unit, it will show how many gallons of hot water it will deliver at whatever starting temp. For small houses, I have used the Rheem Performance Plus 7.0 GPM available at Home Depot for just under $1k. There may also be local rebates available to you.

NOPE.
Love our electric Stiebel Tempra on-demand heater!
3 x 30 amp breakers, but the damn thing is barely ever on.

We've done the math, cost is a joke over the last 15 years of using it.
We recommend to everyone we can, and if you live remotely like we do, no natty gas is needed.
The last thing we want is to need that or any other gas or oil delivery.

 

[Jstumbaugh]

Do your lights dim when it turns on and do you create your own electricity? That’s half of a standard house’s electric panel

 

[journeyman713]

You will regret using an electric on demand hot water heater. They take a lot of juice for a small output. You would be better off getting a propane unit. To size the unit you will want to know the temperature of your water during the coldest time of the year. For me, our well water is always apx. 58-degrees, but City water can be as cold as 40-degrees at times. Then look at the chart for the unit, it will show how many gallons of hot water it will deliver at whatever starting temp. For small houses, I have used the Rheem Performance Plus 7.0 GPM available at Home Depot for just under $1k. There may also be local rebates available to you.

I'll disagree with this. We used electric on-demand water heaters in industrial manufacturing processes for a long time. It works quite well.

For the power question, you definitely will want to run 220 volts. It's better all the way around. Your house already has 220v, you will need to pull a wire from circuit breaker panel anyway.

 

[slingerHB]

I've wired in 2 electric on demand units for people that had municipal electric,so its really cheap electric. The first one required such a demand that the electric company had to install a transformer just for that house because it was causing flickering and dimming at the other two houses on that transformer. The second unit would take 3-1/2 - 5 minutes to get up to temp and would struggle in the winter months. Both units used 4 double 40 breakers which I don't like as well because it uses so much panel space.

Sent from my SM-A426U using Tapatalk

 

[Bluefish]

Had one in my last house and hated it. mine was gas and needed to have a high temp vent which was expensive and thus we put it on an outside wall. Unfortunately this meant that the waterlines were a long run, so you had to run the water for a long time to get warm water. Also if you turned it off it would have a large slug of cold water until it started going again. It lasted about 1 year until we had super cold weather and a strong wind. It froze the coil and ruptured. Didn’t like it enough to replace it.

if I was going to do one again, I would look at ones that have a small tank, 1-2 gal that is kept hot then switches to on demand. Also make sure you Don’t need special venting.

 

[Broomd]

I've wired in 2 electric on demand units for people that had municipal electric,so its really cheap electric. The first one required such a demand that the electric company had to install a transformer just for that house because it was causing flickering and dimming at the other two houses on that transformer. The second unit would take 3-1/2 - 5 minutes to get up to temp and would struggle in the winter months. Both units used 4 double 40 breakers which I don't like as well because it uses so much panel space.

Sent from my SM-A426U using Tapatalk

Garbage units.

 

[Mighty Mouse]

110V tankless water heaters do exist, but they're designed for low flow (less than 1 gallon per minute) applications. To serve two sinks and a shower, you would need a 220V heater.

Power coming into your home's breaker panel is 110/220V split phase carried by two 110V hot wires (red or black) and one neutral wire (white). The two hot wires are 180 degrees out of phase with each other, which produces a 220V differential voltage across them. You could think of one hot wire as 110V positive and the other as 110V negative, which makes for a total of 220V of difference between them. Most circuits in your home run off a single 110V hot wire. Higher demand appliances (stove/oven, clothes dryer, air conditioner) require 220V and thus need to be connected to both ("positive" and "negative") 110V hot wires.

Wiring up a 220V circuit isn't much more complicated than a 110V...double pole instead of single pole breaker(s) and one extra conductor wire.

 

[CB4]

Make sure your water pressure isn't too high. The previous owners of our house ripped out a tankless for a tanked because they couldn't get hot water in the winter. The real issue was the water pressure was over 120PSI throughout the house and no regulator was installed when the house was built. The water didn't have time to heat up it was moving so fast. I curse the previous owners to this day for that.

 

[Splatter]

Thanks very much for all the help and replies. As you can tell by my misuse of terms and inaccurate numbers that this is all new to me so experience is doubly appreciated.

Please continue to offer any advice if you’ve got it. I do have access to gas, right now my stove and heat are from gas. Everything is municipal.

Thanks again.

 

[journeyman713]

Thanks very much for all the help and replies. As you can tell by my misuse of terms and inaccurate numbers that this is all new to me so experience is doubly appreciated.

Please continue to offer any advice if you’ve got it. I do have access to gas, right now my stove and heat are from gas. Everything is municipal.

Thanks again.

Forget the gas, it is not practical and takes away the main benefit. Location near to the demand, As said, you have to think about ventilation for the gas unit as well.

The 110unit will need double the time or amperage to heat. Wiring 220v is just as easy as 100v, as said.

 

[Mighty Mouse]

Operating cost is something I would factor into the decision. At $0.12/kilowatt-hour for electricity vs. $10/dekatherm for natural gas (approximate current prices in my neck of the woods), energy cost of a gas heater would be about a third that of an electric heater. That's a big difference percentage wise, but savings in total dollars depends largely on much you're using it. If it were just providing hot water for one 10 minute shower per day, I came up with an energy cost difference of $7.22 per month.


If you do choose a gas heater, it might be worth checking with your gas provider to make sure their meter and regulator can handle the additional flow. I would think they would be willing to upsize them if necessary since they would be selling you more gas.

 

[Esq]

SlingerHB's account is consistent with my experience. Journeyman713, venting the gas unit is typically very easy with modern condensing models.

 

[Mcnasty]

Can't comment on the electric but I have had 2 Gas units installed. both were/are Rani( SP?) and I love it. both times I had to upsize the gas line. this was not an insignificant additional cost. They take a second or so to get rolling so that plus the length of your line will drive how long it takes to get hot water. Need to consider your mounting locations as well as they do vibrate a lot you front want to mount it to studs say below the floor that will vibrate when ever it runs. Only draw back for me is my 2 teenage boys no longer understand the meaning of a quick shower before the hot water runs out, this =$$$. Lastly they also need to be descaled every so often depending on you water.