Tankless water heater?
- Thread starter MJO21
- Start date
Re: Tankles water heater?
They are energy hogs when in use. you will need 240 for sure, and probably a 30 or 40 amp unit to get decent flow of HW .
They are energy hogs when in use. you will need 240 for sure, and probably a 30 or 40 amp unit to get decent flow of HW .
Re: Tankles water heater?
I know you are asking about electric, but I have some input on my gas tankless system which may be germane. I have a Navien unit that we put in our new construction house in 2016. Supposedly it was the best. Our builder liked Navien and used it multiple times.
Never running out of hot water is nice. However, we have had to have repairs done on it twice since we got it. First time was just out of warranty. That repair was 700 something. After complaining to the company they sent us a check for $200. About 8 months later it quit making hot water again. That was another repair in the approximate $700 dollar range. The plumbing company tankless specialist told us that unfortunately they break a lot. I watched a video, the build show, and he talked about how people misunderstand tankless units. They don’t save money, they are a luxury. If mine breaks again, I may replace it with a different brand.
In summary, don’t do it to save money. It won’t. Only do it if you like really long hot showers
I know you are asking about electric, but I have some input on my gas tankless system which may be germane. I have a Navien unit that we put in our new construction house in 2016. Supposedly it was the best. Our builder liked Navien and used it multiple times.
Never running out of hot water is nice. However, we have had to have repairs done on it twice since we got it. First time was just out of warranty. That repair was 700 something. After complaining to the company they sent us a check for $200. About 8 months later it quit making hot water again. That was another repair in the approximate $700 dollar range. The plumbing company tankless specialist told us that unfortunately they break a lot. I watched a video, the build show, and he talked about how people misunderstand tankless units. They don’t save money, they are a luxury. If mine breaks again, I may replace it with a different brand.
In summary, don’t do it to save money. It won’t. Only do it if you like really long hot showers
Stuart in MN
Well-known member
Re: Tankles water heater?
Unless you take very short showers, a tankless electric may require 100 amps or more at 240vac.
Unless you take very short showers, a tankless electric may require 100 amps or more at 240vac.
walta
Well-known member
Re: Tankles water heater?
The gods of physics say 120V 20 amps = 2400 watts =8100 BTU per hour.
If the incoming water is 40° and you want 115° shower = a 75 ° change
8100/ 75= 108 pound of water per hour you can warm.
108/8.3= 13 gallons per hour.
13/60=.21 gallons per minute.
At .2 gallons a minute you will not enjoy your shower very much.
My electric water heater uses four 40 amp 240 circuits.
Walta
The gods of physics say 120V 20 amps = 2400 watts =8100 BTU per hour.
If the incoming water is 40° and you want 115° shower = a 75 ° change
8100/ 75= 108 pound of water per hour you can warm.
108/8.3= 13 gallons per hour.
13/60=.21 gallons per minute.
At .2 gallons a minute you will not enjoy your shower very much.
My electric water heater uses four 40 amp 240 circuits.
Walta
shade
Well-known member
Re: Tankles water heater?
Totally disheartening to hear. I am on the cusp of putting a Navien 240 in for the endless hot water.
I thought the units had like a 7 year warranty on them?
Totally disheartening to hear. I am on the cusp of putting a Navien 240 in for the endless hot water.
I thought the units had like a 7 year warranty on them?
Re: Tankles water heater?
Endless problems come with the theory of endless hot water.
Water quality and scale issues are not warranty......they are maintenance.
The other surprise is install cost when the electrical service or gas line is not adequate.
Then there’s the long wait for hot water.
The last one is no real savings or payback when it all adds up. Example my hot water cost for 50 gal NAT gas is less than $8.00 per month. With no service/maintenance issues, never run out or wait for hot water. Gravity return to every faucet.
There at least 20 prior threads on endless hot water with all the good bad and the ugly.
Yes, own one in a condo in Florida 120 amp works OK, but the wait for hot water is huge problem.
Running the water at the kitchen for minutes to get hot water for the dish washer is just one small issue.
It’s a vacation home so it works good enough.
Endless problems come with the theory of endless hot water.
Water quality and scale issues are not warranty......they are maintenance.
The other surprise is install cost when the electrical service or gas line is not adequate.
Then there’s the long wait for hot water.
The last one is no real savings or payback when it all adds up. Example my hot water cost for 50 gal NAT gas is less than $8.00 per month. With no service/maintenance issues, never run out or wait for hot water. Gravity return to every faucet.
There at least 20 prior threads on endless hot water with all the good bad and the ugly.
Yes, own one in a condo in Florida 120 amp works OK, but the wait for hot water is huge problem.
Running the water at the kitchen for minutes to get hot water for the dish washer is just one small issue.
It’s a vacation home so it works good enough.
Last edited:
theoldwizard1
Well-known member
Re: Tankles water heater?
It can be done. You probably will not enjoy it for 2 reasons:
A 20 gallon water heater might solve the first problem, but NOT the second !
It can be done. You probably will not enjoy it for 2 reasons:
- Even "tankless" WH have a small tank. The key is to take a short enough shower to not completely empty that tank. One solution is a "push and hold button" to start the water flow. I saw one installation on a boat were the button was on the floor ! To do this requires that the water temperature be pre-set. Check into "tempering" valves.
- Second, also related to tank size, is the recovery time.
A 20 gallon water heater might solve the first problem, but NOT the second !
Last edited:
Re: Tankles water heater?
Many times the rebates associated with tankless are the driving force for installation .. same with the heat pump electric tank units. If you need endless hot water the tankless are the solution -- I have one at my beach house that just feeds the outdoor shower.
The heat loss of a tank unit is all dependent on application -- I have a small 120v tank unit for my outdoor kitchen that's on a timer to only run on the weekends.
Running it all week would be foolish as we don't use it ...
My indirect tank unit connected to my cast iron boiler has a timer that keeps the recharge off after 10pm and will not recharge until the morning. It's set for our common schedule -- the tank is still holding it's hot water if you need a shower. So typically it reheats just before we use the bathroom and the boiler is still hot when the tank drops from use -- so there is less waste from heating a boiler just to heat the tank. This is in the summer -- so the boiler only fires for hot water. Most days the tank never need to reheat until the later afternoon when we get home.
I see that there are many more condensing gas tank unit on the market -- I think for many this may be the future. Simple and reliable. I did a Polaris unit years ago ... some people had lot of problems with them. Mine went thorough the igniters .. always kept one around
Many times the rebates associated with tankless are the driving force for installation .. same with the heat pump electric tank units. If you need endless hot water the tankless are the solution -- I have one at my beach house that just feeds the outdoor shower.
The heat loss of a tank unit is all dependent on application -- I have a small 120v tank unit for my outdoor kitchen that's on a timer to only run on the weekends.
Running it all week would be foolish as we don't use it ...
My indirect tank unit connected to my cast iron boiler has a timer that keeps the recharge off after 10pm and will not recharge until the morning. It's set for our common schedule -- the tank is still holding it's hot water if you need a shower. So typically it reheats just before we use the bathroom and the boiler is still hot when the tank drops from use -- so there is less waste from heating a boiler just to heat the tank. This is in the summer -- so the boiler only fires for hot water. Most days the tank never need to reheat until the later afternoon when we get home.
I see that there are many more condensing gas tank unit on the market -- I think for many this may be the future. Simple and reliable. I did a Polaris unit years ago ... some people had lot of problems with them. Mine went thorough the igniters .. always kept one around
Last edited:
59 wagon man
Well-known member
Re: Tankles water heater?
1- 220 v 110 will give you luke warm water with a minimal amount of warm water
2- tankless or tank doesn't affect the time to heat the water. the difference comes in the amount of heat that leaves the heater even when the heater is off. the microsecond it takes to kick on and make hot water is negililable and you might add a second due to the heater itself
3- not sure about your incoming water temp as this has a great affect on your hot water temp leaving a tankless. for example I live in fla and the avg incoming water temp is 70 degrees to a 40 degree rise in temp gets me 110 degree water whereas in the winter lets say your incoming water temp drops to 50 that same 40 rise only gets you 90 or lukewarm.
4- certain faucets cant be used with a small tankless such as a roman tub as when the faucet is wide open the flow of water is too fast and the heater doesn't have a chance to heat it. close the faucet halfway and you get hot water but then it takes so long to fill the tub that the water in the tub is cooling off
1- 220 v 110 will give you luke warm water with a minimal amount of warm water
2- tankless or tank doesn't affect the time to heat the water. the difference comes in the amount of heat that leaves the heater even when the heater is off. the microsecond it takes to kick on and make hot water is negililable and you might add a second due to the heater itself
3- not sure about your incoming water temp as this has a great affect on your hot water temp leaving a tankless. for example I live in fla and the avg incoming water temp is 70 degrees to a 40 degree rise in temp gets me 110 degree water whereas in the winter lets say your incoming water temp drops to 50 that same 40 rise only gets you 90 or lukewarm.
4- certain faucets cant be used with a small tankless such as a roman tub as when the faucet is wide open the flow of water is too fast and the heater doesn't have a chance to heat it. close the faucet halfway and you get hot water but then it takes so long to fill the tub that the water in the tub is cooling off
dcg9381
Well-known member
Re: Tankles water heater?
If you're at 110V, my advice would be to use a small water heater - 10 gallons or perhaps a bit more. These will only pull moderate amperage and can build up heat.
A point-of-use system for anything beyond basic hand washing, at 110V, it's gonna pull a lot of amps... If you've got the power, go for it.
In my shop, I wanted tankless. After looking at what it would take to do a basic 3GPM, I went to a $240 tankless water heater - but did propane and a 100 lb propane tank. We're basically living at the shop now and that tank lasts us 2 months or so.
To some degree, it's also highly dependent upon the temperature of your incoming water. Our water is rarely below 60 degrees, so power/fuel required to heat it to 108 degrees isn't that bad.
If you're at 110V, my advice would be to use a small water heater - 10 gallons or perhaps a bit more. These will only pull moderate amperage and can build up heat.
A point-of-use system for anything beyond basic hand washing, at 110V, it's gonna pull a lot of amps... If you've got the power, go for it.
In my shop, I wanted tankless. After looking at what it would take to do a basic 3GPM, I went to a $240 tankless water heater - but did propane and a 100 lb propane tank. We're basically living at the shop now and that tank lasts us 2 months or so.
To some degree, it's also highly dependent upon the temperature of your incoming water. Our water is rarely below 60 degrees, so power/fuel required to heat it to 108 degrees isn't that bad.
napaul
Active member
Re: Tankles water heater?
ive had my rinnai tanlkess running off natural gas in for 9yrs now. have a water softner hooked up as well in house hold never had any scale build up or break downs. only maintenance is every couple years cycle water with vinegar through the manifold to clean it. as for hot water furthest tap away takes 20-30 sec to get hot water. cant speak for anyone else but I saw savings right away not having an 50gallon of water being heated 24hrs a day even when not in use. so for the increased btu that it will run when you do use it to me still offset by the non use the other hrs of the day.
ive had my rinnai tanlkess running off natural gas in for 9yrs now. have a water softner hooked up as well in house hold never had any scale build up or break downs. only maintenance is every couple years cycle water with vinegar through the manifold to clean it. as for hot water furthest tap away takes 20-30 sec to get hot water. cant speak for anyone else but I saw savings right away not having an 50gallon of water being heated 24hrs a day even when not in use. so for the increased btu that it will run when you do use it to me still offset by the non use the other hrs of the day.
Leaflessshadetree
Well-known member
Re: Tankles water heater?
It's all about gallons per minute.
I have a small 220V unit. I can run a decent stream of very hot water for hand washing. If I turn the faucet up to even half flow all I get is cold water.
It's all about gallons per minute.
I have a small 220V unit. I can run a decent stream of very hot water for hand washing. If I turn the faucet up to even half flow all I get is cold water.
dcg9381
Well-known member
Re: Tankles water heater?
It's about GPM and the temperature of the incoming water... Those two things are the biggest factor.
The tankless heater I have has an adjustable "flow regulator" so that I can limit the GPM coming in. Most of these setups have pretty good information on their performance at GPM and degree temperature rise. I couldn't do electric, just the cost of bringing 60A of wire over to the other side of the shop - and I was going to get close to being able to max out the shop electrical feed if I pulled another 60A.
I actually have our tankless water heater plumbed into a host bib outside the shop, as we're living in the RV right now... went from a 6 gallon water heater (RV) to something that can sustain infinite hot water as long as flow is < 3GPM and 40 degrees...
It's about GPM and the temperature of the incoming water... Those two things are the biggest factor.
The tankless heater I have has an adjustable "flow regulator" so that I can limit the GPM coming in. Most of these setups have pretty good information on their performance at GPM and degree temperature rise. I couldn't do electric, just the cost of bringing 60A of wire over to the other side of the shop - and I was going to get close to being able to max out the shop electrical feed if I pulled another 60A.
I actually have our tankless water heater plumbed into a host bib outside the shop, as we're living in the RV right now... went from a 6 gallon water heater (RV) to something that can sustain infinite hot water as long as flow is < 3GPM and 40 degrees...
Re: Tankles water heater?
If you really have 110V or 220V, the water heater will operate at a reduced wattage, since standard water heaters are 120V or 240V. A tankless electric WH has huge power requirements, if natural gas is not available as much as I hate propane, I would still recommend gas over electric.
If you really have 110V or 220V, the water heater will operate at a reduced wattage, since standard water heaters are 120V or 240V. A tankless electric WH has huge power requirements, if natural gas is not available as much as I hate propane, I would still recommend gas over electric.
pmiranda
Well-known member
Re: Tankles water heater?
110 mounted right under the sink works great for washing hands with a low-flow faucet. We have these at work, and I've used them in other public places. They're fine and you only have to plumb cold water and wire it up.
A totally different problem for whole house. Electric will be a challenge. I'm putting in a 24KW unit at my new shop since it's going to be mounted on the wall right behind the sink and shower.
At our house, we have a big gas Rinnai tankless, and coupled with a small electric tank unit and a recirc pump with timer and motion sensor, it's fantastic. The recirc pump keeps the fixtures primed with hot water when we're around the house, and the gas unit can run hot for hours.
The key to long life is to have flush valves installed and use them every year to remove scale, unless you happen to already have a water softener upstream.
110 mounted right under the sink works great for washing hands with a low-flow faucet. We have these at work, and I've used them in other public places. They're fine and you only have to plumb cold water and wire it up.
A totally different problem for whole house. Electric will be a challenge. I'm putting in a 24KW unit at my new shop since it's going to be mounted on the wall right behind the sink and shower.
At our house, we have a big gas Rinnai tankless, and coupled with a small electric tank unit and a recirc pump with timer and motion sensor, it's fantastic. The recirc pump keeps the fixtures primed with hot water when we're around the house, and the gas unit can run hot for hours.
The key to long life is to have flush valves installed and use them every year to remove scale, unless you happen to already have a water softener upstream.
Re: Tankles water heater?
I don’t remember all the details on warranty, but I do know that labor warranty is only year. Obviously, the labor of a plumber adds up. Navien wasn’t very helpful. As someone else mentioned, you have to be careful about scale build up. We had a water softener installed at the same time. I think it’s pretty much a requirement. The flushing with vinegar every 6 months is easy. Plenty of videos on you tube on how to do it.
I have a recirculator pump so no real wait for hot water to reach farther away rooms.
I don’t remember all the details on warranty, but I do know that labor warranty is only year. Obviously, the labor of a plumber adds up. Navien wasn’t very helpful. As someone else mentioned, you have to be careful about scale build up. We had a water softener installed at the same time. I think it’s pretty much a requirement. The flushing with vinegar every 6 months is easy. Plenty of videos on you tube on how to do it.
I have a recirculator pump so no real wait for hot water to reach farther away rooms.
555
Well-known member
Re: Tankles water heater?
We have a 120/20A unit at the farm. It's OK for washing your hands and/or cleaning equipment. We "tested" it one day and after 7 gallons the water starts cooling. At 10 gallons it is done. When the tankless dies, it will be replaced with a gas 30 gallon water heater.
We have a 120/20A unit at the farm. It's OK for washing your hands and/or cleaning equipment. We "tested" it one day and after 7 gallons the water starts cooling. At 10 gallons it is done. When the tankless dies, it will be replaced with a gas 30 gallon water heater.
I have a Liquid Propane Rinnai that I'm happy with and I don't see myself going back.
Mine is in a central location so the wait isn't bad and it will never ever run out of hot water unless the electricity goes out because it has electric controls. I've had zero issues with it unlike tank heaters crapping out every 5 years. If you guys think those little 110v or even 220v under the sink units are for anything much more than washing your hands you're delusional. You have to calculate the BTU's required to properly size the heater needed for the task you're asking it to do. If it's not big enough the blames on you.
Mine is in a central location so the wait isn't bad and it will never ever run out of hot water unless the electricity goes out because it has electric controls. I've had zero issues with it unlike tank heaters crapping out every 5 years. If you guys think those little 110v or even 220v under the sink units are for anything much more than washing your hands you're delusional. You have to calculate the BTU's required to properly size the heater needed for the task you're asking it to do. If it's not big enough the blames on you.
Re: Tankles water heater?
How much savings ....?
We have min charge .... but even in the off season ...my bills are low 20's. With 3 people / dryer and range? 40 tank in that house.
How much savings ....?
We have min charge .... but even in the off season ...my bills are low 20's. With 3 people / dryer and range? 40 tank in that house.
When I was doing my place, the plumber wouldn't install electric, tankless on-demand water heaters. He said too many issues and not great performance. He does recommend natural gas ones though, so that's what I used. No complaints whatsoever.
theoldwizard1
Well-known member
Most interesting thing I recently saw about tankless water heaters. A family of 5 living "off grid" WITH propane, actually installed TWO propane fired, tankless water heaters in series. Builder/husband is a plumber by trade and wanted the family to have "endless" hot water !
Re: Tankles water heater?
Saving ?
Exactly the question.........if your bill is $6-8 for NAT gas usage, it’s not ever possible to make a tankless cost plus install pay off. Unless of course your never home.
My NG bill is in the low $20’s witha $17 fixed charge. That’s hot water, gas drier and cook top.
Saving ?
Exactly the question.........if your bill is $6-8 for NAT gas usage, it’s not ever possible to make a tankless cost plus install pay off. Unless of course your never home.
My NG bill is in the low $20’s witha $17 fixed charge. That’s hot water, gas drier and cook top.
pmiranda
Well-known member
Hmm... I know when we got our NG tankless installed we were lucky to have a "medium pressure" meter (red face) so we could make the required flow without needing to go to bigger pipes.
Maybe with a propane tank you can only get low pressure, so to get enough BTUs to make hot water in winter it takes two smaller units, each drawing less volume than our one big unit?
theoldwizard1
Well-known member
Hope they have an endless supply of propane.........
The guy has the biggest tank I have ever seen ! I have seen refill places that had smaller tanks !! (He also uses it for his back up generator when he has insufficient solar.)
pmiranda
Well-known member
Shameless plug for my employer: He should look into a Tesla Powerwall.
Silent backup energy since Zombies can hear generators
dcg9381
Well-known member
Not sure. I'm in Texas, so it doesn't get cold (very often) - yesterday it was in the 40s and full tanks registered a substantial pressure drop. I don't understand the need for 2 tankless units in series - you'd think you just need one with appropriate temperature rise capacity.
One unit works fine for us here with a family of 3, but we currently use a single shower while we are "shop living". Our shower seems to consumer less than 1.7 GPM at full flow, so we use a 3 GPM "capable" propane tankless. It's got a 3/4 line and a regulator sitting on a 100 lb propane tank...
My guess is they are doing two or more showers at once and have very cold incoming water..
100 lb of "portable" propane lasts us 2 months...
dcg9381
Well-known member
Shameless plug for my employer: He should look into a Tesla Powerwall.
Silent backup energy since Zombies can hear generators
K, the comment about Zombies is the most solid reason I've heard of to use a Tesla power wall! That makes sense in all circumstances.
Outside of that, I can't see using one of those things unless you're on variable rate power and can store cheap / use when expensive. They appear to require specific "backup" circuits - which makes sense - IE, they won't cover the whole house.
The only other "upside" I could see is that these might be able to function with PV solar systems while the grid is down? You can't do this with a generator - at least not without some additional equipment...
pmiranda
Well-known member
I don't know the details since I don't have one myself, but there is a user forum where I saw some people were able to use 2 or 3 in parallel to run a "whole house". Obviously some houses are bigger than others, and the limiting factor beyond run time is the capacity of the output inverters. Maybe they just had to spread out the loads to stay under the output rating for each unit?
Most generator installs I've seen use a basic on/off load switch, so you can lose power for a second or more after power goes down before the genny picks back up. Doesn't help with a brownout so you still need a UPS for anything that needs to keep running.
Cool stuff, I'm sure there are other threads about it.
Most generator installs I've seen use a basic on/off load switch, so you can lose power for a second or more after power goes down before the genny picks back up. Doesn't help with a brownout so you still need a UPS for anything that needs to keep running.
Cool stuff, I'm sure there are other threads about it.