Have tankless water heaters gotten better?

[Tommy2000GT]

I'm currently in the process of remodeling and I'm considering changing to a tankless gas water heater to save space.

Are complaints like cold water sandwich and reliability still a concern?

 

[Greenman]

They're pretty good, as long as you buy a quality unit. Where they stumble is on small use. That heater will fire off at 100k BTU's when you need a gallon of warm water to wash your hands, not efficient. I've installed a few and haven't had a complaint.

 

[NutBucket]

That's my complaint so far; low flow situations. Especially in socal I feel like I'm wasting water just have hot water. Personally I'll stick with tanks. In warm climates the energy savings is minimal IMHO.

 

[Micrornd]

I switched from an LP std. water heater to a "whole house" tankless electric.
Even with the price of electricity being higher here than LP (comparing dryers and ranges), I'm saving over $30 a month.

As long as I start wide open for 6-8 seconds, dropping back to very low flow is not an issue.
The unit I picked has 2, staged, 12KW@240v heaters, and turns them on based on flow and temp. Most of the time it only uses one of them.

Dishwasher, clothes washer and tub filling at the same time hasn't been a problem. My wife prefers the temp set @ 180F, so that may also be a factor.

 

[Murloc]

That's my complaint so far; low flow situations. Especially in socal I feel like I'm wasting water just have hot water. Personally I'll stick with tanks. In warm climates the energy savings is minimal IMHO.

yeah also in sunny-summer places solar water heating is convenient and I think you need a tank for that.

 

[Greenman]

I switched from an LP std. water heater to a "whole house" tankless electric.
Even with the price of electricity being higher here than LP (comparing dryers and ranges), I'm saving over $30 a month.

As long as I start wide open for 6-8 seconds, dropping back to very low flow is not an issue.
The unit I picked has 2, staged, 12KW@240v heaters, and turns them on based on flow and temp. Most of the time it only uses one of them.

Dishwasher, clothes washer and tub filling at the same time hasn't been a problem. My wife prefers the temp set @ 180F, so that may also be a factor.

180 degree water is very dangerous.

 

[NutBucket]

Seriously. 180 is scalding hot!

 

[Nashemon]

I switched from an LP std. water heater to a "whole house" tankless electric.
Even with the price of electricity being higher here than LP (comparing dryers and ranges), I'm saving over $30 a month.

As long as I start wide open for 6-8 seconds, dropping back to very low flow is not an issue.
The unit I picked has 2, staged, 12KW@240v heaters, and turns them on based on flow and temp. Most of the time it only uses one of them.

Dishwasher, clothes washer and tub filling at the same time hasn't been a problem. My wife prefers the temp set @ 180F, so that may also be a factor.

Is your wife an amphibian, or are you exaggerating?

 

[NutBucket]

yeah also in sunny-summer places solar water heating is convenient and I think you need a tank for that.

When we were selling our house it was unoccupied for a couple of months. The gas bill was less than $5 a month. So yeah, at that rate it would take a long while to recoup the extra cost of a tankless.

 

[NetWareHead]

Just redid my boilers and hot water system in my new house. I considered a tankless water heater but in the end I went with an indirect fired water heater. Here are some points that made me turn away from tankless:

-Electrical requirements: the draw some of them needed required a panel upgrade. This added cost of install was not feasible.
-Venting requirements: I have natural gas in the house and two boilers for heating already unload into existing chimney. Chimney could not handle drafting requirements for 2 boilers AND 2 instant hot water heaters. Meaning the heaters would neeed to be hung on exterior foundation wall and then holes drilled in side to exhaust there. Required routing gas and water piping to that side of house when that already existed near boilers. Extra expense.
-My system was installed in NH, those living at northern latitude have lower incoming water temps and therefore the system has a higher workload, so perhaps lower performance.
-These are rental units and I wanted to avoid tenant complaints about the cold water sandwich these units sometimes produce.
-We have hard water here and the units I looked at do not cover damages arising from hard water. I will need to get the unit descaled and risk damage.
-None of the units I looked at had a warranty longer than 10, maybe 15 years. Pretty much the same if not a little longer than a regular tank water heater.
-Efficiency, units I looked at had efficiency ratings between 80-86%. Not bad but not record breaking enough to justify extra cost (plus natural gas is cheap now)

In the end, I decided to go with an indirect fired hot water heater. Basically looks like a standard hot water heater except instead of a burner, it has a heat exchanger. Hot water from the boiler circulates through this coil when the tank gets cold. In the end I went with HTP superstor ultra 45 gallon tank

Reasons why I decided on this:
-Indirect water heater needs a boiler to provide the heat meaning your boiler works all year round. Boilers like to work and when they are idle, the heat abandoned in the boiler water when thermostat is satisfied is slowly lost to ambient. Also, idle boilers are suceptible to corrosion etc... Think of a car that hasnt been started in a long time. That time idle is when problems creep in.
-Hot water is heated at fuel efficiency of the boiler, usually higher than most water heaters.
-Indirect water heater has a lifetime warranty. It may cost more than regular tank heater but will be the last heater I buy.
-Since tank has no flue penetration, allows for far better insulation than typical tank. Chimney is one of the biggest heat thiefs in a typical home. This model has half degree per hour loss.

All in all, the installation costs for each are close in price depending on size of equipment and install difficulties. What decided for me was the life expectancy and warranty of the indirect vs the on demand. And the added bonus of extending the boiler life by not keeping it idle. If you have a boiler, an indirect is the way to go. If you have a hot air furnace, a tankless is probably a good choice.

 

[Tommy2000GT]

They're pretty good, as long as you buy a quality unit. Where they stumble is on small use. That heater will fire off at 100k BTU's when you need a gallon of warm water to wash your hands, not efficient. I've installed a few and haven't had a complaint.

I was just looking at the 199,000 BTU units offered by Rheem, Rinnai, and Navien.

I like the Navien because it has a small internal tank for a buffer against cold water sandwiches. But then a lot of people were complaining about reliability.

The Rinnai seems pretty popular in terms of reliability but doesn't work as good in preventing cold water sandwiches because it use electronics to control that.

So I'm not sure what one to get yet. Do you have any recommendations?

 

[Tommy2000GT]

How come most tankless water heater installations use a hard line for the water and gas? Most tank water heaters use flex lines. I rather use flex lines so it will be easier in the future if I have to replace the water heater.

 

[paperfist]

What kind of heat do you have for your home?

 

[Tommy2000GT]

What kind of heat do you have for your home?

gas fired central furnace

 

[Greenman]

I was just looking at the 199,000 BTU units offered by Rheem, Rinnai, and Navien.

I like the Navien because it has a small internal tank for a buffer against cold water sandwiches. But then a lot of people were complaining about reliability.

The Rinnai seems pretty popular in terms of reliability but doesn't work as good in preventing cold water sandwiches because it use electronics to control that.

So I'm not sure what one to get yet. Do you have any recommendations?

I've had very good luck with Rinnai. It's what I generally use.

 

[Greenman]

How come most tankless water heater installations use a hard line for the water and gas? Most tank water heaters use flex lines. I rather use flex lines so it will be easier in the future if I have to replace the water heater.

It should be installed with a factory install kit, that includes the isolation valves that make it easy to service. That's also why it gets plumbed with hard lines, they don't ever have to be moved. If they use a ridged gas line there will be a service union near the appliance.

Remember that most of the tankless units use proprietary flue pipe, and some of them charge absurd prices for it, so be sure to include that in your shopping.

 

[Micrornd]

180 degree water is very dangerous.

Yeah, very bad typo.
Meant to write 120F. :$

 

[Greenman]

Yeah, very bad typo.
Meant to write 120F. :$

That's more sensible, but still the high side of safe. If you have small children you should turn it down a bit more.

 

[paperfist]

gas fired central furnace

Got ya. If you said boiler I would have said indirect hotwater.

Though I did see some sites say you could heat water with a furnace, I never heard of that scenario before.

 

[NetWareHead]

Got ya. If you said boiler I would have said indirect hotwater.

Though I did see some sites say you could heat water with a furnace, I never heard of that scenario before.

Some air handlers for forced hot air have a water to air heat exchanger. Air blows through this exchanger and directed to home air ducts. Fluid is circulated through exchanger heated by a zone on the boiler system.

 

[Binky]

When we first moved into out house with a tankless, we kept getting seemingly random cold water during the shower. It turned out to be the low-flow showerhead! The damned tankless was shutting down about 8 min into a shower because it wasn't seeing enough flow. Once we installed a proper showerhead, we have minimal shower issues, even when we turn the water one and off during the shower.

Your climate should probably impact your decision. Tankless may not make as much sense in cold climates. Even in our (Los Angeles) home, hot water on our second floor is essentially not usable except for showers. Given the time for the tankless to get fired up, then send water all the way upstairs, it's just not usable for hand/face washing. We don't get very cold weather here, so this isn't much of a problem. But if your tap water is very cold, running the water for 5 minutes just to splash some water on your face might be an issue. We have have this damned drought here, so that's not an option either.

 

[paperfist]

Some air handlers for forced hot air have a water to air heat exchanger. Air blows through this exchanger and directed to home air ducts. Fluid is circulated through exchanger heated by a zone on the boiler system.

I know running a boiler to heat water in the summer isn't exactly efficient, but since they get up to temp so quick it isn't so bad. I can't imagine though using forced hot air to heat water is going to be so great for your bottom line.

Do they block off the air to the rest of the home when heating the water in the summer like how a separate zone would work?

 

[NetWareHead]

I know running a boiler to heat water in the summer isn't exactly efficient, but since they get up to temp so quick it isn't so bad. I can't imagine though using forced hot air to heat water is going to be so great for your bottom line.

Its not really inefficient from the boiler perspective, it will run summer or winter. Perhaps you mean there would be more idle time since its only duty in the warmer months is to make heat for hot water. There are also issues with the chimney where the warmer summer weather will result in a weaker draft may affect boiler performance. I have never seen a forced hot air system also make water unless a boiler was present to exchange heat to the forced air component of the system.

Do they block off the air to the rest of the home when heating the water in the summer like how a separate zone would work?

The thermostat in this situation calls for heat and the controls fire the boiler to circulate hot water through the heat exchanger zone plumbing and then turn on the blower on the forced air system to convey heat to ducts. In the summer, there should not be a call for heat and the forced air component can be used for cooling if needed. If the boiler is also sending heat to an indirect hot water heater, that is plumbed in as another zone and treated just like any other zone. Usually, hot water zone is set as a priority zone and the boiler will favor this zone to satisfy demands for hot water before returning to heating the structure.

 

[Micrornd]

That's more sensible, but still the high side of safe. If you have small children you should turn it down a bit more.

Sorry, can't agree with that at all.
120F/49F is the recommended temp by virtually all PSCs and HOs.

The main reason is that it is safe (takes 5min. direct contact to produce 2nd degree burns) and going lower (95F-115F) is considered the ideal temp range for Legionellae bacteria (Legionnaires’ Disease) to grow in the pipes (or tank, if you have one), as well as other infectious bacteria .

There's a push on in Canada and the US to mandate/codify that hot water be produced and/or stored 140F/60c and reduce it to a regulated (and no lower than) 122F/50c at the point of delivery through anti-scald valves, to prevent contagious bacterial growth in the hot water pipes and/or tank.
Cold water lines aren't affected because below 68F/20c most water-borne bacteria are dead or dormant.

My guess is that it will pass in Canada in 2 years or less (if their economy doesn't stall in it's recovery).
In the states, well Cali, would be where I expect it to be mandated/codified first.

 

[Anubis]

Yeah, very bad typo.
Meant to write 120F. :$

That's more sensible, but still the high side of safe. If you have small children you should turn it down a bit more.

pretty sure ours is set at 128 to account for the run from the basement to the closest sink

ours also does our hotwater baseboard heating as well

we have a buderus