A.K.A. on demand hot water. I think these are popular in Europe.
Does anyone have experience with the inline, tank-less water heater? I am remodeling and the extra space saved would be a BIG bonus over a conventional reservoir type tank water heater.
This is for a two person house with no children.
Yes, we had a gas combi boiler at our last house; never again!
Firstly, they aren’t usually as efficient as conventional boilers (heating a whole tank of water ‘in bulk’ allows the boiler to start up and shut down once(this is when most machines are least efficient); heating the same volume of water on demand for, say ten different jobs requires the boiler to start up and shut down ten times).
Next, they often require the water pressure (and therefore ultimately the rate of flow) to be dropped so that the water passes through the heat exchanger slowly enough to be heated fully, so you get a piddly trickle of nice hot water; by the time your bath is full, much of the heat has been lost.
Next, they work very poorly with mixer type showers, partly because of the reduced flow mentioned above, but also partly because they have a tendency to switch on and off intermittently (to approximate being ‘partly on’) if the flow drops below a certain rate, making the act of showering an exhilarating rollercoaster of boiling hot/freezing cold.
Next, since they tend to end up overheating the water that is left in the exchanger when the flow is stopped, they have a greater tendency for scaling up if you live in a hard water area.
Does it show that I hate them?
They’re pretty much the only type I saw in Japan. I had a brand new one in my apartment in Sapporo. Overall it worked well, but the pressure was a bit lower than I like. As for cost, it’s hard to compare between Japan and the US, but it did seem rather expensive.
I never had a problem with alternating hot/cold showers – the temperature generally stayed where I liked it.
hmmmm,
It sounds like the unit itself will lower the flow of water to keep a specified temperature. Yep, that would be a problem in a shower, or mixed hot-cold situation. I already get that with our pump on our well.
So, does the unit change the flow to keep the hot water at a specific temp?
One of the reasons I’m am very skeptical about this type of system is that our incomming water is at 40 F.
Might be good for a cabin but not so fun year round every morning.
Mangetout,
I don’t know if we are on the same page. You refer to a boiler.
The type of system I am talking about is
I hope its ok to post a commercial link as this, I am kinda new here.
But the just of the system is - no tank - no boiler just hot water on demand.
I’m very skeptical of this claim - do you have a cite? I’d think that conventional boilers are less efficient because the water in the tank is always losing heat, no matter how slowly. When an instant heater is off, there is no hot water which would lose heat.
As Ace_Face said, here in Japan we only have the instant heaters. I have no complaints about ours or any I have used - water pressure is sufficient for a comfortable shower, even on cold winter days. But that may not mean much, considering Japanese houses consume far less hot water than American houses - usually just one bath/shower and no hot water feeds to washing machines or dishwashers. My parents do have two showers - the one upstairs is fed by a separate heater located upstairs. Their dishwasher has a built-in electric water heater.
That’s what I thought. Tank, or conventional water heaters will lose heat all day compared to your 4-5 hot water needs.
Mangetout referred to a “combi gas boiler”. This may be a combination of heating the house as well as the hot water but I am not sure. I have never heard that term before.
I am not as concerned with the efficiency of the unit as its ability to provide hot water. I am trying to find room in a very small area, and changing over to an on demand, tank-less system is a possibility.
just want to second the opinions of those who say that on-demand might be ok for a cabin, but not for a typical american household. My information comes from my heating contractor who put one in his own house & found it far from adequate. I contacted him about putting one in & he strongly advised against it. (yes, he was the one doing the installation, but I don’t question his interests. I got a conventional water tank, but didn’t buy any equipment from him).
I have no complaints about the efficiency of my new water tanks. They are very well insulated & loss very little heat.
If you’re most concerned with ability to provide hot water, I can heartily endorse my SuperStor tanks.
Yea, that’s pretty much my take on them as well. I was hoping to find some good stories but didn’t really expect too many. I was looking for ways to save some room on a remodel. I think I will look for the extra space elsewhere.
hhhhmmmmmmm
Be careful with that ax Eugene.
Thanks all.
Well my combi (ie hot water supply and heating) is excellent.
I have no problems with water pressure, we can take ten consecutive showers if we choose without worrying about running out of water and we never heat water which we don’t need. I would never, under any circumstances, go back to a storage boiler.
I grew up in a house with one of these and I HATE HATE HATE them. No amount of money could ever make me put on in my own house. Two people can’t take a shower one after the other – you need to wait at least 45 minutes for the water to get hot again. This type of tank has also lowered our water pressure so much that we have to keep the thermostat at 180 degrees; thus, we turn the hot water all the way up and have to turn on lots of cold water in order to make the hot water bearable, thereby increasing the overall water pressure, and it’s still like taking a shower under a garden sprinkler. Even then, after 10 minutes there is so little hot water left that you must turn the cold almost or completely off in order to have a just barely warm-enough shower. I’m not talking boiling, just something that is of normal shower temperature. It’s so bad that when I visit mum, I take a shower before I go and try and avoid taking one the whole time I’m there - thank goodness my visits are usually short.
I know it’s not some problem with some other aspect of our plumbing, as we have had numerous plumbers and HVAC guys come in and evaluate the system. Plus, the two houses on either side of us are identical; they were built to the exact specs and at the same time and neither one has this problem – and they both have regular water heating tanks.
I don’t see why anyone would get one of these unless they were literally living in a closet. Never, never, never!!
(My mum think’s it’s fine; I think because she’s never had a decent shower to compare it to; and also, her skin is very sensitive so she thinks a regular shower is too hard and too hot, even though it wouldn’t be to most people.)
This combi system confuses me.
I am talking about a completely tank-less system. I do not heat my house with water, gas, or electricity. The heat for the house is solar and a very efficient wood stove. We don’t have a boiler, never have, never will (at least in this house).
I think that some people are talking apples and oranges here.
The thankless system I refer to is just that. No tank no boiler. It heats the water as it comes in and delivers it to the shower or whatever.
um, that should be tank-less system, not thankless. Freud at work again.
No, I don’t have a cite on the heating in bulk thing, just lots of bitter experience; our tank is excellently insulated, so loses very little heat.
A conventional boiler heats the domestic hot water indirectly; it heats what is effectively the same loop of water as it is pumped around a circuit that flows through the boiler to the heat exchanger in the tank, then back to the boiler; it can afford to heat this water more ‘gently’ and efficiently in order to reach the working temeperature.
Combi boilers directly heat the domestic hot water; they have no choice but to burn hot in order to reach the demand temperature almost immediately, it’s my WAG that this has to be a less efficient way of heating a volume of water equivalent to a tankful.
But anyway, my talk of combi boilers is a red herring, since the OP is talking about electric water heating.
enipla, I am quite familiar with the heaters you mention and can answer any specific questions. They’re generally referred to as “demand” heaters as they heat the water on demand rather than accumulating it.
I dislike them with passion for several reasons, the main one being that the temperature regulation is awful and you cannot take a comfortable shower. They also present problems with low pressure.
Yes, they are most common in Europe and Japan and other places where space is at a premium. For me the savings in space are not worth the uncomfortable showers.
I can give you more specifics if you are interested. There are several types (modulating etc). On the whole I’d stay away from them. They are more expensive, more complicated and give worse results. They only make sense on a boat or somewhere where space is really at a premium. (And I don’t have one even on my boat, I have an accumulator)
Mangetout, I believe we are not talking about electric heaters but gas. On demand electric heating is only possible in tropical places where the water is quite worm to begin with. Otherwise the power needed is too much for a home installation.
We have an on-demand electric water heater at one of the offices where I work; I believe it heats up a big block of iron, then runs the water through it, we also have small wall-mounted electric on-demand water heaters for handwashing, but these are nothing more than small electric shower units with a different outlet.
The heaters in the link enipla posted are definitely electric.
FYI, this site (which is hardly unbiased) claims the tankless gas systems are more efficient than tank systems.
http://www.controlledenergy.com/html/whygo/tank_vs_tankless.html
Well, two things: (1) If it generates the heat while it is not needed then it is not an “on demand” heater but an “accumulator” heater, no matter where the heat is stored, and it has the characteristics (and drawbacks) of any accumulating system and (2) I find it extremely difficult to believe anyone would design a water heater which stores the heat in anything else than water itself because this is the most simple and efficient system by far.
Electric “on demand” heaters require huge amounts of electric power if they are to heat substantially a reasonable amount of cold water. I have seen them in Cuba but the water there did not require much heat. Calculate what kind of power would be required to heat 4 gallons per minute from 40F to 120F and you’ll see what I mean.
In other words, for all practical purposes, electric “on demand” water heaters are not practical for residential homes in any kind of cold weather.
Gas “on demand” water heaters can supply all the heat you need but their temperature and flow regulation is awful. They might save energy… especially since I tend to shower as little as possible. I’d much rather have a regular tank heatr, thank you very much.
Hiya Sailor (boy I never thought I would use that phrase :D),
You and I seem to be on the same page. Yep, I am talking about a completely tankless electric hot water heater. Cost is always an issue but performance comes first. I would love to be able to save space but not at the expense of ability.
I am going stick with the standard reservoir tank system. Now I need to come up with the space.
I was suspicious of this system for home hot water from the beginning. I was hoping that it may solve my space problems. The SDMB has helped confirm my suspicions.
I am trying to add a water softener and stacked washer dryer into an already cramped space.
Thanks all