Faucet without mixer? Only hot/cold?

2016-07-24 11:50:57

Hello Saruss, thank you very much for the detailed explanation. Exactly such a thing is very interesting.. I just didn’t quite understand what the 20 days are that come out in your calculation.. Is that the time the instantaneous water heater could now heat to compensate for the heat loss of the storage tank (cost-wise)? Best regards Steffi.

The 20 days are the time you can keep the water in the storage warm without it being more expensive than with the instantaneous water heater, i.e. if you need more hot water in 20 days than the storage tank can hold (which is probably usually the case....), the hot water from the storage is cheaper than with the electric instantaneous water heater. How much cheaper then depends on the details, which tariffs you have, how much hot water you need, etc... If you keep that in mind, it’s immediately clear that you could never pay for the hot water via instantaneous water heater just based on the loss costs. The only thing you can calculate is whether the investment in storage and boiler, etc., pays off within 10 years; for that you have to calculate with your actual consumption. From on the go

2016-07-24 12:46:51

I think it also strongly depends on how much water the storage tank can hold and how much hot water is used daily. You certainly can't state that generally with 20 days. It makes perfect sense that a tankless water heater is more worthwhile the less hot water is needed. For us, with 2 people and only showers and 33 cubic meters of water consumption (hot and cold) per year, the tankless water heater definitely pays off. Calculated down, we use 90 liters of water per day with 2 people, including cold water. Compared to the rental apartment, we probably end up at about the same, although there we also paid for the neighbors' hot water. So the operating costs are similar; it's just a question of whether a new installation is worthwhile. The hot water heat pump would cost about 700 euros, which is hardly recoupable. The only advantage would be that it could be charged during the day via photovoltaics, so the kWh would then only cost 10 cents. Here, showers are taken mainly at night and noon, with a large gap in between, so I don't expect any problems with storage capacity. Initially, we also thought that for the KFW 100 certification we would definitely need the heat pump instead of the tankless water heater, but that was not the case, as the share of renewable energy from the pellet boiler alone was easily exceeded.

2016-07-24 13:02:10

The 20 days refer to the values from my storage tank. If the hot water is consumed from the storage tank within a few days, it costs about one third in energy costs compared to the instantaneous water heater. This was asked, so I calculated how little the storage losses are. Operating costs with storage are therefore lower; whether it is worthwhile depends, as you say, on the amount per year. For us, this would be (difference between heat pump with storage and fictitious instantaneous water heater) about 350 euros difference in favor of storage; with gas, the difference should be similar because the kWh of gas is cheaper than electricity. If you can get a small storage tank and a boiler cheaply enough, it could be worthwhile. When the children are a bit older, it might be even more worthwhile. With the mentioned price of 700 euros for the heat pump and a bit more for storage, it would be worthwhile for me.

from unterwegs

2016-07-24 13:25:39

Hi,

For us with 2 people and only a shower and 33 cubic meters of water consumption (hot and cold) per year, it definitely pays off with the instantaneous water heater.

It will probably look similar for us. Since we are currently wavering between gas-BWT with solar thermal and air-water heat pump for our small project, we also came up with the idea of the instantaneous water heater. That these devices can be precisely adjusted is new to me, but a really good idea. Thanks.
I found the Junkers ELAFLUX ED 18/21-3 ES as an example, where the temperature can be set directly on the device. Or do you have a control unit separate from the device?

Maybe this way the separation can still be postponed

Kermit

ps: on Spiegel online under "Technikärgernis Einhebelmischer: Mischen impossible" there is a somewhat older article about it.

2016-07-24 13:45:49

Saruss, ok I must have overlooked that the calculation specifically referred to your case, but it's interesting to have hard facts and figures as a guideline. Kermit, I believe the newer tankless water heaters can all be set to half a degree accuracy, my older one still has a rotary dial without a display, with a scale like on a stove, so it's not quite that precise. The newer one is a Stiebel Eltron DHE 18 kw, although it’s certainly already got its 10 years on the back. Some new tankless water heaters can even be adjusted with a remote control. Mixing impossible haha. Yeah, I already thought so. Everything we've bought here for the house in terms of electrical appliances has already broken down at least once (air conditioner after 6 months, refrigerator twice in 3 months, inverter after 1 year, front door lock after 1 year....). Whatever can break will probably break, unless it’s already 10 years old, then it lasts forever.

2016-07-24 15:17:35

The hot water temperature is set directly at the heat generator, and it would be nonsense to then mix the expensively heated water back down with cold water. Swiveling, of course, is also possible with a single-lever mixer, which we currently do, but you can also set intermediate positions there, and since we don't need that, it would simply be unnecessary. Just like with the shower, actually, where we would only need an on/off button because the water is set to the exact degree at the heat generator. By the way, very practical, in my opinion. Previously, in rental apartments, you had to endlessly turn the controls until you finally got the right temperature, and that didn't stay constant, so you constantly had to readjust, including squeaky moments when it suddenly became ice cold or super hot. With us, hot water always comes at 42°C, which is okay for all purposes, and if it ever needs to be hotter, I can briefly set 60° (where the 60° are immediately available), or in summer also 37°. This also saves quite a bit of energy, and the lack of constant adjusting saves water.

@Kermit Two-handle faucet, I will look into that! This Retro Almendro is exactly the kind of thing I don't want, a rotary controller. You crank and crank.... But the direction is more or less right. They would only have to be buttons that, at the push of a button, immediately release the full flow.

That is not quite correct. If the heated water is mixed down, there is also less flow through the hot water pipe. If, for example, 5l/min comes from the faucet when fully opened, and it is set to 50/50 hot/cold, only 2.5l/min comes from the hot water pipe. This is more ecologically sensible than fully opened hot water with 5l/min.

By the way, our faucet is adjusted via a rotary axis. The first centimeters set the volume (0-100%), but only cold water. If you turn further, the temperature changes from cold to hot (still 100%).

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Faucet without mixer? Only hot/cold?

Saruss

Elina

Saruss

Sir_Kermit

Elina

daniels87