Electric Instantaneous Water Heater for Central Heating: Anti-Freeze Solution for CO Circuit

Hello!

Is there such a thing as an electric instantaneous water heater for central heating? I mean such a "device" that could be connected to the CO circuit to maintain / raise the temperature if necessary.

what for?
A house heated with a coal boiler with a pump controller, etc. but let's say we go skiing for two weeks - the controller has some theoretical anti-freeze protection (but this only turns on the central heating pump when the temperature drops below the set temperature) If there was such a heater, it would "take care of the headache "that something will freeze.

Such a device can be found on alledrogo under the name: "Heater for the boiler", it can also be a "thermostat".

harnasx wrote:

Is there such a thing as an electric instantaneous water heater for central heating?

Keywords: electric boiler.
The Kospel company, for example.

Rather, you will not find anything like that, for example, compare the power of the stove, which is a dozen or so kW, to the power of the heater that would have to be included in the circuit to get the same power. Perhaps you should rather insulate it against losing temperature. I conclude that you are afraid of the water freezing in the furnace in the basement; maybe instead of investing in a coal-electric furnace, it would work to warm it up at least partially, so that there would be no negative temperatures there?

Jdubowski , electric boilers usually have a 3-phase power supply and this is where you have to start. In this case, some inexpensive alternative solution must be used to "plug" into the existing CO installation, keeping the temperature in the circuit at a level that does not allow it to freeze.

harnasx wrote:

If there was such a heater, it would "take care of the headache" that something would freeze.

@jdubowski he does well. You connect such an electric boiler to the installation and if the coal furnace fails, the electric boiler will maintain the temperature of the water in the system. Admittedly, after a week of such work, your electricity bills will inflate your pressure, but at least no pipe will burst or water will spill anything over.

the house is insulated 15cm styro made of organic lamb 0.038 (windows, foundations, doors and stuff, according to the standard) last year, after two weeks of absence, it got from 22 ° C to 7 ° C (outside it was on average -5 during the day at night, probably less)

it came to my mind after your statements that you could actually use a hot utility water boiler for this purpose (coil + el heater) - use only an additional controller which, after detecting the temperature

Ryszard49 wrote:

Jdubowski, electric boilers usually have a 3-phase power supply

I mean? It is obvious, it is difficult to imagine a continuous consumption> 3kW from one phase.

Ryszard49 wrote:

you have to start with that.

This starts with an estimate of the power. As it will be estimated and will not exceed 3kW, it is indeed:

wowka wrote:

"Heater for the boiler", it can also be a "thermostat".

The heater must be installed in something, a 5/4 or 6/4 inch pipe (depending on the heater thread), a tee and a reducer, all connected to the water current in the circuit.

michalek1988 wrote:

I conclude that you are afraid of the water freezing in the furnace, in the basement; maybe instead of investing in a coal-electric furnace, it would work to warm it up at least partially, so that there would be no negative temperatures there?

In the basement, it is the temperature that drops the slowest, worse with the rest of the circulation on the floors. The heater must heat up the water in circulation to at least 5 degrees above zero, and if it is also to protect other home installations (water supply) from freezing, you will probably need to keep 5 degrees C in the rooms.

harnasx wrote:

after two weeks of absence, from 22 degrees C it became 7 degrees C (outside it was on average -5 during the day at night, probably less)

This is a relatively good result, and a power of 3 to 6kW should solve the problem.

harnasx wrote:

Is there such a thing as an electric instantaneous water heater for central heating? I mean such a "device" that could be connected to the CO circuit to maintain / raise the temperature if necessary.

I was also looking because I need to use excess electricity from photovoltaics.

I found http://www.elterm.pl/pl/produkty-elektryczny-...plywowy-ogrzewacz-instalacji-co-strzelec.html

The Elterm ST heater (Strzelec) is the simplest solution that allows the construction of a hybrid boiler room based on traditional fuel (gas, coal, wood) and electricity obtained from photovoltaics.
The device is connected to the heating circuit at the outlet of a traditional furnace in a boiler room.

Xantix wrote:

@jdubowski is doing well. You connect such an electric boiler to the installation and if the coal furnace fails, the electric boiler will maintain the temperature of the water in the system. Admittedly, after a week of such work, your electricity bills will inflate your pressure, but at least no pipe will burst or water will spill anything over.

There is one more but.
Everything is cooled down by an excellent heater, which is a coal stove, and the loss of empty chimney draft also applies to photovoltaics # 9.
Nothing but losses. It is better to invest in a fully controllable one good heat source, not two, in this case with a fines feeder, packages, etc.

In my case, a gas boiler in the bathroom on the ground floor, so the "losses" go to heating this room, the boiler with a closed KS, i.e. losses to the chimney.
I will try to what temperature outside this 6KW is enough for me, I will install the heater on the return, because if he can't do it, it will be supported by a gas boiler and a fireplace. The radiators are oversized and I heat no more than 45C.
I assume that the electric heater will be able to reach -2C, and in severe frosts, I light the fireplace anyway.
The Sagittarius heater will fit me on the right side of the stove.

surfing wrote:

In my case, a gas boiler in the bathroom on the ground floor, so the "losses" go to heating this room, the boiler with a closed KS, i.e. losses to the chimney.

A boiler with a closed combustion chamber, it is so good that there are no chimney losses!

With the participation of a 6 KW electric heater, always one of several heat sources, be it a gas or coal stove or a fireplace, alternately one of them will generate unnecessary additional chimney losses during the standstill. Unless it's Kol. Jt. indifferent.

How big are these losses ... because it is probably not worth dealing with. The closed combustion chamber works with a fan. It won't work here. Can you determine these losses for a low temperature of the heating medium?

I am trying to buy such a heater to mount it on the return, but I wonder what will happen if the gas stove gets an input temperature higher than the set temperature? Will it not be that the radiators will be cold because the stove finds that they have enough return temperature and will not turn on the pump?
However, is the heater better to install at the exit of the stove?
The stove is a Vaillant EcoTec plus with an external temperature sensor.

But why do you need an additional heating device and expensive electricity if you have a fully autonomous gas boiler, which does not need fuel and can work unattended for months? All he needs is a weather reading or a room programmer and you can go on vacation for a month.

Such a solution as an additional heater or an electric boiler plugged into the circulation is only in the variants of solid fuel boilers, where even the feeder (coal or pellet) in frost will not be able to keep its work for more than a few days, if no one adds fuel.

I do not want to write about the reasons, but only consider the problem.
While browsing the boiler manual, I came across the information that the control is factory set to the flow temperature. So I guess it should work fine if the stove doesn't set the return temperature to the feed only.

The gas boiler sets the power modulation so as to maintain the SUPPLY temperature at CH. The modulation will depend on the CH return temperature (boiler flow). If there is little work to be done by the boiler (the water temperature entering the boiler will be high), it will start to overheat CH above the set temperature and if it exceeds the hysteresis, it will turn off the burner.

And the rational reasons, let me guess, can only be 2:
- the willingness to fit into the W-2 tariff, which you may slightly exceed (and the cost of, for example, additional 300kWh in electricity will be cheaper than the increased subscription for W-3)
- excess energy from photovoltaics due to the installation of spare panels

I bet on goal number 2

BINGO :)

This is probably the most convenient way to use up this energy reserve.

If I had to play something like this on a low budget, I would:
Thermostat> relay> heater in the hot utility water heater + hot utility water and central heating pumps

I have a similar idea: an electric heater on the return of the central heating installation powered by surplus electricity from photovoltaic panels, or a small buffer with a heater. The main source of heat is a gas boiler. Does this solution make sense? I plan a 10kw photovoltaic installation and replacement of a coal furnace with a gas one. Medium insulated house 140m2 from the nineties. I will be grateful for all suggestions.

If you plan to heat with gas, why do you need 10kWp PV? PV installations above probably 6.5kW, now need the opinion of a fire protection expert in terms of compliance with fire protection requirements (and there are very few of them, so $$$). In addition, the larger the PV installation, the greater the problem may be with the collection of the energy produced by PV and its transfer to the power supply (inverter shutdown). I will add that the larger the installation, the greater the currents and the greater the risk of fire.

Instead of spending about PLN 35k on 10kWp PV, spend about 1/3 of it so that it covers the annual demand for household electricity (you probably use about 3000kWh per year), what you have to spend on gas is spend, and what you will not spend on PV (some 20k) spend on better woodwork, attic insulation or whatever you need to improve insulation at home. You better come out on this.

Alternatively, as soon as you have a gas connection made, and you have the floor heating only (or almost the same), instead of gas, you can go to the air PC and then actually with 5-6kWp on the roof would be useful. But then you do not spend on gas connection.

And do not listen to PV sellers that heating with electricity from PV pays off after 7 years as you heat / will be heating with coal or gas.

kWp from PV costs about PLN 3-3.5 thousand. this 1kWp will produce about 950kWh of electricity per year (if you have good conditions), some will be returned to the network, some will be consumed immediately. Taking into account 80% of the surplus from ZE to be used, it will turn out that you actually have 800kWh at your disposal with 1kWp of PV.

The cost of kWh from coal and gas is 17-21 gr (coal 17 but you know, service, gas 21). For further calculations, let's assume 20 gr / kWh.

When will every 1kWp from PV pay off when we replace coal / gas with heating with electricity with 99% efficiency (heaters, radiators, convector heaters and other such tatajstwo)? PLN 3000 / (800kWh x PLN 0.20 / kWh) = 18.75 years.

In the fall of 2020, I was renovating the chimney (ceramic insert) and replacing the boiler with 5 eco. All this lasted (with the expectation of a new boiler) a month, when at the end of October the temperatures dropped to + 2 degrees - in order not to freeze quickly (5 hours with the purchase of details and venting the installation) I installed such a contraption:
heater 3x 1.4kW
pipe 5/4 "
reductions
pump

It was connected with the "quick and short" method to the 3f power supply to distribute the load - it worked
To obtain a temperature of 22 degrees at home, it was necessary to turn on two heaters and they had to work practically 18 hours / 24 to maintain this temperature.

During the assembly of the boiler, this "invention" was installed on the power supply to the installation - we will see how much electricity will be left after the summer, it will be used in the fall


with such data, we have 50kWh of consumption per day - 1500kWh per month, it is about PLN 933 a month - unless we have some "own" electricity

but to heat only with electricity in this way, we have a little, counting 6 months at 1500 = 9000kWh plus you would have to take 2-3 thousand more for the situation when the temperature drops below zero and you will have to turn on the third heater - i.e. 10kW on the roof is not enough

Wojewoda82 wrote:

I will add that the larger the installation, the greater the currents and the greater the risk of fire.

Larger currents, larger conductor cross-sections, the same risk. Your theory has just been thrown in the trash.

All the arguments presented make very sense, but the idea of a 10kw installation is still on my mind. I have been living in my house for 20 years, I heated the first 10 with gas when five of them broke down, I decided to use a coal feed. It may be cheaper, but the quality of life is not comparable. I want to go back to gas heating. Now I use it for the stove and hot water in the summer. I use about 5500kwh (500m3) for this for PLN 1220 per year, if I heated domestic hot water in winter, my bills would be around PLN 1600. When I was heating with gas, I used an average of 10 m3 of gas per day, which is about PLN 600-700 per month today, which, multiplying for 6-7 months, it gives up to PLN 5,000, plus a stove and hot water for the remaining months and the bill can be up to 6,000. What can I do to get it reduce? Of course, improving the thermal insulation of the building. I plan to replace the woodwork, the cost of which is about PLN 25,000. When it will pay off - it's hard to count in 10-15 years. I cannot produce gas, so I have to replace it with electricity that I am able to generate. I will replace the gas stove with an electric one, and I am going to heat the domestic hot water with a heater mounted to the 200l tank, which I already have, it will probably come back soonest. For this purpose, I would need some 2KW plus 3KW, which I am using so far, it gives a photovoltaic installation with a power of 5KWp. My dilemma is that the idea was born in my head to set up a 10KW installation and what will be used to support the gas boiler by installing an electric heater on the return of the central heating installation. The panels will be mounted on the ground, the amount of space is not limited for me, the garden is large, if the gas price becomes very expensive, I can add enough to heat the house with an electric stove. I do not take heat pumps into account due to the lack of floor heating in the house, and the price for 30-40 thousand I can add panels and heat with an electric stove, I know that then the power plant will take 30 percent of the energy produced. There is one more issue, namely if I reduce gas consumption, it can fit into the W-2 gas tariff, where transmission fees are much lower. The second solution is not to install any heaters in the central heating installation, but to heat the house in the transitional months (October, March, April) with electricity obtained from the surplus of the photovoltaic installation, using infrared panels that can be hidden when not used for the rest of the year. I will definitely install an installation that will be enough for my current needs, plus hot water, i.e. about 5-6 kW, but I do not know if it is a good idea to heat the house with electricity from the surplus if I had 10kw installations. Maybe someone is already doing that? Thank you for all your help and interest in the topic.

surfing wrote:

I will try to see what temperature outside this 6KW is enough for me, I will install the heater on the return, because if he can't do it, it will be supported by a gas boiler and a fireplace. The radiators are oversized and I heat no more than 45C.
I assume that the electric heater will be able to reach -2C, and in severe frosts, I light the fireplace anyway.

IMG_202105...112918.jpg Download (391.02 kB)
For me it worked without any problems all winter, I added the possibility to turn on each phase separately, with -5C outside the heater 2kW (only 1 phase is on) keeps the radiators at 45C.
Conclusion, I could only heat my house with electricity from a 6kw heater
https://www.technika-grzewcza-sklep.pl/sklep/...grzewacz-instalacji-co-kod-214004.html#/]Link [/url]

And what was your electricity consumption? I am wondering about such a solution myself. Is this wind in the power supply?

Hello,
I have overproduction from micro PV installations and I also want to install an ST heater on the CO return. But I have a question because I found two types. One ST "regular", the other ST with a clutch ??
I have a gas condensing furnace and I don't know which one to choose.
Regards

Bodek428 wrote:

But I have a question because I found two types. One ST "regular", the other ST with a clutch ??

They differ in the number of nozzles, because one of these models replaces the clutch. The question is how do you want to include it in the installation ...

I was thinking about the ST version which has 2 holes and mounting it on the CO return. Set the temperature of 40 on the heater and 35 on the boiler. In this way, the boiler will either turn off the burner or it will run gently, but the circulation pump will continue to run.




I just don't know what the practical difference is between these types. What does this clutch give and do I need it?
Regards

It's great that I found this topic, because I'm just thinking about installing a CO additional heater on the return from the installation. I am targeting the 2-3kW, single-phase version, because this is the only electricity I have with a gas CO furnace
The additional heater would use the excess electricity from PV, there will be some 700kWh to be utilized. I called Termet (producer) but they can't really tell me how many degrees such an additional heater can raise the water temperature. The documentation on their site is less than poor. I heat with low temperature, currently 38 degrees. This goes to the heaters on the first floor and the floor heating on the ground floor.

However, I think that 700kWh is not a lot and if I connect a 3kW auxiliary heater, it will "pull" it out of the network in about 10 days.
Theoretically, you can even determine how it will affect your gas bill. If last year I used 5160kWh of gas from 2.12 to 3.02 (from the bill), then taking into account the cost of the variable network fee of 1kWh of gas, it cost me PLN 0.1616. These 700kWh are worth about PLN 113. Not much, but gas prices are rising and I have a surplus of electricity.
Looking at these numbers, the cost of installing such an additional heater will pay off in a few nice years (if the heaters last). Of course, the change in gas prices will affect this, but it should not be expected that the return will be faster than 5 years (cost of purchase + installation). In conclusion: on average it pays off with such a surplus. You can think about adding panels, but it only worsens the balance, because gas is still relatively cheap. But in the long run, who knows what it will be like?