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Mantle vs Double Coil Boiler: Elektromet & Kospel Comparison, Warranty, & Replacement Tips

Alfred_92 9393 17
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Czy do poziomego bojlera lepszy będzie płaszcz czy wężownica, i na co zwrócić uwagę przy wyborze oraz trwałości?

Do poziomego zasobnika zwykle lepszy będzie płaszcz niż wężownica/U-pętla, ale tylko wtedy, gdy masz dość mocne źródło ciepła i dobrze dobraną instalację [#16835078][#16842918] W wątku padło, że w poziomych zbiornikach wężownice U są raczej słabszym rozwiązaniem, a płaszcz daje większą powierzchnię wymiany, ale może szybciej wychładzać obieg CO, więc trzeba uważać na dobór pompy i ewentualnie dać zawór zwrotny lub osobną pompę dla bojlera [#16835078][#16835250][#16848229] Jeśli kocioł nie dostarcza wystarczająco dużo ciepła, to z płaszczem można stracić komfort, np. przy podgrzewaniu wody dla 4 osób po kilku poborach [#16848229] O trwałości bardziej niż marka decyduje eksploatacja anody: jedna z opinii mówi o wymianie co 12–18 miesięcy, a przy anodzie tytanowej rzadziej [#16834607] Jako alternatywę ktoś proponował używany zasobnik ze stali nierdzewnej, ale padła też uwaga, że stal nierdzewna nie jest niezniszczalna i wyższa cena może się nie zwrócić [#16835655][#16842918]
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  • #1 16833627
    Alfred_92
    Level 33  
    Gentlemen, it's time to replace my grandfather from 73 (old galvanized).
    Elektromets and Kospele both double-coil and mantle are available in stores nearby.
    The mantle parameters crush the coil, but there are probably some disadvantages that as a regular user I do not know ??
    which of the above enjoy a better reputation, Elektromet has a 5 or 6-year warranty and Kospel 3 (the condition is apparently the annual replacement of the magnesium electrode).
    Maybe you recommend something else?
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  • #2 16834179
    Anonymous
    Anonymous  
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  • #3 16834227
    Alfred_92
    Level 33  
    theoretically, two coils can be connected in series, because this is not a problem, and then you have a double heat exchange surface.
    The question is what are the disadvantages of a mantle exchanger, because there are certainly some.
  • #4 16834250
    Anonymous
    Anonymous  
  • #5 16834291
    Romulus7874
    Level 29  
    But with two coils, it occurs in the vertical version (with different variations - type Slim etc.), and double-jacketed in the horizontal versions (?) Only.
    Maybe you are wrong description "double coil" which means only one coil pipe bent inside the boiler twice.
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  • #6 16834307
    Alfred_92
    Level 33  
    I didn't see them physically, but it's probably like that.
    On paper, the mantle beats two coils per head, with heating power (27kW and 12kW makes a huge difference.
    I wonder if such a coat will not cool the CO installation too quickly after the furnace fire (daily heat loss).
    There remains the question of which products are more durable, my current galvanized boiler is from 1973, and I realize that the new enamelled one will not withstand half this, but I would be happy if I had 10-15 years of peace, I will add that I have water in the heating system (not glycol).
  • #7 16834557
    Sstalone
    Level 31  
    Maybe soon you won't have a choice, only mantles will remain on the market due to energy efficiency ...

    I would prefer a coil, due to less cooling of the return water to the boiler.
  • #8 16834607
    tronics
    Level 38  
    Sstalone wrote:
    Maybe soon you won't have a choice, only mantles will remain on the market due to energy efficiency ...

    I would prefer a coil, due to less cooling of the return water to the boiler.

    Nonsense. 2 and 3 vertical coils are and will be doing well. Especially that really big ones (400L and more) are usually vertical with a coil. And what does a colleague understand by energy efficiency? The nominal power of the exchanger is given with certain assumptions. Is your colleague absolutely sure that a typical installation reflects laboratory conditions? Because the power of radiators is given the same, e.g. 5kW ... assuming the flow of so much L / min and the temperature of the medium 95 ° C.

    Incidentally, I have 2 Stalmet 200L coil as a supplement to the existing 120L Galmet double jacket. A heater warms up in Galmet in summer, and the heating is on a solar collector that usually pulls out 40 ° C on a sunny day, over 50 ° C on a hot day. So far, I've exchanged the anode 3x in galmet and 1x in stalmet (assuming replacement every 18msc). The durability of both would say similar, galmet is worse in disassembly because you need to unscrew many nuts and remove the heater with the anode.
  • #9 16834676
    Alfred_92
    Level 33  
    Sstalone wrote:

    I would prefer a coil, due to less cooling of the return water to the boiler.

    This is also what I am afraid of, among others, which is why I wanted to hear the opinion of people who install, service or even use this type of equipment.
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  • #10 16834840
    Sstalone
    Level 31  
    tronics wrote:
    Nonsense.


    I wrote about horizontal boilers. What energy efficiency is set out in the directive. You can read e.g. https://www.junkers.pl/files/JUNKERS_Dryrekaże_ErP_PL.pdf

    Quote from page four: "From 2019 new energy classes will be in force. Then class A +++ will be added for heat sources, and at
    domestic hot water preparation equipment class A +. The lowest classes G to E will be withdrawn in both product groups. "
  • #11 16834848
    Alfred_92
    Level 33  
    Yes, I forgot to add that we are talking about horizontal boilers.
  • #12 16835078
    tronics
    Level 38  
    Sstalone wrote:
    tronics wrote:
    Nonsense.


    I wrote about horizontal boilers. What energy efficiency is set out in the directive. You can read e.g. https://www.junkers.pl/files/JUNKERS_Dryrekaże_ErP_PL.pdf

    Quote from page four: "From 2019 new energy classes will be in force. Then class A +++ will be added for heat sources, and at
    domestic hot water preparation equipment class A +. The lowest classes G to E will be withdrawn in both product groups. "

    In horizontal tanks, coils are usually called U, a double coil, it is a relatively weak solution and in this situation I also highly recommend a double-shell tank since colleague Alfred_92 explained that it is horizontal.

    Why did I want my colleague to "develop energy efficiency"? Because the speed of heat transfer from one medium to another has nothing to do with energy efficiency (efficiency). At most, I would say that it is more about ensuring adequate thermal insulation of the reader, low daily losses (heat emissions from the tank to the environment), which is completely different to how the exchanger is built. Anyway, in the linked discussion of the directive it is also clearly indicated:
    Quote:
    Minimum requirements have been defined for indirectly heated hot water tanks. The basis of the calculation is in this case parking loss .
  • #13 16835250
    Sstalone
    Level 31  
    tronics wrote:
    In horizontal tanks, coils are usually called U, a double coil, it is a relatively weak solution and in this situation I also highly recommend a double-shell tank since colleague Alfred_92 explained that it is horizontal.

    Why did I want my colleague to "develop energy efficiency"? Because the speed of heat transfer from one medium to another has nothing to do with energy efficiency (efficiency). At most, I would say that it is more about ensuring adequate thermal insulation of the reader, low daily losses (heat emissions from the tank to the environment), which is completely different to how the exchanger is built. Anyway, in the linked discussion of the directive it is also clearly indicated:
    Quote:
    Minimum requirements have been defined for indirectly heated hot water tanks. The basis of the calculation is in this case parking loss .


    In my opinion, why should I spend PLN 200 more on a double-shell tank compared to e.g. a U coil, since I do not need such coil power per unit of time? And what was the exchanger in the existing tank? Heated the hot water at a sufficient rate?
    I don't know which boilers are more durable. If double-skinned were more durable, one could think about it. In addition, the diameter of the CO connection stubs can be important, the double-jacketed ones have a smaller diameter ... if someone changes the installation, this may be an option to think about.

    I noticed that horizontal boilers no longer have four hot water connectors, but only two, because the parking losses are lower. In addition, if we have a forced circulation system, it matters how much the pump will have to run to exchange heat, then the double wall wins, as the boiler circuit protects the boiler return, the U coil wins, because we do not want to significantly reduce the boiler water and the pump and so it must walk, as the boiler is in gravity circulation, it does not matter, and the larger diameter of the connectors and pipes favors it.

    As for the market, I heard that one of the producers will focus only on mantles, due to ErP, maybe it's just an excuse for customers.
  • #14 16835655
    andexp
    Level 23  
    Think about buying a used stainless steel boiler from brand manufacturers. On the Popular Auction Portal they are available in different variants and capacities, the fact of buying will probably be more expensive, just take into account that you will no longer need to replace it. I have a vertical with a double coil, with the possibility of installing a heater on GZ5 / 4 ". The 25 kW boiler outside the heating season with an incomplete wood bucket heats 160 l of water to a temperature of 55-60 ° C in 30-40 minutes. And the problem with anodes falls away keep the warranty and a matter of unavoidable replacement in the future.
  • #15 16835731
    tronics
    Level 38  
    Quote:
    matter of inevitable exchange in the future

    The anode is precisely to make this inevitable replacement avoided by regular replacement every 12-18 months depending on wear (in "acid" or oxygenated water it will undergo faster regardless of the number of microcracks in enamel and corrosion centers). In the case of titanium, replacement is several times less frequent. Stainless steel is a nice material, but let's not get paranoid. As a rule, the price difference will not pay back over its useful life.
  • #16 16842918
    andrzej lukaszewicz
    Level 42  
    andexp wrote:
    Think about buying a used stainless steel boiler from brand manufacturers. On the Popular Auction Portal they are available in different variants and capacities, the fact of buying will probably be more expensive, just take into account that you will no longer need to replace it.

    And here you can be surprised. Stainless steel also breaks from stress, alloy steel gets tired with age.

    Returning to the topic: I recommend two-coat if it is to be horizontal + protection against cooling. In addition, the question arises: what heat source, which boiler, how many people use hot water?
  • #17 16847277
    Alfred_92
    Level 33  
    25kW coal stove without feeder, one-story house, usually 4 people use CWO.
    I care about good heat losses primarily because a morning shower in cold water (no oven with a feeder) is not pleasant.
  • #18 16848229
    roman 18
    Level 24  
    Welcome. Buddy, a lot depends on whether you give the right amount of heat for the double walled boiler, because if it is not enough, I warm up after comfort. with this you won't have. a very good solution is to mount a vertical, hanging or standing boiler, on a separate pump with a check valve to make the central heating pump. it did not take heat from the boiler.
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Topic summary

✨ The discussion centers around the comparison between mantle and double coil boilers, specifically focusing on Elektromet and Kospel brands. Users highlight the advantages of mantle boilers, such as a larger hot water surface, but express concerns about rapid cooling and energy efficiency. The double coil boilers are noted for their adaptability to multiple heat sources, but there are questions regarding their durability and performance. Warranty periods differ, with Elektromet offering 5-6 years and Kospel 3 years, contingent on regular maintenance. Participants also discuss the importance of heat loss management, the impact of installation type, and the potential benefits of stainless steel boilers. Recommendations include considering used stainless steel models for longevity and efficiency.
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FAQ

TL;DR: A 25 kW boiler “heats 160 l to 55–60°C in 30–40 minutes,” showing what to expect from a well‑matched tank. For horizontal setups, pick double‑jacket (mantle) with anti‑cooling protection; coils suit dual‑source systems. [Elektroda, andexp, post #16835655] Why it matters: This FAQ helps homeowners replacing legacy DHW tanks choose between mantle vs double‑coil, avoid morning cold‑shower surprises, and plan maintenance.

Quick Facts

For a horizontal hot‑water tank, which is better: mantle or double coil?

Choose a double‑jacket (mantle) tank for horizontal installations. U‑shaped double coils in horizontals transfer heat less effectively. Add return‑cooling protection in the boiler loop to prevent unwanted CH cooling while charging DHW. “Highly recommend a double‑shell tank” for horizontals. [Elektroda, tronics, post #16835078]

What is a double‑coil tank actually for?

A double‑coil tank connects two heat sources, such as a solid‑fuel boiler plus solar collectors or a heat pump. That use case makes one‑to‑one comparisons with single‑source mantle tanks misleading. If you only have one source, a double coil offers limited benefit. [Elektroda, 762302, post #16834179]

Can I connect two coils in series to increase heat transfer?

Yes, you can pipe two coils in series to enlarge effective exchange area. However, flow resistance rises and horizontal U‑coil layouts still underperform versus a well‑sized mantle. Consider whether series piping complicates purging and maintenance before committing. [Elektroda, Alfred_92, post #16834227]

Will a mantle tank cool my heating circuit after the fire goes out?

It can if you lack proper control. Mantles expose a large area, so they may draw heat from CH and speed night‑time cooling. Install controls or check valves to stop unwanted thermosiphon when the boiler is cold. [Elektroda, 762302, post #16834250]

Does exchanger type affect energy efficiency labels?

Standby loss dominates rating outcomes, not mantle vs coil geometry. Better insulation and fewer unused connectors reduce daily heat loss and improve ErP class. Focus on tank insulation and fittings rather than exchanger shape for efficiency. [Elektroda, tronics, post #16835078]

Which brand has the longer warranty and what’s the catch?

Reportedly, Elektromet offers 5–6 years and Kospel 3 years. Coverage often requires annual magnesium anode replacement. Skipping anode service risks corrosion and voided warranty, even if enamel looks fine. Keep receipts and dates for claims. [Elektroda, Alfred_92, post #16833627]

How quickly can a 25 kW boiler heat a family‑size tank?

A 25 kW solid‑fuel boiler heated 160 L from cold to 55–60°C in 30–40 minutes in user testing. This benchmark helps size tanks for four‑person households. Quote: “heats 160 l… in 30–40 minutes.” [Elektroda, andexp, post #16835655]

How often should I replace the magnesium anode? Is titanium worth it?

Plan magnesium anode checks every 12–18 months, sooner with aggressive water. Replace if worn. Titanium anodes reduce service frequency but cost more; savings may not justify the price in typical homes. Keep a maintenance interval log. [Elektroda, tronics, post #16834607]

Are stainless‑steel DHW tanks a buy‑once solution?

Not always. Stainless can crack from stress and metal fatigue. You still need proper hydraulics and water chemistry control. For horizontal layouts, experts still suggest a double‑jacket tank with anti‑cooling safeguards. [Elektroda, andrzej lukaszewicz, post #16842918]

Have horizontal tank connections changed, and does it matter?

Yes. Many newer horizontals moved from four DHW ports to two to reduce standby loss. Double‑jacket models may also use smaller CH stubs. Confirm stub sizes and recirculation needs before swapping, to avoid flow bottlenecks. [Elektroda, Sstalone, post #16835250]

Which option protects boiler return temperature better?

A U‑coil in a horizontal tank tends to protect boiler return temperature better than a mantle, because it extracts heat less aggressively. Use this when return temperature protection is a priority for boiler longevity. [Elektroda, Sstalone, post #16835250]

What’s a practical way to stop CH from stealing heat from the DHW tank?

Use a vertical DHW cylinder on a dedicated pump with a check valve, separate from the CH pump. This prevents back‑circulation that cools stored hot water. It also improves recharge times during shoulder seasons. [Elektroda, roman 18, post #16848229]

I need hot morning showers with a non‑automated coal stove. What should I prioritize?

Prioritize low standby loss, good insulation, and anti‑thermosiphon measures. A horizontal mantle tank with check valves and controls keeps water hot longer overnight. Size for four users and confirm recharge time with boiler output. [Elektroda, Alfred_92, post #16847277]

Do I really need dual coils if I don’t have solar or a second source yet?

No. Without a second source, you pay for unused capacity and complexity. Pick a well‑insulated mantle for horizontal installs, or a single‑coil vertical if you plan to add solar later. [Elektroda, 762302, post #16834179]

How do I replace or check a magnesium anode (3 steps)?

  1. Isolate, depressurize, and open the inspection flange; measure anode diameter and length.
  2. Replace if heavily pitted or below manufacturer minimum; torque per spec.
  3. Refill, bleed air, and log the date for 12–18 month follow‑up. [Elektroda, tronics, post #16834607]

Any gotchas when choosing horizontal vs vertical models?

Verticals offer more coil options and strong solar pairing. Horizontals often favor mantle for performance. Confirm placement, connector count, and pump strategy before buying to avoid underperforming U‑coil setups in horizontals. [Elektroda, Romulus7874, post #16834291]
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