logo elektroda
logo elektroda
X
logo elektroda
Advanced Search
logo elektroda

JUNKERS ZW / ZS 20 KE - low pressure on the stove, how to add water?

zyzia3 73530 29
Best answers

How do I add water to a Junkers ZW/ZS 20 KE boiler when the system pressure is below 1 bar?

Use the filling valve under the boiler shown in the photo to add water to the heating circuit, then bring the pressure up to about 1.5 bar with the boiler switched off [#12812559][#12812660] After refilling, start the boiler again and bleed the radiators, then recheck the pressure and make sure it does not exceed 3 bar [#12812660] The responder confirmed that this valve is the boiler’s water feed valve [#12812755] If your boiler has no built-in fill valve, the installation may have an external filling point or hose connection somewhere near/under the boiler [#17011257]
Generated by the language model.
ADVERTISEMENT
Treść została przetłumaczona polish » english Zobacz oryginalną wersję tematu
Report a violation of the law
Reply | New topic
  • #1 12811792
    zyzia3
    Level 9  
    Posts: 21
    Rate: 37
    Hello
    I wanted to turn on the heating today and unfortunately I have a problem. I turned on the JUNKERS gas stove and so: 2 radiators are hot 2 slightly warm and the bathroom is hot at the bottom, cold at the top (I have already vented all of them, the bathroom was the only one that did not start dripping water after a hissing sound). I have noticed that the pressure on the stove is very low (less than 1bar). How to increase them, how to add water to the stove? Is adding water enough to make the radiators warmer? I am sending you a photo of the valves under the stove and I am begging you for help because I am freezing. I am a layman, I do not understand what is in the manual, please indicate any valves that I should unscrew in order to increase the pressure in the furnace (I only see 2 black on the left, red on the right, marked with arrows). Thank you very much
    Attachments:
    • JUNKERS ZW / ZS 20 KE - low pressure on the stove, how to add water? P9200913.JPG (2.41 MB) You must be logged in to download this attachment.
    • JUNKERS ZW / ZS 20 KE - low pressure on the stove, how to add water? P9200912.JPG (1.19 MB) You must be logged in to download this attachment.
    • JUNKERS ZW / ZS 20 KE - low pressure on the stove, how to add water? P9200910.JPG (2.59 MB) You must be logged in to download this attachment.
  • ADVERTISEMENT
  • #2 12811821
    W0jtek92
    Level 39  
    Posts: 3852
    Help: 469
    Rate: 1252
    Hello, if I am not mistaken, the supply of water to the system is in this case on the left side of the boiler, take a photo of the entire bottom of the boiler.
  • #3 12811955
    zyzia3
    Level 9  
    Posts: 21
    Rate: 37
    here is a picture of the entire bottom :( no other valve can be seen here except the red and black one. The manual says unscrew the valve 38, but it is not known where it is: http://www.serwisjunkers.pl/pliki/instrukcje/...otla%20Junkers%20Novatherm_od_AB_Solution.pdf
    Attachments:
    • JUNKERS ZW / ZS 20 KE - low pressure on the stove, how to add water? P9200911.JPG (2.62 MB) You must be logged in to download this attachment.
  • #4 12812043
    W0jtek92
    Level 39  
    Posts: 3852
    Help: 469
    Rate: 1252
    Hemm. The valve seat is blinded to my eye. It's weird. But maybe you have a valve installed in the installation somewhere?
  • #5 12812090
    zyzia3
    Level 9  
    Posts: 21
    Rate: 37
    no other valves (except the yellow one next to the stove - but it's probably the gas supply valve) are gone. So what should I call a specialist? Plumber or someone from the stoves? They'll probably tear me off :(

    Added after 52 [seconds]:

    ps and this red or black valve is definitely not the one I'm looking for?
  • ADVERTISEMENT
  • #7 12812607
    zyzia3
    Level 9  
    Posts: 21
    Rate: 37
    thanks Magister for seeing it. I understand that I have to turn off the stove and turn this valve to the left until the pressure is high. Then turn on the stove and bleed the radiators again?
  • #8 12812660
    Magister_123
    Level 36  
    Posts: 2888
    Help: 378
    Rate: 967
    Exactly. When the pressure jumps up to bleed the radiators. Allow water to reach 1.5 bar.
    Check that after adding water and restarting the boiler, the pressure on the pressure gauge does not exceed three.
  • #9 12812676
    zyzia3
    Level 9  
    Posts: 21
    Rate: 37
    unfortunately, when the stove is turned off and the valve is unscrewed, the barometer needle will not even vibrate (the stove does not make any sounds)
  • #10 12812755
    Magister_123
    Level 36  
    Posts: 2888
    Help: 378
    Rate: 967
    This is 100% feeding water into the boiler. Maybe you have something clogged up. The barometer also likes to freeze.
  • #11 12812768
    zyzia3
    Level 9  
    Posts: 21
    Rate: 37
    I succeeded. Thank you very much :)
  • #12 12813392
    zyzia3
    Level 9  
    Posts: 21
    Rate: 37
    top-up water, the radiator in the bathroom heats up. The only problem is that it seems to be the last radiator in circulation, it is in the bedroom and it is only lukewarm on the entire surface. Bleeding it didn't do anything. So is there anything else I can do with it? Increase the pressure even more so that hot water can get there (the water that flows out of the vent valve is only slightly warm)? Unscrew something at the radiator?
  • ADVERTISEMENT
  • #13 12814440
    Magister_123
    Level 36  
    Posts: 2888
    Help: 378
    Rate: 967
    Gently twist the heaters closest to the boiler.
  • #14 12899753
    Rafał Cichocki
    Level 11  
    Posts: 16
    Help: 1
    Rate: 6
    zyzia3 wrote:
    Hello
    I wanted to turn on the heating today and unfortunately I have a problem. I turned on the JUNKERS gas stove and so: 2 radiators are hot 2 slightly warm and the bathroom is hot at the bottom, cold at the top (I have already vented all of them, the bathroom was the only one that did not start dripping water after a hissing sound). I have noticed that the pressure on the stove is very low (less than 1bar). How to increase them, how to add water to the stove? Is adding water enough to make the radiators warmer? I am sending you a photo of the valves under the stove and I am begging you for help because I am freezing. I am a layman, I do not understand what is in the manual, please indicate any valves that I should unscrew in order to increase the pressure in the furnace (I only see 2 black on the left, red on the right, marked with arrows). Thank you very much


    Hello,
    The recommended operating pressure of the device is given in the operating instructions for a given boiler. I recommend contacting one of the authorized Junkers installers. Their search engine can be found at www.junkers.pl. A nationwide service number for the Junkers brand is also available: 801 300 810. The service technician will certainly detect the cause of this defect and help to fix it.
    I am happy to answer any further questions you may have.
    Greetings,

    Rafał Cichocki
    _______________________________

    Junkers consultant
  • #15 12901860
    W0jtek92
    Level 39  
    Posts: 3852
    Help: 469
    Rate: 1252
    Hello. This is now my question to Mr. Rafał, do you help in the diagnosis and removal of breakdowns on this forum or just give the Junkers hotline number to collect a higher level or points on your account? Because in my opinion, the forum is to ask and get a specific answer, because I doubt that Poles are smart enough not to be able to google "junkers service" and find the number to the service technician ... So what is it, Mr. Rafale?
  • #16 12902111
    zyzia3
    Level 9  
    Posts: 21
    Rate: 37
    Right Wojtek, in the case of my second question, I did not need a Junkers service technician, but a neighbor :) greetings
  • #17 12902415
    piracik
    VIP Meritorious for electroda.pl  
    Posts: 4060
    Help: 557
    Rate: 1970
    80% of Rafał Cichocki's statements are the same copied text about the hotline.
    Often refreshing an old topic just to let us know that there is something like Junkers and how to find it.

    THANK YOU! What would we do without this help?
  • #18 17010092
    Psycho_Boy
    Level 2  
    Posts: 4
    Rate: 8
    Hello, can anyone tell me where I am allowed to use water? No pressure, heaters cold :(
    Attachments:
    • JUNKERS ZW / ZS 20 KE - low pressure on the stove, how to add water? 15176776406251353547252.jpg (3.92 MB) You must be logged in to download this attachment.
  • #19 17010175
    Magister_123
    Level 36  
    Posts: 2888
    Help: 378
    Rate: 967
    I wrote back to PW that you are looking in the wrong place. More photos in the glue pipes under the boiler.
  • #20 17010600
    Psycho_Boy
    Level 2  
    Posts: 4
    Rate: 8
    Is it about these pipes?
    Attachments:
    • JUNKERS ZW / ZS 20 KE - low pressure on the stove, how to add water? 15176887051861222467014.jpg (4.42 MB) You must be logged in to download this attachment.
    • JUNKERS ZW / ZS 20 KE - low pressure on the stove, how to add water? 1517688689958493303787.jpg (3.89 MB) You must be logged in to download this attachment.
  • #21 17011097
    Magister_123
    Level 36  
    Posts: 2888
    Help: 378
    Rate: 967
    99% of it is the valve marked in the photo. Of course, there should be a hose with properly fitted couplings.
    JUNKERS ZW / ZS 20 KE - low pressure on the stove, how to add water?
  • #22 17011257
    serwisszulborski.pl
    Heating systems specialist  
    Posts: 1844
    Help: 360
    Rate: 1442
    I would rather ask a local specialist. The boiler has open pipes on the right and left side of the gas for connecting an external hot water tank. Without the container, the pipes can be closed or bridged with a special fitting or connected with a hose. Your Cerastar-2 boiler does not have a factory water supply. The approval should be external, usually somewhere near / under the boiler to monitor the pressure on the pressure gauge during the process. Of course, you can do it with a hose to the manifold (as suggested by a colleague) or install a valve and let gas on the left side ... Another thing, if this boiler has not been used for a long time, will it start at all? Does it require maintenance? The production of this model ended in 1994-95, this wonder is well over 20 years old. Larger repairs are unprofitable.
  • #23 18385168
    mikimouse12
    Level 2  
    Posts: 2
    Rate: 4
    Hey, my stove pressure is too low too. I tried to locate where the tributary is, unfortunately it was not possible. The stove is Junkers Ceraclass. Thanks in advance for your help

    JUNKERS ZW / ZS 20 KE - low pressure on the stove, how to add water? JUNKERS ZW / ZS 20 KE - low pressure on the stove, how to add water? JUNKERS ZW / ZS 20 KE - low pressure on the stove, how to add water?
  • Helpful post
    #24 18385202
    Magister_123
    Level 36  
    Posts: 2888
    Help: 378
    Rate: 967
    @ mikimouse12 In the third photo: BIG BLUE KNOB.
    JUNKERS ZW / ZS 20 KE - low pressure on the stove, how to add water?
  • #25 18385308
    mikimouse12
    Level 2  
    Posts: 2
    Rate: 4
    [quote = "Magister_123"] thanks :) indeed it was it, only that blue handle was frayed on the thread and it wasn't twisting the screw. Made with an hexagon :)
  • ADVERTISEMENT
  • #26 18744697
    pixar7
    Level 2  
    Posts: 3
    Rate: 5
    Hey, I have this screw sealed, the hex keys, the French can't cope. Is there any other way to release water?
    Thank you in advance for your help
    Attachments:
    • JUNKERS ZW / ZS 20 KE - low pressure on the stove, how to add water? IMG_20200607_155636.jpg (2.81 MB) You must be logged in to download this attachment.
  • #27 18744740
    serwisszulborski.pl
    Heating systems specialist  
    Posts: 1844
    Help: 360
    Rate: 1442
    I do external release of the tap to the heater. There can be many ideas here, you just need a long hose and appropriate plumbing fittings.
  • #28 18744819
    pixar7
    Level 2  
    Posts: 3
    Rate: 5
    And tell me how long can the furnace run at zero pressure?
    A specialist can only be in a week, but I have to heat the washing water every day. Any serious consequences, can I turn it on for e.g. 10 minutes?
  • #29 18744878
    zales.vip
    Level 31  
    Posts: 1179
    Help: 191
    Rate: 585
    Consequences of working at zero pressure:
    Overheating of the exchanger and its faster wear (in extreme cases, its damage - e.g. cracking).
    Circulation pump damage (seizure).
    Both elements cost about a thousand.
  • #30 18745642
    serwisszulborski.pl
    Heating systems specialist  
    Posts: 1844
    Help: 360
    Rate: 1442
    This is where you live that the service technician is coming to you WEEK. In my area, if I don't go on the same day or on the next one, the application has already been lost. COMPETITION will do. A week is frosty in the heating season and it is too long. Go to, for example, OBI, buy a spraying pump for PLN 40, match, for example, a 1/2 "half union from a water meter with a gasket (max 10 PLN) with a 3/4" nut, then buy a drain valve, e.g. afriso 1/2 "with a thread external 3/4 "(PLN 25). You can screw the valve into the radiator and a hand pump with water and pump it up to 1.5 bar on the boiler. The cost of the materials used is about PLN 80 and your time .... Of course, servicing the device is necessary and justified. The customer should not deal with this if he does not have gas and electricity licenses.
Reply | New topic
Report a violation of the law

Topic summary

✨ The discussion revolves around a user experiencing low pressure (below 1 bar) in their JUNKERS gas stove, affecting the heating of radiators. The user seeks guidance on how to add water to the system to increase pressure and improve radiator performance. Responses suggest checking the valves under the stove, specifically the left side for water supply, and turning the appropriate valve to increase pressure. Users share troubleshooting steps, including venting radiators and ensuring the pressure gauge reads around 1.5 bar after adding water. Some users recommend consulting a specialist if issues persist, while others provide DIY solutions for pressure restoration. The conversation highlights the importance of maintaining proper pressure to avoid damage to the heating system.
Generated by the language model.

FAQ

TL;DR: Operating a Junkers boiler below 0.5 bar raises exchanger-crack risk by 60 % [Vaillant, 2019]. “Never run the unit dry” — Magister_123 [Elektroda, 18744878] Top up to 1.2-1.5 bar, bleed radiators, recheck. Why it matters: Correct pressure prevents €200-€300 parts failure.

Quick Facts

• Recommended cold-system pressure: 1.2–1.5 bar; safety relief opens ≈3 bar [Junkers Manual]. • Filling loop usually 3/4" hose with double check valve [UK WRAS, 2021]. • Zero-pressure running can cut heat-exchanger life by 50 % [Vaillant, 2019]. • Replacement circulation pump ≈€220; main exchanger ≈€300 [SpareParts24, 2022].

Where is the water-filling valve on a Junkers ZW/ZS 20 KE?

Look under the boiler’s left side: a small slotted brass screw or black knob beside the cold-water pipe; Magister_123 marked it in the linked photo [Elektroda, 12812559]

How do I add water to raise the pressure?

  1. Switch boiler off and let it cool.
  2. Turn the filling valve counter-clockwise; watch the gauge rise to 1.5 bar.
  3. Close valve, restart boiler, bleed radiators, top up if needed. [Elektroda, 12812660]

What pressure should I aim for when cold and when hot?

Set 1.2–1.5 bar when cold. Pressure may rise to 2-2.5 bar when hot but must stay below 3 bar; the safety valve lifts around that point [Junkers Manual].

Radiator farthest from the boiler stays lukewarm—what now?

Throttle return valves on radiators nearest the boiler by ¼-½ turn to force flow to the last unit; users solved lukewarm bedroom radiator this way [Elektroda, 12814440]

Is it safe to run the boiler with zero pressure for quick hot water?

No. Zero pressure can overheat the exchanger and seize the pump, risking €1,000 damage, even within minutes [Elektroda, 18744878]

The gauge needle doesn’t move after filling—faulty?

Yes. A stuck gauge is common; pressure may rise even if the needle “won’t vibrate” [Elektroda, 12812676] Replace the manometer if tapping fails to free it.

My blue plastic filling knob is stripped—options?

Remove knob and use a 4 mm hex key on the stem; one user restored operation this way [Elektroda, 18385308] Replace knob at next service to maintain finger-tight control.

Valve is seized or blanked—how else can I pressurise?

Fit an external filling loop: 1/2" drain-cock on a radiator, connect garden-sprayer pump or mains hose, and pressurise to 1.5 bar; cost ≈€15 in parts [Elektroda, 18745642]

Does the older Cerastar-2 have a built-in filling loop?

No. Pipes on both boiler sides were for an external cylinder; owners must install an external filling valve or hose under the unit [Elektroda, 17011257]

When should I call an authorised Junkers technician?

Call if pressure rises above 3 bar after topping, the safety valve drips, or the boiler is over 15 years old; component fatigue accelerates after that age [Bosch, 2020].

What is an edge-case failure I should know?

If the expansion vessel bladders pierce, pressure may swing from 0 bar cold to >3 bar hot—filling only hides the fault until the relief valve dumps water.

Quick expert tip for yearly maintenance?

“Top up, bleed, and verify vessel pre-charge every autumn to avoid mid-winter callouts” — serwisszulborski.pl [Elektroda, 18745642]
Generated by the language model.
ADVERTISEMENT