logo elektroda
logo elektroda
X
logo elektroda
Advanced Search
logo elektroda

[Solved] The central heating furnace pump is aerated and the water in the furnace boils.

puchacz2420 13419 15
ADVERTISEMENT
Treść została przetłumaczona polish » english Zobacz oryginalną wersję tematu
Report a violation of the law
| New topic
  • #1 16969722
    puchacz2420
    Level 6  
    Posts: 90
    Rate: 42
    Hello. Defro Optima Plus oven mounted for heating a 180 m2 house. This is an ordinary oven without a feeder. śmieciuch. The cycle is short. A differential valve is installed at the exit of the furnace and a pump bypassing this valve and access to the heat exchanger and then return to the boiler. Expansion tank placed above the stove about 1.5 meters under the ceiling. The problem is that from time to time the pump airs up, the pressure drops and the water boils. Today I replaced the differential valve and it seems better, but after about 8 hours of smoking the pump again announced itself, but the water did not boil anymore because maybe the differential valve worked. Everything works very well until the knock the pump will not get air. Where does this air come from in such a small system? How exactly to bleed this system? Or maybe there is another reason? Can anyone suggest something? Thanks in advance......
  • ADVERTISEMENT
  • Helpful post
    #2 16969749
    Magister_123
    Level 36  
    Posts: 2888
    Help: 378
    Rate: 967
    Draw a diagram or paste photos of the layout.
  • #3 16969984
    puchacz2420
    Level 6  
    Posts: 90
    Rate: 42
    The central heating furnace pump is aerated and the water in the furnace boils. The central heating furnace pump is aerated and the water in the furnace boils. The central heating furnace pump is aerated and the water in the furnace boils. The central heating furnace pump is aerated and the water in the furnace boils. The central heating furnace pump is aerated and the water in the furnace boils.
    I took photos of only a small circuit from the exchanger, only pumps for CH, DHW and floor supply.
  • #4 16970153
    Sstalone
    Level 31  
    Posts: 2176
    Help: 72
    Rate: 396
    puchacz2420 wrote:
    Hello. Defro Optima Plus oven mounted for heating a 180 m2 house. This is an ordinary oven without a feeder. śmieciuch. The cycle is short. A differential valve is installed at the exit of the furnace and a pump bypassing this valve and access to the heat exchanger and then return to the boiler. Expansion tank placed above the stove about 1.5 meters under the ceiling. The problem is that from time to time the pump airs up, the pressure drops and the water boils. Today I replaced the differential valve and it seems better, but after about 8 hours of smoking the pump again announced itself, but the water did not boil anymore because maybe the differential valve worked. Everything works very well until the knock the pump will not get air. Where does this air come from in such a small system? How exactly to bleed this system? Or maybe there is another reason? Can anyone suggest something? Thanks in advance......


    The boiler circuit is connected to the expansion vessel? From the return side? Is this a closed system because you write that the pressure drops?

    What is the power of the central heating boiler? What is the power of the exchanger? What temperature do you keep on the boiler? What temperature do you keep in the radiator circuit at the outlet of the exchanger? The gray tank in the picture is an expansion vessel?
  • ADVERTISEMENT
  • #5 16970283
    puchacz2420
    Level 6  
    Posts: 90
    Rate: 42
    This gray vessel is a balancing tank connected directly to the boiler. Boiler with a thermal power range from 8 to 25 kw. I can't read the power on the exchanger so I will write what I see. .Max work Press (bar) 30, max work temp 230, min work temp -190, test pressure bar 64, volume letters 0.7. There is something else HTA (m2) / weight (kg) - 0.9 / 5.3.
  • ADVERTISEMENT
  • #6 16970291
    Sstalone
    Level 31  
    Posts: 2176
    Help: 72
    Rate: 396
    Then take a photo of the connection of the vessel to the boiler and throw it here.
  • ADVERTISEMENT
  • #7 16970305
    puchacz2420
    Level 6  
    Posts: 90
    Rate: 42
    One more thing ... a leveling vessel connected to the boiler next to the return ... as in the picture.
    Attachments:
    • The central heating furnace pump is aerated and the water in the furnace boils. 1516269531784-826261985.jpg (1.82 MB) You must be logged in to download this attachment.
  • #8 16970330
    Henio65
    Level 16  
    Posts: 177
    Help: 11
    Rate: 18
    The expansion vessel must be connected at the highest point of the installation. Do not measure the height from the oven only at least "1cm" above the highest point of the installation. The pump does not ventilate it just seems so because the system is aerated and the pump works with all its strength.
    In addition, the pump may be on the return, it will start working at the right time with a delay when the need arises.
  • #9 16970334
    Sstalone
    Level 31  
    Posts: 2176
    Help: 72
    Rate: 396
    Dude, you have a "bomb" at home. Who did this to you? Answer yourself, how and where should steam escape from the boiler while boiling water?

    Installation for immediate conversion ... connection of expansion vessel.
  • #10 16970387
    puchacz2420
    Level 6  
    Posts: 90
    Rate: 42
    Ok. As for the tank it is approx. It is about 70 cm above the highest point. I fired and heated the oven to 76 degrees and at 70 the system was announced the pump was running dry. I vented at the pump and keep it going for now. I set the temperature on the boiler 55 degrees and so far nothing is happening. Popale so for 2-3 days and raise the temperature again to 75 I will see if it is announced again. Thanks for help ... greetings ...

    Added after 9 [minutes]:

    That's right Stallone. Only where to connect this reservoir now. Constantly when it boils water it is thrown out through the reservoir ...
  • #11 16970464
    Henio65
    Level 16  
    Posts: 177
    Help: 11
    Rate: 18
    Drain the water from the system and fill it again. After filling, you already have air in the system because which way it will go out.
  • Helpful post
    #12 16970501
    Sstalone
    Level 31  
    Posts: 2176
    Help: 72
    Rate: 396
    puchacz2420 wrote:
    That's right Stallone. Only where to connect this reservoir now. Constantly when it boils water it is thrown out through the reservoir ...


    Straight from the boiler from the top from the Dutch to the expansion vessel from above with an inch steel pipe while maintaining the slope to the boiler, i.e. first leaving the boiler to the expansion vessel, and only then going sideways to the existing system with the pump. The easiest way instead of this tee after the Dutch is to screw in a tee such as exit from the boiler through, give a reduction on the top for 1 inch and a pipe to the vessel, and connect the existing system to the side of the tee. Connect the bottom of the expansion vessel to the boiler return, overflow from the side of the vessel to the sink.

    Here you have described https://www.elektroda.pl/rtvforum/topic1900517.html
  • #13 16970526
    puchacz2420
    Level 6  
    Posts: 90
    Rate: 42
    OK thanks. Heniu. I will do it tomorrow and write the effect. At the highest point I have a breather valve and maybe it's too weak and it's not enough to replace it with a regular closing valve ... thanks.
    Attachments:
    • The central heating furnace pump is aerated and the water in the furnace boils. 1516275027957-826261985.jpg (447.75 KB) You must be logged in to download this attachment.
  • #14 16970552
    puchacz2420
    Level 6  
    Posts: 90
    Rate: 42
    Thanks Stallone. I will do it too. In the end I have to find a mistake. pozdr
  • Helpful post
    #15 16970878
    Henio65
    Level 16  
    Posts: 177
    Help: 11
    Rate: 18
    Drain some water, open the venting valve and then extend with a hose and fill it up listening for air leaks.
  • #16 17010471
    puchacz2420
    Level 6  
    Posts: 90
    Rate: 42
    Hi. Sorry that I did not speak but after the fault I had to leave immediately. The topic is completed. Thanks to Heni for the simple hints and I used it. The stove works like this doll. Thanks also because it really is puzzling but after installing the valve as Henio 65 described everything is ok. In the spring after the season I will do as Sstalone wrote. Wife doesn't complain, the oven doesn't cook. Thanks for you .... Regards.
| New topic
Report a violation of the law

Topic summary

✨ The discussion revolves around issues with a Defro Optima Plus central heating furnace, specifically regarding aeration in the pump and boiling water in the system. The user describes a setup with a differential valve and an expansion tank positioned above the stove. Despite replacing the differential valve, the pump continues to air up, leading to pressure drops and boiling water. Various suggestions are made, including ensuring the expansion vessel is at the highest point of the installation, proper venting of the system, and checking connections. The user successfully implements some of the advice, leading to improved performance of the heating system.
Generated by the language model.

FAQ

TL;DR: A 8–25 kW solid‑fuel boiler kept “airing” the pump and boiling until the open expansion vessel was re‑piped to the boiler flow/top and return, per expert advice: “Installation for immediate conversion … connection of expansion vessel.” [Elektroda, Sstalone, post #16970334]

Why it matters: This FAQ shows how to stop pump cavitation and boil‑overs in small open‑vented heating systems, fast, safely, and cheaply—ideal for DIYers and installers troubleshooting aeration on solid‑fuel boilers.

Quick Facts

How do I fix a central heating pump that keeps getting air and causes boiling?

Treat the root cause: wrong expansion‑vessel connection. Pipe the vessel directly from the boiler top (flow) with continuous fall to the boiler, connect the vessel’s bottom to the return, and take the overflow to a drain. This re‑establishes proper venting and stops pump cavitation and boil‑overs. [Elektroda, Sstalone, post #16970501]

Where should the open expansion vessel connect on a solid‑fuel boiler?

From the boiler’s top outlet straight to the vessel’s top, keeping a gravity fall back toward the boiler. Connect the vessel’s bottom to the boiler return. Add an overflow to a safe drain. This layout gives steam and air a free path. [Elektroda, Sstalone, post #16970501]

What does “pump running dry” mean here, and what causes it?

It means the circulator impeller spins in air and vapor instead of water. Misplaced venting and vessel piping let air accumulate at the pump, especially around 70°C in this case. The pump then loses prime and flow collapses. [Elektroda, puchacz2420, post #16970387]

How do I bleed this small system correctly?

Do a simple refill purge. Drain some water, open the vent, attach a hose, and refill while listening for escaping air. Close the vent when only water flows. Restore levels, then recheck after heat‑up. [Elektroda, Henio65, post #16970878]

Is an automatic air vent at the highest point enough?

No, not if the expansion vessel piping is wrong. The poster suspected the auto vent was too weak, but stable operation came only after correcting the vessel connections, not by changing the vent. [Elektroda, puchacz2420, post #16970526]

What immediate safety warning did experts give in this case?

“You have a ‘bomb’ at home. Installation for immediate conversion … connection of expansion vessel.” This stresses that boiling steam needs an unobstructed path to the open vessel. [Elektroda, Sstalone, post #16970334]

Can a differential valve alone stop boiling or pump aeration?

It can help maintain flow during pump stop or restriction, but it did not solve the aeration here. After replacement, the pump still caught air until the expansion vessel was re‑piped. [Elektroda, puchacz2420, post #16969722]

Should the pump be on the return or the flow in such systems?

Placing the pump on the return can improve operation, starting when heat demand appears. However, correct expansion vessel connection remains the priority for air and steam handling. [Elektroda, Henio65, post #16970330]

What quick changes actually stabilized this system?

Re‑piping per the guidance and operating at moderate temperature restored stable circulation. The user confirmed normal operation and no more boiling after the fix. [Elektroda, puchacz2420, post #17010471]

What specs were noted for the plate heat exchanger in the thread?

The markings reported were HTA 0.9 m², weight 5.3 kg, test pressure 64 bar, and volume 0.7. Use these only as the case’s data point, not a universal spec. [Elektroda, puchacz2420, post #16970283]

How hot was the boiler when the issue appeared?

The pump announced itself around 70°C, and earlier the system had boiled at higher setpoints. Reducing the setpoint to 55°C temporarily avoided symptoms before the permanent fix. [Elektroda, puchacz2420, post #16970387]

What is an expansion vessel in an open system?

It is an open tank at the highest point that accepts expanding water and gives steam and air a safe escape path via an overflow. Correct connections are essential for safety. [Elektroda, Henio65, post #16970330]

What is a differential valve in heating systems?

It is a bypass valve that opens under high differential pressure to maintain minimum flow when circuits close or pumps stop. It is not a substitute for proper venting and vessel piping. [Elektroda, puchacz2420, post #16969722]

Three‑step how‑to: re‑pipe an open expansion vessel on a solid‑fuel boiler

  1. From the boiler’s top outlet, run a 1" pipe directly to the vessel’s top, sloping toward the boiler.
  2. Connect the vessel’s bottom to the boiler return.
  3. Pipe the vessel’s overflow to a safe drain and verify free passage. [Elektroda, Sstalone, post #16970501]

Edge case: Why did water discharge from the vessel during boil‑over?

With misconnected piping, steam pushed water out via the vessel. Without a free, direct path from the boiler top to the vessel, boiling forces discharge and leaves the pump air‑bound. [Elektroda, puchacz2420, post #16970387]

Final verdict from the homeowner after the fix?

“The stove works like a doll. Wife doesn’t complain, the oven doesn’t cook.” That confirms stable, boil‑free operation after re‑piping. [Elektroda, puchacz2420, post #17010471]
Generated by the language model.
ADVERTISEMENT