Intro

When you see “Pompa obiegowa szarpie, zawór różnicowy.” on a job, you know the system is hunting. Flow stops, starts, and the pump kicks. Clients hear banging or whistling. The fix is simple once you confirm the cause. In this guide, we explain what the jerk means, how the differential bypass works, and how to set it right. You’ll get quick tests, exact pressures, and steps that take minutes, not hours.

Quick Answer

“Pompa obiegowa szarpie, zawór różnicowy.” usually means the pump is fighting a pressure spike when TRVs or zone valves shut. Set the differential bypass to around 0.1–0.2 bar (10–20 kPa), bleed air, clean the strainer, and match pump speed to design flow. The jerking stops when delta‑P is stable and there’s a steady bypass path.

Table of Contents

• Key Takeaways
• What the Symptoms Mean When “Pompa obiegowa szarpie, zawór różnicowy”
• Fast On‑Site Tests To Confirm The Cause
• Fixes That Work: Air, Cavitation, Valves, Flow
• Set the Differential Bypass Valve (Zawór różnicowy) Right
• Pump Commissioning Checklist For Stable Flow
• Explain and Quote Clearly
• FAQ
• Conclusion

Key Takeaways

• Jerking pump = unstable delta‑P. The bypass is shut or mis‑set.
• Start with simple checks: air, strainer, pump speed, valve positions.
• Typical bypass setting: 0.1–0.2 bar (10–20 kPa) across flow/return.
• Aim for steady flow: 10–20 l/min on small domestic circuits.
• Commission once: 20–30 minutes saves call‑backs all winter.

What the Symptoms Mean When “Pompa obiegowa szarpie, zawór różnicowy”

The phrase “Pompa obiegowa szarpie, zawór różnicowy.” points to a circulation pump that surges. Flow stops, then restarts with a kick. You may hear rattling pipes, valve chatter, or a short howl.

Why it happens:

• TRVs or a zone valve close, system resistance rises.
• Pump head spikes to 3–6 m. Delta‑P climbs fast.
• The differential bypass stays shut, so pressure keeps rising.
• The pump cavitates, then flow collapses. It repeats.

What the differential bypass (zawór różnicowy) does:

• It opens at a set pressure (say 0.15 bar).
• It gives a short path from flow to return.
• It keeps the pump working against a steady load when circuits throttle.

Fast On‑Site Tests To Confirm The Cause

You can confirm “Pompa obiegowa szarpie, zawór różnicowy.” in under 10 minutes.

1. Feel the pipes (1 minute).

   • Flow roasting hot, return lukewarm? Bypass likely shut.
   • Both hot but pump still jerks? Air or cavitation.

2. Open 3–5 TRVs fully (2 minutes).

   • If jerking stops, the bypass or pump setting is the issue.

3. Crack the bypass by hand (2 minutes).

   • Turn the adjuster anticlockwise a quarter turn.
   • If noise drops in 5–10 seconds, you’ve found the fault.

4. Listen at the pump (1 minute).

   • Gravel sound = cavitation (starved inlet or blocked strainer).
   • On/Off surge = control or valve chatter.

5. Check the strainer (3–5 minutes if accessible).

   • If it’s 50% blocked with magnetite, clean it.

Fixes That Work: Air, Cavitation, Valves, Flow

Most “Pompa obiegowa szarpie, zawór różnicowy.” jobs need only a few simple fixes.

1) Remove Air And Stop It Coming Back

• Bleed the pump and the top rads. Allow 5–10 minutes.
• Set the automatic air vent cap one turn open.
• Keep static pressure 1.2–1.5 bar cold on domestic sealed systems.

2) Stop Cavitation

• Clean the strainer. Replace if the mesh is torn.
• Check isolation valves are fully open both sides of the pump.
• If the pump is on the wrong side of the vessel, move the connection or reduce speed. The pump should “pump away” from the expansion vessel.

3) Tame The Pump

• Drop the speed from III to II or from II to I.
• On ECM pumps, set constant pressure mode at ~0.15–0.20 bar.
• Aim for 10–20 l/min total flow in a small house loop.

4) Set Or Replace The Bypass

• If there is no bypass and TRVs are fitted, add one.
• Use a spring‑loaded differential bypass between flow and return.
• Pipe short, 22 mm, with isolation both ends.

5) Balance The System

• Half‑close the closest lockshields. Open the furthest more.
• Don’t leave all TRVs at 5. Start with 3–4 and adjust.

Common trap: a check valve fitted backwards near the pump. If you see unexplained dead‑heading and “Pompa obiegowa szarpie, zawór różnicowy.” persists, recheck flow arrows on every valve you touched.

Set the Differential Bypass Valve (Zawór różnicowy) Right

Here’s a clear, repeatable method. This section is the heart of solving “Pompa obiegowa szarpie, zawór różnicowy.”

1. Prepare (2 minutes).

   • Open all TRVs and zone valves.
   • Set pump to mid speed or constant pressure mode.

2. Close the bypass fully.

   • Turn clockwise to the stop.

3. Create a throttled condition (3 minutes).

   • Close 60–80% of emitters: shut 6 of 10 TRVs, for example.
   • This simulates a typical part‑load.

4. Open the bypass to first flow (1–2 minutes).

   • Crack anticlockwise until pipe temp rises on both sides.
   • You should hear the system calm within 10 seconds.

5. Fine‑tune by delta‑P.

   • Target opening pressure: 0.1–0.2 bar (10–20 kPa).
   • If you have gauges, adjust to keep pump head stable within that band at part‑load.

6. Lock the setting and re‑open circuits.

   • Open all TRVs and check that rads heat evenly.

7. Re‑check at full load.

   • If the boiler short‑cycles, close the bypass a quarter turn.

Notes:

• Don’t set the bypass too low. Below 0.05 bar it may steal flow from rads.
• Don’t set it too high. Above 0.25 bar you’ll still get jerks and noise.

Pump Commissioning Checklist For Stable Flow

Run this once after any call‑out with “Pompa obiegowa szarpie, zawór różnicowy.” It saves repeat visits.

• Expansion vessel: set pre‑charge to match system cold pressure (often 1.0 bar). Check with a tyre gauge.
• System pressure: 1.2–1.5 bar cold; 1.8–2.0 bar hot. No wild swings.
• Strainer: clean to shiny mesh. Refit with new fibre washer if needed.
• Pump mode: constant pressure if available; otherwise speed II is a safe start.
• Bypass: 0.1–0.2 bar set point; lock the ring.
• Balancing: lockshields set for quiet return temperatures (approx. 15–20°C drop across rads).
• Safety: verify discharge pipe not dripping. If it is, vessel may be flat.

On most jobs, this takes 20–30 minutes. On dirty systems, allow 1–2 hours for a power flush and inhibitor dose. After that, “Pompa obiegowa szarpie, zawór różnicowy.” should be gone.

Explain and Quote Clearly

Clients worry when pipes bang and pumps “kick.” A short explanation wins trust.

• Show the old setting and the new bypass position. Note 0.15 bar on the work sheet.
• List the parts you cleaned or replaced: strainer, auto vent, bypass.
• Add an optional upgrade line: ECM pump with constant pressure saves energy and noise.

When you want to turn that fix into a clear proposal fast, tools like Donizo help. You can speak the job notes on site, generate a branded proposal, get an e‑signature, and convert it to an invoice in one click. It keeps your day moving while the heating stays quiet.

This pairs well with creating professional proposals and using solid invoice templates so your pricing and paperwork are as smooth as your flow settings.

FAQ

Why does the pump jerk only at night?

At night, more TRVs shut as rooms hit setpoint. Resistance rises and the bypass is mis‑set, so the pump sees high delta‑P and surges. Re‑set the bypass to 0.1–0.2 bar and lower the pump speed. The issue usually disappears.

Do I need a bypass if there are no TRVs?

If there are no TRVs and zone valves stay open, a bypass may not be needed. But if any valve can close a loop, fit a differential bypass. It protects the pump, reduces noise, and stabilises the boiler.

How do I know the bypass is stealing heat?

Rads stay lukewarm while the bypass pipe is hot at both ends, even with most TRVs open. Close the bypass a quarter turn and check radiator returns. If they warm up and noise stays low, you’ve hit the sweet spot.

Can wrong pipe size cause “Pompa obiegowa szarpie, zawór różnicowy.”?

Yes. A long 15 mm main can choke flow, push delta‑P up, and trigger jerks. If simple fixes fail, check mains are 22 mm where needed and that there’s no hidden kink or stuck check valve.

What pump mode is best for TRVs?

Constant pressure mode is best. Set around 0.15–0.20 bar. It keeps delta‑P steady as TRVs open and close, so the pump doesn’t hunt and the system stays quiet.

Conclusion

“Pompa obiegowa szarpie, zawór różnicowy.” means unstable pressure and a bypass that isn’t doing its job. Set the bypass to 0.1–0.2 bar, bleed air, clean the strainer, and match the pump mode to the system. The noise stops and flow stays smooth.

Next steps:

• Set the bypass using the 7‑step method today.
• Drop pump speed or set constant pressure.
• Balance the nearest radiators and re‑check returns.

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