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PUMPS & MOTORISED VALVES

Heating Only Works Downstairs

If downstairs heats but upstairs stays cold, the upper circuit may have trapped air, a closed or failed zone valve, poor pump performance or restricted flow.

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Isolate electrical power before opening pumps, actuators or wiring centres

Heating pumps and motorised valves may contain mains voltage and hot water. Stop if a pump is seized, very hot, leaking or if a valve actuator is buzzing continuously.

MOST LIKELY CAUSES

Start with these

Upstairs zone valve fault The upper heating circuit may not open.
Trapped air Air often collects at high points.
Weak circulation The pump may not overcome the higher route.
Balancing or valve issue Downstairs may take most of the flow.
◫ Symptom variations Match the exact circulation or zone pattern. ⌄
  • Downstairs radiators hot
  • Upstairs radiators cold
  • Upstairs thermostat has no effect
  • Gurgling upstairs
  • Heat improves after bleeding
✓ Quick checks Simple checks before removing covers. ⌄
  1. Confirm a heating demand exists.
  2. Check whether one zone or the whole system is affected.
  3. Listen for pump or actuator operation.
  4. Check system pressure and trapped air.
  5. Do not force seized valves or hot pumps.
1 Step 1 — Bleed upstairs radiators Isolate power before removing covers or touching wiring. ⌄

Turn heating off and remove trapped air safely.

2 Step 2 — Check upstairs thermostat and zone demand Isolate power before removing covers or touching wiring. ⌄

Confirm the control is requesting heat.

3 Step 3 — Check upstairs valve positions Isolate power before removing covers or touching wiring. ⌄

Make sure radiator valves and any zone valve can open.

⌁ Common causes explained Why pumps and zone valves fail. ⌄

If downstairs heats but upstairs stays cold, the upper circuit may have trapped air, a closed or failed zone valve, poor pump performance or restricted flow.

⌘ Advanced diagnostics Heating-engineer checks and repair work. ⌄
  • Check upstairs zone valve.
  • Measure pump performance.
  • Inspect high-point air vents.
  • Balance the system.
  • Check upstairs pipe restrictions.
▣ Parts that may need replacing Common components linked to this fault. ⌄
  • Zone valve
  • Circulation pump
  • Automatic air vent
  • TRV
  • Lockshield valve
! When to call a heating engineer Conditions that should end basic troubleshooting. ⌄
  • The pump or actuator contains mains wiring.
  • The pump is seized, leaking or overheating.
  • A valve body is stuck.
  • One or more zones remain uncontrollable.
  • Internal testing is required.
? Frequently asked questions Common pump and valve questions. ⌄

Can I force a motorised valve open?

Use only the normal manual lever as described by the manufacturer. Do not force a seized valve body.

Why is a heating pump hot?

Some warmth is normal, but excessive heat with no circulation may indicate a seized rotor or failed motor.