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No heat from my ZEB / not responding to call for heat

This article helps you understand why your ZEB is not discharging heat 

Use this article to:

  • Quick checks in the tepeo app, on the ZEB, and on your heating controls
  • Things you can safely try yourself
  • When to contact tepeo Support or your installer

If your ZEB is heating but your home still doesn’t feel warm enough, see:
“My ZEB is fully charged but my heating isn’t coming on, is this normal?”

 

1. Quick safety notes

  • Do not open the ZEB casing or attempt internal repairs.
  • Never bleed radiators or work on valves when the system is hot.
  • If you notice burning smells, smoke, or persistent unusual noises, turn the system off if it is safe to do so and contact tepeo Support or your installer immediately.

 

2. Check ZEB power and basic status

Is the ZEB powered on?

  • Check the ZEB’s comms box lights:
    • Are any lights or indicators on?
    • Does anything suggest the unit has no power?

If the ZEB appears completely off (no lights) and your home has electricity:

  • Check the local isolation switch for the ZEB to make sure it is turned on.
  • If there are no lights on the ZEB comms box, you can power cycle by switching off and back on again at the local isolator switch.
  • If it’s safe and you feel comfortable doing so, check the ZEB’s fuse at your consumer unit/fuse board to see if the breaker has tripped. If it has, you can try resetting it once
  • If you are unsure or uncomfortable checking these, contact your installer or a qualified electrician.

If there is an obvious problem or the fault indicator is flashing, skip to When to contact tepeo Support or your installer.

 

3. Check the tepeo app and call for heat

Is there an active call for heat?

Open the tepeo app and check:

  • Is there an active call for heat?
  • Does the app show the ZEB is discharging or idle?

Scenarios:

  • No call for heat
    The ZEB will not send heat to the radiators if no one is asking for it. Move on to Check your thermostat and valves.

  • Call for heat shown, but ZEB is idle and radiators are cold
    There may be a communication or control issue. Continue with the checks below.

Is the ZEB Charged?

In the app, check the Charge level:

  • If Charge is 0% or very low, the ZEB may simply not have energy to deliver heat:

    • Check your charging schedule (and any custom charging settings you use).
    • You may need to Boost or adjust your charging times.
  • If the ZEB shows a healthy Charge but radiators are still cold during a call for heat, continue to the next section.

4. Check your thermostat and radiator valves

Thermostat/clock checks

On your main thermostat or heating controls:

  • Confirm the target temperature is set above the current room temperature.
  • Make sure the thermostat is set to heating on, not off or “holiday/away”.
  • If you use schedules on the thermostat:
    • Confirm that the current time is inside an active heating period.
    • Check for any eco/holiday modes that might limit heating.

If changing the thermostat setpoint (e.g. turning it up a few degrees) does not create a call for heat, there may be an issue with the thermostat, its wiring, or wireless link to the ZEB system. In that case, contact your installer/heating engineer.

Radiators and valves

When you know there is an active call for heat (from the app/controls/comms box):

  • Check a few radiators:
    • Are the flow pipes (usually the side with the control valve or TRV) getting warm at all?
    • Are TRVs fully open in rooms you’re testing?
  • If all radiators are cold:
    • The ZEB may not be sending hot water to the system (possible pump, valve, or control issue).
  • If some radiators are hot and others stay cold:
    • Cold radiators may have:
      • Closed valves or TRVs
      • A stuck valve
      • Balancing issues

Only make adjustments you feel confident doing (e.g. opening TRVs fully). For anything more involved (such as suspecting a stuck valve), contact your installer or a heating engineer.

When to contact tepeo Support or your installer

You should contact tepeo Support or your installer if:

  • The ZEB has power, but:
    • There is a clear call for heat, and
    • The ZEB shows a reasonable Charge, yet
    • Radiators remain cold.
  • The ZEB:
    • Turns on and off rapidly (rapid cycling),
    • Makes unusual noises, or
    • Appears to start to heat but then immediately stops, with no clear reason.
  • The ZEB appears to be unreachable in the app for long periods, despite your home Wi‑Fi working normally.

Information to have ready

To help us diagnose the issue quickly, please include:

  • Whether the ZEB currently has Charge (and the approximate percentage).
  • A brief description of:
    • What you see in the tepeo app (call for heat status, any errors).
    • What your thermostat is set to (mode and temperature).
    • Whether any radiators get warm at all, or all stay cold.
  • Any recent changes:
    • To your heating system (new thermostat, plumbing work, radiator changes).
    • To your controls or tariff (new time‑of‑use tariff, changes to schedules).