E035 on a Trianco heat pump: Low Water Flow Prot
Short answer
On a Trianco heat pump, E035 means: Low Water Flow Prot. The manual does not say whether the heat pump stops. An engineer is needed to fix the cause. The wording differs by model range — each is shown below.
Reviewed 23 September 2026 · 3 sources
What it means
On the Activair Commercial R290 50kW (FG9550)
The manual says: Low Water Flow Prot.
Part involved: water flow / water temperature.
Likely causes:
- The system has no water or too low volume of water.
On the Activair R290 Indoor (3.2kW wall hung / 5kW floor standing)
The manual says: Low Water Flow Protection.
Part involved: water flow / water temperature.
Likely causes:
- Water flow is too low.
On the Activair Pro (AI) R290 6/12/17kW
The manual says: Low Water Flow Protection.
Part involved: water flow / water temperature.
Likely causes:
- Water flow is too low.
Is it safe?
| Does the heat pump stop? | Not stated |
|---|---|
| Engineer needed? | Yes |
The manual does not say whether the heat pump stops.
What you can check
- Note the exact code shown on the controller (a photo helps) and report it to your installer or the manufacturer's service line.
- Check the heat pump's supply breaker/isolator at the consumer unit is on (do not open any casing).
- Check the heating system pressure gauge reading (if one is fitted) and tell your engineer if it is below the level set at commissioning; do not attempt to refill unless you have been shown how.
What the engineer will check
On the Activair Commercial R290 50kW (FG9550)
- Check if the water flow of water pipe meets the requirements and if the water pump is damaged.
Who to ask for: heating / hydraulics.
Certification: Competent heating engineer (manufacturer training recommended).
On the Activair R290 Indoor (3.2kW wall hung / 5kW floor standing)
- Increased water flow.
Who to ask for: heating / hydraulics.
Certification: Competent heating engineer (manufacturer training recommended).
On the Activair Pro (AI) R290 6/12/17kW
- Increased water flow.
Who to ask for: heating / hydraulics.
Certification: Competent heating engineer (manufacturer training recommended).
What you might notice
Sources
- Trianco Activair Commercial High Temperature Air Source Heat Pump (R290 50kW FG9550) - Installation Operation and Service Manual ↗ · 2024-10 · page 39 · Reviewed 23 September 2026
- Trianco Activair R290 High Temperature Indoor Air Source Heat Pump (3.2kW wall hung) - Installation Operation and Service Manual ↗ · 2026-08 · page 33 · Reviewed 23 September 2026
- Trianco Activair Pro Air Source Heat Pump (R290 6/12/17kW) - Installation Operation and Service Manual ↗ · 06/2026 · page 40 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026