Playbook: ERV Delivery and Effectiveness

Adapted from HVAC FDD Reference v1.0, Remediation Playbooks (pp. 166–167).

Step 1 — Confirm mode and frost state

1. Confirm the ERV is scheduled to run and both air streams should be moving. Exclude smoke, purge, commissioning, manual test, and maintenance modes.
2. Read the actual frost-sequence state and compare its configured engagement and release settings with OAT. Verify OAT against a second local sensor.
3. For ERV-0002/0003, command the frost sequence through one safe transition and confirm the flag means active, not enabled or available.
4. Suspend ERV-0005 during frost strategies that intentionally unbalance the core paths; otherwise verify its measurements are at a whole-unit boundary where the intentional core-path offset is not being diagnosed.

Step 2 — Prove the active recovery device

1. On wheels and runaround loops, compare the final recovery command with an independent rotation, speed, current, flow, or work proof.
2. A wheel motor current switch proves the motor, not the belt or wheel; inspect the belt/coupling whenever ERV-0001 is active with motor proof present.
3. Release HOA/local and software overrides. Record drive or pump fault history before resetting it. Passive plate cores skip this step.
4. Confirm any automatic wheel-jog/exercise command is included in the final command binding or excluded from evaluation.

Step 3 — Compare the two air streams

1. Confirm supply and exhaust flow sensors belong to the same ERV, use L/s, have nonnegative polarity, and share an averaging interval.
2. Compare the measured offset with the design pressure strategy. Normalize an intentional offset before treating the residual as imbalance.
3. Inspect filters, outdoor/exhaust openings, dampers, fan belts/speeds, and the recovery core on both streams. Use ERV-0005’s direction only as evidence of which measured flow is higher; it does not isolate restriction or sensor cause.

Step 4 — Verify temperature effectiveness

1. Calculate the sensible effectiveness during conditions with adequate temperature difference between outdoor and indoor air — minimum |OAT − RAT| > 10 °F for a reliable measurement.
2. Compare it to the commissioning baseline or the manufacturer’s rated effectiveness.
3. If effectiveness has dropped below 50% of the rated value, degradation is confirmed.
4. Check whether the effectiveness drop is seasonal — some units perform differently in heating vs. cooling mode.

Step 5 — On-site service

1. Inspect and clean the enthalpy wheel or plate core: accumulated dust and particulate reduces heat transfer surface area. Use low-pressure compressed air or a vacuum on plate cores; for enthalpy wheels, follow the manufacturer’s cleaning procedure.
2. For enthalpy wheel units, verify the wheel itself spins — a failed drive motor, belt, or coupling leaves it stationary. Check belt tension, alignment, rotation proof, speed, and motor amperage.
3. Check the seal and purge section for cross-contamination between the airstreams.
4. If the core is permanently fouled or physically damaged, replace it ($2,000–$5,000).
5. Verify that the bypass damper (if equipped) is not stuck in the bypass position, which would route air around the recovery core entirely.

Step 6 — Confirm resolution

1. Command active equipment through stop→start→stop and confirm both proof directions clear inside their configured windows.
2. Confirm frost mode engages and releases at the commissioned boundaries.
3. Rebalance/normalize both streams and verify ERV-0005 stays clear through a full operating transition.
4. Recalculate effectiveness. Target: return to within 15 percentage points of the commissioning or rated value.