Two boilers, four modules, zero loss of heat
Replacement of two dual-module condensing boilers with low-loss headers, a plate heat exchanger of about 750 kW, primary and secondary pumping, a twin-wall stainless flue, gas manifold modification and full BMS integration. Wards, theatres and clinical areas stay served by a temporary boiler arrangement throughout. The changeover is one Sunday, one shift, one signature.
- Client
- St Aldwyn's Hospital
- Site
- Wessex Road, Bath · BA2 6QF
- Work type
- Mechanical, gas and controls
- Reference
- BAI-RAMS-SAH-MEP-001
- Sector
- Healthcare
- Status
- For approval
Illustrative example: fictional project and parties.
What gets installed, and what stays warm
Two dual-module condensing boilers, free-issue, land on low-loss headers feeding a plate heat exchanger for hydraulic separation. Only the hospital secondary is touched at the interface; the existing distribution is left undisturbed. The mechanical scope carries primary and secondary pumps, air and dirt separation, magnetic filtration and balancing. Gas, flue, electrical, controls and BMS complete the package, with flushing and dosing to BSRIA BG 29 and commissioning by an authorised engineer.
Heating continuity is held by a client-supplied temporary boiler, function-tested and signed as serving before any strip-out begins. The new plant is fully built, tested, flushed and commissioned before the live circuit is touched. The final changeover is a single planned out-of-hours event under hospital coordination.
Eleven phases, eight permits
Mobilisation day 1, cutover day 14, handover day 15. Two activities sit on the critical path: the gas commissioning, and the cutover itself. Hospital sites run a permit-driven culture, so every intrusive activity carries a permit and none proceeds without one.
| Permit | Covers | Authorised by |
|---|---|---|
| P-01 Permit to work | Plantroom access and intrusive works, daily renewal | Estates |
| P-02 Electrical isolation | Boiler, pump and control supplies, prove dead | NICEIC and Estates |
| P-03 Gas works | Isolation, purge, modification, recommissioning | Gas Safe and Estates |
| P-04 Mechanical isolation | Heating flow and return, controlled drain-down | Estates |
| P-05 to P-07 Hot works, height, pressure | Welding, flue access, pressure testing | Estates and supervisor |
| P-08 Out-of-hours changeover | The cutover window, notified 7 days ahead | Trust executive and Estates |
Prove dead, then hold the gates
Every isolation runs the same six steps: identify, notify, isolate, drain and purge, prove, release. Nothing is dead until it has been proven dead, and nothing is live again until Estates have witnessed it. Eight mandatory hold points then gate the build, each with a name and a named authority, none bypassed without written change control.
| Hold point | Signed off by |
|---|---|
| Isolation confirmed before any strip-out | Estates witness |
| Pressure tests passed before insulating | BuiltAI supervisor |
| Flue penetration and fire-stopping verified | Estates witness |
| Gas tightness certified before gas to appliances | Gas Safe engineer |
| Electrical inspection and certification complete | NICEIC electrician |
| BG 29 flush, dose and water sample accepted | BuiltAI supervisor |
| BMS enable and fault paths proven end to end | BuiltAI and Estates |
| Witness test passed and Estates training delivered | Estates and Trust |
Hospital hazards, reduced to ALARP
Sixteen hazards specific to hospital boiler replacement, scored on a 5 by 5 scale before and after controls. Hospital emergency procedures override contractor procedures at all times.
| Hazard | Initial | Key controls | Residual |
|---|---|---|---|
| Loss of heating to clinical areas | 20 VH | Temporary boiler live and witnessed before strip-out, out-of-hours cutover, rollback available | 8 MED |
| Gas escape or explosion | 20 VH | Gas Safe only, controlled isolation, tightness test before gas to appliances | 8 MED |
| Electrical contact or shock | 16 VH | Lock-off and tag-off, prove dead, NICEIC competent persons, permits | 6 MED |
| Lifting heavy plant | 16 VH | Handling plan, certified equipment, exclusion zones, no persons under loads | 6 MED |
| Hot works fire risk | 15 HIGH | Permit, fire watch, extinguishers, post-work checks at plus one hour | 4 LOW |
| Asbestos disturbance, legacy plantroom | 15 HIGH | Register reviewed, refurbishment survey, stop-work on suspect material | 3 LOW |
| BMS misconfiguration on cutover | 12 HIGH | End-to-end functional proving, rehearsed sequence, rollback plan, Estates witness | 4 LOW |
After the listed controls, residual risks reduce to ALARP. Emergency arrangements defer to hospital procedures throughout.