# Why does a hospital vacuum plant run all the time?

**Why can a hospital vacuum plant run continuously, and how are running hours and leakage checked?**

A hospital vacuum plant is designed to run often or continuously: HTM 02-01 (2026), the NHS England guidance, says all vacuum pumps should be designed for high-frequency stop/start or continuous operation, and the ULTRAVAC CLP datasheet says its variable speed pump matches production to consumption, stopping when there is no consumption.

## How the plant is controlled

HTM 02-01 asks for a vacuum vessel sized to minimise the stop/start cycles of the plant, with the number of cycles per hour not exceeding the manufacturer's recommendation, typically six. The pump start (cut-in) setting allows for the pressure drop across the pipeline and the bacteria filters and should be set around 550 mmHg, subject to plant design. The off (cut-out) setting should be chosen on the pump performance curve to minimise stop/start cycling, at a vacuum level the pump can achieve and that suits a demand-led control arrangement, and may be expected at about 650 mmHg.

ULTRAVAC systems aim to provide medical vacuum continuously, with fully automatic operation, using 1 to 12 pumps and vacuum vessels of 24 to 6,000 litres. In the variable speed [ULTRAVAC CLP](https://library.ultracontrolo.com/products/ultravac-clp/), the drive adjusts the pump speed to the vacuum required by the network; the datasheet says production equals consumption, and with no consumption the pump goes into standby mode and stops.

## What to record

HTM 02-01 asks for these readings and records:

- a total hours counter for each pump, in the starter unit or the plant control unit;
- weekly: hours run for each pump, the vacuum cut-in and cut-out levels on the duty pump gauge, the running current of the duty pump and any alarm conditions on the control panels;
- at planned maintenance: the hours run for each pump and, for VSD plant, the running current and stabilised vacuum level under normal load;
- BMS connections that include the running status of each vacuum pump.

HTM 02-01 Part B says the hours-run readings can be used with the manufacturers' recommendations to adjust the maintenance programme. For design, Part A states the intention to use the most efficient pumps and compressors and to remove unused and unnecessary gases and terminal units.

## How leakage is checked

- At commissioning, the HTM 02-01 vacuum leakage test expects no loss of vacuum over at least two hours once the system has settled.
- Among the HTM 02-01 Part B permit-to-work tests, the pipeline vacuum leakage test (PVL) isolates an area, drops the vacuum to a set level and monitors it with digital gauges for 15 minutes.
- Terminal units are tested quarterly: a blank probe checks gas-specificity, mechanical function and leaks, and a test instrument checks flow and pressure drop.

### How often should a vacuum pump start and stop?

HTM 02-01 (2026) says the number of cycles per hour should not exceed the manufacturer's recommendation, typically six, and sizes the vessel to minimise stop/start cycles.

### Can a variable speed vacuum pump stop completely?

The ULTRAVAC CLP datasheet says that when there is no consumption, the variable speed pump goes into standby mode and stops.

## Sources

- [NHS England, HTM 02-01 Medical gas pipeline systems (2026), Part A, 1.8, 10.18, 10.19, 10.31, 10.32, 10.50, 10.56 and 19.219](https://www.england.nhs.uk/wp-content/uploads/2016/05/health-technical-memorandum-02-01-medical-gas-pipeline-systems-part-a-design-installation-validation-verification-aug-2026.pdf)
- [NHS England, HTM 02-01 Medical gas pipeline systems (2026), Part B, 11.113, weekly tasks for vacuum plant, central vacuum plant maintenance tasks, PVL test and 11.213](https://www.england.nhs.uk/wp-content/uploads/2016/05/health-technical-memorandum-02-01-medical-gas-pipeline-systems-part-b-operational-management-aug-26.pdf)
- [ULTRAVAC datasheet, p. 2, p. 3 and p. 5](https://www.ultracontrolo.com/products/ultravac)
- [ULTRAVAC CLP datasheet, p. 2](https://www.ultracontrolo.com/products/ultravac-clp)

Reviewed: 2026-10-22. Ultra Controlo engineering. https://library.ultracontrolo.com/answers/why-does-a-vacuum-plant-run-all-the-time/