Steam generator location and service access

The short answer

• Dry, frost-free, ventilated and indoors. Harvia’s generators must be installed in a dry interior space, away from frost and harmful substances, with ventilation if they sit in a cabinet.
• No hotter than 30 °C around the unit for Harvia generators. Other makers set different limits, and the selected model’s manual governs.
• Close to the room. Harvia allows up to 10 m of well-insulated steam pipe and prefers under 6 m, at the same level, laid to fall towards the room with no dips.
• A floor drain in the plant space, not directly under the generator, for discharge water at about 70 °C. It never drains into the steam room.
• Controls outside the steam room. The Harvia control panel goes in a dry area; only the sensor and steam outlet go in the room.
• Access for servicing. Plan the space around the jobs that have to be done there, not only around the box.

Why location matters

A steam generator is a small electric boiler with a water supply, a hot drain, a steam pipe, a control cable and a sensor cable. Where it goes affects four things:

1. Performance. Every metre of steam pipe loses heat. A long or poorly laid run delivers less steam to the room and can collect condensate that spits from the outlet.
2. Reliability. Electronics and valves are designed for a limited ambient temperature. A generator cooking in a hot cupboard or roof space is working outside its design conditions.
3. Safety. The discharge water is hot, and steam lines and the generator body get hot. They need to be where nobody can be scalded.
4. Servicing. Sediment cups, level sensors, elements and valves all need hands on them over the life of the room. A generator hidden where technicians can’t reach it turns routine servicing into a building problem: cutting linings, removing joinery or working in a hot roof space.

That is why the location is fixed early in design, alongside the steam room itself, and why it feeds back into sizing the generator.

The space itself

Harvia’s current HGX, HGD and HGP manuals set out the same basic rules:

• A dry interior space. Not outdoors, and not where the generator could get wet from hose-down or condensation.
• No frost. Water left in the tank or pipes must not freeze. In South East Queensland heat is the bigger concern, but the rule is still in the manual.
• No harmful substances. Keep the generator away from chemicals. Several manufacturers specifically warn against air carrying chlorine, such as a pool plant room or chemical store.
• A floor drain in the room, but not directly under the generator. Steam rising from the drain wets the unit and can cause faults.
• Ventilation in a cabinet. If the generator sits in a cabinet or similar closed space, there must be enough ventilation around it. A generator gives off heat while it works, and without air movement an enclosed cupboard warms up.
• Firmly fixed. Harvia’s generators are screwed to a wall or base. The HGX can be fitted left- or right-handed by swapping its covers, and laid horizontally in a low space by turning the mounting parts and shortening the sediment cup.

Ambient temperature, and why Queensland roof spaces are usually unsuitable

Manufacturers cap the air temperature around their generators because the control electronics, valves and seals are rated for it.

For a Harvia generator, 30 °C is the limit, whatever another brand allows.

Roof spaces in South East Queensland can run well above 30 °C in warm weather, before the generator adds any heat of its own. Following Harvia’s ambient limit therefore usually rules them out. They are also hard to reach for servicing and a poor place for a hot discharge drain. The same reasoning applies to an unventilated cupboard on a western wall, a garage that bakes in the afternoon, or a space shared with a hot-water system or pool equipment.

The safer plan is a ventilated cupboard or plant room inside the building’s conditioned envelope, or at least out of direct heat, at the same level as the steam room. Where there is doubt, the mechanical designer can confirm the temperature the space will reach in summer.

Steam pipe: length, fall and insulation

Why these rules exist:

• Length. Steam loses heat to the pipe walls. The longer the pipe, the more condenses before it reaches the room, and the less output the room actually gets. One commercial maker treats extra pipe length as extra room volume when sizing.
• Fall and no dips. Condensate forms in every steam pipe. If the pipe falls towards the room, it runs out of the outlet. If there is a dip, it collects as a water pocket that the steam pushes through in spurts, which can spit hot water from the outlet.
• Insulation. It reduces heat loss and keeps the pipe surface from becoming a burn hazard.
• Free flow. If the nozzle or pipe is blocked, Harvia’s generators release steam through an overpressure valve at the unit, which is one more reason the plant space needs a drain and nothing sensitive nearby.

The transparent hose at a Harvia generator is there so problems such as water collecting in the line can be seen. Leave it visible and accessible. Different manufacturers’ pipe rules are not interchangeable: the selected generator’s manual governs.

Water supply and drainage

Water supply. Harvia’s HGX manual asks for a stop valve and a vacuum breaker on the supply, a maximum pressure of 4.0 bar and a flow of 8–12 L/min. Too little flow interrupts steam production; too much can push water out through the steam pipe. Leave room on the supply for a filter or softener if the water needs one. See steam generators and water quality.

Discharge. The generator empties its tank after use and, with Harvia’s automatic discharge valve, rinses during long sessions as well. Harvia’s manuals say:

• the discharge pipe goes to the plant space’s floor drain;
• the water is very hot, about 70 °C, so it must not be led to the steam room;
• the pipes fall away from the generator.

Other manufacturers add details: some keep the drain and safety-valve lines separate, and some dump several litres in a few seconds, so the drain must cope with the flow and the heat. Never connect a drain line to the steam pipe.

The steam room itself also needs its own floor drain for condensate and cleaning. That is a separate drain from the one in the plant space.

Water supply, backflow prevention and drainage are designed and installed by a licensed plumber to the Plumbing Code of Australia and the manufacturer’s manual.

Controls, cabling and the sensor

Control panel. Harvia’s manuals say the control panel can be installed in a dry area such as the bathroom, dressing room or living area, but not in the steam room. Other makers allow a control inside the room in some models, so this is model-specific.

Cabling. Harvia’s 2023 manuals for the HGX, HGD and HGP describe Ø 20 mm conduit inside the wall so the panel’s data cable can be run concealed; otherwise it is surface-mounted. They also recommend keeping the data cable apart from power cables to avoid malfunctions. Plan the conduit before the walls are lined. The generator’s power supply is designed and installed by a licensed electrician to AS/NZS 3000 and the manual.

Temperature sensor. The sensor tells the generator when the room is warm enough, so it has to read the air bathers sit in, not the steam jet or a draught.

A sensor too close to the steam outlet, door or a vent makes the room cycle erratically, feel cold or run hot near the outlet. Our guide to steam room design and construction covers the steam outlet position.

Service clearance and access

Harvia’s manuals show minimum clearances around each generator in their installation drawings. Other manufacturers recommend clearances of roughly 300 mm to 600 mm around the unit for servicing. Use the selected model’s figures, then plan the space around the jobs that happen there:

The access door matters as much as the clearance. A generator behind a fixed panel or a narrow cupboard door can be impossible to service even with clearance around it. A hinged door or removable panel big enough to work through, with light in the space, keeps routine visits routine. Our service page explains how servicing is arranged.

Commercial plant rooms

Commercial steam rooms run for many hours a day and are serviced on a schedule, which changes the plant space:

• A dedicated, lockable plant room. One manufacturer strongly recommends a locked utility room accessible only to authorised staff for its commercial generators. It keeps guests and cleaners away from hot surfaces and controls.
• Not in the pool plant room. Chlorinated air can corrode generators, and several manufacturers rule it out. If a plant space has to be shared, confirm the arrangement with the generator manufacturer and the mechanical designer.
• Multiple generators. Large rooms may use several generators on one control, for capacity and so some steam is still available while one unit flushes or is serviced. Each needs its own clearances, drain connection and pipe route as its manual specifies, and one manufacturer forbids two generators sharing one steam line.
• Drainage capacity. Several generators rinsing during the day put repeated hot discharges into the plant-room drain. The plumber sizes it for the flow and temperature.
• Ventilation and temperature. A room of generators gives off heat. The mechanical engineer confirms how the plant room stays within the generator’s ambient limit.
• Room for the water treatment and for a technician to work on one generator while the others run.

See commercial saunas and steam rooms for duty, servicing and operator routines.

Planning checklist

• Generator model selected, and its current manual on hand
• Plant space indoors, dry and frost-free, away from chemicals and chlorinated air
• Summer temperature in the space within the generator’s limit (30 °C for Harvia)
• Ventilation provided if the generator is in a cabinet or closed space
• Steam pipe route within the manual’s maximum (Harvia 10 m; under 6 m preferred), at the same level, falling to the room with no dips, insulated
• Floor drain in the plant space, not directly under the generator; discharge pipes falling away from it
• Water supply with the isolation and backflow protection the manual and plumber require, and space for a softener if needed
• Control panel location outside the steam room, with conduit for the data cable
• Sensor and steam outlet positions agreed for the room
• Clearances and an access door that let every service task be done without removing linings or joinery
• Commercial: lockable plant room, drain capacity, plant-room ventilation and space for multiple units