Industrial and commercial LTHW unit heaters
CiRRUS LTHW Unit Heaters are wall or ceiling mounted fan heaters that blow a powerful jet of warm air down into high-ceilinged industrial and large commercial buildings. Each CiRRUS Unit Heater runs on low temperature hot water (LTHW, also called LPHW) and pairs an axial fan with an EC motor and a copper tube, aluminium finned coil, in four sizes (Ci5 to Ci8) for mounting heights from 2 to 6 metres.
Manufactured in Leicester, CiRRUS Unit Heaters suit factories, warehouses, distribution centres and workshops, as well as large commercial spaces such as fire station appliance bays, sports halls, leisure centres and supermarkets. Deeper 3 and 4 row coils keep CiRRUS working at the lower flow temperatures of heat pump and condensing boiler systems.
Wall or ceiling
Horizontal and vertical models, no floor space used
Low flow temperatures
3 and 4 row coils for heat pump systems
BMS ready
0 to 10V fan control, BACnet via the Delta controller
Made in Leicester
Manufactured and supported by SPC in the UK
Up to 37.0 kW
Heating at 80/70°C from a Ci8 unit with the standard 2 row coil (high fan speed, 18°C air)
Up to 22.1 kW
Heating at 45/35°C from a Ci8 unit with a 4 row coil (high fan speed, 18°C air)
2 to 6 m
Recommended mounting heights across the range, Ci5 at low speed to Ci8 at high speed
Up to 27 m
Throw from a horizontal Ci8 unit at high fan speed
What are CiRRUS LTHW Unit Heaters?
A CiRRUS LTHW Unit Heater draws in air from the space, blows it across a heat exchanger fed with low temperature hot water, and discharges the warm air through adjustable, angled louvres. The CiRRUS casing is powder coated heavy gauge mild steel, with the fan at the back, the coil at the front and the electrical box on the side.
The CiRRUS EC fan is continuously variable via a 0 to 10V signal, so fan speed can be set to suit the height at which each unit is mounted.
Rear of a CiRRUS Unit Heater, showing the axial EC fan and basket guard.
What sizes do CiRRUS Unit Heaters come in?
CiRRUS Unit Heaters are made in four sizes. Smaller units suit lower mounting heights and smaller areas; larger units cover more floor area from higher up.
| Model | Connection (BSP) | Approx. dry weight (kg) | Recommended mounting height (m) |
|---|---|---|---|
| Ci5 | 1″ | 30 | 2.0 to 3.5 |
| Ci6 | 1″ | 45 | 2.5 to 4.5 |
| Ci7 | 1¼” | 55 | 2.5 to 5.5 |
| Ci8 | 1¼” | 70 | 2.5 to 6.0 |
Comparing heating options for a large space? Read our guides: Why Industrial Unit Heaters Excel in Warehouses and Factories and Fan Convectors vs Unit Heaters for Warehouse Heating.
How do CiRRUS Unit Heaters perform with boilers?
The standard CiRRUS coil is 2 rows deep, matched to conventional boiler flow temperatures close to 80°C.
- Performance published at 80/70°C, 82/71°C and 80/60°C
- Optional 3 row coil raises output at boiler temperatures
- Fan speed sets output, throw and coverage together
Can LTHW unit heaters work with heat pumps?
Yes. CiRRUS LTHW Unit Heaters can be fitted with 3 or 4 row coils to hold output as flow temperatures drop with heat pump and condensing boiler systems.
- Performance published at 60/40°C and 45/35°C
- 4 row coils are for low temperature systems only
- CiRRUS Ci6 units run at 45/35°C at Blackley Community Fire Station
Horizontal or vertical mounting?
CiRRUS horizontal units fix to the wall and angle air down to the floor; vertical units hang from the roof and blow straight down.
- Horizontal: adjustable front louvres, aim 30 to 45° downwards
- Vertical: drop rods or unistrut, optional 4-way diffuser
- Stagger units on opposite walls for even coverage
Full CiRRUS performance data for every size, coil and fan speed is in the CiRRUS brochure.
CiRRUS Unit Heater mounting, controls and options
CiRRUS horizontal units are wall mounted on unistrut or SPC angle brackets, fixed to all four hexserts with M8 bolts. CiRRUS vertical units hang from the roof structure on drop rods or unistrut using four mounting brackets. Casings and louvres are finished in white or black textured powder coat as standard.
SPC recommends controlling CiRRUS output on the waterside, because reducing fan speed also reduces throw and coverage. The SPC Delta Waterside Controller modulates a 2-port valve via a 0 to 10V signal, with master/slave control for multiple units, volt-free terminals and BACnet compatibility. CiRRUS units can also run on manual on/off and speed switches, or directly from a BMS.
CiRRUS accessories include coils to suit different LTHW temperatures, a 4-way diffuser (vertical models), IP rated electrical boxes, hanging brackets and suspension options, and a 2-port modulating valve package. Contact SPC for anything not listed.
Project support from SPC: from survey to commissioning
SPC manufactures and supplies CiRRUS Unit Heaters for installation by your chosen mechanical and electrical contractor, and supports the project at every stage.
Site surveys
SPC can visit site to check mounting heights and unit positions before order.
Selection
Send us your heat loss, floor plan and mounting heights and SPC will select sizes, coils and fan speeds.
Decarbonisation CPD
Our CIBSE approved CPD, Decarbonisation of Industrial and Commercial Heating Systems, can be delivered to your practice.
Area Sales Managers
Your local SPC Area Sales Manager is on hand for questions, site visits and installation queries.
- CIBSE approved CPD: SPC’s CPDs are listed in the CIBSE CPD directory.
- Installation and operation: the CiRRUS IOM manual covers installation and operation, and is in the literature below.
Specifying CiRRUS Unit Heaters
Free tools to select units and add them to your BIM model.
Select units online
Size and configure CiRRUS Unit Heaters with our free online configurator, which also covers our fan convectors and air curtains.
Download BIM objects
Add CiRRUS Unit Heaters to your BIM model. Our BIM objects are free to download from SPC on bimstore, alongside the rest of the SPC range.
CiRRUS Unit Heaters in UK projects
CiRRUS Unit Heaters are installed in fire station appliance bays, supermarkets, leisure centres and workshops across the UK, including Blackley and Stockport Central Community Fire Stations in Manchester, Wantage Leisure Centre and Tesco stores in Mold and Holbeach. See all SPC unit heater projects.
CiRRUS Unit Heater specification summary
| Detail | Spec |
|---|---|
| Models | Ci5, Ci6, Ci7, Ci8 (horizontal and vertical) |
| Dimensions (width x height x depth) | Ci5 500 x 500 x 335 mm, Ci6 600 x 600 x 360 mm, Ci7 700 x 700 x 360 mm, Ci8 800 x 800 x 395 mm (depth includes the fan guard; casing depth 252 to 290 mm) |
| Casing | Heavy gauge mild steel, textured powder coat, white or black as standard |
| Louvres | Fully adjustable, painted to match casing |
| Fan | Axial, EC motor, sealed-for-life bearings rated for continuous operation up to 60°C |
| Fan control | Continuously variable via 0 to 10V DC signal |
| Heat exchanger | Copper tubes expanded into aluminium fins; 2 row standard, 3 and 4 row options |
| Water connections | Male taper BSP, mild steel, 1″ (Ci5, Ci6) or 1¼” (Ci7, Ci8), vent and drain points included |
| Test pressure | Air under water to 22 bar |
| Power supply | 230V / 1 phase / 50Hz (water heated units) |
| Power draw | 70 W to 700 W per unit, depending on size and fan speed |
| Noise | 41 to 66 dBA, depending on size and fan speed (approx. free field, 3 m from the unit) |
| Manufactured | Leicester, UK, by S & P Coil Products Limited (ISO 9001:2015) |
Full CiRRUS performance data (output, airflow, water flow and pressure drop by size, coil and fan speed) is available in the literature below.
Discuss your unit heater project
Whether it is a factory, warehouse, fire station or sports hall, send us your floor plan and mounting heights for a CiRRUS selection, request a site survey or book the Decarbonisation CPD. Call +44 (0)116 249 0044, email spc@spc-hvac.co.uk or use the form below.
Frequently Asked Questions
Yes, in practice. LTHW (low temperature hot water) and LPHW (low pressure hot water) both describe hot water heating systems running below 100°C, and the two terms are used interchangeably in UK specifications. CiRRUS LTHW Unit Heaters suit both conventional boiler and heat pump flow temperatures.
For heat pump systems running at around 45/35°C, choose the 4 row coil; a CiRRUS Ci8 with a 4 row coil delivers up to 22.1 kW at 45/35°C. The 3 row coil suits flow temperatures around 60/40°C, or can raise output at boiler temperatures. The 4 row coil should not be used with conventional boiler temperatures.
Yes. CiRRUS Unit Heaters suit any large, high-ceilinged space that needs warm air delivered from height. SPC has supplied CiRRUS units for fire station appliance bays at Blackley and Stockport, Wantage Leisure Centre, and Tesco stores in Mold and Holbeach.
Mounting height depends on unit size and fan speed: smaller CiRRUS units suit lower heights, while larger units cover more floor area from higher up. Aim for a leaving air temperature of 30 to 45°C, as units selected with excess airflow add draught and noise.
SPC recommends waterside control. Turning the fan down reduces output but also shortens the throw, so warm air may not reach the working area. A modulating 2-port valve keeps the throw constant while output follows demand.
CiRRUS Unit Heaters move large volumes of air at height, so they suit factories, warehouses, appliance bays and sports halls rather than offices or classrooms. Where noise matters, select a larger unit running at low or medium speed.
Yes. The CiRRUS Ci5 is available with a 9 kW electric element for horizontal mounting, on a 400V three phase supply, with a medium/high speed switch.
Yes. CiRRUS Unit Heaters can be set up as master and slave units, where one unit linked to the controls sends a two-wire signal to the others in the same zone.
SPC manufactures and supplies CiRRUS Unit Heaters for installation by your mechanical and electrical contractor. SPC can survey the site and select units beforehand, and the CiRRUS IOM manual covers installation and operation.
