Metropolitan Electric Trench Heaters are fan-assisted electric trench heaters from SPC, recessed into the floor beneath full height glazing to counter cold down-draughts and heat the room, for buildings without an LTHW heating system or where running pipework to the heaters is not practical. Each unit has ceramic PTC electric heating elements and one or more EC/DC crossflow fans, runs on a 230 V single phase supply and gives 1, 2 or 3 kW from three standard lengths.
Manufactured in Leicester by S & P Coil Products Limited, Metropolitan Electric Trench Heaters suit commercial, public and residential buildings with large glazed areas, including offices, reception areas, showrooms, hotels, restaurants, extensions and refurbishments where a wet heating system cannot reach. The 225 x 125 mm units fit screeded or suspended floors, with a roll-up grille that sits level with the finished floor and simple on/off control from a room thermostat, switch or BMS enable signal.
230 V electric
Single phase supply, with no hot water pipework
PTC elements
Self-regulating, with auto-resetting overheat cut-outs
BMS ready
On/off by room thermostat, switch or BMS enable signal
Made in Leicester
Manufactured and supported by SPC in the UK
1 to 3 kW
Heat output per unit: 1.00 kW at 1,000 mm, 2.00 kW at 1,750 mm and 3.00 kW at 2,500 mm long
No pipework
Runs on a 230 V single phase supply, for buildings with no LTHW system or where pipework is not practical
125 mm deep
Unit size: 225 mm wide x 125 mm high, for screeded or suspended floors, with 30 mm of height adjustment
On/off control
From a room thermostat, switch or BMS enable signal, with the fan speed set to suit the heat output
What are Metropolitan Electric Trench Heaters?
A Metropolitan Electric Trench Heater is a black powder coated steel casing set into the floor, holding ceramic PTC electric heating elements, EC/DC crossflow fans and a roll-up grille that sits level with the finished floor. The fans draw room air into the trench, blow it across the heating elements and send the warmed air up the glazing and into the room. The elements are self-regulating, with auto-resetting overheat cut-outs that trip the unit if the elements or casing become too hot, and the fans and elements sit behind perforated guards. Because they need only a power supply, Metropolitan Electric Trench Heaters suit buildings with no LTHW heating system, and areas such as extensions and refurbishments where running pipework to the trench is not practical.
SPC Metropolitan trench grilles set level with the floor beneath full height glazing at Berkhamsted Sixth Form, Hertfordshire
What sizes do Metropolitan Electric Trench Heaters come in?
Metropolitan Electric Trench Heaters share one unit size, 225 mm wide x 125 mm high, in three standard lengths, each with its own heat output.
| Length (mm) | Width (mm) | Height (mm) | Heat output (kW) |
|---|---|---|---|
| 1,000 | 225 | 125 | 1.00 |
| 1,750 | 225 | 125 | 2.00 |
| 2,500 | 225 | 125 | 3.00 |
These are fixed standard sizes. For a bespoke size, contact SPC’s sales team.
Planning trench heating for a glazed building? Read our guides: Why Trench Heating is Ideal for Modern Buildings and How Do You Stop Cold Down-Draughts from Full Height Glazing? For SPC’s other electric products, read Explore SPC’s Range of Electric HVAC Products, or see the full SPC trench heating and cooling range.
How much heat do Metropolitan Electric Trench Heaters give?
Each Metropolitan Electric Trench Heater gives a set heat output for its length, so a run along the glazing is sized by choosing and combining lengths.
- 1.00 kW from a 1,000 mm unit, 2.00 kW from 1,750 mm and 3.00 kW from 2,500 mm
- Fan speed is set to suit the heat output, so the elements always have enough cooling air
- Output is switched on and off by a room thermostat, switch or BMS enable signal
- No water temperatures to design around: the heaters need only a 230 V supply
Where can electric trench heaters be installed?
Metropolitan Electric Trench Heaters suit indoor spaces with large glazed areas, as single units or longer runs.
- Screeded (concrete) or suspended floors, with levelling screws at each corner, adjustable support feet and 30 mm of height adjustment
- Each unit needs its own 230 V supply and earth, plus control wiring for a thermostat, switch or BMS
- Indoors only: not outdoors or where the heaters could get wet
- Grilles suit occasional foot traffic, not point loads such as chair legs, doorways or areas of constant footfall
Dimensions, heat outputs and the full specification are in the Metropolitan Trench Heating and Cooling brochure, with wiring and installation details in IOM 82.
Metropolitan Electric Trench Heater grilles, controls and options
Metropolitan Electric Trench Heaters are supplied as standard with an anodised aluminium roll-up grille, with stainless steel springs and black plastic spacers, and a matching trim for the edge of the casing. The double-T profile blades give a free area of 60%. Grilles and trim come in satin silver, black and a range of Anolok bronze, gold, umber and blue-grey finishes. Stainless steel grilles are available on request (grille trim is not available in stainless steel). Roll-up grilles suit occasional foot traffic, but not point loads such as chair legs.
Metropolitan Electric Trench Heaters are controlled on/off. The fans run at a speed set to suit the heat output, so the elements always have enough cooling air.
- Room thermostat or switch: a wall mounted room thermostat or a remote switch turns the heaters on and off
- BMS: the heaters can respond to an enable/disable signal from the building management system (BMS) through a relay in the unit, specified at the time of order
- Several units on one thermostat: units can follow a single thermostat, but each unit still needs its own power supply
- Self-regulating elements: ceramic PTC elements limit their own temperature, and auto-resetting overheat cut-outs trip the unit if the elements or casing get too hot
- Guards: perforated guards shield the fans and heating elements
- Keep the grille clear: the heaters need uninterrupted airflow, so the grille must never be covered
Each Metropolitan Electric Trench Heater arrives fully assembled, with transverse bracing and a protective cover to keep in place while the floor is finished. The grille and trim are packed separately and fitted once the unit is installed. Knock-outs in the casing take the power and control cables, which are secured with suitable glands, and in a screeded floor the cables are brought into the casing before the screed is laid. Heaters are installed close to the glazing they protect, ideally with the heating elements on the window side. Metropolitan Electric Trench Heaters come in three fixed standard sizes; for a bespoke size, contact SPC to discuss your project.
Project support from SPC: from survey to commissioning
SPC manufactures and supplies Metropolitan Electric Trench Heaters for installation by your chosen mechanical and electrical contractor, and supports the project at every stage. Our Trench CPD is CIBSE approved and can be booked for your practice.
Site surveys
SPC can visit site to review trench positions, dimensions and layout before order.
Selection and layout
Send us your drawings and heat losses and SPC will select heater lengths and the layout for each space.
Trench CPD
Our CIBSE approved CPD, Design Considerations for Trench Heating, 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.
- Ready for site: each unit is labelled with its serial number, model reference and site reference, and arrives with a protective cover to keep in place until the grilles are fitted.
- Installation, operation and maintenance: IOM 82, the Metropolitan Electric Trench Heaters manual covering installation, wiring, commissioning, maintenance and fault finding, is supplied with every unit, with its wiring diagram.
Specifying Metropolitan Electric Trench Heaters
Free help to select heaters and plan the installation.
Get a unit selection
Send us your drawings and heat losses, and SPC will select Metropolitan Electric Trench Heater lengths and the layout along the glazing for your project.
Technical drawings and IOM
Download the brochure for dimensions and heat outputs, and IOM 82 for installation, wiring, commissioning and maintenance details.
SPC trench heating in UK projects
SPC trench heating and cooling has been installed beneath full height glazing in buildings across the UK, including offices, schools, libraries, museums, hotels, restaurants and visitor centres. Recent SPC trench projects include The Orangery at Aynho Park in Oxford, Berkhamsted Sixth Form in Hertfordshire, 8 Salisbury Square in London, 42 Park End Street in Oxford, the Museum of Two Halves in Wrexham, Hanley Library in Stoke-on-Trent, 244-254 Cambridge Heath Road in London, The Grand York Hotel, Archway Tower in London and the Midlands Goods Shed at King’s Cross. See SPC’s projects.
Metropolitan Electric Trench Heater specification summary
| Detail | Spec |
|---|---|
| Type | Fan-assisted electric trench heater with ceramic PTC heating elements and EC/DC crossflow fans |
| Size | 225 mm wide x 125 mm high |
| Lengths and heat outputs | 1,000 mm (1.00 kW), 1,750 mm (2.00 kW) and 2,500 mm (3.00 kW) |
| Heating elements | Single phase 230 V ceramic PTC electric heaters: inherently safe and self-regulating, with auto-resetting overheat cut-outs that trip the unit if the elements or casing become too hot |
| Fans | One or more EC/DC crossflow fan assemblies, with the fan speed set to suit the heat output; fans and elements shielded by perforated guards |
| Electrical | 230 V single phase supply to each unit; every unit must be earthed |
| Controls | On/off by room thermostat, switch or BMS enable signal (BMS relay specified at the time of order) |
| Casing | 1.2 mm mild steel, black powder coated, with knock-outs for cable entry, levelling screws at all four corners, adjustable support feet, 30 mm height adjustment, transverse bracing pieces and a protective cover |
| Grilles | Anodised aluminium roll-up grille with stainless steel springs and black plastic spacers, 60% free area, with matching trim; stainless steel blades on request |
| Grille finishes | Satin silver, black and a range of Anolok bronze, gold, umber and blue-grey colours |
| Floors | Screeded (concrete) or suspended floors; indoor use only |
| Bespoke sizes | Three fixed standard sizes; contact SPC about bespoke sizes |
| Manufactured | Leicester, UK, by S & P Coil Products Limited (ISO 9001:2015) |
Dimensions, heat outputs and the full specification are in the Metropolitan Trench Heating and Cooling brochure.
Discuss your electric trench heating project
Send us your layout for a Metropolitan Electric Trench Heater selection for your office, reception, showroom, hotel, restaurant or public building, or request a site survey or book the Trench CPD. Call +44 (0)116 249 0044, email spc@spc-hvac.co.uk or use the form below.
Frequently Asked Questions
Water (wet) trench heaters, such as Metropolitan Natural Trench Heaters, Metropolitan Powered Trench Heaters and Metropolitan HC trench heating and cooling, connect to the building’s heating system through flow and return pipework. Metropolitan Electric Trench Heaters have ceramic PTC electric heating elements instead of a water coil, so they need only a 230 V power supply, for buildings without an LTHW heating system or where running pipework to the trench is not practical. SPC’s sales team can advise which suits your project.
Each Metropolitan Electric Trench Heater needs a standard 230 V single phase mains supply and must be earthed. An on-board power supply runs the EC/DC fans, so the power wiring to the unit is 230 V only. Every unit needs its own supply, even where several units follow one thermostat, and the power cable should be sized for that unit’s full load current, which is given in IOM 82. Control wiring is also needed for the thermostat, switch or BMS.
Metropolitan Electric Trench Heaters are controlled on/off by a room thermostat, a remote switch or a BMS enable signal. For BMS control, the heaters respond to an enable/disable signal through a relay in the unit, which needs to be specified at the time of order. The fan speed is set to suit the heat output, so it is not adjusted on site.
Metropolitan Electric Trench Heaters use ceramic PTC heating elements, which are self-regulating, with auto-resetting overheat cut-outs that trip the unit if the elements or casing become too hot, and the fans and elements are shielded by perforated guards. The heaters must be installed by experienced heating contractors and electricians, used indoors and kept dry, and the grille must never be covered, as blocking the airflow makes the elements overheat and trip out.
Yes. LTHW (low temperature hot water) and LPHW (low pressure hot water) both describe the wet heating systems that water trench heaters connect to, and SPC’s trench literature uses LPHW. Metropolitan Electric Trench Heaters do not connect to an LTHW or LPHW system at all: they are heated electrically, for buildings where hot water pipework is not available or not practical.
Metropolitan Electric Trench Heater roll-up grilles are suitable for occasional foot traffic. They should not take point loads such as chair legs, and trench heaters should not be fitted directly in front of doorways or in areas of constant footfall, where there is a risk of damage and debris from footwear getting into the unit.
Yes. Metropolitan Electric Trench Heaters suit screeded (concrete) floors and suspended or hollow floors. In a screeded floor, the trench is cut wide enough for the support feet, with extra space if electrical conduit runs alongside. Before the screed is laid, the bracing pieces stay in place, the grille and trim are removed, the holes in the casing are taped over, a cover is fitted and the power and control cables are brought inside. In a suspended floor, the support feet and levelling screws set the grille level with the finished floor.
Isolate the electrical supply, lift the roll-up grille and vacuum the inside of the trench regularly, more often in dusty areas, keeping litter and debris out of the unit. A dry cloth can also be used, but never water or spray, as moisture must not reach the inside of the heater. Clear any obstructions from the fan and element guards. The fans have sealed for life bearings, so no lubrication is needed. The grille can be cleaned off the unit with a dry cloth or mild detergent and dried before refitting. Full guidance is in IOM 82.
