Steam heating coils for air handling units and ductwork
SPC steam coils heat a stream of air with steam in air handling units (AHUs) and ductwork. Steam condenses inside the coil’s tubes and gives up its heat through the tubes and fins to the air passing across them, and the condensate drains away to a steam trap. SPC makes steam coils to order for legacy steam systems and for the new systems that still use steam for air heating.
Manufactured in Leicester by S & P Coil Products Limited, SPC steam coils are built from higher specification, thicker tube and braze materials, with seamless copper tubes, aluminium or copper fins and a casing to bolt into ductwork or sit inside an AHU. They are used in commercial, public, industrial and process buildings, in new plant and as replacements in existing plant, and every steam coil is pressure tested before it leaves the factory.
Made to order
Designed for each steam duty and space
Steam air heating
For legacy and new steam systems
Pressure tested
Tested to 22 barg, air under water
Made in Leicester
By S & P Coil Products Limited
Up to 6 barg
The maximum safe working pressure for SPC steam coils. Tell us the steam pressure on site when you ask for a selection.
Sized to duty
No standard sizes: each steam coil is selected for your airflow and duty with SPC’s free online coil selector or our technical team.
Thicker tubes
0.7 mm walls on 12 mm tube or 0.9 mm on 5/8″ tube, typically used for steam, with higher specification braze.
BSP or flanged
Steel connections with a tapered male BSP thread as standard, or screwed or welded flanges, for the steam pipework.
What are steam coils and how do they work?
Steam coils are finned tube heat exchangers that heat air with steam. Steam enters the coil’s header and condenses inside the tubes, releasing its heat through the tubes and fins into the air flowing across the coil. Because steam transfers heat at a high rate, steam coils were once a common choice for air heating, and many legacy systems and a limited number of new ones still need them.
Steam systems run at higher pressures and temperatures, so SPC builds its steam coils from higher specification and thickness tube and braze materials. The condensate must leave the coil as fast as it forms: if it is held in the tubes, differential thermal expansion will quickly damage the coil. That is why SPC steam coils must be installed in well-engineered steam systems, with the steam supply kept dry and the condensate drained to a correctly sized steam trap.
An SPC steam coil, made in Leicester.
SPC also makes water coils, refrigerant coils, runaround coils and electric heater batteries. See the full range on our Heating and Cooling Coils page.
What steam coils can SPC make?
SPC steam coils have no standard sizes. The face size, number of rows, fin spacing and tube circuits are worked out for each project from the airflow, the duty and the steam pressure, so the coil fits the duct or AHU. The table below shows the options SPC can build from, taken from the SPC Coil Heat Exchanger Brochure.
| Feature | SPC steam coils |
|---|---|
| Coil type | Steam heating coils for air heating, for legacy steam systems and new systems |
| Maximum working pressure | 6 barg (maximum safe working pressure) |
| Tubes | Seamless copper, 12 mm or 5/8″ outside diameter |
| Tube wall | 0.7 mm (12 mm tube) or 0.9 mm (5/8″ tube), typically used for steam |
| Braze | Higher specification braze materials |
| Fins | Plain aluminium as standard; precoated (vinyl coated) aluminium; postcoated, such as Blygold; or copper |
| Fin profile | Rippled; louvred fins available on 12 mm tube for special applications |
| Casing material | Galvanised sheet steel, 1.5 mm, as standard; brass, copper or aluminium to special order |
| Casing types | Economy and standard (flanged, for ductwork); enclosed (flanged, with sealed coverboxes over the headers and return bends); unitary (for inside AHUs); bespoke casings on request |
| Connections | Steel with a tapered male BSP thread as standard; screwed or welded flanges; plain copper connections also available |
| Connection handing | Left hand or right hand side, looking in the direction of airflow, specified before manufacture |
| Testing | Pressure tested to 22 barg, air under water; higher test pressures can be specified |
| Selection | Free online coil selector (registration needed), or selection by SPC’s technical team |
| BIM objects | Standard and Enclosed Steam Coil Heat Exchanger Range objects on bimstore |
| Manufactured | Leicester, UK, by S & P Coil Products Limited (ISO 9001:2015) |
SPC steam coil casings, materials and options
Choose the casing by where the steam coil will sit and how much air leakage the system can accept.
- Economy and standard casings have flanged trays all round to bolt to the adjoining ductwork. The return bends and headers sit outside the casing and the tubes can expand and contract within the tubeplates, so some air leakage is expected.
- Enclosed casings are also for duct-mounted steam coils, and add sealed coverboxes over the return bends and headers to minimise air leakage.
- Unitary casings sit inside an air handling unit rather than bolting into ductwork. The casing is sized to fill the open area inside the AHU, with baffle plates over the return bends and headers to stop air bypassing the coil.
- Bespoke casings are available for special requirements: contact SPC with the details.
SPC steam coils have seamless copper tubes, with thicker walls and higher specification braze materials for steam, plain aluminium fins and a galvanised steel casing. Other materials protect against corrosion or suit particular duties.
- Thicker tube walls of 0.7 mm on 12 mm tube or 0.9 mm on 5/8″ tube are typically used for steam.
- Precoated aluminium fins have a thin vinyl coating applied before the fins are formed: a cost effective choice for mildly corrosive air.
- Postcoated fins, such as Blygold, are sprayed on after the coil is made so they cover the whole fin block and all edges, giving more protection at a higher price.
- Copper fins can be used, though they add to the weight and cost of the coil.
- Louvred fins on 12 mm tube increase heat transfer, but add airside resistance, so they are only used where performance matters more than fan power.
- Other casing materials, such as brass, copper or aluminium, are available to special order.
Read more in Protecting HVAC Coils from Corrosion: Another Successful Site Survey in the South.
Tell SPC the steam pressure, the connection type and the handing you need before the steam coil is made, and plan the condensate drainage with the coil.
- Connections: SPC steam coils have steel connections with a tapered male BSP thread as standard, or screwed or welded flanges. Hold the connections when tightening the pipework so the joints are not damaged; flange gaskets are supplied by others.
- Handing: connections can be on the left or right hand side, looking in the direction of airflow. Specify which before the coil is made.
- Dry steam: the steam supplied to the coil must be dry.
- Condensate drainage: the condensate must drain at the rate it forms. Fit a vertical leg between the coil outlet and the steam trap, size the steam trap correctly (float type traps are recommended for coils) and avoid back pressure in the condensate line.
- Vacuum breakers: where regulating valves are used, fit vacuum breakers so the pressure in the coil cannot fall below atmospheric.
- Specialist advice: if you are unsure about any part of the steam system, consult a steam specialist.
SPC steam coils are supplied for installation by your mechanical contractor. Steam coils must be installed into steam systems by an experienced installer, otherwise premature coil failure is likely. The SPC Coils for Heating and Cooling IOM gives full instructions.
- Duct-mounted coils bolt to the adjoining duct flanges, with a gasket supplied by the installer. Where the coil is larger than the duct, transformation pieces are fitted on both faces, with straight ducting before and after the coil for even airflow.
- AHU coils are blanked off against the inside of the unit so all the air passes through the finned area, and fixed so they cannot move.
- Coil casings are supplied uninsulated; any insulation is fitted by the installer, and coils mounted outside need weather protection. Never lift or carry a coil by its pipe connections.
- Commissioning is carried out by a specialist, with flow rates matching the design data in SPC’s quotation.
- Clean the finned surfaces with compressed air, a vacuum or a low pressure spray with mild detergent, not a pressure washer, and check them regularly, especially when the coil is new.
Where are SPC steam coils used?
SPC steam coils heat air in commercial, public and industrial buildings and in process plant, wherever steam is available. Typical applications include:
Air handling units
Steam heating coils in unitary casings, sized to the inside of the AHU, for new units or to replace coils in existing ones.
Ductwork heating
Flanged steam coils that bolt into the duct run, with enclosed casings where air leakage must be kept to a minimum.
Legacy steam systems
New steam coils for buildings and sites that still distribute steam for heating, designed for the steam pressure on site.
Process air heating
Air heating in industrial and process buildings where steam is already generated on site.
Corrosive environments
Precoated, postcoated or copper fins for coastal or polluted air, with brass, copper or aluminium casings to special order.
New steam coils for existing AHUs and ductwork, made to match the original dimensions as closely as possible to keep rework on site to a minimum.
Planning a coil replacement? Read How Does HVAC Coil Replacement Work in Commercial Buildings? and SPC HVAC Solutions: AHU Burst Coil Replacement Made Easy.
Selection and design support for steam coils
Free tools, BIM objects, training and surveys to help you specify the right coil.
Select coils online
Size steam coils with SPC's free online coil selector and download each quote as a PDF.
Download BIM objects
Standard and enclosed steam coil BIM objects on bimstore, plus a type catalogue for each coil you select.
Coil heat exchanger CPD
SPC's CIBSE approved CPD: An Introduction to Coil Heat Exchangers.
Replacement coil surveys
Book a site survey or send the details on SPC's coil survey sheet.
Listed on the CIBSE CPD directory.
Discuss your steam coil requirements
Need a steam coil for a new air handling unit, a duct run or a replacement in a commercial, public or industrial building? Send us the airflow, duty, steam pressure and space available, and our technical team will select the right coil. Call 0116 249 0044 or email spc@spc-hvac.co.uk.
Frequently Asked Questions
The maximum safe working pressure for SPC steam coils is 6 barg. Every steam coil is pressure tested to 22 barg, air under water, before it leaves the factory in Leicester, and higher test pressures can be specified. Coils are designed and made under SPC’s ISO 9001 quality system, to sound engineering practice as the Pressure Equipment Directive (Article 3) requires for this type of equipment. Equipment in this category is not CE or UKCA marked, so you will not see either mark on an SPC coil.
As steam gives up its heat in a steam coil it condenses to water inside the tubes. That condensate must drain away at the rate it forms. If it is held in the coil, differential thermal expansion between tubes quickly leads to damage. The SPC Coils for Heating and Cooling IOM asks for a dry steam supply, a vertical leg between the coil outlet and the steam trap, a correctly sized trap, no back pressure in the condensate line and vacuum breakers where regulating valves are used.
Float type steam traps are recommended for coils, sized correctly for the condensate load and fitted after a vertical leg from the coil outlet. The steam trap and the rest of the steam system are supplied by others, so if you are unsure about the trap or the condensate line, consult a steam specialist.
Both heat air passing across finned tubes. In a steam coil, steam condenses inside the tubes and gives up its heat, and the condensate drains to a steam trap, so the coil is built from thicker tube and braze materials for the higher pressures and temperatures of steam. A hot water coil carries water pumped round a heating circuit. Which suits depends on the heating system on site, and SPC makes both: see our water coils page for hot water, chilled water and changeover coils.
SPC manufactures and supplies steam coils for installation by your mechanical contractor. The SPC Coils for Heating and Cooling IOM says steam coils must be installed into steam systems by an experienced installer, otherwise premature coil failure is likely, and commissioning is carried out by a specialist. The IOM is in the Downloads section below.
Yes. SPC makes replacement coils for existing AHUs and ductwork, including steam coils from other manufacturers, matching the original dimensions as closely as possible to keep rework on site to a minimum. Send the details on the SPC Coil Survey Sheet in the Downloads section below, or contact us to arrange a site survey for a coil that cannot be removed. Read more in How Does HVAC Coil Replacement Work in Commercial Buildings?
Yes. SPC’s free online coil selector covers steam coils as well as water and refrigerant coils. Registration is needed. If you would rather not select the coil yourself, send the airflow, duty, steam pressure and space available through the form above and SPC’s technical team will select it for you.
Yes. SPC’s Standard Steam Coil and Enclosed Steam Coil Heat Exchanger Range BIM objects are on bimstore. When you select a steam coil with SPC’s free online coil selector, it also gives you a type catalogue for that coil to load with the Revit family, so the BIM object carries your project’s selection data.
