Do I need trace heating on a boiler condensate pipe?

Only if the condensate pipe runs outside or through an unheated space. A frozen condensate is the single most common winter boiler fault in the UK and trace heating is the tidiest permanent fix. The alternative is to reroute the pipe in a larger diameter so it drains faster, but that is not always practical.

Can I cut self-regulating trace heating cable to length?

Yes, that is one of the main features of a self-regulating cable. It has continuous parallel bus wires and a conductive matrix between them, so you can cut it to any length and terminate the end. Pre-terminated kits come with a factory-made cold tail; you cut and terminate the far end.

What thermostat setting for pipe frost protection?

Manufacturer's own line thermostats are usually pre-set at 3 to 5 °C, which is sensible: it switches the heat on before the water actually freezes, but not so early that it runs all winter unnecessarily. Adjustable stats are worth the small extra cost for a longer run.

What fuse should the fused connection unit have?

Follow the trace heating manufacturer's instructions. Most domestic self-regulating kits (10 to 25 W/m) draw only a few amps and are usually specified with a 13 A BS 1362 fuse in the switched FCU, but always check the label on the cold tail or the fitting instructions.

Does trace heating need RCD protection?

Yes. BS 7671 requires 30 mA RCD or RCBO protection for any circuit that supplies equipment outdoors or in a wet location. The trace heating manufacturer's fitting instructions will confirm the RCD type (usually Type A is adequate for a domestic kit).

How to Install Pipe Trace Heating for Frost Protection (UK)

Helpful video reference. An installer's UK tutorial "How to Install trace heating on condense pipe" is a walkthrough of the exact scenario most Sandwich houses need: a plastic condensate pipe from a wall-hung combi boiler that runs outside for a short distance before terminating at a gully. Worth a look before you order a kit so you can visualise the cable path.

Before you start. Trace heating cable is a fixed electrical installation, not a plug-in appliance. The connection into the property needs a switched fused connection unit on an RCD-protected circuit, and the whole install has to be tested and certified before it is left running. Isolate the circuit you plan to spur from at the consumer unit and confirm dead before touching a terminal.

1. Pick a self-regulating cable, not constant-wattage

Two types of trace heating are sold in the UK: self-regulating and constant-wattage. Self-regulating cable changes its output as the pipe warms up, so it cannot overheat, and it can be cut to length in the field. Constant-wattage cable puts out the same power along its whole length regardless of temperature: fine for industrial use where the exact length is known, wrong for a domestic pipe that varies in diameter and exposure.

For a Sandwich condensate pipe or an outside tap feed, choose a 10 to 25 W/m self-regulating cable in kit form with the cold tail already terminated. Warmup, Elektra FreezeTec, First Trace Heating and PipeTrace all sell UK-market kits.

2. Measure the run before you order

Measure the exposed pipe run from where it leaves the warm envelope of the house (the inside of the external wall) to its termination (the gully for a condensate, the tap head for an outside tap). Add 300 mm for the thermostat capillary and 500 mm for cold-tail slack inside the wall cavity. Order the next kit size up: 3 m, 6 m, 12 m and 18 m are the usual pre-made lengths.

3. Fix the cable straight along the pipe

Lay the cable straight along the length of the pipe, on the underside if the pipe is horizontal so meltwater does not sit on top of the cable. Fix it every 300 mm with aluminium foil tape, running the full length of each fixing so the tape also spreads the heat around the pipe circumference.

Do not use PVC electrical tape for this: the plasticiser dries out in cold weather and the tape falls off within a season. Aluminium tape holds and helps conduct heat around the pipe.

4. Place the thermostat at the coldest point

Wrap the thermostat capillary bulb around the pipe at the coldest point of the run: usually the far end, or the most exposed elbow. Tape it in place with aluminium tape. The stat then switches the whole cable on when the coldest bit of the pipe drops to about 3 to 5 °C.

If your kit has a fixed thermostat pre-set at the factory, that is fine for a domestic run. Adjustable stats are worth the small extra for anything above about 6 metres.

5. Lag over the top

Cover the cable and pipe with foam pipe insulation with a UV-stable outer sleeve. Uninsulated trace heating loses most of its heat to the air instead of the pipe, uses far more electricity, and often fails to keep up in a real cold snap. The lagging is not optional.

Slit the lagging lengthways to fit it around the cable-plus-pipe assembly, and tape the split closed with UV-stable tape or cable ties.

6. Bring the cold tail into the house

Route the cold tail into the house alongside the pipe, through the same wall penetration if there is room, and seal the penetration with intumescent mastic afterwards. Do not create a fresh hole through the cavity if you can avoid it.

Terminate the cold tail at a 13 A switched fused connection unit inside the property, on an RCD-protected circuit. Spur off the nearest suitable ring final circuit socket. Label the FCU 'Trace heating' and, importantly, 'Leave on all winter'.

7. Test and certify

Before energising: insulation resistance between the trace heating conductors and earth (self-regulating cable is more delicate to physical damage than it looks, and it is worth catching any issue before it is buried under lagging). Energise, then confirm earth fault loop impedance at the FCU and RCD trip time under 40 ms at ×5. Issue a Minor Works Certificate.

Stop and call an electrician if: the socket circuit you planned to spur from is not RCD protected, the boiler condensate pipe runs through an inaccessible cavity, the outside tap is on a lead pipe that needs replacing anyway, or the initial insulation-resistance test on the trace heating cable is below the manufacturer's minimum. Any of those and the job needs planning properly before you fit cable that will end up buried under lagging.

When to call us

Trace heating is one of those jobs where getting it right first time saves you from a January call-out with no heating. Richard fits self-regulating trace heating on boiler condensate pipes and outside taps across Sandwich and east Kent, wires the switched FCU, and leaves you with the Minor Works Certificate.

Frozen pipes last winter in Sandwich?

Richard installs trace heating and boiler condensate frost protection ahead of the winter so this year the boiler keeps running when the temperature drops. Part P registered, fully insured.

Contact Richard

How to install pipe trace heating for frost protection