Baxi Boiler Error Codes E133 And E28 And How To Fix Them

If your boiler has stopped on a cold morning and the display is flashing E133 or E28, the most likely culprit is a frozen condensate pipe. Of all the Baxi boiler error codes, these are among the ones you can often clear yourself, safely and without tools. This guide explains what the codes mean, how to thaw the pipe, how to reset the boiler and when to hand over to a Gas Safe registered engineer.

What Baxi Boiler Error Codes E133 And E28 Mean

Baxi’s own help pages say that most Baxi boilers show E133 or E28 when the condensate pipe may be frozen. On some displays the code alternates between E1 and 33 rather than showing all three digits at once. Baxi also lists E23, E53, E119 and E128 as codes that can point to the same frozen pipe problem.

Baxi boiler error codes are not identical across every model, so the same number can mean something else on a different boiler. Always check the user manual for your model, or the Baxi guide to thawing a frozen condensate pipe, before you assume the cause. If the code on your screen is not one of those listed, do not guess; contact the manufacturer or an engineer.

Why A Frozen Condensate Pipe Stops Your Boiler

A condensing boiler produces waste water, called condensate, as it runs. This drains away through a small plastic pipe, usually white or grey, that often leaves the boiler, passes through an outside wall and runs down to a drain. If that outside section freezes, the water has nowhere to go.

Rather than let water back up into the boiler, the boiler shuts itself down as a safety measure. You may hear gurgling noises from the boiler or the pipe before it stops. Baxi notes that pipes are more likely to freeze where they are exposed, poorly insulated or where water flows slowly and has time to turn to ice.

Where The Blockage Usually Is

The ice tends to form at the most exposed part of the pipe outdoors, often at the open end, at bends or at dips where condensate collects. If your boiler is in an unheated garage or outbuilding, treat the whole pipe as if it were outside.

How To Thaw A Frozen Condensate Pipe Safely

This is a job for the outside of the pipe only. You should never remove the boiler casing or try to reach anything inside the boiler. Follow these steps, based on Baxi’s guidance:

1. Switch the boiler off at the control panel, then turn off the electricity supply to it at the wall switch or fused spur.
2. Find the frozen section. Follow the pipe from where it leaves the wall and look for the most exposed stretch, the end and any bends or dips.
3. Warm the pipe gently. Hold a hot water bottle or microwaveable heat pack against it, wrap it in a cloth soaked in warm water, or pour warm water over it slowly from a watering can.
4. Never use boiling water straight from the kettle. It can damage the plastic pipe.
5. Restore the power and restart the boiler. If it does not fire up, repeat the warming and try again.

Pouring water outside in freezing weather can leave ice on paths and steps, so wrap up warm, wear sensible footwear and take care not to slip. Do not climb ladders to reach a high pipe; that is a job to leave to a professional.

Resetting Your Boiler After The Pipe Has Thawed

Once the pipe is clear, the fault code may need clearing before the boiler will run. The reset method varies between models, so check the operating instructions for your boiler or the manufacturer’s website for how to clear the fault on your model. Only use the reset button or procedure described in the manual.

While you are at the controls, glance at the pressure gauge. Baxi says the pressure should normally sit between 1 and 2 bar. If it has dropped below 1 bar, many households can top it up themselves by following the instructions in the manual for their filling loop or filling link. If you are unsure, or the pressure keeps falling, leave it to an engineer.

How To Stop The Condensate Pipe Freezing Again

Prevention is far easier than thawing a pipe on a frosty morning. Baxi recommends:

• Lagging the outside pipe with waterproof, weatherproof pipe insulation, which you can buy from DIY shops and fit around the exposed length.
• Keeping your home warm enough overnight, with Baxi suggesting you keep it above 16°C during cold spells.
• Having the boiler serviced before winter so any drainage problems are spotted early.

Changes That Need An Engineer

Some fixes involve altering the installation, and these are for a Gas Safe registered engineer, not a DIY job. According to Baxi, an engineer can reroute the pipe to run inside the house, fit a wider diameter pipe, or install a trace heater that warms the pipe in freezing weather. If your pipe freezes every winter, it is worth asking about these options at your next service.

Keeping the home warm also helps your wider energy use, and our guide on why energy efficiency matters has more ideas for keeping bills down in winter.

When To Call A Gas Safe Registered Engineer

Thawing the external pipe, resetting the boiler and topping up the pressure as your manual describes are the limits of what you should do yourself. Call a Gas Safe registered engineer if:

• the boiler still will not start after you have thawed the pipe and reset it a few times
• the code on the display is not one of the frozen condensate codes in your manual, as other Baxi boiler error codes can mean a different fault altogether
• you see water leaking from the boiler, or the pressure keeps dropping
• you smell gas, or anything suggests a fault inside the boiler

By law, anyone working on gas appliances in the UK must be on the Gas Safe Register. Ask to see the engineer’s ID card and check the back shows they are qualified for the work you need. The Gas Safe Register explains how to check an engineer’s ID card. If the water side of your system is also giving trouble, see our guide on whether turning off the water supply affects your boiler.

Quick Checklist For Baxi Boiler Error Codes E133 And E28

• Check your manual to confirm what the code means on your model.
• Switch the boiler off and isolate the power.
• Find the frozen section of the outside condensate pipe.
• Thaw it with a hot water bottle, heat pack or warm (never boiling) water.
• Restore the power and reset the boiler as your manual describes.
• Lag the pipe and ask an engineer about longer-term fixes.
• Never open the boiler casing; call a Gas Safe registered engineer for anything else.

Most Baxi boiler error codes linked to a frozen condensate pipe clear within minutes once the ice has gone. You will find more practical home guides at Beyond The Garden Gates.

Kaan Rassad

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