Guides: boilers, heat pumps, air conditioning and plumbing

In short

61 practical guides in English: what a fault code or symptom means, which spare part fits, what you can check yourself and when to call a qualified engineer.

Boilers & heating 39
Heat pumps 8
Air conditioning & ventilation 4
Plumbing & hot water 5
Costs & energy 5

Boilers & heating

Automatic air vents on boilers and manifolds: cap position, faults and the right thread

How float and hygroscopic air vents work, why the cap stays open, how to spot a leaking or seized vent and which one fits your boiler.

Bleeding radiators and the boiler circuit: signs, steps and air that keeps returning

Cold radiator tops, gurgling pipes? Bleed from lowest to highest radiator with the pump off, then check pressure. Steps, tools and why air returns.

Boiler gas valve faulty? How to confirm it, what it costs and who may fit it

Gas valve codes for Remeha, Vaillant, AWB, Bosch and Intergas, what to rule out first, typical part prices and why fitting needs a flue gas analyser.

Boiler rating plate: where to find it and what to photograph for a part

Where the rating plate sits on Intergas, Remeha, Nefit, Vaillant and ATAG boilers, how to read it in any EU language and what photo to send us.

Boiler repairs: green, amber and red parts and who should fit each one

Which boiler parts can you safely change yourself and which are for a registered gas engineer? A traffic-light guide from thermostat to heat exchanger.

Boiler running but radiators cold: finding the fault from air to pump

Boiler firing but radiators cold? Diagnose air, low pressure, a seized pump or a stuck diverter valve, with error codes and genuine pumps we ship EU-wide.

Boiler ticks but no flame appears: tracing the ignition fault step by step

Boiler sparks but never lights? Learn what the start sequence tells you, what the codes per brand mean and why the electrode comes before the gas valve.

Bosch EasyControl with a Remeha boiler: OpenTherm, R-bus and the adapter

Remeha Avanta, Tzerra, Calenta and Quinta work with Bosch EasyControl through the EasyControl Adapter on OpenTherm. What to buy and how to connect it.

Bosch EasyControl with a Vaillant ecoTEC: eBus, the VR 33 module and the adapter

Vaillant ecoTEC boilers use eBus. Bosch EasyControl only modulates with a VR 33 OpenTherm module plus the adapter; otherwise it is on/off. What to buy.

Bosch EasyControl with an Intergas boiler: why you need the adapter

Intergas boilers use OpenTherm, Bosch EasyControl uses EMS bus. With the EasyControl Adapter your Kombi Kompakt or Xtreme keeps modulating. How to wire it.

Choosing a Bosch EasyControl set: single, with adapter or with radiator valves

Single, adapter set or a set with smart radiator valves? Pick the right Bosch EasyControl (CT200) for your boiler brand and home, delivered across the EU.

Cold floor? Troubleshooting water underfloor heating at the manifold

Water underfloor heating stays cold in one room or everywhere? Test the manifold, pump, mixing valve, actuators, air and flow in a logical order.

Communication error or dead PCB? A checklist before you buy a boiler circuit board

Communication codes rarely mean a dead PCB. Check power, thermostat wire and harness first, then avoid the software-version trap when ordering a new board.

Condensate traps by boiler brand: matching part, seals, cleaning and pumps

Condensate traps are brand-specific. Find the trap and seal for Intergas, Nefit, Remeha, Vaillant, ATAG, AWB or Ferroli, plus cleaning tips and prices.

Connecting a Bosch EasyControl to an ATAG boiler: adapter, wiring and limits

ATAG boilers use OpenTherm, the Bosch EasyControl uses EMS. With the EasyControl Adapter it works and the boiler keeps modulating. Wiring steps and limits.

EasyControl on Nefit and Bosch boilers: series list, EMS bus or adapter

Which Nefit and Bosch boilers take Bosch EasyControl directly on the EMS bus and which need the adapter: ProLine NxT, EcomLine, HRC Top and more.

EU heating rules explained: the EPBD, the end of fossil boiler subsidies and what it means for your boiler

No EU ban on existing boilers: no subsidies for stand-alone fossil boilers since 2025, phase-out aimed at 2040, zero-emission new buildings from 2030.

Faulty boiler pressure sensor or real pressure loss? Codes, tests and parts

Boiler shows a pressure fault but the gauge reads 1.5 bar? Tell a failed sensor from real pressure loss, the codes per brand and which sensor fits.

Genuine, equivalent or pattern part: which boiler parts you can safely swap

Which boiler parts can be replaced by an equivalent and which must be genuine, how it affects your warranty and the EU two-year guarantee on parts.

Heating pressure falling again after a top-up: how to find the cause

Boiler pressure falls again after topping up? Four checks to spot a flat expansion vessel, dripping safety valve or leak, plus vessel prices and codes.

Heating works but the taps run cold: finding the faulty boiler part

Radiators warm but no hot water from the taps? Rule out the plate exchanger, hot water sensor, diverter valve and flow sensor in the right order.

How to choose a new radiator: watts, panel type, height and valves

Pick the right panel radiator in four steps: room output, type 11 to 33, height and length. Plus EN 442 ratings, heat-pump sizing and valves.

How to top up boiler pressure: target 1.5–2 bar, safe steps and brand codes

Boiler pressure below 1 bar? Fill a cold system to 1.5–2 bar with the filling loop, bleed, recheck. Steps, brand codes and what to do if it keeps dropping.

Intergas Kombi Kompakt HRE and the missing diverter valve: what to check instead

The Intergas Kombi Kompakt HRE has no three-way valve: one two-in-one heat exchanger does the job. Which part to check for hot water or heating faults.

Ionisation electrode in a gas boiler: how flame detection fails and which part to order

Flame-detection codes per brand, why a new ionisation electrode sometimes fails to help, and genuine electrodes for Intergas, Remeha, Nefit and Vaillant.

Nefit TopLine hydro blocks by series: flow or return, part numbers and prices

Leaking Nefit TopLine? Which hydro block fits the HR II, first-generation HR or TopLine Compact, flow or return, with part numbers and prices.

Noisy boiler fan or fan-speed fault: diagnose first, then order the right one

Rattling boiler fan or a fan-speed code? Rule out dirt, a blocked flue and wiring first, then find the exact fan part number for your model and output.

Overheat or bad reading? Why your boiler keeps stopping on a temperature fault

Boiler shuts down on temperature? Learn to tell real overheating from a faulty NTC sensor by the code wording, what to check and which part to order.

Panel radiator types explained: what 10, 11, 21, 22 and 33 really mean

What the digits in a panel radiator type mean, how depth and output compare from type 10 to 33, the Irish K1/P+/K2 names and which type suits your room.

Plate or main heat exchanger? Symptoms, part prices and when repair still pays

Plate or main heat exchanger failing? Compare the symptoms, see genuine part prices from EUR 205 and use our rule of thumb for repair versus a new boiler.

Radiator sizing: how to work out the watts each room needs

Estimate radiator output per room with W/m² rules, adjust for ceiling height and climate, and correct EN 442 ratings for lower flow temperatures.

Remeha flashing A, B or C: a service reminder, the kit to order and who resets it

A blinking A, B or C on a Remeha Tzerra, Calenta or Avanta is a service reminder, not a fault. What each level covers and which service kit fits.

Sizing an underfloor heating manifold: loops, pump and material

How many loops, with or without pump and mixing valve, composite or steel? Size your underfloor heating manifold for a boiler or heat pump in three steps.

Swapping a radiator yourself: measuring up, valves and the job step by step

Measure the old radiator, match side or bottom connections, renew the valves and swap it step by step: draining, refilling to 1.5–2 bar and bleeding.

Thermostat on, boiler silent? How to find the broken link step by step

Boiler not reacting to the thermostat? Check batteries, cable and wireless receiver, and whether on/off, OpenTherm or EMS/eBus match your boiler.

Thermostatic radiator heads: which thread you have and how to swap the head

Identify M30 × 1.5, Danfoss RA or RAVL valves, decide between a new head or a new valve body, and compare mechanical, programmable and smart heads.

Water dripping from a condensing boiler: condensate, trap or leak?

Puddle under your boiler? Use the pressure gauge to tell condensate from a heating leak, clean a blocked trap safely and find the right replacement part.

Which boiler part do I need? Four ways to find it, from part number to photo

Search by part number, choose brand and model, start from the symptom or send us a photo: how to order the right boiler part from anywhere in the EU.

Will Bosch EasyControl work on my boiler? EMS, OpenTherm and on/off explained

Bosch EasyControl connects directly to EMS-bus boilers and via the adapter to Intergas, Remeha, ATAG and Vaillant. Check your boiler

Heat pumps

Heat pump or air con compressor failed? Check the cause before you pay for a new one

A heat pump or AC compressor costs EUR 450 to 1,500 plus F-gas certified labour. Which codes mislead, what to check first and when a new unit is wiser.

Hybrid heat pump or going fully electric: a decision guide for European homes

Hybrid or all-electric heat pump? Decide on insulation, radiators, boiler age and energy prices. Decision table, five checks and common mistakes.

Ice on your heat pump's outdoor unit: normal defrost or a fault to fix?

Frost on an air-to-water heat pump is normal in damp cold weather. How to tell a healthy defrost from a fault, what to check and which codes mean trouble.

Itho Daalderop heat pump error codes: what A, E, F, P and S mean

Itho Daalderop WPU, HP-S, HP Cube or Base Cube showing a fault? What each code letter means, what you can clear yourself and which genuine part fits.

Keeping your radiators with a heat pump: the 50 °C test and what to upgrade

Will your radiators work with a heat pump? Do the free 50 °C test, see how output drops at low flow temperatures and which rooms need a bigger radiator.

Sizing a heat pump: work out the kW from your fuel bill, your home and your climate

How many kW heat pump does your home need? Estimate it from your gas or oil bill or floor area, adjust for your climate and avoid oversizing.

The fault codes our international visitors look up most (Aug to Nov 2026)

Which boiler and heat pump fault codes did our EU visitors look up most in autumn 2026? Top 20 from our Search Console data, with what each code means.

Where to put a heat pump outdoor unit so neither you nor the neighbours hear it

How loud is a heat pump outdoor unit? Sound power vs sound pressure, distance tables, the best spot, enclosures and why noise limits are set locally.

Air conditioning & ventilation

MVHR filter replacement: find the right set for your heat recovery unit

Which filter set fits your Itho Daalderop, Brink, Zehnder or Ferroli MVHR unit, how often to change it, G4 vs F7 explained, and a five-minute swap.

MVHR unit too loud or blowing cold air? Bypass, fans and heat exchanger

Heat recovery unit blowing cold air or getting louder? Check the bypass setting, filters, fans and heat exchanger, with Brink and Zehnder codes explained.

Split air con blowing warm air? Check filters, outdoor unit and settings first

Split air conditioner no longer cooling? Check filters, the outdoor unit and settings yourself; why low refrigerant always means a leak for an F-gas pro.

Water dripping from your split air con: the condensate route and four causes

Indoor unit of your air conditioner dripping water? It is condensate that cannot drain. Four causes, what you can check yourself and when to call a pro.

Plumbing & hot water

Choosing a CW class for hot water: shower flow, bath size and EU load profiles

What CW3, CW4, CW5 and CW6 mean in litres per minute, how they compare with EU load profiles, and which class suits your shower, bath and household size.

Cylinder sensor failing? Symptoms, fault codes, a multimeter test and the right NTC

Cylinder cold or scalding, or a code like Intergas 40, Vaillant F.03 or Nefit H12? Test the NTC cylinder sensor and pick the one that fits your boiler.

Electric water heater gives no hot water: element, thermostat or scale?

Electric water heater gone cold? Check the RCD, safety thermostat and heating element in order, plus why hot water runs out faster. Genuine parts EU-wide.

Running Geberit toilet: find the leaking valve and replace it yourself

Geberit concealed cistern keeps running? A colour test tells a faulty fill valve from a leaking flush valve seal. Fix it behind the flush plate.

Water heater anode: when to check it and how to replace it

When to check and replace the anode in your water heater or cylinder, which type fits, warning signs and genuine anodes shipped across the EU.