Boiler help • Heating and hot water
Hot taps. Cold rooms.
Combi boiler hot water but no heating? Working tap water does not prove that the space-heating request, controls and connected heating circuit work. Some combi boilers pause heating during domestic hot-water use. If heat stays unavailable beyond that normal sequence, describe when it happens and arrange assessment rather than assuming a particular valve has failed.
Tell SkyLimit the model and whether heating ever returns. Confirm equipment support, diagnostic scope and appointment availability.
First, establish what supplies the hot water
If you are researching replacement layouts rather than an active fault, read the combi boiler vs indirect water heater guide for the household-use and installation comparison.
The same symptom means different things in different installations. If you are unsure, share the accessible model label and explain what equipment you can see. Do not open covers or trace hidden piping.
Combi boiler
Space heating and tap water come from one appliance. They are different demands and operating functions. Describe which one fails and when.
Indirect hot-water tank
A connected tank stores domestic hot water. Warm stored water alone does not establish that the boiler is currently heating or responding to the room controls.
Independent water heater
A separate water heater can work while the boiler does not. Tell the assessor that the two functions use different equipment.
Brand names do not identify the arrangement. Navien, for example, has distinct boiler, combi and tankless-water-heater product families. For an existing Navien appliance, see Navien boiler repair and provide the full model when enquiring. Confirm the supported family before booking.
For a broader whole-home or single-zone complaint, use the gas boiler not heating the house guide. This article focuses on the combination of working tap water and missing space heating.
A normal pause is different from persistent no heat
During hot-water use
Some combi appliances give domestic hot water priority. The Navien combi-boiler FAQ explains that its described systems pause space heating during that demand and switch back afterwards.
That sequence is not, by itself, evidence of a failed heating component.
Heating stays unavailable
Tell the assessor if rooms remain cold when ordinary hot-water use has ended, or if heating never works at any time.
Do not apply a fixed waiting period from another appliance. Controls, emitters and the installed sequence affect what the correct behaviour should be.
Record what happened in normal use rather than deliberately stressing a faulty system. Note whether the complaint appears during every shower, occurs randomly or started after a control change. A relevant history gives the assessor a better question to investigate.
Do not disable hot-water priority or change installer parameters to try to force heating. The correct configuration belongs to the actual appliance and installation.
Combi boiler hot water but no heating: follow the heating request
Start with familiar owner controls, then leave technical testing to the assessor. Check the room thermostat’s heating mode, displayed target and schedule using its owner instructions. Report the result; do not alter wiring or bridge terminals.
- Room control: which thermostat is requesting heat, and what does it display?
- Appliance status: what code, mode or demand indication is safely visible?
- Heat delivery: are all rooms cold, or only one floor or circuit?
- Timing: does heating resume in normal use, or remain unavailable?
The Navien NFC-H owner manual distinguishes space-heating and domestic-hot-water demand information. Use the documentation for the exact model; a display symbol on that family is not a universal code for every boiler.
A lit screen, pump sound or hot tap should not be treated as proof that the whole heating path is working. If only one zone stays cold, identify that zone separately. If every zone is affected, say so rather than naming a pump or board you think needs replacing.
If the heating pressure also drops repeatedly, report both symptoms and consult the boiler losing pressure guide. Do not top up or bleed an unfamiliar system to test a theory.
Ask for evidence before choosing a part
“Hot water works” does not automatically diagnose a diverter valve. The relevant components vary by model and connected system. The assessor should explain what was tested and why the proposed correction addresses the missing function.
| Assessment area | Question worth asking | Useful distinction |
|---|---|---|
| Thermostat and connected controls | Is the expected heating request reaching the relevant equipment? | A missing request versus a request that is not being fulfilled. |
| Operating mode and demand sensing | What demand and mode does the appliance recognize? | Normal hot-water priority versus an unexplained persistent state. |
| Diverting components, where fitted | What test confirms a problem with this model’s component? | A symptom-based guess versus a verified finding. |
| Pumps, zone valves and heating circuit | Does the affected circuit receive the required heat delivery? | An appliance function versus a connected-zone problem. |
Use the gas boiler parts guide to prepare compatibility questions. Confirm the exact part, model suitability and availability. Ask what remains untested and how the affected heating sequence will be checked after the work.
You can describe the missing function without buying a part first.
Send four details when booking
“Tap water works, but [all rooms / named zone] stay cold.” Add the following details to make the enquiry specific:
- The full appliance model and whether hot water comes from the same unit.
- When the complaint occurs and whether heating ever returns.
- The accessible display message and thermostat mode.
- Any recent service, renovation or control changes.
Start with gas boiler repair for an active heating fault. Local enquiries can use boiler repair in Port Coquitlam or boiler repair in North Vancouver. Confirm the address, equipment acceptance and available appointments.
In a suite or strata property, identify who authorizes access to shared equipment. A privately controlled room thermostat does not necessarily mean the heating plant is privately owned. Explain the access arrangement before scheduling.
Repair scope should follow the confirmed cause. Routine boiler service and maintenance and a replacement assessment are different requests; persistent no heat should first be explained.
Photo space: identify the appliance and controls
This illustration is a placeholder. An approved photo can show the actual appliance label or accessible controls without presenting an unverified diagnosis.
Quick answers about working hot water and missing heating
Why does my combi boiler give hot water but no heating?
Hot water confirms only that the domestic-hot-water function works under the conditions you noticed. Space heating also needs a valid demand, the correct operating mode and heat delivery through its connected circuit. Report whether heating ever returns and whether one zone or the whole home is cold.
Is it normal for heating to pause during a shower?
Some combi boilers prioritize domestic hot water and temporarily pause space heating while that demand is active. Check the exact model guidance. Heating that remains unavailable after normal hot-water use is a separate complaint that needs assessment; there is no universal waiting time for every installation.
Does this always mean a faulty diverter valve?
No. A diverting component is relevant only where the appliance uses that arrangement. Heating demand, controls, sensors and circulation may also need investigation. A technician should confirm the cause and model-specific component before recommending replacement.
Can a thermostat cause hot water to work but heating to fail?
A missing space-heating request can leave heating unavailable while domestic hot water still works. Review familiar thermostat mode and schedule using its owner instructions, and report the display. Wiring, installer settings and connected-control testing belong in the professional assessment.
What if only one heating zone is cold?
Name the affected rooms, thermostat and emitters, plus zones that still warm normally. The assessment should include that circuit and its controls. Working zones do not prove that every valve, pump or control operates correctly.
Is a tankless water heater the same as a combi boiler?
No. A combi appliance supplies space heating and domestic hot water. A tankless water heater may supply domestic hot water without being the home’s heating appliance. Provide the actual model and arrangement rather than relying on appearance or the brand name.
Should I increase boiler temperatures or keep resetting it?
Do not change installer settings or repeatedly reset an unexplained fault. Record any code and use the owner guidance for the exact model. Changing domestic hot-water temperature does not establish a repair to a heating-demand or circulation problem and may create a scald risk.
Which function is missing?
Tell SkyLimit the model, affected rooms and whether heat returns after ordinary hot-water use. Confirm the assessment scope and availability before booking.
A useful repair explanation connects your symptom to a tested finding.
Last updated: October 8, 2026. Official appliance and safety resources are linked above.
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