Daikin 7H fault codewhat it means and how to fix it
A water flow problem. The sub-code matters more than the code: 7H-01 clears itself, 7H-04 to 7H-06 need a manual reset, 7H-08 is the pump, and 7H-07 is the unit freeing a stuck pump.
Take care
What 7H means
The 7H family is where Daikin’s sub-codes earn their keep, and where looking up only the first two characters will actively mislead you. All of them concern water flow, but they mean different things and imply different work. 7H-01 is the self-resetting one. Daikin publish the mechanism: when the flow falls below the minimum for what the unit is doing, it stops, displays 7H-01, and after some time resets itself and resumes. On the Altherma 3 M those minimums are 6 litres a minute in heating, 10 in cooling, 12 during a defrost or when the backup heater is running, and 25 for hot water; the older LT split had 6 in heating and 12 in defrost on the 4 and 8 kW units; the 3 H F publishes a single 20. Those figures explain the pattern owners see. A system that heats fine at 6 litres a minute can fail the moment a defrost asks for double, which is why the code arrives on cold mornings.
If 7H-01 keeps happening, Daikin’s older installer guide says the unit stops and shows a code that has to be reset manually, and which one depends on when the flow failed: 7H-04 during hot water production, 7H-05 during heating or the periodic sampling run, 7H-06 during cooling or defrost. The same guide adds that 7H-06 might be an indication of frost damage to the plate heat exchanger, in which case contact your dealer. 7H-08 is different in kind: a pump abnormality detected from the pump’s own feedback signal, a blockage or an electrical fault at the pump itself, and the unit keeps running while the code shows. 7H-07 is the one most often misread, including by an earlier version of this page. Daikin’s service manual gives the trigger as the unit detecting that the water pump might be blocked; the unit does not stop, it starts a pump de-blocking routine of up to thirty minutes, the code stays on the display for as long as that runs, and it clears automatically when the pump is freed.
There is nothing to do but wait for it, and a 7H-07 that keeps coming back is a pump that keeps sticking, not a routine. Flow faults are the single most common category of heat pump call-out, and the reason is worth understanding. A heat pump works across a much smaller temperature difference than a boiler and moves a great deal more water to deliver the same heat, so a restriction that a boiler would compensate for by simply running hotter will stop a heat pump outright. Daikin’s own checklist for 7H-01 runs: stop valves open, purge air, check flow, check pressure, check a bypass is fitted, clean the integrated filter in the shut-off valve, then the flow sensor, the 3-way valve, the pump and the hydro PCB. Their installer guide also warns that where heating loops are controlled by remotely controlled valves, the minimum flow has to be guaranteed even with every valve closed, or 7H follows — which is the zone valve and the shut radiator valve in the language of a manual.
What causes it
| Cause | What is actually happening | How likely |
|---|---|---|
| Magnetic filter or strainer clogged | The commonest real cause on a system a few years old, and routine maintenance that is frequently skipped. | Common |
| Air in the primary circuit | Introduced by any work on radiators, valves or the cylinder. Air displaces water and the flow rate falls. | Common |
| System pressure low | Check the gauge first. It costs nothing and it is a genuine cause rather than a coincidence. | Common |
| Zone valve stuck, or every loop shut with no bypass | Daikin warn that where loops are controlled by remotely controlled valves the minimum flow must be guaranteed even with all of them closed, or 7H follows. A bypass is item five on their checklist. | Occasional |
| Circulation pump sticking or failing | What 7H-07 and 7H-08 report from the pump itself: 7H-07 is the unit suspecting a blockage and running a de-blocking routine, 7H-08 is a blockage or electrical fault seen in the pump feedback. | Occasional |
What to try yourself
Note the full code including the suffix. 7H-01, 7H-07 and 7H-08 are three different situations and the suffix is the only thing that distinguishes them.
If it is 7H-07, wait. Daikin publish that the unit has detected the pump might be blocked and has started a de-blocking routine of up to thirty minutes; the code stays on the display while it runs and clears itself when the pump is freed. If it comes back, that is a pump that keeps sticking, and it goes on the list for the installer.
Read the system pressure gauge and note the figure before you ring anyone. Pressure is the fourth item on Daikin’s own checklist.
Think about recent work. Anything done to radiators, valves or the cylinder in the last few weeks will have introduced air, which is Daikin’s second check.
If it is 7H-04, 7H-05 or 7H-06, Daikin publish a manual reset via the user interface. Reset it once if you have been shown how, and if it returns, stop resetting and book: the guide says a recurring 7H-06 can indicate frost damage to the plate heat exchanger.
Ask your installer when the filter was last cleaned, and book a visit. Daikin’s own position is that clearing codes is the installer’s job, and the filter in the shut-off valve is item six on their list.
Cleaning the filter means isolating and opening the primary circuit. Ask for it to be done rather than attempting it.
Get an F-Gas certified heat pump engineer to look at your Daikin 7H
We do not pass enquiries to a repair firm, so there is no form here. When you book an F-Gas certified heat pump engineer, tell them the make, the model and the exact code or message on the display, and ask whether they carry parts for this make — that is what turns one visit into a repair rather than a quote.
What it costs to fix
Typical repair cost
£90–£450
Time on site
20 minutes
An installer visit is typically £90 to £180. A circulation pump replaced runs to £250 to £450; filter cleaning and air purging add little beyond the visit.
Typical UK prices including parts and labour, updated September 2026. Your quote may differ.
Parts you may need
We may earn a commission if you buy a part through one of these links. It does not change what you pay, and it does not affect which parts we list.
Central heating circulating pump
CH-PUMP-15-60£90–£180Plumbing merchant
Price checked 28 September 2026
Magnetic system filter, 22mm
MAG-22£65–£120Plumbing merchant
Price checked 28 September 2026
Own this appliance and had this code? . Nothing is published until a person has read it.
Related Daikin fault codes
- A5Get it checkedHigh pressure peak cut in heating, freeze protection in cooling. On an Altherma, Daikin’s first four checks are all water-side: pressure, flow, stop valves and air. Not the indoor filter of an air conditioner.Related: water flow
- C0Get it checkedFlow sensor malfunction: the sensor sees water moving 45 seconds after Daikin’s pump has stopped. Low pressure, air and an external pump running are on the list before the sensor itself.Related: water flow
- Bill has jumpedGet it checkedThe most important heat pump fault has no code. If your electricity cost has stepped up with no change in habits, the backup heater is probably doing the work.Related: same brand
- Ice on the outdoor unitGet it checkedNormal in cold damp weather, and the unit clears it itself. Daikin specifically forbid helping — no hot water, no de-icer, no scraping.Related: same brand
- Water at the tap is too coldGet it checkedDaikin give two causes and a remedy that costs money. Before using it, check what your schedule is actually asking the cylinder to do.Related: same brand
- U0Get it checkedShortage of refrigerant in the Altherma outdoor unit. Daikin’s own checklist ends with a leak test, the circuit is sealed, and on an R32 unit this is F-Gas certified work by law.Related: same brand
Own a Daikin heat pump? Save it and its codes come first next time.
Related guides
Common questions about Daikin 7H
My code is just 7H with no suffix. Which one is it?
Your display shows only the two-character error code, which is how Daikin UK’s own owner leaflet describes it: "typically a number and a letter, for example 7H". The fault family is water flow, and an engineer can read the detailed code from the unit. Start with pressure, air and the filter regardless.
Is 7H-07 a fault?
It is the unit dealing with one. Daikin’s service manual says the trigger is the unit detecting that the water pump might be blocked; it does not stop, it runs a de-blocking routine for up to thirty minutes, and the code clears automatically when the pump is freed. Once, in a system that has been idle, it is unremarkable. Repeatedly, it is a pump that keeps sticking.
Why does it only happen when it is cold?
Because a defrost needs twice the water flow of ordinary heating. Daikin publish 6 litres a minute for heating on the Altherma 3 M and 12 during a defrost, so a circuit that is marginal in October fails on the first frosty morning, usually as 7H-01 that clears itself, then 7H-06 if it keeps happening.
Technical review
Not reviewed by an engineer
No engineer has read this page. Severity follows what the manufacturer publishes, and we would rather tell you that than let a byline imply a sign-off.
Sources and how we verified this
We establish the facts from the sources below and then write the explanation ourselves. We do not copy manufacturer wording and we do not host their manuals.
- Manufacturer technical and service documentation
This page has not been reviewed by an engineer, and we would rather tell you that than imply otherwise. The severity rating follows what the manufacturer publishes: where they say isolate the appliance and call someone, so do we.