Worcester Bosch boilers — including the Greenstar, CDi, Ci, Si and Junior ranges — are reliable and efficient. Like any appliance, they last longer with regular care, which is why an annual service is recommended (and usually needed to keep a new boiler’s warranty valid).
If you’ve just had a new Worcester Bosch boiler fitted, you might see an HH or hh symbol on the display, sometimes with digits missing. Don’t reach for the fault-finding section of the manual — you won’t find it there.
Is HH a fault code?
No. HH is not a fault code.
It means the boiler is in commissioning mode — running through a set-up routine to check everything’s working before it starts heating properly. Let it finish the cycle. There’s nothing to fix and no reason to panic.
If you’re seeing a different symbol that does point to a problem, our guide to Worcester Bosch fault codes runs through what each one means
What the boiler is doing in commissioning mode
Commissioning is the boiler’s start-up check. It has to complete this cycle before you can use it normally or run any tests. Until it’s done, the HH symbol stays on the display.
Why the HH code can come back
Sometimes the HH code shows up again after the boiler has already been running. A power cut, or a dip or surge in the supply, can send it back into commissioning mode. It’s the same harmless cycle — just wait for it to finish.
What if the boiler goes into ‘Locked Out’ mode?
Now and then a Worcester Bosch boiler drops into ‘Locked Out’ mode. The gas supply shuts off until the boiler resets itself and returns to normal.
If this happens, leave it. The boiler needs to sit in lockout for 20 to 30 minutes before it’ll run again. A combi will usually still give you hot water during this time, but central heating won’t be available. The reset button won’t speed it up — you just have to wait it out.
When to call a Worcester Bosch engineer
If the HH code won’t clear once the cycle should have finished, or the boiler keeps locking out, it’s worth getting it checked.
If it keeps happening, book a boiler repair in London and we’ll get an accredited engineer out to you.
Still seeing the HH code, or stuck in lockout? Call Serviceteam and we’ll send an accredited Worcester Bosch engineer to put it right.
