Electrical

Earthing for a pool shed- what resistance do I need for an earth rod and why?

Kieran Seeburn 16/06/2025 - 11.01 AM

Hi folks, I have bought a house that has a pool heated with a 5kWh ASHP. We quickly discovered that the electrics for this were undersized and the main fuse out to the pool shed was replaced with bare copper. Fun. I've had the electrician I've used before in and he's put in a new supply from the main consumer unit through to the pool building that big enough to support the ASHP, and a new child consumer unit within the pool shed. All is working fine but he can't sign off due to an issue with the earthing. Basically the pool shed is connected using 'TT not PME'. So he's run a new earth out into the garden and driven an earth rod in. This is reading around 50ohms. If we try anywhere else in the garden we get around 200ohms. He says the regs say we need 20ohms or under, and has advised we dig out for an earth mat. However when I've spoken to a builder to do the grunt work his own electrician said as it's TT and not PME, the regs are actually under 200ohms, so we're fine and not to bother. Who is right, or are both wrong? If it helps, the pool shed board has a 100A breaker, and the separate breaker for the heat pump is 30mA.