Installing a consumer unit in a garden office

Right, been through this with my motorhome setup so here's the lowdown:

Location & Protection
Mount it on an interior wall if possible — keeps moisture out of your face. If it has to be external, get a weatherproof IP66 cabinet. Your RCD modules will weep otherwise.

Cable Entry
Drill entry holes at the bottom, use proper cable glands (not just whatever you've got lying about), and run conduit up from your consumer unit to your batteries/inverter. Keeps the rodents honest.

Earthing
This is where most people cock it up. You need a proper earth rod driven into the ground outside, bonded back to your consumer unit with 16mm² cable minimum. It's not optional, it's Building Regs. Your insurance won't touch you otherwise.

Incoming Supply
If you're pulling from solar/battery, size your main switch and MCB accordingly. I used a 63A isolator on my setup — took a bit of head-scratching but Victron's wiring guide sorted me out.

Labelling & Testing
Label everything as you go. Seriously. Future you (or your insurer) will thank you. Get a qualified electrician to do the sign-off if you're not approved — costs a few quid but keeps everything above board.

Pro tip: Don't cheap out on the enclosure itself. A £200 Fogstar beats a £60 eBay special when water's dripping on your circuits.

Good shout on the interior mounting, @FormerCop. I learned this the hard way with my barn conversion — put mine on an external wall initially and the damp got in something chronic before I relocated it.

One thing worth adding: if you're running off-grid or hybrid power like I am, you'll need to think about your earthing setup differently than a grid-tied install. My sparky insisted on a proper earth rod outside the office, which meant running the main bonding back through the wall. Took more planning than I expected.

Also consider cable entry points carefully. I used oversized glands with proper seals — moisture finds the tiniest gaps. Worth spending a bit extra on decent ones rather than bodging it with silicone later.

What's your power source for the office? That might affect where you position everything relative to your inverter or distribution board.

Cheers for the thread, @FormerCop. Worth adding that if you're going exterior on a garden office, you'll want proper IP65 or better rated enclosure — moisture creep is real, especially in UK damp. I've got a Fogstar setup in my tiny house and learned the hard way that condensation inside the unit causes more grief than you'd think.

Also consider cable glands and drainage holes at the bottom. Some installers miss the drainage bit entirely — water pools and you're looking at corrosion within months. Cable entry from above works better than side entry if you can manage it.

One more thing: ensure it's positioned so you can actually access the switches without crouching. Sounds daft but you'll be resetting that RCD when you least expect it, and back strain isn't worth the saving on a slightly more compact placement.

Mate, if you're bolting it to the outside of a shepherd's hut or boat, just accept you're now maintaining it like a marina does — religiously. Moisture finds every gap known to physics, and corroded breakers are nobody's friend. Interior wall is genuinely the move if your setup allows it. With my boat I compromised: recessed box under the covered side, still gets checked quarterly. The IP rating chat is spot on, but even IP66 is just "delayed catastrophe" if you're not vigilant. Budget for replacement terminals every few years if exterior-mounted — Victron gear handles it better than cheap imports, but nothing's truly weatherproof forever.

The IP rating point @DODQueen raised is spot on, but equally important is what's inside that enclosure. If you're running off-grid with batteries, you'll want your DC disconnects and monitoring gear protected from the same moisture ingress.

I've got mine mounted internally in my narrowboat's cabin — the consumer unit itself is standard 17th Edition compliant, but the real headache is managing humidity around the battery terminals. Victron's isolation switches are supposed to be weatherproof, but condensation still finds a way. If you're forced exterior, consider a secondary sealed enclosure just for DC-side components.

One thing worth flagging: cable glands. Standard cable entries aren't rated for the temperature swings you get in an unheated garden office. I learned that the hard way when my inlet glands started weeping after a few freeze-thaw cycles. Upgrade to proper IP67-rated ones with drain holes, and use self-amalgamating tape around entries.

Also check whether Building Control requires your unit to be accessible for inspection — some local authorities want it in a designated service area rather than tucked in a corner. Worth a

Been down this road with my van conversion setup. The interior mount is definitely the way if you can swing it — keeps the whole thing drier and you're not wrestling with IP ratings in the UK damp.

That said, if exterior's your only option, consider a proper weatherproof cabinet rather than just relying on the consumer unit's casing. I've seen too many installations where moisture creeps in around the knockouts. Victron do some decent enclosures if you're running hybrid setups, though they're pricey.

@JohnBaker's spot on about what's inside — if you're feeding it from batteries or a solar array, make sure your DC isolation switches and any DC breakers are also rated for the location. Nothing worse than watching condensation wreck your protective devices.

One thing worth mentioning: get a qualified sparky to sign it off regardless. Garden office regs have tightened up, and insurers can be finicky if something goes pear-shaped later.

The van conversion angle @WonkyMechanic mentions is spot on. I've got mine mounted inside the habitation area of my van and it's made a world of difference for access and longevity.

Key thing nobody's mentioned yet — think about your cable routes. If it's external, you're running conduit everywhere which gets messy fast. Interior means you can thread stuff through the walls properly without the unit itself getting hammered by weather.

Also consider the RCD testing schedule. External units need checking more frequently because moisture creeps in. Pain in the arse if you've got a remote garden office.

One practical note: make sure you've got decent ventilation around it regardless. I've seen too many installations where the unit's tucked away and condensation just sits there waiting to cause grief. Leave a bit of air gap.

If you absolutely must go external, seriously invest in a proper weatherproof enclosure — not the cheap plastic box job. Victron do some decent stainless options if budget allows.

Been through this exact scenario with my van setup, and the one thing nobody's mentioned yet is cable entry and condensation management. You'll get moisture pooling inside that enclosure if you're not careful, especially in a garden office where you're not constantly using it.

What I did was drill weep holes in the bottom of the consumer unit enclosure — sounds daft, but it stops water accumulating when you're not actively drawing power. Pair that with an interior mount on a north-facing wall (away from direct sun cycling), and you've sorted both the IP rating issue and the thermal cycling problem.

One more thing: if you're running this off-grid with batteries (which half of us here are), make sure you've got adequate cable gauges for your DC side before it hits the AC circuits in that unit. I've seen too many setups where someone's picked a Victron or Fogstar unit but undersized the incoming cables because they were focused on the consumer unit specs alone.

If you do end up mounting externally, invest in a proper weatherproof cabinet — not just an IP65 rated box. The difference in longevity is worth

Cheers for the thread. One thing worth flagging — if you're pulling cables from outside into your consumer unit, condensation is a genuine headache. I've had this in my boat setup and it's a nightmare to troubleshoot.

Best approach: run your incoming cables through the wall with a proper gland and drip loop on the outside. Stops water pooling at the entry point. Then let them drop vertically inside before they hit the consumer unit — gravity's your mate.

Also, if you're mixing renewable inputs (solar, wind, whatever) with grid supply, think carefully about your RCD arrangement before you start. The earthing can get wonky if you're not careful, especially in outbuildings. Might be worth a quick chat with a sparky if you're combining sources.

Interior mount is definitely the play here. Keeps the whole thing drier and easier to work on. Just make sure you've got decent ventilation around it — they do generate a bit of heat under load.

Mounted mine inside the shepherd's hut and the condensation issue is real — think your breath on a car window but it's slowly killing your electrics. Victron breakers don't appreciate moisture, turns out.

The trick nobody mentions: a small desiccant box mounted near the consumer unit costs about a tenner and saves you a grand in failed components. I rotate mine monthly because the UK's basically a sauna with planning permission.

Cable glands with IP67 ratings aren't optional either — they're mandatory if you're running anything from outside. @PaddyDavies is spot on about that.

One more thing: if your garden office isn't insulated properly, you're fighting a losing battle. Mine stayed damp until I sorted proper ventilation (extractor fan on a timer). Now it's almost pleasant, only slightly moorland-ish instead of full swamp.

The condensation crew are absolutely right — that's the silent killer nobody talks about until it's too late. Had this exact problem in my van conversion before I sorted it properly.

What actually worked for me was installing a breather membrane around the cable entry point. Sounds fancy but it's just a one-way valve that lets moisture vapour escape without letting water in. Cost me about a tenner from an electrical supplier.

More importantly though — your consumer unit location matters. If it's genuinely external, you need either:

• A weatherproof enclosure (Weatherseal or similar) with proper ventilation holes (not sealed, despite what it sounds like)
• Or better yet, run it to an internal utility cupboard if the garden office layout allows

The real issue is thermal cycling. Cold exterior temps hit your metal enclosure, moisture condenses on the terminals, and you're playing with fire electrically speaking.

@FormerCop's interior wall suggestion is genuinely the best option if feasible. Even a thick insulated box on an internal wall of your garden office beats external every time.

What's your actual setup — is it a dedicated garden building or more of a temporary hut situation?

Had the same headache on the narrowboat. Vapour barrier tape round any cable entries is essential — @CamperCarl's right about condensation being sneaky. Also worth considering a small thermostat-controlled heater near the unit during winter months if you can manage it. Keeps everything dry and your RCDs actually functional. Desiccant packets are cheap insurance too.

Has anyone dealt with condensation on a consumer unit in an unheated shepherd's hut over winter? I'm looking at a Victron setup for mine and wondering if a small heated cabinet or moisture absorber would be overkill. @CamperCarl and @MarinePhil — did you end up installing any active drying, or just vapour barrier and ventilation?