Short answer: use a shaded, manufacturer-rated NEMA 4X / IP66 cabinet for the electronics and design the battery compartment separately. The worked layout below uses a 36 x 24 x 12 in (H x W x D) stainless enclosure on a 3-4 ft pad; confirm the equipment layout and anchors before setting those dimensions. Our cabinets are manufacturer-rated and not UL listed. Bring electronics cables through sealed bottom glands and size cooling for their losses. Flooded lead-acid, AGM and gel banks need a ventilation design, not a gas-tight cabinet beside the inverter. A lithium bank needs the installation, temperature and fault-protection provisions specified for its exact battery system.
What the pad has to beat
The site is rain, sun, dust, 0 F winter nights and an empty property most of the year. Each condition maps to one line on the order, and four numbers drive the whole design.
| Site condition | The number that matters | What it decides |
|---|---|---|
| Summer sun | about 1 kW/m² on a sun-facing face at noon | the shade roof; without it, add hundreds of watts of absorbed heat |
| Winter low | 0 F (-18 C) design low, freezing routine | the battery plan and the door gasket |
| Hot-afternoon air | 35 C (95 F) shaded design ambient | the heat budget in the worked example below |
| Dust | no filter to clog in a sealed box | sealed gland entries only |
| Weeks unattended | one lock, no outside hardware | inside anchors and a lockable handle |
Sun is the load you cannot fan away. A vertical face catches about 1 kW/m² at noon, so the 3 x 2 ft face of this cabinet (0.56 m²) intercepts roughly 560 W and absorbs a few hundred even on bare stainless. That is three to four times what the electronics themselves waste, which is why the corrugated roof over it beats any accessory mounted on the box. Leave the sides of the shelter open so the shaded air moves, and set the roof high enough to work under with both hands.
Rain still reaches the gasketed faces as wind-driven spray, which is exactly the condition a Type 4 rating covers; the outdoor enclosure guide walks the rest of outdoor siting. the outdoor electrical enclosure guide The 0 F nights are a battery problem, not a stainless problem, and the battery section below handles them. Dust settles on anything horizontal, but a sealed box gives it nowhere to go, with no filter to clog and no louver to sweep.
Why Type 4X, and not a job box
A job box is thin painted steel with drip rails and a latch that is not a rating. It keeps rain off hand tools; it does not keep spray off a charge controller. Order NEMA 250 Type 4X instead, paired with IP66 on the same nameplate. Type 4 covers outdoor rain, splashing and hose-down water. The X adds corrosion resistance, demonstrated per NEMA 250 Table 5-1D as 200 hours of salt spray against an AISI 304 stainless specimen. IP66 is the IEC 60529 partner: the first 6 is dust-tight, and the second 6 takes powerful jets from a 12.5 mm nozzle at 100 L/min. In US installations, NEC 110.28 states that IP ratings are not a substitute for enclosure type ratings, so the spec carries both numbers. The enclosure types guide lays out what each type test covers. the NEMA enclosure types guide
The rating survives only if the box stays whole. Every added opening sets the whole assembly at that part's rating: a vent, a louver, a drain, or a fan-and-filter kit, which typical kit datasheets rate about IP54. So a breather vent gives back the rating you ordered; the breather-vent article shows the test numbers. why a breather vent costs a NEMA 4X rating Keep every entry a sealed gland and the nameplate stands.
Set the installation requirements before choosing the cabinet. Private property and work that does not require a permit can still be subject to the adopted electrical code and equipment instructions. Where listed equipment is required, specify equipment accepted for that installation; a manufacturer rating does not supply that listing. Our cabinets are manufacturer-rated and not UL listed. The guide to UL 50E and NEMA 250 explains the distinction.
Sealed or vented: let the battery chemistry decide
Flooded lead-acid gasses while it charges, and the gas is hydrogen, whose lower flammable limit in air is 4%. Battery-room ventilation guidance holds the concentration at or under 1%, a quarter of that limit, and that takes real airflow rather than a louver. Flooded cells therefore live in their own outside-vented compartment or box beside the cabinet, and the sealed 4X box keeps the electronics dry and dust-free. That split is the safety line of this design: flooded cells inside a sealed cabinet walk the gas toward its explosive limit.
AGM and gel are valve-regulated lead-acid batteries: gas recombination reduces emissions, but hydrogen can still escape during charging or a fault. Battery enclosure guidance requires airflow for these batteries too. Keep them out of a gas-tight electronics compartment and size the battery compartment ventilation for the exact battery, charging current and ambient temperature. A membrane breather selected for pressure equalization does not demonstrate adequate hydrogen removal. For lithium, select the location, compartment, temperature controls and fault protection from the exact battery-system installation instructions; the chemistry name alone does not establish a safe enclosure design.
Winter decides the rest. Lithium cells take a charge only above 0 C (32 F) unless the cell datasheet says more; charging below that plates lithium inside the cell for good. Store the bank at about 60% state of charge, the middle of the 50-60% range cell-makers recommend for storage, and let the BMS low-temperature cutoff hold the line. Lead-acid wants the opposite: leave it at a full charge, because battery-industry tables put a fully charged electrolyte's freezing point near -70 F and a near-empty one near +20 F. The simplest winter plan is the one that needs no electronics at all: pull the bank and take it home, and let the cabinet look after only the controller and inverter. For the winters the bank stays, the heat check below sizes a 150 W pad heater.
304 or 316L for the grade
For rain, dust and mountain air, order 304 stainless, the same grade the salt-spray test behind the 4X rating uses as its specimen. Step to 316L when salt is in the picture: coastal air, or a pad near a plowed road that gets de-icing spray. Both grades sit at the same chloride stress-corrosion threshold around 60 C (140 F), and the molybdenum in 316L buys pitting and crevice resistance rather than a higher threshold. At the temperatures this cabinet sees, neither limit comes close. If the quote asks you to choose a door gasket, silicone spans about -60 to 200 C and nitrile about -30 to 120 C, so either rides through a 0 F winter without stiffening shut. Decide by salt: inland 304, salt on site 316L.
Heat check: a sealed 36 x 24 x 12 in box at 35 C ambient
This is the decision behind sealing the box without cooking it. The inputs come from the size on the order, this site's heat-guide values, and typical vendor datasheet figures for the two conversion boxes. Replace the load figures with your own datasheets before you lock the order.
- Surface area, from the 36 x 24 x 12 in (H x W x D) outside size: 2 x (3 x 2) + 2 x (3 x 1) + 2 x (2 x 1) = 22 ft² ≈ 2.0 m² over all six faces.
- Wall heat transfer: k = 3.7 W/m²K for stainless in still air, the value this site's heat guides use.
- Component limit: 40 C (104 F) ambient, the default rating for drives and most electronics unless a named datasheet allows more.
- Design ambient: 35 C (95 F), hot-afternoon air under an open shelter.
- Heat load, worst hour at midday bulk charge: an MPPT converts at about 97% in vendor datasheets, so a full 2 kW harvest wastes about 3%, or 60 W. An inverter serving 300 W at about 92% efficiency (a 5-6 kWh/day cabin load averages about 230 W, evenings higher) wastes 300 x (1/0.92 - 1) = 26 W. Total ≈ 86 W.
The rule in words: in a sealed box, the steady rise over ambient equals the losses divided by the wall's conductance, k x A.
The arithmetic: k x A = 3.7 x 2.0 = 7.4 W/K, so the rise is 86 / 7.4 = 11.6 K. At a 35 C afternoon the interior sits at 35 + 11.6 ≈ 47 C (116 F).
That is about 7 C past the 40 C limit in the worst hour, so the bare sealed wall fails at midday charge. Read the budget the other way: 5 K of rise carries 5 x 7.4 ≈ 37 W of continuous loss, and that is the threshold. Up to about 37 W, the sealed wall alone holds the rating and the limit. Above it, fit a sealed-to-sealed heat exchanger sized so exchanger plus wall carry the load at 5 K: 86 / 5 = 17.2 W/K total, so the exchanger adds about 10 W/K. An enclosure air conditioner covers bigger loads and keeps the rating too. Both mount through sealed cutouts. A fan-and-filter kit drops the assembly to its own roughly IP54 rating, and an open louver is worse still.
The same 7.4 W/K can illustrate the electronics cabinet's winter heat loss: holding 0 C (32 F) inside at a 0 F (-18 C) night requires about 18 K x 7.4 = 133 W in this simplified example. A 150 W heater is a provisional electronics heat-budget example, not a battery-heater selection: wind, mounting, controls and heater clearances still determine the actual design. Calculate the separate battery compartment with its required ventilation and battery temperature limits. The sealed IP66 cooling article covers closed electronics cooling.
Bolt it down: pad, anchors, entries and grounding
Pour the pad 3-4 ft square; that holds a 36 x 24 in footprint with room to work around it. Set anchor bolts in the pour, or drill in wedge anchors once it has cured, and bolt through the mounting feet or a pedestal from inside the box so there is nothing loose to attack from outside. The freestanding floor-mounting guide walks the bolt pattern and the torque. the freestanding floor-mounting guide
Set the height with the code numbers in mind. NEC 240.24(A) puts the center of the highest breaker handle no more than 2.0 m (6 ft 7 in) above the pad, and NEC 110.26(A) asks for clear working space in front, at least 3 ft (900 mm) deep for 0-150 V-to-ground equipment in Condition 1. A cabinet on a 12 in pedestal under an open shelter meets both with room to spare.
Bring every cable in from below through a bottom gland plate, with each gland matched to that cable's outside diameter. The bottom-entry guide for NEMA 4 floor-mounted boxes covers cutting and sealing the plate. the bottom-entry guide for NEMA 4 floor boxes
Bond exposed conductive cabinet parts and array frames through the equipment grounding system specified for the installation; earth is not an effective ground-fault current path under NEC 250.4(A)(5). A ground rod does not replace the equipment grounding conductor. Keep protective earth, AC neutral and the DC current-carrying return distinct: make a DC-to-ground connection only where the equipment instructions and system design require it, not automatically at battery negative. The grounding and bonding guide covers cabinet bonding. The control-panel explanation of separating protective earth from DC return helps with that terminal-level distinction; it does not replace the inverter's PV-system grounding instructions or the applicable installation code.
What goes on the order
Hand the quote a drawing rather than a description, and let the table do the talking.
| Order line | Spec |
|---|---|
| Material | 304 stainless; 316L if salt reaches the pad |
| Outside size | 36 x 24 x 12 in (H x W x D), inside the 6 x 4 x 4 to 60 x 36 x 16 in range the size finder covers |
| Rating | Manufacturer-rated NEMA 4X / IP66; not UL listed |
| Door | Hinged gasketed door, lockable handle, wall-mount feet for the pedestal |
| Panel | Removable mounting panel; keep about 25% spare, common panel-layout practice, for future breakers and shunts |
| Cutouts | Bottom gland plate, one sealed gland per cable run, positions marked on the drawing |
| Cooling | Electronics-only example: about 37 W through the sealed wall; size additional cooling from the actual losses and ambient |
| Battery compartment | Separate from electronics; ventilation, temperature controls and fault protection from the exact battery-system instructions |
| Installation approval | Confirm the adopted code and required equipment listing before ordering; no exemption based on private ownership or lack of a permit |
| Delivery | Delivered in 10 business days from the order; custom work counts from your approval of the drawing |
Start from the stainless size finder to set the exact height, width and depth, or let the enclosure selector shortlist by environment and inside dimensions. the stainless size finder the enclosure selector Mark every cutout on the drawing and nothing more, because each opening is a rating you have to defend. Orders run through the checkout of Industrial Monitor Direct, who builds, ships and supports every box.
Catalog dimensions to compare
Compare these catalog dimensions with your component layout. Open each enclosure for its rating, material and usable space, then check those specifications against your application.
| Enclosure | Material | Outside H x W x D / display | Rating |
|---|---|---|---|
| 36 × 24 × 12 in | 304 stainless | 36 x 24 x 12 in | Rated NEMA 4X / IP66 by the manufacturer; not UL listed |
| 10 × 8 × 6 in | 304 stainless | 10 x 8 x 6 in | Rated NEMA 4X / IP66 by the manufacturer; not UL listed |
| 12 × 10 × 6 in | 304 stainless | 12 x 10 x 6 in | Rated NEMA 4X / IP66 by the manufacturer; not UL listed |
| 16 × 12 × 8 in | 304 stainless | 16 x 12 x 8 in | Rated NEMA 4X / IP66 by the manufacturer; not UL listed |
Questions
Does the box still need NEMA 4X if the ramada covers it?
Yes. The shade roof deletes about 1 kW/m² of sun but not the wind-driven spray that reaches the gasketed faces, and spray is what Type 4 is tested against. In stainless the X costs little more: it is 200 hours of salt spray behind the same rain rating. Order NEMA 4X / IP66 and let the ramada handle heat, not water.
Can I vent the enclosure for the batteries?
Keep the battery bank in a separate compartment designed for its chemistry and charging conditions. Flooded lead-acid needs hydrogen removal, and AGM or gel still needs airflow even though the battery is called sealed. A gas-tight electronics cabinet is not a battery ventilation design. For lithium, use the exact system instructions for location, venting, temperature and fault protection.
What happens to lithium batteries at 0 F?
Use the battery model's stated storage and charging temperature limits at 0 F (-18 C). Keep the BMS low-temperature charge protection enabled. A heater must be selected for the separate battery compartment, including ventilation and safe clearances; the electronics cabinet's 150 W worked example is not a battery-heater specification.
Do I need a UL listed enclosure for this?
Private ownership or the absence of a permit does not waive adopted electrical-code requirements. Establish the equipment and enclosure approval requirements before ordering. Where the installation requires listed equipment, choose equipment accepted for that use; our manufacturer-rated NEMA 4X / IP66 cabinets are not UL listed, and that distinction remains on the specification.
How much heat can the sealed wall take before adding a heat exchanger?
About 37 W of continuous loss at a 35 C shaded ambient. The 2.0 m² wall of a 36 x 24 x 12 in stainless cabinet moves heat at 7.4 W/K, and a 5 K rise up to the 40 C component limit gives 5 x 7.4 = 37 W. A typical 2 kW rig loses around 86 W at midday charge, so most builds add a sealed heat exchanger of about 10 W/K.
304 or 316L for a mountain site?
304, unless salt reaches the pad. Coastal air or de-icing spray from a plowed road is what 316L is for. Both grades share a chloride stress-corrosion threshold near 60 C (140 F), and the molybdenum in 316L buys pitting and crevice resistance rather than a higher threshold, so at this box's temperatures 316L adds margin at the crevices and nothing else.
