These are the genuine Jean Müller NH fuse-links for the KETO-1 battery disconnector — the replacement and spare fuse elements used with the KETO size 1 NH fuse-switch-disconnector body in solar and battery storage DC protection applications. The KETO-1 is rated for a maximum DC current of 250 A at 250 V DC, and these fuse-links are available in ratings of 80 A, 100 A, 125 A, 160 A and 200 A to suit different battery and inverter configurations. Each KETO-1 disconnector body takes two fuse-links (one per pole — positive and negative), so order in pairs when replacing or commissioning. Built to IEC 60269, gL/gG characteristic, with a combi blown-fuse indicator on each link for rapid visual fault detection. Manufactured by Jean Müller — a specialist German electrical safety company with over 125 years of history in fuse technology.
NH1 Size
KETO-1 fuse format
250V DC
DC voltage rating
80–200A
Available ratings
IEC 60269
Standard
gL/gG
Characteristic
Combi Indic.
Blown-fuse indicator
⚠ Qualified electrician or technician installation only: DC battery protection circuits carry significant fault energy. Selection of the correct fuse rating, installation and commissioning must be performed by a qualified electrician or technician. All installations must adhere to local wiring regulations and standards.
ℹ Two fuse-links required per KETO-1 disconnector: The KETO-1 is a two-pole disconnector (positive and negative conductors). Each pole carries one NH1 fuse-link. Order two fuse-links per disconnector body — one for the positive pole, one for the negative. Both fuse-links must be the same current rating.
ℹ KETO-1 fuse-links are not interchangeable with KETO-00 fuse-links: The KETO-00 uses NH00-size fuse-links; the KETO-1 uses NH1-size fuse-links. These are different physical sizes and cannot be substituted. Check the size designation on your disconnector body before ordering. KETO-00 fuse-links are available separately.
Fuse-Link Rating Selection — Choose the Correct Ampere Rating
Select the fuse rating based on the maximum continuous DC current of your battery system with an appropriate safety margin applied. The fuse rating should typically be set at 125 % of the maximum continuous battery current to allow for brief transients while still protecting against sustained overcurrent faults.
Rating
Jean Müller Part No.
Typical use case
Max system current (at 125% factor)
80 A
N1013907 (M1gL80)
Small 12V battery banks; low-current DC systems
~64 A continuous
100 A
N1014207 (M1gL100)
Mid-size residential battery storage
~80 A continuous
125 A
N1014605 (M1gL125)
5 – 10 kWh storage at 48V; standard hybrid inverter DC feeds
~100 A continuous
160 A
N1014905 (M1gL160)
High-capacity residential or light commercial systems; larger 48V banks
~128 A continuous
200 A
N1015205 (M1gL200)
Large battery banks; commercial storage; high-power inverters
~160 A continuous
Part numbers shown are Jean Müller manufacturer references. Always size fuses based on a full fault current calculation by a qualified engineer. The 125 % guidance is a starting point, not a substitute for a proper system design assessment.
How to Choose Your Fuse Rating
NH fuse-links in battery DC circuits must be sized to protect the cable, not to match the inverter’s input current rating. The correct sizing method follows these steps:
1. Determine maximum battery current
Find the maximum continuous discharge current of your battery bank in amps. For example: a 10 kWh system at 48 V nominal discharging at 5 kW = 5,000 W ÷ 48 V = approximately 104 A.
2. Check the cable rating
The fuse must not exceed the rating of the DC cable it protects. Select a fuse-link rating equal to or below the cable’s current-carrying capacity (derated for installation conditions). The cable is the protected component.
3. Apply the 125 % rule
Size the fuse at no more than 125 % of the maximum continuous current to allow for brief transients without nuisance tripping. For 104 A continuous: 104 × 1.25 = 130 A → select the 125 A fuse.
4. Verify against KETO-1 maximum
The KETO-1 body is rated to a maximum DC current of 250 A. Do not select a fuse rating above 250 A for a single KETO-1 disconnector. For higher currents, a KETO-2 body (rated 400 A) would be required.
5. Always use a qualified engineer
Battery fault currents can be extremely high and potentially lethal. Fuse selection must be verified by a qualified electrician who can perform a full fault current calculation for the specific installation.
Key Features
Genuine Jean Müller Components — Designed Specifically for the KETO-1 Body
These are genuine Jean Müller NH1 fuse-links, not generic NH1 fuses. While dimensionally compliant with the NH1 standard, Jean Müller design their KETO fuse-links as an integrated system with the KETO disconnector body — matching the contact interface, striker mechanism, and indicator window geometry. Using non-genuine or generic NH1 fuse-links can result in poor contact reliability, incorrect indicator function or failure to seat correctly.
The gL/gG characteristic means the fuse provides full-range protection: both overload protection (the ‘g’ prefix) and short-circuit protection (the ‘L’/‘G’ suffix). An overload (moderate overcurrent sustained over time) causes the fuse to blow gradually; a short-circuit causes it to clear in milliseconds. This dual protection is exactly what is required between a battery bank and an inverter, where both conditions must be guarded against.
Each fuse-link includes a combi indicator: a visual striker that activates when the fuse element blows. Without this indicator, identifying a blown fuse in a DC battery circuit requires a voltage measurement across each fuse — a time-consuming and potentially dangerous process if the battery is still energised. The combi indicator makes fault identification immediate and safe, reducing diagnostic time significantly.
250 V DC Rating — Correct for Battery DC Applications
Many standard NH fuse-links are rated for AC applications only or are not rated for DC use at all. AC fuses cannot be used in DC circuits because the lack of a natural current zero-crossing means the arc generated when the fuse clears does not extinguish in the same way. These Jean Müller fuse-links carry an explicit 250 V DC voltage rating, confirming they are designed and tested for DC battery circuit protection where the KETO-1 body is used.
250V DC ratedDC arc extinction testedNot AC-only
Halogen-Free, Self-Extinguishing Materials
The fuse-link body is manufactured from halogen-free, self-extinguishing materials. In the event of a fault, the fuse body will not propagate flame or emit toxic halogen gases. This is a critical fire safety property for enclosures mounted in battery storage installations, where the risk of secondary fires or toxic gas release during a fault event must be minimised. Compliance with IEC 60269 includes testing of the arc extinction and post-fault safety of the fuse body.
Halogen-freeSelf-extinguishingIEC 60269
EN 60947-3 Compliant KETO-1 System
The KETO-1 disconnector body to which these fuses are fitted is designed and tested to EN 60947-3 (the standard for switch-disconnectors and fuse-combination units). Compliance with this standard verifies that the complete switching and protection system — disconnector body plus fuse-link — performs correctly under the rated conditions, including make and break operations, fault clearance, and temperature rise limits. This is important for UK BS 7671 and IET Wiring Regulations compliance in battery storage installations.
EN 60947-3 system complianceBS 7671 compatible
KETO-1 Body Quick Reference
These fuse-links are designed for use with the KETO size 1 disconnector body. Key KETO-1 body specifications for reference:
KETO-1 Disconnector Body
Maximum DC current (Ie)
250 A
DC voltage rating
250 V
Overall width
184 mm
System size
300 mm
Terminals
M10 lugs, 25 – 150 mm² cable capacity
Mounting
Baseplate / DIN-rail / busbar
Poles
2-pole (positive + negative)
Fuse size accepted
NH1 (this product)
Standard
EN 60947-3
Related product
Jean Müller NH Fuse-Links for KETO-00 (NH00 size — sold separately)
1 fuse-link (order 2 per KETO-1 disconnector body)
Compatibility
Compatible disconnector body
Jean Müller KETO-1 (size 1) only
NOT compatible with
KETO-00 body (uses NH00 fuse-links — different physical size)
Application
DC protection between battery bank and inverter
Manufacturer
Brand
Jean Müller (Jean Müller GmbH & Co. KG, founded 1897)
Origin
Germany
Frequently Asked Questions
Why do I need two fuse-links per KETO-1 disconnector?
The KETO-1 is a two-pole disconnector — it breaks both the positive and negative DC conductors simultaneously. Each pole has its own fuse-link. Breaking both conductors is essential in a DC battery circuit: unlike AC, DC has no natural current zero-crossing, so a fault cannot self-extinguish if only one conductor is broken. Both poles must be fused and isolated together. The KETO-1 body is supplied without fuse-links — you select the appropriate current rating for your application.
Can I use a standard NH1 fuse-link from another manufacturer?
The NH1 fuse-link is a standardised size under IEC 60269, so physically any NH1 fuse-link will fit in the KETO-1 body. However, for the combi indicator to function correctly, the fuse-link must be compatible with the KETO body’s indicator mechanism. Non-Jean-Müller NH1 fuse-links may not trigger the KETO indicator correctly. Jean Müller recommend using their own fuse-links with the KETO body to guarantee the indicator and contact interface perform as designed.
What is the difference between gL, gG and aM fuse characteristics?
gL/gG fuses provide full-range protection: they protect against both sustained overloads and short-circuits across the entire current range. They are the correct choice for protecting cables and general DC loads. aM (motor starting) fuses provide back-up protection only: they only clear short-circuits and high overcurrents; they do not provide overload protection for the cable. For DC battery-to-inverter protection, gL/gG is the correct characteristic. aM fuses must not be used for cable protection.
How do I know if a fuse-link has blown?
The combi indicator on each fuse-link provides a visual signal when the fuse element has ruptured. Without the indicator, you would need to use a voltmeter across each fuse-link (with the circuit live) or a continuity tester (with the circuit isolated) to identify a blown fuse. With the indicator, a visual inspection of the disconnector window is sufficient. After identifying and replacing a blown fuse, always investigate and rectify the fault that caused the fuse to blow before restoring power.
Can I replace just one fuse-link if only one has blown?
Technically yes — the fuse-links are individual components. However, if one fuse in a pair blows, the other fuse has experienced the same fault current and may be close to or at the end of its service life. Best practice in a two-pole DC circuit is to replace both fuse-links simultaneously to ensure both poles have matched and verified protection. Also check the cable and all connections for damage before re-energising.
What is the maximum DC voltage the KETO-1 system can handle?
The KETO-1 disconnector body is rated at 250 V DC. For low-voltage battery systems (12 V, 24 V, 48 V nominal) this is more than sufficient. For high-voltage battery systems (e.g. Pylontech PowerCube H1/H2 at 200 – 1,000 V DC), the KETO-1 is not suitable. High-voltage DC battery protection requires fuse switches and fuse-links specifically rated for the system voltage. Always verify the complete circuit voltage before selecting any DC protection device.
Related Products
Jean Müller KETO-1 Fuse-Switch Disconnector Body
The disconnector body these fuse-links are designed for
Jean Müller NH Fuse-Links for KETO-00
NH00-size fuse-links for the smaller KETO-00 body
Jean Müller KETO-1 Battery Disconnector with Fuses
KETO-1 body supplied with a matched pair of fuse-links
Pylontech PowerCube H2 H48074 Battery Module
High-voltage LFP battery for larger solar + storage systems
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