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header-product Automatic Phase Switcher FF PF-421-TRMS with Adjustable Upper and Lower Voltage Thresholds
73.99 €

Automatic Phase Switcher FF PF-421-TRMS with Adjustable Upper and Lower Voltage Thresholds

FF PF-421-TRMS Automatic Phase Switcher Photo 1

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Automatic Phase Switcher FF PF-421-TRMS with Adjustable Upper and Lower Voltage Thresholds

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Automatic Phase Switcher FF PF-421-TRMS with Adjustable Upper and Lower Voltage Thresholds

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Short description

The FF PF-421-TRMS automatic phase switcher is designed to ensure uninterrupted power supply to single-phase loads from a three-phase network. It features adjustable upper and lower voltage thresholds and True RMS measurement for precise voltage monitoring. This device protects sensitive electrical equipment from voltage drops and surges, making it ideal for residential, commercial, and industrial electrical systems requiring high reliability.
Available for order: 7 pcs.
Warranty: 2 Years
SKU: 12760394
Manufacturer: FF
free shipment

Cheapest delivery:

Unisend LV

Pick-up points

Unisend LV

Cost

1.99 €

Deliver

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Customer service center
2b. Kengaraga str., Riga, Latvia, LV-1063
24.11.2026 {{selectedOffer.officeDeliveryString}}
free
Courier Delivery Please note that in case of a large parcel additional delivery costs may apply!
27.11.2026 {{selectedOffer.courierDeliveryString}}
From 4.99 €
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Unisend LV / Venipak Pickup LV / Venipak Locker LV / DPD Paku skapis / Omniva LV / Latvijas Pasts pakomāts / Latvijas Pasts nodaļa
27.11.2026 {{selectedOffer.parcelStationDeliveryString}}
From 1.99 €
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All payment Methods:
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36 months installment: from 2.06 euros per month
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Product information

Description

The FF PF-421-TRMS automatic phase switcher is designed to ensure uninterrupted power supply to single-phase loads from a three-phase network. Equipped with True RMS measurement capabilities and adjustable upper and lower voltage thresholds, this device provides precise voltage monitoring and protects sensitive electrical equipment from power drops and surges.

Advantages

The phase switcher delivers reliable protection for electrical equipment by continuously monitoring the stability of the three-phase network. True RMS measurement ensures high accuracy regardless of the waveform distortion, while adjustable voltage thresholds allow for flexible adaptation to specific operational requirements and local grid conditions.

Suitable for

  • Residential electrical installations requiring backup phase selection
  • Commercial setups powering sensitive single-phase equipment
  • Industrial control panels and automation systems
  • Protecting sensitive electronics against phase loss and voltage fluctuations

When it may not be suitable

This device is not designed for three-phase motor loads or applications that require simultaneous three-phase output. It is strictly intended for managing single-phase loads supplied by a three-phase source.

Key specifications

  • True RMS voltage measurement
  • Adjustable upper and lower voltage thresholds
  • Designed for three-phase network input
  • Supplies single-phase loads

How to use

Installation should be performed by a qualified electrician in accordance with local electrical safety regulations. Connect the three-phase input lines and the single-phase output line to the designated terminals of the device. Configure the upper and lower voltage thresholds according to the specifications of the connected load and the operating parameters of the electrical grid.

What to consider before purchase

  • Verify that your electrical system utilizes a three-phase supply and a single-phase load
  • Ensure the load requirements match the specifications of the switcher
  • Check available space in the electrical distribution board for installation
Usage recommendations: Regularly inspect the terminal connections and verify the threshold settings during routine electrical maintenance to ensure continued reliable operation.

Description

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Product comparison

The automatic phase switcher Automatic Phase Switcher FF PF-421-TRMS with Adjustable Upper and Lower Voltage Thresholds is designed to guarantee an uninterrupted power supply for single-phase loads from a three-phase network using adjustable voltage thresholds, whereas the alternative device FF CKF-320-TRMS Phase Sequence and Loss Relay with Adjustable Voltage Window functions as a phase monitoring and protection relay for three-phase systems. Both models utilize True RMS measurement for precision, but serve distinct roles in power protection.

⚙️ The table below compares the device type, core protection functions, measurement capabilities, and operational use cases.

ParameterAutomatic Phase Switcher FF PF-421-TRMSFF CKF-320-TRMSPractical Significance
Device TypeAutomatic phase switcherPhase monitoring relayThe switcher transfers load to a healthy phase, while the relay monitors and protects three-phase lines.
Primary PurposeEnsuring uninterrupted single-phase power supplyProtecting three-phase equipment from phase loss and asymmetrySelection depends on whether you need power backup or general three-phase line monitoring.
Measurement TechnologyTrue RMSTrue RMSBoth devices deliver high measurement accuracy regardless of waveform irregularities.
AdjustmentsAdjustable upper and lower voltage thresholdsAdjustable voltage windowEnables precise customization of protection limits for sensitive electrical loads.

◎ The table below outlines which product is more suitable for specific user needs and operational scenarios.

Use CaseRecommended ProductWhy
Protecting sensitive single-phase loads with automated power backupAutomatic Phase Switcher FF PF-421-TRMSThe unit automatically switches the load to an active phase if voltage falls outside set thresholds.
Monitoring three-phase networks and safeguarding industrial equipmentFF CKF-320-TRMSThe device accurately detects phase loss, asymmetry, and incorrect sequence in three-phase systems.

The Automatic Phase Switcher FF PF-421-TRMS is best suited for applications requiring continuous single-phase power through automated phase switching. The alternative FF CKF-320-TRMS is designed for comprehensive three-phase network monitoring and fault protection. Choose the phase switcher for power continuity or the monitoring relay for three-phase line safety.

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Customer reviews

Customer questions

FAQ

How much does the FF PF-421-TRMS Automatic Phase Switcher cost, and is it available for purchase?

The price is 73.99 € (valid at the time of publication and already includes all taxes). The item is available for order — 7 pcs. are in stock, and you can place your purchase right now with delivery across Latvia and Europe or choose pickup at the Riga collection point. We offer favorable purchase terms, including the option to split the payment into convenient monthly installments. Availability and price are updated in real time, so we recommend placing your order in advance.

If I order this product today, when will I receive my order?

If you place your order today, delivery will be as fast and convenient as possible. You will be able to pick up your order on 24.11.2026 at the Riga pickup point or choose delivery across Latvia and Europe. We carefully inspect every purchase and pack it securely for safe transportation.

What payment options are available?

AiO.lv offers several payment methods: Bank transfer, Bank cards on-line, Apple Pay, Google Pay, Installment. All transactions are 100% secure and encrypted.

Can FF PF-421-TRMS Automatic Phase Switcher be purchased with a lease?

Yes, the purchase is available both on credit and with an interest-free installment plan. We work with leading banks and leasing companies in Latvia, allowing you to make your purchase on convenient terms — with a minimal down payment and a repayment period from 3 to 36 months. You can apply for credit or installments for the FF PF-421-TRMS Automatic Phase Switcher online, and the application process is as simple as possible:
  • Select the product on the website and add it to your cart;
  • When placing your order, choose the payment method “Installments”;
  • Fill in the required details for the lending partner;
  • Receive a decision within a few minutes.
For more information about available payment options, interest-free installment terms, and credit conditions in Latvia, please visit the Payment page.

Can this product be purchased for a company (with VAT)?

Yes. AiO.lv works with legal entities in Latvia and across Europe. The product price already includes VAT. For certain product categories, as well as for companies from other EU countries with a valid VAT number, a 0% VAT rate may apply. We issue the invoice immediately after the order is placed, support electronic BIS invoices, and automatically generate all necessary accounting documents. You can complete the purchase for a company online — simply select the company profile and choose bank transfer as the payment method during checkout.

What is the warranty period?

All FF products come with an official 2 Years warranty. It covers all manufacturing defects and malfunctions that may occur during use. The warranty is valid at all authorized FF service centers and through AiO.lv

Can the product be returned after purchase?

Yes, you can return the product within 14 days of purchase if you bought it as a consumer (not a legal entity). Returns are possible without giving any reason — the main condition is that the product retains its original appearance and full set of accessories. We will make the process as simple and convenient as possible: just contact our customer support team, and we will help you arrange the return.

Where should I contact for warranty service?

For warranty-related questions you can contact the AiO.lv (SIA VSPRO) customer support team. We will assist with consultation, warranty claim processing, and coordination with certified service centers.
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