# Control Unit TECH ST-21 CWU for Hot Water Pump — anti-stop, anti-freeze, tank cooling protection, white

**URL:** https://aio.lv/en/product--tech-st21cwuwh--6519211
**Data updated:** 2026-03-07 15:16 (EET)
**Category:** Control Systems
**Manufacturer:** TECH
**Manufacturer code:** ST21CWUWH
**EAN:** 5901445470654
**Warranty:** 2 Years
**Availability:** Available for order
**Price:** 95.99 €
**Prices and availability valid until:** 2026-07-11 23:59
**Price without VAT (21%):** 79.33 EUR
**Can be purchased by legal entities:** Yes (invoice)
**Buy:** https://aio.lv/en/product--tech-st21cwuwh--6519211

## Delivery options

| Delivery method | Delivery time | Cost |
|---|---|---|
| Office pickup (2b. Kengaraga str., Riga, Latvia, LV-1063) | 02.07.2026 | free |
| Pickup points | 07.07.2026 | 1.99 EUR |
| Courier delivery to door | 07.07.2026 | 4.99 EUR |

## Summary description

TECH ST-21 CWU is a control unit designed for domestic hot water (CWU) pump management. It provides anti-stop functionality to prevent pump seizure, anti-freeze protection to avoid freezing in low temperatures, and protection against tank cooling. The unit is intended for integration with CWU pump systems to ensure reliable circulation, protect equipment during inactivity, and maintain hot water availability.

## Long description

TECH ST-21 CWU is a compact control unit for domestic hot water (CWU) pump systems, designed to maintain reliable circulation and protect equipment from operational risks. The unit incorporates anti-stop function to periodically activate the pump and prevent seizure, anti-freeze protection to guard against low-temperature damage, and tank cooling protection to avoid excessive heat loss from the hot water cylinder. The device is supplied in white and intended for integration with standard CWU pump circuits where automatic maintenance and protection features are required.
Advantages
The control unit automates pump maintenance and protection tasks without manual intervention, reducing the risk of pump failure and extending equipment life. Anti-stop operation prevents long-term idle seizure by initiating programmed run cycles, while anti-freeze logic activates circulation when temperatures approach freezing. Tank cooling protection helps maintain hot water temperature by reducing unnecessary heat loss through controlled pump operation. The compact design and simple interface support straightforward installation and integration into existing domestic hot water systems.
Suitable for
 Domestic hot water circulation systems in single-family homes and small multi-family buildings
 Systems where pumps can remain idle for extended periods (anti-stop requirement)
 Installations in unheated or partially heated spaces requiring anti-freeze protection
 Hot water tanks where prevention of unwanted cooling is needed
Key specifications
 Functionality: anti-stop pump activation, anti-freeze protection, tank cooling protection
 Application: control unit for domestic hot water (CWU) circulation pumps
 Installation: panel or surface mount compatible with standard CWU pump wiring
 Enclosure color: white
 Operating environment: indoor use in domestic hot water systems
How to use
Install the TECH ST-21 CWU in accordance with local electrical and plumbing regulations, connecting it to the CWU pump and temperature sensors or inputs provided by the circulating system. Configure the unit according to the system requirements so that anti-stop cycles occur at appropriate intervals and anti-freeze thresholds match the installation environment. Verify correct power supply and test automatic functions after installation to ensure the pump starts and stops as intended and protection features respond to low-temperature or tank cooling conditions.
Usage recommendations
Follow manufacturer installation instructions and local codes. For reliable performance, schedule periodic inspections of wiring and sensor connections, and confirm that anti-stop and anti-freeze thresholds are suitable for seasonal temperature variations. If the installation is in a location with frequent power interruptions or extreme temperatures, consider additional backup or insulation measures.

## FAQ

### How much does the Control Unit TECH ST-21 CWU cost, and is it available for purchase?

The price is 95.99 € (valid at the time of publication and already includes all taxes). The item is available for order — 5 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 02.07.2026 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 Control Unit TECH ST-21 CWU be purchased with a lease?

Yes, the purchase is available both on credit and with an interest-free installment plan. Learn more about installments and credit options: https://aio.lv/en/payment#b3

### 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 TECH 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 TECH 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. More information about warranty service: https://aio.lv/en/warranty

## Image

https://aio.lv/img/cache/product/6519211/68546088_large.webp