# Pressure differential bypass valve Herz model 4004 DN15

**URL:** https://aio.lv/en/product--herz-1400431--11829358
**Data updated:** 2026-03-09 14:38 (EET)
**Category:** Heating Radiators
**Manufacturer:** Herz
**Manufacturer code:** 1400431
**EAN:** 9004174438103
**Warranty:** 2 Years
**Availability:** Available for order
**Price:** 30.99 €
**Prices and availability valid until:** 2026-07-17 23:59
**Price without VAT (21%):** 25.61 EUR
**Can be purchased by legal entities:** Yes (invoice)
**Buy:** https://aio.lv/en/product--herz-1400431--11829358

## Delivery options

| Delivery method | Delivery time | Cost |
|---|---|---|
| Office pickup (2b. Kengaraga str., Riga, Latvia, LV-1063) | 09.07.2026 | free |
| Pickup points | 14.07.2026 | 1.99 EUR |
| Courier delivery to door | 14.07.2026 | 4.99 EUR |

## Summary description

Herz pressure differential bypass valve model 4004 DN15 designed to maintain stable system pressure by bypassing excess flow when differential pressure thresholds are exceeded. Suitable for hydronic heating and cooling systems, it helps protect pumps and control valves, reduces noise and prevents system imbalance. Compact DN15 size for small to medium installations.

## Long description

The Pressure differential bypass valve Herz model 4004 DN15 is designed to maintain stable differential pressure in hydronic heating and cooling systems by automatically diverting excess flow when pressure differentials exceed set thresholds. The compact DN15 size is suitable for small to medium installations and supports continuous, reliable operation of pumps and control valves. The valve construction is intended to reduce water-borne noise, prevent system imbalance and limit wear on circulating pumps and regulating components.
Advantages
This bypass valve provides automatic pressure regulation to protect pumps and sensitive control valves from excessive differential pressure. Its compact DN15 form factor allows installation in tight spaces while ensuring consistent hydraulic performance. The model 4004 reduces hydraulic noise and minimizes the risk of valve hunting and oscillation in closed-loop systems. Its mechanical design enables stable operation without electrical power, reducing complexity and maintenance needs.
Suitable for
Hydronic heating systems in residential and small commercial buildings
Closed-loop cooling circuits and fan coil units
Protection of circulation pumps and modulating control valves
Retrofit installations where space is limited
Key specifications
Nominal size: DN15 suitable for small to medium pipework
Function: automatic differential pressure bypass to maintain system balance
Operation: mechanical, spring-loaded bypass mechanism
Connection type: compact threaded connection for inline installation
Application: compatible with hot water heating and chilled water systems
How to use
Install the Herz model 4004 DN15 in parallel to the control valve or in the return line according to hydraulic design to provide a bypass path when differential pressure rises. Ensure the valve orientation and threaded connections match the system piping and use appropriate sealing materials. Commissioning requires verification of differential pressure set point and observing system behaviour during normal and peak flow conditions. No electrical supply is required; adjust and test hydraulically during system start-up.
Usage recommendations
Place the valve close to the pump or control station to ensure effective pressure stabilization. During commissioning, monitor for proper bypass activation and verify that the valve reduces noise and prevents pump overload. Periodic visual inspection and flushing during scheduled maintenance are advised to avoid debris accumulation; follow local regulations and Herz installation guidelines for best results.

## FAQ

### How much does the Herz pressure differential bypass valve 4004 DN15 cost, and is it available for purchase?

The price is 30.99 € (valid at the time of publication and already includes all taxes). The item is available for order — 1 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 09.07.2026 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. All transactions are 100% secure and encrypted.

### 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 Herz 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 Herz 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

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