One of the most common questions we get here at Anchor Pump is: “How do I choose the correct central heating pump size for my home?”

A few times we’ve even had customers sending us pipe layout diagrams, boiler metrics and insulation ratings.

Central heating pumps come in various sizes and configurations to accommodate the specific needs of different heating systems. Factors such as the size of the property, the total heat output required, the height differential between floors, and the resistance within the system all influence the size and type of pump needed.

This guide will cover the following:

Which central heating pump do I need?

If you’re looking to buy a central heating pump, but are unsure on which pump to choose from, here are some options:

  1. Grundfos UPS3 15-50/65
  2. Grundfos Alpha 3
  3. Lowara Ecocirc Premium 25-4 (180)
  4. Lowara Ecocirc 25-4 (180)
  5. Stuart Turner ST 15/60

If you suffer from particularly poor insulation, you'll want to pick a larger option of central heating pump.

What is a variable speed dial?

Most central heating pumps will be sold with a variable speed dial. This allows you to control the speed at which water is circulated around your home. If the pump is circulating water too fast, simply adjust the dial and slow the circulation. If the pump is circulating water too slowly, simply adjust the dial and speed up the circulation process.

How do I size a central heating pump in a large house?

If you have a much larger home (lucky you), then it does get a tad more complicated. This is because when sizing a central heating pump for a large house, a heating engineer would consider various factors to ensure effective heating distribution throughout the entire property.

These considerations are:

Number of Storeys

The number of storeys in the house impacts the vertical distance the pump must overcome to circulate water to all radiators. More storeys typically require a pump with higher head pressure capability to ensure consistent flow to the upper floors.

Total Floor Area

Larger houses generally have a greater heat demand due to the increased floor area. Calculating the total heat loss of the property helps determine the pump's flow rate requirements.

Number and Size of Radiators

Large houses may have numerous radiators or heating zones to distribute heat evenly. The total heat output and flow rate required to supply all radiators adequately must be considered when sizing the pump.

Unusually Long Pipe Runs

Long pipe runs increase friction losses and resistance within the system, requiring a pump with higher head pressure capability to maintain sufficient flow rates throughout the house.

Complex Piping Configurations

Houses with complex piping configurations, such as multiple branches may require a pump with variable speed control or multiple pump units to optimise flow rates in different sections of the system.

Boiler Capacity and Efficiency

The boiler's capacity and efficiency must match the heating demands of the large house. A properly sized pump ensures the whole of the building will get the benefits of the heating system.

As a general guideline, houses with more than 5 bedrooms or extensive floor areas may benefit from a more in-depth assessment of their heating requirements. While basic calculations can provide a starting point for pump sizing, larger properties often have more complex heating needs that may not be adequately addressed by a simple rule-of-thumb. 

Consulting with a qualified heating engineer or conducting a detailed heat loss calculation can ensure that the central heating pump is sized appropriately for the specific demands of the property.

Heat loss calculation

An important step in sizing a central heating pump is to work out the overall heat the building loses due to different factors, whether environmental or infrastructurally. 

Note that this is not essential for most houses.

This calculation should consider factors such as:

Heat Loss Through Windows and Doors

Windows and doors are areas of the building that often contribute significantly to heat loss. Heat loss through these openings is calculated based on their area, U-value, and any additional factors such as air leakage.

Ventilation

Heat loss through ventilation is typically estimated based on the volume of air exchange per hour and the temperature difference between indoor and outdoor air.

Insulation Levels

Insulation levels significantly impact heat loss. Walls, roofs, and floors with higher insulation levels lose less heat. Adjustments are made in the calculations to reflect the insulating properties of the building materials.

The Size of the Building

The surface areas of all walls, windows, doors, ceilings, and floors in the building will also contribute to heat loss. Each surface area is multiplied by a corresponding U-value, which represents the thermal conductivity of the material. This accounts for the rate at which heat flows through each surface.

Climate

Colder climates result in higher temperature differentials between indoor and outdoor environments, leading to increased heat loss. The greater the temperature difference, the higher the rate of heat loss.

The calculated heat loss value is then used to size heating equipment such as boilers, radiators, and central heating pumps. Properly sizing these ensures that the heating system can provide sufficient heat to the whole building.

Free Advice

If you’re struggling for advice, ring our dedicated pump experts for free advice on 0800 112 3134 or 0333 577 3134.

We’re open Monday to Friday 07:00 - 17:30 and Saturday 08:30 - 12:30.