A combi boiler, short for combination boiler, is a compact and efficient heating system that provides both central heating and domestic hot water on demand. One of the common questions homeowners have is whether a combi boiler can handle the simultaneous demand of running two showers. The answer is yes, but it depends on several critical factors that must be carefully considered.
Water Pressure and Flow Rate
The primary requirement for running two showers with a combi boiler is sufficient water pressure and flow rate. Combi boilers are designed to provide a specific flow rate, typically measured in liters per minute (l/min). For two showers to function effectively, the combi boiler must be able to deliver a combined flow rate of at least 15-16 l/min.
To achieve this, the combi boiler must have a high-performance pump that can generate the necessary water pressure. Factors such as the pipe size, length, and configuration of the plumbing system can also impact the available flow rate. Homeowners should consult with a professional installer to ensure the combi boiler and plumbing system are properly sized and configured to meet the simultaneous demand of two showers.
Boiler Capacity
The capacity of the combi boiler is another crucial factor in determining its ability to run two showers simultaneously. Larger, high-capacity combi boilers are better equipped to handle the increased hot water demand.
For example, the Worcester Bosch 42 CDi and the Vaillant Eco Tec 838 Plus are both high-capacity combi boilers that can produce up to 15.9 l/min of hot water, which is sufficient for two showers. These models have a higher heat output, typically ranging from 30 to 40 kW, allowing them to meet the simultaneous demand more effectively.
It’s important to note that the boiler capacity should be selected based on the specific requirements of the household, including the number of bathrooms, the size of the property, and the expected hot water usage patterns.
Shower Type
The type of showers installed in the home can also impact the performance of the combi boiler when running two showers simultaneously. Thermostatic mixer showers are generally more efficient and compatible with combi boilers compared to other shower types.
Thermostatic mixer showers have a built-in temperature control mechanism that maintains a consistent water temperature, even when the water pressure or flow rate fluctuates. This helps to ensure a comfortable and consistent showering experience, even when both showers are in use.
In contrast, non-thermostatic showers may experience temperature variations or reduced water pressure when the combi boiler is trying to meet the simultaneous demand of two showers. Homeowners should consider upgrading to thermostatic mixer showers to optimize the performance of their combi boiler.
Incoming Water Temperature
The temperature of the incoming water supply can also play a role in the combi boiler’s ability to run two showers simultaneously. During the summer months, when the incoming water temperature is typically warmer, the combi boiler can more easily meet the hot water demand of two showers.
In colder months, when the incoming water temperature is lower, the combi boiler may struggle to heat the water to the desired temperature, especially if the hot water demand is high. This can result in reduced water pressure or temperature fluctuations in the showers.
To mitigate this issue, homeowners can consider installing a combi boiler with a higher heat output or a larger hot water storage tank. This can help the boiler maintain the necessary water temperature and flow rate, even during periods of high hot water demand.
System Design
The overall design and configuration of the plumbing system can also impact the combi boiler’s ability to run two showers simultaneously. Factors such as the size and layout of the pipes, the location of the boiler, and the placement of the showers can all play a role.
Properly sized pipes, with a minimum diameter of 22mm, are essential to ensure adequate water flow and pressure. The configuration of the plumbing system should also be designed to minimize pressure drops and ensure an even distribution of hot water to both showers.
Additionally, the location of the combi boiler within the home can affect its performance. Ideally, the boiler should be positioned as close as possible to the showers to minimize the distance the hot water needs to travel, reducing the risk of temperature loss or pressure drops.
By working with a professional installer, homeowners can ensure that the combi boiler and plumbing system are designed and configured to meet the specific requirements of running two showers simultaneously.
Conclusion
In summary, a combi boiler can indeed run two showers simultaneously, but it requires careful consideration of several key factors, including water pressure and flow rate, boiler capacity, shower type, incoming water temperature, and overall system design. By understanding these critical elements and working with a qualified installer, homeowners can ensure their combi boiler is capable of providing a comfortable and consistent showering experience, even when both showers are in use.
References:
- https://www.mumsnet.com/talk/property/2075145-Is-there-a-combi-boiler-that-can-give-water-for-two-showers-at-once
- https://www.mybuilder.com/questions/v/52596/combi-boiler-for-two-showers
- https://www.diynot.com/diy/threads/the-final-say-combi-boilers-and-two-showers.476115/
- https://forums.moneysavingexpert.com/discussion/6088190/will-i-be-able-to-run-two-showers-at-same-time-off-combi-in-new-house
- https://community.screwfix.com/threads/can-a-second-shower-run-off-a-combi-boiler.71362/