Condensing boilers are growing in popularity

Customer Services and Marketing Manager for Saniflo UK, Ann Boardman, explains what’s so good about condensing boilers and the problem that they solve

Condensing boilers are highly efficient boilers that have much lower fuel and running costs than conventional boilers. Take up of them was slow initially when they were first introduced in the early 1980s due to a number of misconceptions and a general lack of awareness. Since then the technology has improved and there has been an increase in the number of trained installers.

Condensing boilers offer tangible benefits by reducing carbon dioxide emissions thereby helping to combat global warming and improving household efficiency thus reducing fuel bills.

However, one of the challenges of working with domestic condensing boilers can be the need to dispose of acidic condensate safely. This condensate is formed when steam produced by the boiler is converted back to water droplets on cooling. In most installations it can be safely removed through the normal gravity drain in conjunction with the boiler manufacturer’s instructions. However, if a boiler has to be installed on internal walls or within a basement, for example, the use of a boiler condensate tank pump or soak away can often be the only solution for the installer.

The principle behind condensate pumps is a simple and proven one, ensuring reliable and effective operation. Working in the opposite way to a water turbine (whereby energy from flowing water is transferred to a propeller), a condensate pump transfers energy from a powerful motor to the condensate water via a rotating impeller.

This action creates the pressure needed to pump condensate water up and away through an unobtrusive, thin clear tube (provided with the pump). Condensate water is then disposed of in a soil stack or outside drainage point.

Condensate pumps usually run intermittently through the use of a small tank in which the condensate water accumulates. When it reaches a preset level, a float is raised to energise the pump. This then runs until the level of liquid in the tank is suitably lowered. Intermittent – rather than constant – operation ensures minimal energy usage to keep your costs as low as possible.

Go for a small pump that may be used to pump condensate from condensing boilers, HVAC system, water heater systems, etc. Choose one that will pump condensate water up to 4.5metres in height and/or 50 metres away from a soil stack. Look inside the pump for a float mechanism, which starts and stops the unit, and the motor, which should drive the pump.

Check that when the water enters the pump, it activates the float mechanism, which in turn should start the motor. Check the motor is sealed for life in an oil filled enclosure with a spindle/shaft that drives the impeller so the moving parts are kept to an absolute minimum. Water should enter the chamber and be pumped away into the sanitary sewer.

The unit should pump the effluent upward to 4.5metres and/or 50 metres horizontally (with gravity fall). Once the water is discharged and the water level in the container goes down, the float should deactivate the unit until water enters it again.

A normal operating cycle can be as short as 2 – 10 seconds depending upon the discharge pipe run configuration; power consumption is therefore minimal.

The discharge connection on the top of the unit must come equipped with a non-return valve, which prevents back flow into the unit.

It is also highly recommended for the condensate pump to be connected to a Ground Fault Interrupter (GFI) circuit.

Go for a small, powerful pumping unit that can be floor or wall mounted. It should come with an auxiliary external overflow switch that will shut down the appliance or alert the consumer in the event of overflow. It should also include all necessary hardware for ease of installation; 6m of vinyl tubing, inlet adapter, discharge adapter.

Another good option is to fit an acid neutraliser and pump specifically designed for the disposal of acidic condensate from gas boilers.

Look for a pump that incorporates a tray with a neutralising agent and a low level set point. These are designed so that as the boiler starts, the condensate runs into the tray. At a fixed higher set level a float switch can be set to activate the pump and the neutralised condensate is pumped out through the non-return valve. Choose one that is environmentally friendly, small and powerful with a quiet and light design that can be floor or wall mounted. They’re best with a pumping height of up to 4.5m and a maximum flow rate of 342litres/hour vertically at a mean temperature of 35 degrees C.

A great example of where such pumps can provide the perfect heating solution is in an older property in a rural area where the drainage isn’t suitable to allow for gravity drainage and where the waste water discharges to a septic tank.

Guidelines for the disposal of acidic concentrate recommend it be neutralised prior to running into the foul drainage system to the tank (because it is detrimental to the friendly bacteria that break down effluent).

In such a case, the safest and simplest option is to install a condensing pump with built in acid neutralizing chamber – overcoming both installation problems with one easy-to-install product.

Many industry professionals find such pumps to be the best solution for pumping away neutralised acidic condensate when the alternative would be several runs of unsightly pipework or an external lime chipping soakaway. They find the compact units are incredibly easy to install and have been well proven in many domestic household jobs.

And remember, a condensing boiler will always have a better operating efficiency than a non-condensing one, due to its larger and more efficient heat exchanger. The benefits of condensing boilers are therefore quite clear.