The knowledge

Condensing boilers are energy efficient but you can push efficiency on Priority Domestic Hot Water (PDHW) to the max using X-Plan. Ross McKenzie discovered X-Plan when he became an engineer for Intergas. He’s now an X-Plan addict. It helps that he’s an eco-warrior who built own house with energy efficiency at its heart. The result? An annual energy bill of £400 year. If he rates X-Plan, then it’s a plan worth considering.

Why do we need X-Plan?
You only need X-Plan if you want an effective PDHW system. It’s a simple way of setting up the Intergas boiler (less wiring complexity and far greater energy efficiency compared to S- and Y-Plan) to provide two distinct flow temperatures, one for space heating, the other for water heating, without one impacting on the other. But this is just the start of a raft of benefits. During a hot water demand from the cylinder NTC sensor, for example, the boiler would ramp up to full load, as set up in the parameters to match the cylinder coil input size, and the pre-set target temperature of, say, 70⁰C. This heats the water in the fastest possible time; in fact, the recovery is so rapid that a 175-litre unvented cylinder with a 30kW-rated coil* can recover the cylinder (from 10⁰-60⁰C) in around 12 minutes. With recovery that fast, you can opt for a smaller cylinder, saving space and energy. Like a combi boiler, the heating is not operational during hot water demand to help facilitate the rapid recovery of the cylinder. For maximum efficiency, the space heating should be controlled through an OpenTherm-compliant device and, when the boiler switches from water heating to space heating, no excess heat can enter the space heating and room temperatures can’t overshoot. Standard TPI controls can also be used via the 230V switching facility incorporated within the PCB.

Upgrade the system
If the boiler is being replaced and the system upgraded from S- to X-Plan, then it’s a very simple wiring exercise, but the heating zone must be replaced with a 22mm ‘normally open’ type valve. Using X-Plan you can upgrade the Intergas Xtreme, Xclusive, Eco RF and HRE system boilers (see Intergas website for wiring diagrams for each boiler: click on ‘product’, then on the boiler, followed by the model and finally click on ‘documentation’), and customers benefit from the immediate convenience of superfast hot water inexpensively. But the benefits don’t end with X-Plan. Condensing boilers were introduced here in 2005 to help improve energy efficiency, reduce emissions and save the customer money, but 15 years on many boilers don’t always achieve condensing mode for long periods due to poorly designed heat exchangers or heating systems.

Click here for X-Plan Wiring Diagram

Bithermic matters
The Intergas boiler is different because its bithermic heat exchanger has a very large surface area and increased waterways, specifically designed to cool the flue gas temperatures down, prior to exiting the boiler, therefore using the latent heat within them to reduce the energy used in recovering the cylinder or warming the heating system. When an Intergas appliance is used as a combination boiler it can condense virtually all the time it is producing domestic hot water… this is unique within the industry.

*Cylinder capacity and coil input rating should be designed to suit the system and customer’s requirements; the 175/30 used in the Intergas training room in Kidderminster should not be used as the normal or standard option.