With regard to combination boilers / gas water heaters, what is meant by fully-modulating and step-modulating?
Answer – The heat output from a fully-modulating combination boiler / gas water heater can be varied from full off to full on, giving you fine control between the minimum and maximum temperatures it produces. This is performed by the boiler’s gas control valve varying the amount of gas it allows through in direct relation to the water outlet flow. Therefore a mixer shower fed from a fully-modulating combination boiler / gas water heater will allow total control over the blend temperature the shower delivers from full cold to full hot.
