As your machine only takes water through the one line, the water taken in will either always be cold (when cold is connected) or hot (if hot connected). As already pointed out if connected only to hot then every intake will be hot, including all the rinses and any fabric conditioner. Also, the intake will be at the temperature of the incoming water, i.e. say 60 or more, which may ruin certain articles. A way out would be to arrange a twin connection with a manual switchover. Washes usually only involve heating (or taking in hot) on the very first fill. If you have a switchover then you would set it to hot intake immediately on starting the cycle (load being suitable) and once it is full just switch over to cold and let the machine complete the cycle automatically.