Hot water hot when heating is on is this righ

Good morning 

When my heating in on I have noticed  the hot was is HOT but is is not on on the control  unit.

Is this right.???

Thanks

Do you have the Truma or Whale system?

Not sure exactly what you mean - it would be helpful if you corrected your messages before posting.

Hello. It is the truma system. Heating on gas hot water off. Water is hot . Not sure if this is correct???

Regards

Yes, this is correct. Means if leave heating on overnight then have nice hot water ready for morning ablutions.

My (vague) understanding is that the water jacket around the burner contains your domestic hot water, and the heat is transferred through this to the air heat exchanger for heating. Thus there will usually be about ten litres of hot water in the water side of the heat exchanger if the heating is turned on, but if the air thermostat is not triggering a demand on the heating your hot water supply will just be that ten litres. If hot water is turned on at the control then the boiler will fire up to provide additional hot water as soon as it senses the need. If turned off it won’t.

Everything said is correct.  I would just add that if you want hot water its still best to turn the hot water on.  If not the water will heat up more slowly because a) when the central heating fan is running most of the Truma's heat will be used to heat up the van rather than the water and b) as Bargee has said when the van reaches the temperature set on the Truma's control panel, the heater will cut out so no heat will go into the water.  If the central heating is on and hot water is needed in a hurry, its best to use the 'boost' function which temporarily gives priority to heating the water over heating the van.