Winter usage

Well, the dump valve isn't on the pump, as such, it's on the inlet to the hot water tank. It opens below circa 3c and dumps the water to prevent the tank from freezing damage.
As it's right beside the tank (Not familiar with Nuevo but similar on Warwick I think) then it's always warm in that area, certainly much more than 3c as its also inside the van.

If setting off, fill the water tank, close the dump valve and run the hot taps until they stop gurgling. Then put the water heater on and leave it on until its thermostat switches it off, you may hear the gas solenoid valve closing.

Then, for at least that day if nothing else is done it'll be warm enough in there to keep it closed.

The valve opens when its temp drops to 3 degrees and can't be closed until it has risen to 7 degrees.  If at the start of a winter trip you are on an EHU and the valve is exceptionally cold e.g. minus 7 as it was at the start of our trip last month, you may want to use a fan heater or hairdryer to warm up the valve more quickly.  Once the valve is closed the Truma Combi should keep it closed providing the heating is left on with a minimum temp of say 10 to 14 degrees.  It's always a good idea to turn the water pump off on the CP when leaving the van should the heating fail or a leak develop.

Just to be clear, the dump valve will open if the temp falls below the expected value INSIDE the van. If will not open just because there's low temperatures outside.

Weegie wrote:Just to be clear, the dump valve will open if the temp falls below the expected value INSIDE the van. If will not open just because there's low temperatures outside.

Being utterly pedantic it is neither the inside nor outside temp that matters.  It is the temp of the valve that matters.  Last month when we arrived on pitch the inside temp was good but it had been so cold that the valve was still very cold and took some warming with a fan heater.  Normally its not as bad as this and the valve quickly warms up when the Truma Combi is turned on.