Frost Control safety/drain valve

Hi. It has not reached zero here in Kent yet but the boiler safety/drain valve has opened and drained the boiler. It must have been around 3ºC. Now I would not want this to happen while away in the motorhome. I see that Truma have a heating element (part no. 70070-01). It looks easy to fit. Would it prevent an early drain of the boiler before the temperature goes below freezing. Has anyone had this heating element fitted and found it useful?
Bernie.

Annoying as it is this is really important. You don't want the boiler to freeze as the replacement cost is really high.

My advice is to leave the heating running on low if your using the vehicle and it will keep the temperature above the drop temperature. If your not using the van then let the dump valve do its job.

If you want to ensure the water stays above 3c then tank blankets are very good. However the dump valve in a cold van might still empty the boiler.

I know this is quite an old thread, but I was under the impression that the valve opened at 3˚C, not 0˚.
We keep the heating on in our van ( on the driveway) set at about 10˚C when we are not using it, the valve stays nice and warm and hasn't opened on us yet. 
As far as I know, the heater valve just allows you to fill the water tank and boiler in colder temperatures so you can close the dump valve and it doesn't keep operating.

Allan

Allan, your spot on with your description of the valve heater.

The 70070-01 Frost Control Heating Element fits into the Frost Control Valve and there are two connections to the Combi Boiler. When the boiler is on it heats up the Frost Control Valve preventing it from dumping the boiler water or enabling water to fill the boiler in cold weather. The element is thermostatically controlled so only operates at low temperatures.
 
Bernie

Is this dump valve fitted to all Truma Ultrastore heaters or only Combi heaters?  I ask because surely it needs a power supply to a thermostat for it to operate and although I have what looks like the dump valve (I lift the lever to empty the system) I can't see any wiring going to it.

Not sure if it's fitted to all but it is an automatic device that doesn't need an electrical connection. You can fit a heater to it that is connected to the combo electrics and works as above
Allan

Thanks Pete.

Thanks Bob for confirming that.

There seems to be some confusion about these dump valves. My old Hymer was fitted with what was effectively a drain tap with a yellow lift up lever to open it. If the lever was down and parallel to the flow pipes the tap was closed and vertical meant it was open.
My Lancashire is fitted with an automatic dump valve which works by temperature and has no electrical connections. It is roughly D shaped and about 3 inches high (from memory) and has a turning tap on top and a button which can pop out either by turning the lever on top or automatically if the temperature drops to 3C. It has three water connections, the flow past the rear of it and a concealed drain pipe below it and through the floor. At 3C it trips, the button pops out and the boiler will drain, together with any other water in your system as the pump tries to refill the boiler. To close the valve you have to manually push the button in again - but it will not stay in until the temperature rises above 7C. (I guess that these temperatures are approximate and subject to a manufacturing tolerance). For winterising the button can be tripped manually by turning the lever on top.
Truma are aware that it may be highly inconveneint to have to wait until the boiler compartment or more precisely the area where the valve is fitted rises to 7C before the boiler can be refilled and therefore supply, as an optional accessory, a small heater which can be inserted into the dump valve and will keep the valve at about 10C provided that the boiler is switched on and thus prevent the system draining while it is in operation. That is why some folk have wires to their valve and others do not.
This is all covered in the instructions for the Combi 4E/Combi 6E boilers. I do not think the same valve is normally fitted to the separate boilers that often accompanied the convector type heaters though, in principle, there is no reason why they should not be so fitted.