Rear Heating Aux Pump

[The Flute]

So my MH has a small fan/heater matrix fed off the engine to heat the rear when traveling. So I've just fitted a small electric water pump to it. So now if the fans running the water pump also runs. It means when I park up and are getting set up I can leave it running and keep the back warm without the engine running. Would think it would be good for at least 1hours heat before it starts to chill off.