Stuart Posted October 31, 2010 Share Posted October 31, 2010 Not strictly on topic but what would be the implications of having a heated waste water tank without water? There would be a time after draining when the heater could be on in an empty tank. Is there some kind of float switch in the kit? Stuart Link to comment Share on other sites More sharing options...
Derek Uzzell Posted November 1, 2010 Share Posted November 1, 2010 bakersboy - 2010-10-31 10:47 PM Not strictly on topic but what would be the implications of having a heated waste water tank without water? There would be a time after draining when the heater could be on in an empty tank. Is there some kind of float switch in the kit? Stuart My Hobby's tank-heating system does not prevent operation if there's inadequate water within the tank to cover the heating-elements. I haven't got a Hobby Owner's Manual for my motorhome, so the only information I have about its tank heaters comes from the documentation relating to its CBE-made electrical system. The latter just describes where on the control-panel the heater operating-button is, that the heaters can only work when the vehicle's motor is running or the motorhome is on 230V EHU, and that the 12V supply to the heaters is 10A-fused. As you point out, an empty-tank/heaters-running scenario is completely predictable (and probably commonplace), so I guess the elements are designed to tolerate being run 'dry' and have insufficient output to damage the tank itself. Link to comment Share on other sites More sharing options...
Brian Kirby Posted November 1, 2010 Share Posted November 1, 2010 Re the waste tank heater, I have English manuals from Both Hobby and CBE, and neither gives any special instructions for when to operate/not operate this item. Operation is, as Derek says, automated, to the extent the heater will only work when a 12V supply is available via the mains power pack/charger, or the alternator. The heater must, logically, be "safe" to use with an empty tank since the only indication of tank contents is "full", so there is no opportunity to switch it on when a specified waste level is reached in the tank. I think it should just be switched on when temperatures are liable to freeze the contents. Interestingly, the general instructions for winter use recommend adding salt or an anti-freeze to the waste tank, storing waste water outside the vehicle, and leaving the drain cock on the waste water tank open. This seems to suggest that the heater is only for use when it has not been possible to empty the waste tank, perhaps more especially if having to drive in sub-zero temperatures with grey waste aboard. Logical enough, if poorly explained.Rule 1. When using the van in freezing conditions, open the grey waste tank drain cock, and discharge the grey waste to a bucket.Rule 2. Empty said bucket regularly, and especially before it has a chance to freeze.Rule 3. In conditions where it is not possible to dispose of grey waste in this way, if there is a danger of the tank contents freezing, use the waste tank heater to keep the contents liquid, and seek to dispose of its contents normally as soon as is practicable. Link to comment Share on other sites More sharing options...
flicka Posted November 1, 2010 Author Share Posted November 1, 2010 An interesting point, I had not considered. The Nordelettronica"Control Unit on our Autocruise, has provision for the Water Tank Heater addition. I had assumed that:- a) It would be wired so it can only be operated on 12v with the Engine running or on mains hook-up. b) it would be wired via the Tank Gauges, so it would only operate when the Gauge shows Water is in the Tanks. Time for an e-mail to Autocruise for clarification, me thinks. Will post when I have received their response. Link to comment Share on other sites More sharing options...
flicka Posted November 2, 2010 Author Share Posted November 2, 2010 Received a fast response from Swift technical support. a) The tank heaters will also function on 12V from the leisure battery. b) Yes they will only operate when the gauge shows water in the tanks. c) The winter pack includes 2 x 30W elements that are thermostatically controlled therefore they will only function when required to. The standard battery is sufficient for the winter pack to operate, but if running from the leisure battery alone, please be aware that it will add to the drain on this battery. Link to comment Share on other sites More sharing options...
Brian Kirby Posted November 2, 2010 Share Posted November 2, 2010 That's good, John. I think I would be inclined to insert a relay/relays into the feed to the tank heaters, so that they can only operate if mains/alternator power is available. A prolonged cold spell when off hook-up could result in a constant 5A (2x30/12=5) load from both elements which, in parallel with normal winter use, would soon have your battery struggling. Link to comment Share on other sites More sharing options...
flicka Posted November 2, 2010 Author Share Posted November 2, 2010 I agree Brian, I will ask the Dealer to replicate the method used for running the Fridge on 12 v only when Engine is running. But we anticipate our Winter use will not include Sites without hook-up. So would only be at risk when parking for short periods away from sites during the day & I am thinking the residual warmth will cover those periods. Link to comment Share on other sites More sharing options...
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