JamesFrance Posted July 22, 2011 Share Posted July 22, 2011 I have a Combi 4 fed by a submersible pump. The instructions say that it can be used for hot air without water and as we rarely make use of water heating I decided to drain it. I followed the instructions to turn off the pump, open the hot taps, turn the valve on top of the thermostatic drain unit so that the button comes out. I assumed that this would just drain the heater, but it has also drained the cold water tank. I would have thought that turning the valve at the top so that it was left at 90° to the water pipes would block the connection between the tank and the heater, so that the cold water system would work as normal. What am I doing wrong? :$ Link to comment Share on other sites More sharing options...
Brian Kirby Posted July 22, 2011 Share Posted July 22, 2011 Nothing. I think the reason they say you can use the heater with no water present, is to cope with cold conditions when the dump valve has opened and done what you have just done - and dumped all your water. Then, if you could not operate the heater with no water in it, you could not get the van warm enough to reset the valve, and so refill with water - and would be getting pretty cold yourself! So, I don't think you are doing anything wrong - you just have your telescope the wrong way round for viewing Truma's logic! :-D Link to comment Share on other sites More sharing options...
JamesFrance Posted July 22, 2011 Author Share Posted July 22, 2011 Thanks Brian, so I am just going to have to keep heating water this winter on site when we never use it and keep the heater on all night in case of a sudden frost (Spain). We had an Atwood combi type heater years ago in a Herald Templar and I didn't think much of the arrangement then. I suppose everything has to become more complicated or designers would be out of a job, but a simple silent gas heater left on all night on a low setting would suit us much better. Link to comment Share on other sites More sharing options...
tugga Posted July 22, 2011 Share Posted July 22, 2011 JamesFrance - 2011-07-22 3:29 PM I suppose everything has to become more complicated or designers would be out of a job, but a simple silent gas heater left on all night on a low setting would suit us much better. I so agree with you on the silent gas heater for nightime James. The fan coming on and off keeps waking me up so we tend to turn the heating off and then we get very cold. If we are on EHU its ok as we put a convector heater on low overnight to keep the chill away but if we are not on EHU we do tend to stay in bed as neither of us wants to get up first to put the heating on! No good for extreme weather though! I wish these designers would use the motorhomes that they design and then they would see all the flaws. Link to comment Share on other sites More sharing options...
colin Posted July 22, 2011 Share Posted July 22, 2011 Slightly puzzled by your post. I'm sure we have Combi4 (at wrong house to check) it has 4 settings two for water heating only, one for space heating and one combined water/space, IIRC when using space heating there may be some heat soak into water but thats all. I have a thoery, and this is confirmed by use of our home heating, the heating of the hot water, as long as it's inside insulated area forms a heat store, so this is not nessaarly lost heat. If the vans a keeper, then I would consider moving heater to under dinette seat, it's something we've considered, and I'm guessing as water tank is now at rear on Twin the under seat area is storage? Link to comment Share on other sites More sharing options...
Brian Kirby Posted July 22, 2011 Share Posted July 22, 2011 JamesFrance - 2011-07-22 3:29 PM Thanks Brian, so I am just going to have to keep heating water this winter on site when we never use it and keep the heater on all night in case of a sudden frost (Spain). We had an Atwood combi type heater years ago in a Herald Templar and I didn't think much of the arrangement then. I suppose everything has to become more complicated or designers would be out of a job, but a simple silent gas heater left on all night on a low setting would suit us much better. I think the simple, most practical, answer to the first question is yes. If you run the Combi in heating mode, it does also heat the water, but not as a priority. The advantage, is that once those 12 litre of water are hot, they act as a hot water bottle for the van, because any heat that is lost from the water, is lost into the van. Since a lot of heaters are sited under the bed, this helps keep the bed warm. To the second question, the risk of the dump valve opening can be eliminated via the traditional method of putting a clothes peg on it. Providing the van is reasonably insulated, and is occupied, the risk of the water in the Combi freezing (the risk the dump valve is intended to eliminate) is, I think, quite small. I know the insulation around the Combi is not that great but, for it to freeze, the inside of the van first has to dip below zero, and then stay there long enough to freeze the Combi's 12 litres of water through its insulation. Not quite impossible, I guess, but definitely freak conditions were it to happen. Inland, across the Meseta, you may get temperatures low enough cause the Combi dump valve to open at night. Once down to the coast, however, with the van occupied, I'd think this would be fairly unusual, and it would generally be safe to leave the heater off with a peg on the valve. As ever, weather is weather, and freak conditions can arise anywhere, so keeping an eye on forecasts, and monitoring how the van performs, will give the best protection. The greater danger of freezing may well be while en-route to Spain, if you encounter severe low temperatures while travelling, or very cold winds while static. I guess your waste tank is external, and your fresh water tank may be. If so, with wind-chill, either of those would be more prone to freeze than the Combi itself. If the van heating is on while travelling (likely! :-))it should maintain enough heat even where the Combi is located, to keep it out of trouble. If the fresh tank is inboard, it should be safe to travel with the tank, and the Combi, full. If the fresh tank is underslung, you may have to drain off the lot before you leave each day, and then fire up the Combi on arrival, possibly relying on all year sites with heated facilities for your daily washing etc needs. What you want to avoid at all costs is a frozen fresh water, or grey water, tank - because they could take days to thaw out again at winter temperatures. In the end, you'll just have to vary your strategy to suit the weather as you find it, and the nature of your van. Link to comment Share on other sites More sharing options...
crinklystarfish Posted July 22, 2011 Share Posted July 22, 2011 That's right, as long as the controls are just set to space heating then the water that's heated is done so incidentally. Having the 'warm' water sitting happily in the boiler doesn't really hurt anything and indeed can provide background heat over a long period. We made the most of the 'feature' to air off clothing. If the dump valve is in the same locker as the heater, because of the heat-store effect, it would probably not dump anyway even if the heater were turned off overnight to avoid noise. I figure it would be possible to get round that dump valve issue anyway with a bit of thought. It can't be that hard to fool it.[Edit] Mr K beat me so the above looks out of context. I always shunned the 'clothes-peg' solution and figure there'll be a way to rig the valve to operate electrically via a manual switch rather than the thermostat.That said, if the boilers full of warm water at bedtime and as long as the dump valve is close to the truma, then it shouldn't be an issue with the heating turned off overnight only. Link to comment Share on other sites More sharing options...
JamesFrance Posted July 22, 2011 Author Share Posted July 22, 2011 The main reason I wanted to empty the heater was that there is no point in carrying the weight of 12 litres of water if they are not being used, so I wanted to empty the heater without upsetting the cold water system. I don't think that a clothes peg could be used to keep the current valve closed, as it is a button which pops out when the temperature is 3°C. Maybe it would be possible to block it in some other way. In my van, the combi is placed under one end of the bed next to the gas locker, so it will come in useful in the winter as I am using butane viseo 10kg cylinders which are not available in propane. When in Spain one of these will be replaced by an Elf Cepsa alloy cylinder. Living where I do I am not concerned by the weather conditions on the way there. Link to comment Share on other sites More sharing options...
Derek Uzzell Posted July 22, 2011 Share Posted July 22, 2011 JamesFrance: If a motorhome is fitted with a Truma combination air/water heater and the water system includes a submerged water-pump (ie. the pump is within the fresh-water tank itself) rather than a diaphragm-type pressure-sensitive pump, then there's every chance that, when the Truma safety/drain-valve opens, water will commence siphoning from the main water tank. It's possible that, with some water systems, the siphoning process will stop when the heater is empty, but received wisdom seems to be that it will continue until the main water tank is completely drained. As there seems to be no realistic solution to prevent siphoning happening (other than swapping the water-pump for a diaphragm type), it's something worth being aware of. Truma C-3402, C-4002, C-6002, C6002EH and the COMBI-4/COMBI-6 appliances can all be operated safely empty of water. This capability permits the appliance to provide blown-air heating when the motorhome's water system has ben drained down. But the safety/drain-valve (that you opened to drain the heater and that also caused your water tank to empty) does not isolate the heater from the motorhome's water system. If you wanted a system that allowed you to have cold water only, with the heater drained down, then you'd need to install an ON/OFF valve 'downstream' of the safety/drain-valve in the water hose that connects to the heater. If you refer to the first diagram on Page 15 of the followiing Truma instructions file, you'd insert the ON/OFF valve at the position marked "25". http://www.truma.com/downloadcenter/combi46_installation_fr.pdf I also had a Herald Templar with an Atwood Confort 3+ heater (that could also be run safely empty of water). The Atwood heater was replaced by a Truma C-3402 and I added an ON/OFF valve as I've described above, just in case I wanted to use air-heating with the water system drained down. In my case, the valve broke in half (I've never forgiven Whale for this) with the heater full of piping hot water and while I was eating my tea. My wife told me she'd never seen a human being move so fast when I spotted water beginning to flood out from beneath the under-wardrobe heater cupboard across the carpet. Link to comment Share on other sites More sharing options...
JamesFrance Posted July 22, 2011 Author Share Posted July 22, 2011 Thanks Derek, looking at the diagram it would maybe have been better to fit the On/Off valve upstream of the non return valve. I think I will probably decide to live with the arrangement as they designed it, now that I understand what is going on. I still find it strange that the valve at the top doesn't turn off the supply from the tank when it is at 90° to the pipe direction, as if the auto valve popped out with frost it would still allow the cold tank to drain if it stayed in the parallel position. Link to comment Share on other sites More sharing options...
Derek Uzzell Posted July 23, 2011 Share Posted July 23, 2011 JamesFrance - 2011-07-22 7:29 PM Thanks Derek, looking at the diagram it would maybe have been better to fit the On/Off valve upstream of the non return valve. I think I will probably decide to live with the arrangement as they designed it, now that I understand what is going on. I still find it strange that the valve at the top doesn't turn off the supply from the tank when it is at 90° to the pipe direction, as if the auto valve popped out with frost it would still allow the cold tank to drain if it stayed in the parallel position. If you are looking at the top-left schematic on Page 15 (ie. the diagram that relates to a water system with an immersion pump) then the only non-return valve I can see in the system is the one labelled "21". Athough the diagram shows a separate valve, the valve will usually be either integrated into the immersion pump or attached directly to it. With the water flowing from the water-pump towards the water-taps, "upstream of the non return valve" would (as far as I'm concerned) place the On/Off valve between the non-return valve and the water-pump (ie. 'downstream' of the water-pump), which would either be impracticable if the valve were integrated/attached to the water-pump, or (if there were room to fit the On/Off valve) would shut off the water supply completely when the On/Off valve was in the Off position. Listen to your Uncle Derek about this - for a cold-water-only system with the heater drained down, you'd need to install an ON/Off valve at position "25". On/Off valves are readily available for leisure-vehicle water systems. This is the current Whale version http://www.leisureshopdirect.com/caravan/water/product_21162/New_Whale_System_12_Shut_Off_Valve.aspx Various designs of On/Off valve appear in the "Eau" section of my French accessories catalogues, where they are described as "robinets d'arrêt". (Example on following link): http://www.loisirs-evasion.com/kent/robinet-d-arret-d-15mm-a-48913.html In principle, an On/Off valve should be simple enough to install in the hot-water feed-hose to a COMBI heater: in practice, major preparatory work (like removing the heater) might prove necessary to gain sufficient access to the feed-hose to carry out the installation. You might also be interested in the following French forum-thread, where someone describes installing two On/Off valves in the water system of a camping-car with a Truma combination air/water heater. Although the appliance is a Truma C-Series, rather than your COMBI, the thinking behind the modification is still valid. http://www.aidecampingcar.com/forumO/printview.php?t=32663&start=0&sid=3b16f2da761f00d204297d7ccc2f3480 Regarding your second paragraph, I don't understand your reference to "the valve at the top". I think you may be talking about the item marked "28" on the schematic (and referred to in the text on the right-hand side of Page 15 as "elbow fitting with integrated ventilating valve"). The purpose of the elbow-fitting assembly and its breather-hose is to allow air to enter the heater's water reservoir when the heater's safety/drain valve opens to protect the appliance in freezing weather conditions. Think about an inverted bottle of water with its neck placed beneath the surface of a bowl of water. As no air can enter the bottle it will not drain, and that would be the same for a COMBI heater if there were no ventilating valve. During 'user draining' a hot tap would be opened deliberately to allow air to enter the heater's water reservoir, but obviously that won't be the case when the safety/drain valve opens spontaneously to protect the heater from frost damage. The ventilation valve is designed to have two modes of operation. During normal heater usage (when the reservoir is full of water) the valve remains shut, preventing air from entering the water reservoir via the breather-hose and stopping water from entering the breather-hose from within the water reservoir. When the safety/drain valve opens to protect the appliance from freezing-up, the 'weight' of the water in the boiler 'sucks' the ventilation valve open permitting air to enter the boiler via the breather hose and allowing draining to commence. At no time should water flow from the boiler through the breather-hose in any quantity (though it's not uncommon to see the occasional air/water bubble passing through the breather-hose when the boiler is being filled with water). Link to comment Share on other sites More sharing options...
JamesFrance Posted July 23, 2011 Author Share Posted July 23, 2011 Hi Derek, My reference to fitting the On/Off switch before the non return valve was only because you mentioned yours breaking and flooding the floor with hot water. I was thinking that it would be better to lose the tank contents under the van rather than the hot water inside, however such a failure must be a rarity anyway. I see that the French forum poster has fitted another On/Off valve between the boiler and the taps and I had wondered about that as we don't have seperate hot and cold but the rotating lever type. As I said I will live with what they have provided and carry the extra water, I am unlikely to be overloaded. What I was trying to say in the second paragraph related to item 30 which they call a rotary switch. Not having seen an exploded view of the Frost Control I had imagined that it would cut off the water supply when it rotated to release the button, but it seems that it is not designed to do that. Presumably the boiler has a pressure relief valve with a pipe which drips outside the van. I cannot see mine as it is hidden in a cupboard, but the more complex system I have on my boat has had a failure of that component, allowing the bilge to fill with fresh water. I am still searching the internet for a spare for that one. Thanks again, Link to comment Share on other sites More sharing options...
Brian Kirby Posted July 23, 2011 Share Posted July 23, 2011 I think you are wise, James. 12 litres of water is only 12kg, and it is a lot of work and effort for so small a gain. If you are that close to your MAM you are into dodgy territory, where the differences in accuracy between one weighbridge and another is likely to yield greater discrepancies. On an assumed 3,300kg MAM, 12kg is only 0.4% of MAM. 12kg is a very fine limit for a device intended to weigh up to 40 tonnes. More seriously, I accept it is the weight of 10 bottles of wine - but you could always empty the whole water system when coming home, which would allow for far more bottles than just the Truma! :-D Link to comment Share on other sites More sharing options...
Derek Uzzell Posted July 24, 2011 Share Posted July 24, 2011 JamesFrance - 2011-07-23 10:19 AM ...I see that the French forum poster has fitted another On/Off valve between the boiler and the taps and I had wondered about that as we don't have seperate hot and cold but the rotating lever type.. The French forum member has put a shut-off valve in the RED hose providing water to the heater. This permits the heater to be isolated from the remainder of the motorhome's water system and allows operation of a drained-down heater (ie. blown-air operation) while keeping cold-water outlets usable. This would be what you were looking for - heater empty of water, but everything else working (except for hot water, of course). The other shut-off valve, in the BLUE hose, is 'upstream' of the safety/drain valve (ie. it is in the hose leading from the fresh-water tank to the safety/drain valve). Turning that shut-off valve to the Off position would allow the heater to be drained of water via the safety/drain valve but prevent any likelihood of the fresh-water tank being emptied siphonically (which, as you are aware, can happen when the water system includes an immersed water-pump). After the heater had been drained, the safety/drain valve and the shut-off valve in the RED hose would be closed and the shut-off valve in the BLUE hose would be opened. If one always started with a completely drained-down system (ie. with the fresh-water tank empty) or the water-pump was the diaphragm type, then the shut-off valve in the BLUE hose would be an unnecessary luxury. However, with a water system like your Adria's (with an immersed water-pump), if a shut-off valve were to be installed in the 'RED' hose, it would be "astuce" to also put a shut-off valve in the 'BLUE' hose. The Frost-Control valve, besides reacting to low temperatures, is also designed to act as a pressure-relief valve. Link to comment Share on other sites More sharing options...
Guest JudgeMental Posted September 21, 2011 Share Posted September 21, 2011 James alerted me to this thread a few weeks ago as I asked him where the drain/frost valve was for the Adria going away for a few nights (taking son to Uni/visiting friends) so i put some water in tank.... when I put the pump on water started coming out under the Truma heater. Now, which ever way I turn it (it does not lift like older ones) water continues to flow. (water tank is less then half full) I have attached a pic of valve and can any one tell me is this the right position or not? but like I said whatever position water keeps flowing *-) Link to comment Share on other sites More sharing options...
Guest JudgeMental Posted September 21, 2011 Share Posted September 21, 2011 James alerted me to this thread a few weeks ago as I asked him where the drain/frost valve was for the Adria going away for a few nights (taking son to Uni/visiting friends) so i put some water in tank.... when I put the pump on water started coming out under the Truma heater. Now, which ever way I turn it (it does not lift like older ones) water continues to flow. (water tank is less then half full) I have attached a pic of valve and can any one tell me is this the right position or not? but like I said whatever position water keeps flowing *-) this error 500 is driving me NUTS!!!! :-S Link to comment Share on other sites More sharing options...
Robinhood Posted September 21, 2011 Share Posted September 21, 2011 JudgeMental - 2011-09-21 1:02 PM James alerted me to this thread a few weeks ago as I asked him where the drain/frost valve was for the Adria going away for a few nights (taking son to Uni/visiting friends) so i put some water in tank.... when I put the pump on water started coming out under the Truma heater. Now, which ever way I turn it (it does not lift like older ones) water continues to flow. (water tank is less then half full) I have attached a pic of valve and can any one tell me is this the right position or not? but like I said whatever position water keeps flowing *-) this error 500 is driving me NUTS!!!! :-S No picture, but from your description it will be one of the newer, non-electric frost valves. The "handle" needs to be turned to the operating position, but the valve is then closed by pushing the button in. (Subsequent opening by moving the handle out of the operating position causes the drain to open and the button to pop out). See attachment (or RTFM ;-) ) Link to comment Share on other sites More sharing options...
JamesFrance Posted September 21, 2011 Author Share Posted September 21, 2011 Hi Judge, I expect you have had a night cold enough to operate the automatic drain valve, which pops out a button near the bottom of the unit in front of your heater. I will try to attach a diagram. Link to comment Share on other sites More sharing options...
Guest JudgeMental Posted September 21, 2011 Share Posted September 21, 2011 lets try again :-S Link to comment Share on other sites More sharing options...
JamesFrance Posted September 21, 2011 Author Share Posted September 21, 2011 Snap! lol Link to comment Share on other sites More sharing options...
Guest JudgeMental Posted September 21, 2011 Share Posted September 21, 2011 No one mentioned the blooming button before! :-( Thanks chaps all sorted! :D I'm thinking of paying the tenner and joining the funsters site, as this forum is so slow and throws up soooo many errors it is becoming unusable! *-) Link to comment Share on other sites More sharing options...
JamesFrance Posted September 21, 2011 Author Share Posted September 21, 2011 Eddie, did you not get the multi language handbooks in Germany for all the different systems? Mine all came together in a blue Adria Folder, but no Adria book for their conversion. One each for heater, electrics, loo, fridge etc. Link to comment Share on other sites More sharing options...
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