TheFrenchConnection Posted May 28, 2019 Share Posted May 28, 2019 Our Truma frost control valve is constantly dribbling causing a pressure drop so that the pump kicks in every few minutes — and just increases the flow! In the short term I would like just to bypass it as I need the van the weekend after next, but I am concerned by the fact that it also apparently acts as a pressure relief valve as the water heats and expands. Is this a real problem, as I don't recall any relief valve on our previous gas-fired Truma (ours is now gas/diesel). Any advice and comments much appreciated. Link to comment Share on other sites More sharing options...
BKen1 Posted May 28, 2019 Share Posted May 28, 2019 Tied mine closed with string ..had a slight dribble once.. opened and closed it by hand quiet vigorously and that cured the problem . Link to comment Share on other sites More sharing options...
monique.hubrechtsgm Posted May 28, 2019 Share Posted May 28, 2019 No it is a frost safety valve. You can have it or not. At Home you have a expansion vessel and a drip valve. Because of the Volume capacity the expansion takes place in the truma boiler or ALde. You have to rewew this air cushion regulary by tapping off your boiler. Link to comment Share on other sites More sharing options...
Derek Uzzell Posted May 29, 2019 Share Posted May 29, 2019 TheFrenchConnection - 2019-05-28 4:03 PM Our Truma frost control valve is constantly dribbling causing a pressure drop so that the pump kicks in every few minutes — and just increases the flow! In the short term I would like just to bypass it as I need the van the weekend after next, but I am concerned by the fact that it also apparently acts as a pressure relief valve as the water heats and expands. Is this a real problem, as I don't recall any relief valve on our previous gas-fired Truma (ours is now gas/diesel). Any advice and comments much appreciated. Truma’s operating instructions for the FrostControl safety/drain valve advise as follows Overpressure pressure relief valve With an overpressure of up to max. 4.5 bar (produced e.g. when the boiler heats up), the FrostControl opens auto- matically and releases the overpressure in fits and starts via a drainage socket. All Truma safety/drain valves (old/new design, manual or electric operation) have an overpressure relief capability. I believe the FrostControl valve has a ‘release pressure’ of 2.8bar, but whether the valve’s overpressure relief capability will be triggered during water heating will depend on the temperature that the water is heated to and (possibly) on the characteristics of the motorhome’s water system. My Rapido’s FrostControl valve releases pressure when water is heated to 60 degrees Centigrade - it doesn’t always do it, but it does it pretty commonly, As my Rapido’s Truma Combi gas-only heater and FrostControl valve are under the motorhome’s bed and I normally heat the water before getting up, it’s obvious when the valve activates as it makes a sudden short hissing noise. The first time it did it was a mite startling, but now it doesn’t concern me. The Rapido’s water pipework is hard semi-flexible plastic, so there’s no ‘give’ in it that might be present if the pipework had more flexibility with (perhaps) more capabilty to deform as the heated water pressure rises. Prior to your motorhome’s FrostControl valve starting to leak, if you never noticed it releasing pressure during the water heating process, it (probably) should be OK to bypass the valve temporarily. Having said that, as bypassing the valve will take some effort and (presumably) you’ll want to retain the overpressure protection in future, haven’t you got sufficient time to either replace the FrostControl valve on a like-for-like basis, or fit a Truma manually-operated equivalent, or (before taking the bypassing route) see if you can stop the leakage by opening/closing the valve repeatedly as Bken1 suggests above. On-line comments indicate that this issue is not that rare and this (French) YouTube video advises on how to disassemble a FrostControl valve and shows its internal workings. I’ve never taken one of these valves apart, but the video seems to show that control of the water passing through the valve (or down its drain-tube) is via a black rubber seal that is pressed against the 3-way (inlet/outlet/drain) plastic component that’s held on to the end of the valve by a simple U-shaped wire clip. Removing the 3-way ‘thingie’ will allow the condition of the rubber seal to be checked and, if the seal has lime-scale or muck on it, just cleaning this off could cure your current leakage problem. (If the seal is damaged, I don’t think it is available as spare part.) (The primary purpose of the French YouYube video is to show how to convert a FrostControl valve so that it retains its overpressure capability but removes its temperature-related operation.) Link to comment Share on other sites More sharing options...
BKen1 Posted May 29, 2019 Share Posted May 29, 2019 The valve I have is the older model than the one in the video Derrick posted ...this is mine and seems to be just a Frost dumps valve nothing to do with pressure from the boiler ( from what Ive read )..so yours my need a different approach if newer model. Link to comment Share on other sites More sharing options...
witzend Posted May 29, 2019 Share Posted May 29, 2019 Mines like the picture above and I've had a strong clothes peg on mine for 6 yrs with out any problems only removing it to flush the system once a year. There are manual replacements available https://tinyurl.com/yywpppk9 Link to comment Share on other sites More sharing options...
Derek Uzzell Posted May 29, 2019 Share Posted May 29, 2019 BKen1 - 2019-05-29 8:35 AM The valve I have is the older model than the one in the video Derrick posted ...this is mine and seems to be just a Frost dumps valve nothing to do with pressure from the boiler ( from what Ive read )..so yours my need a different approach if newer model. Although it’s not mentioned in the installation or operating instructions for Truma C-Series heaters that had the electrical safety/drain valve shown in your photo, that valve also has the 2.8bar over-pressure relief feature found on the current FrostControl valve. Link to comment Share on other sites More sharing options...
pepe63xnotuse Posted May 29, 2019 Share Posted May 29, 2019 Derek Uzzell - 2019-05-29 9:55 AM BKen1 - 2019-05-29 8:35 AM The valve I have is the older model than the one in the video Derrick posted ...this is mine and seems to be just a Frost dumps valve nothing to do with pressure from the boiler ( from what Ive read )..so yours my need a different approach if newer model. Although it’s not mentioned in the installation or operating instructions for Truma C-Series heaters that had the electrical safety/drain valve shown in your photo, that valve also has the 2.8bar over-pressure relief feature found on the current FrostControl valve. I also used to retain ours closed but by way of an "R" clip. I hadn't realized that it was also a pressure relief valve though :$ Link to comment Share on other sites More sharing options...
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