Truma heater expansion bottle question

Apr 9, 2013
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Ayr
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Our water system seems to have a number of small leaks that only manifest themselves when the water is heating up. Most of the leaks are coming from the two "Christmas trees" and I've been able to fix them by trimming pipe ends and re-tightening.

It's clear that the large pressure rise caused by heating is aggravating these leaks but there is no external pressure vessel. Does the Truma heater have any internal expansion space or should I just add an external one? Seems an odd omission given how high the pressure seems to get when the water is heated from cold. You get a darned good initial spurt from the hot tap on first opening after heating from cold.

Tim
 

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buckby

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Sep 6, 2013
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I like where your going with this one after having pipes blow apart twice I was going to email truma and ask them how they allow for expansion other than a safety valve also I have unvented hot water qualifications any thing over 15 litres has to have an expansion vessel as per building regulations.
 
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timdownieuk
Apr 9, 2013
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I like where your going with this one after having pipes blow apart twice I was going to email truma and ask them how they allow for expansion other than a safety valve also I have unvented hot water qualifications any thing over 15 litres has to have an expansion vessel as per building regulations.
Hmm, makes me wonder if the safety valve has stuck. I wouldn't mind if it dribbled a bit of hot water through an overflow if it kept the pressure down. Anyone know where it is?

Tim
 

buckby

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Sep 6, 2013
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Think its the one on the hot outlet with the clear tube on mines been in twice the last time it blew a pipe off when the water was on on its own it sounded like the fan was running slowly and when you opened a tap the water would spit because it was that hot since its been in again when the hot water is on the heater is pretty silent can't hear the fan running and the water is hot but not spitting when you open a tap not sure whether they changed a temperature sensor or pc board
 

Terry

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Dec 27, 2007
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Can't remember ;)
I like where your going with this one after having pipes blow apart twice I was going to email truma and ask them how they allow for expansion other than a safety valve also I have unvented hot water qualifications any thing over 15 litres has to have an expansion vessel as per building regulations.

does not come under building regs plus most are 10 ltrs or 15 ltrs anyway so would not need a expansion tank if I am understanding your post about BRegs
terry
 
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timdownieuk
Apr 9, 2013
651
338
Ayr
Funster No
25,458
MH
A class
Exp
Newbie
does not come under building regs plus most are 10 ltrs or 15 ltrs anyway so would not need a expansion tank if I am understanding your post about BRegs
terry
Yep, just checked my manual and it says 10ltrs. Just discovered that the frost dump valve doubles as over-pressure protection so I've opened and closed it a few times just in case it was sticking on its seat. Think I'll still add a pressure vessel though. The pipe connections just don't look that durable to me and I think it'll save aggro in the long run if I reduce the maximum pressure.

Tim
 
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