Truma Ultrastore Water Heater

[gearykyle]

When i first bleed the air out of the hot water tap and switch on the power i get a hot water. After using the hot water for showering etc it starts to run cold suggesting the the thermostat is not working to allow power to return to reheat the water. If i then turn the power off and leave for 5 mins and then turn on again the water will heat up.This happens repeatably. Any suggestions to remedy this problem.

Hi Baz - from NZ - I know this post was a few years ago but I am having same issues with my Truma Waterheater - heats up great from filling it, then I use some water and it goes cold but can only get it hot again by turning the unit on and off.
Element and Thermostat are fine - all tested great. Did you get yours sorted in the end or did you simply replace the element?

 

[IanB1485]

The older heater elements were 450W and later ones 800W also we can get 1200W heater elements (non Truma) The 450W versions weren't the fastest to reheat. How long do you leave it? or have you tried waiting with it on? The simple thermostat is bolted quite close to the heater element and probably has quite a large hysteresis, so will have to cool down quite a lot before switching back on on its own , Removing the power doesn't reset it , a reduction in temperature as its just a simple bimetallic switch. if it is failing ( hysteresis getting bigger) then replacement of the heater element ( the 800W and 1300W come with the thermostat wired in. The 450W had a separate thermostatic switch. You need to open up the outer cardboard cover where the mains wires go into the unit to see which version you have.I have never seen a 450W version , but I believe the 450W heater unit is not physically compatible with the 800W replacement heater assemblies.

 

[gearykyle]

Thx Ian
Its an 800w version. BN-103 Model. I have left it on for a long period hoping it would reheat but the only way to get it back to hot is to turn the main switch off, wait for 5 mins, turn back on again and wait for it to reheat - same issue Baz had. My feel is that it should keep the same heat continuously as we only use it for dishes (no shower or bathroom in the van) ie, there is no way we are using 10L every time we do dishes.
I have tested the existing Element and Thermostat and get good ohm readings - plus the heater does heat up initially so it cannot be an element issue.
Possibly air getting in somewhere but then I have re-inserted all the John Lewis fittings, even replaced a few, and re-tightened all the plastic screw/bolt fittings.

 

[Martin_E]

Have you tested the thermostat when the heater has heated the stopped?
It could be that the heater is getting to hot on heating up and tripping the thermostat, or tripping to early, the kind of give away is that it resets when the mains is interrupted, then off it goes again.

 

[gearykyle]

Have you tested the thermostat when the heater has heated the stopped?
It could be that the heater is getting to hot on heating up and tripping the thermostat, or tripping to early, the kind of give away is that it resets when the mains is interrupted, then off it goes again.

Thanks Martin,
I will try that when back from a current work trip. Though what would cause the heater to get too hot do you think,?

 

[Martin_E]

It could possibly just be the thermostat isn’t resetting as well I guess

 

[Dustydog]

This video may help

View: https://www.youtube.com/watch?v=CsCvUHPb-wE


Note not all have two levels of heating but the principle is the same.