Hot Water Stops Flowing at 117F (SOLVED)

VinneyTaB

TAB400 2021

Hot water was working perfectly well last season. After de-winterizing we had the following problem on our first trip:

We filled up the fresh tank with Nautilus set to Powerfill.

We set the Nautilus to Dry Camping and set hot water control to electric power and 1KW.

The cold water works perfectly at all times when the faucets are turned on. 

When hot water is demanded from any of the faucets we found the following after much experimentation:

• While the hot water is heating up the pump operates and hot/warm water flows perfectly.
• When the water reaches about 117F the hot water flows for about 5 seconds and then the pump turns off and the hot water stops flowing
• If you open the hot water faucet again the pump does not turn on and only a small trickle comes out.
• The water will heat up to about 127F.    
• If you turn the hot water control off and allow the water to cool, the hot water will flow again on demand at about 113F.

My conclusion is that something (sensor?) is disabling the pump when the water temperature reaches about 117F and them enables the pump to operate again when the system has cooled down. .    

I would appreciate any help or suggestions as to what is causing this problem. Thank you. 

Sharon_is_SAM

The pump is not controlled via thermostat.  Are you certain that your Alde hot water tank and Flow tank are filled?
Try turning the power up to heat on 2 kw and boosting the shower on the control panel.  The water temp will be limited on 1 kw.
Very cold water will require longer to heat, so give it time.

Have you tried using the Alde on LPG?

Denny16

Did you reset the Alde Bypass valve (center red handle) to the correct position to fill the hot water and Flo tanks?  The red handle should be in the horizontal position to allow cold water into the Alde boiler.  If the red handle is vertical, the hot water tanks are being bypassed, and no water is going into them to get heated.  Another cause could be the hot water mixing valve?

Cheers 

VinneyTaB

@Denny16. Yes the bypass valve is in the correct position. 

VinneyTaB

I connected to city water electric power and 2KW. The water flowed from the hot tap perfectly while the water was cold. As the water heated up I kept trying the hot tap and it was working until about 113F water temperature. At that point the hot water flow started to slow down and at about 117F it was just a trickle. It happens each time like clockwork. Reading a previous post from DougWW in April https://tab-rv.vanillacommunity.com/discussion/comment/166053#Comment_166053 it sounds like the same problem which was fixed by changing out the mixer valve. I am going to adjust it in and out first so see if I can potentially dislodge any debris that might be in there. If that doesn't work I am going to remove it and try to clean it out. Does anyone have any instructions on how to remove the hoses/fittings?

Sharon_is_SAM

It is not uncommon for the hot water flow to be less volume.  Have you tried adjusting the mixer valve?  

XenanMe

I haven’t ever removed the fittings for the Alde mixing valve but according to the manufacture documentation, the valve is attached using John Guest fittings (12mm).  There are several YouTube videos on removing and reinserting these fitting types.  Seems simple enough (but everything does on YouTube. Good luck and hopefully you find something simple like a piece of debris in the strainer.

Denny16

Is yourTaB still under warranty, if so, sense the issue is not something quickly sorted, you might consider contacting your dealer to have them take a look at the issue.
 Cheers 

VinneyTaB

Tab is 15 months old so if I understand correctly warranty for this type of thing is only valid for 12 months,

Denny16

Worth checking with your dealer, the Alde may have a longer warranty on it.
 Cheers 

VinneyTaB

Problem solved. I fitted a new mixer valve and the system is now working correctly. My diagnosis: the check valve that allows cold water into the mixer valve is stuck. Therefore when hot water was demanded the hot water from the Aldi was flowing directly through the mixer valve to the tap. When the mixer valve sensed that the water had reached 117F it shut of flow completely. This is a safety feature to avoid scolding. FYI the new valve cost $184.

Denny16

Glad you got it sorted.  The mixing valve was the only other option, after checking all the other possible causes, that could send hot water to the cold water lines.  I had forgot about the max temp safety cutoff point in the valve.
Cheers