LK 550 Mixing Valve - Faulty?

RetireeBC

Greetings all.  I would would like to know if any other TAB owners have had a faulty LK 550 mixing value?  The specific problem I've been trying to correct is that I do not get any water (hot or cold) at any of the hot water taps. I've read several threads on the various problems with hot water and how to fix this issue in our forum.  I've adjusted the mixing valve (turned the hot water up) confirmed that all valves are in the camping mode and so on. The only way for me to get any water is to open the Bypass valve.  When I do, I do get about 10 seconds of warm / hot water before it returns to cold.  The Bypass valve should obviously be closed, but it is a symptom of what is going on. As an aside, I contacted ALDE support who worked through a trouble shooting process with me to confirm that the ALDE itself is working fine. I should mention that their support was excellent.  In any case, I'm now wondering if anyone has had a similar problem and if it was due to a faulty LK 550 mixing valve?

Cheers,

2019 TAB 320s

Sharon_is_SAM

I believe you outlined your hot water problem in this thread.
https://tab-rv.vanillacommunity.com/discussion/comment/168561#Comment_168561

If you did the full mixing valve adjustment by loosening the knob screw with no results, then you will benefit by changing the mixing valve.  There are multiple reports of owners with faulty mixing valves.

RetireeBC

Right.  Good to know that others have had to replace faulty mixing valves.

RetireeBC

Although I have adjusted the black knob by adjusting the screw on top, I see that there is another screw on the cold water intake. I have not touched this screw.  Does anyone know if this plays any part in the problem of no water at the hot water taps? I should mention that I have reached out to the manufacturer as well and will share any information that may be of use in explaining this problem.

Cheers

Bayliss

@RetireeBC, it doesn't answer your question, but the below thread includes some discussion about what was referred to as a "bleeder screw" as a possible contributing cause to a water leak at the mixing valve.  Others on this site may be able to provide additional details on how it functions, or its specific purpose, but I doubt it would impact the temperature of the water.  @BrianZ and @cuomo seemed to have some knowledge about that screw (back in 2018), so maybe one or both of them will chime in here.  I'm interested in learning more about it myself.

https://tab-rv.vanillacommunity.com/discussion/comment/91346#Comment_91346

Sharon_is_SAM

@RetireeBC - just to clarify because I don’t know how new you are to your TaB:

have you been able to get prolonged hot water in the past?
Do you know how to tell when the Alde water tank is full?  
how long are you waiting to heat the water?
is the Alde circ pump set to “Therm” on the control panel?  (If set to “Continuous” the heated glycol never gets a chance to concentrate the heat at the water tank.)

BrianZ

Sorry, @Bayliss, but I don't know anything about that screw on the mixing valve body that was identified by others back then as a "bleeder screw".  I only know that it was leaking water back then and when I tightened it with a screwdriver, the leak stopped.  We've never had to make any other adjustments to our mixing valve.

RetireeBC

Sharon_is_SAM said:

@RetireeBC - just to clarify because I don’t know how new you are to your TaB:

have you been able to get prolonged hot water in the past?
Do you know how to tell when the Alde water tank is full?  
how long are you waiting to heat the water?
is the Alde circ pump set to “Therm” on the control panel?  (If set to “Continuous” the heated glycol never gets a chance to concentrate the heat at the water tank.)

No problem.  I appreciate the questions as you never know what I might be missing. This is our first year where we have planned significant use of the trailer in view of retirement. So here I go with answers as follows:

1. We have had hot water in past camping seasons - Fall of 2019 & 2020.  We made little use of it though, in view of our limited outings. The issue this year,as you know, is that we get no water at all at the hot taps when all valves are in camping mode.

2. I think I do? I placed a bucket under the relief valve when trouble shooting with the ALDE technician this week. His assessment was that the volume of water and temperature were appropriate.

3. I waited 30 minutes for heating and did confirm the water temperature via the service menu and also by inspecting the water in the bucket mentioned above.

4. The ALDE is set to Therm.

The more I trouble shoot, the more I think there is something wrong with the mixing valve. I'm awaiting a reply from the manufacturer and have also contacted NuCamp in case they can shed any light on the problem.

Thanks to all for your questions and input.  I don't have convenient access to a dealer and so find this forum very helpful.

Cheers.

RetireeBC

Thanks Bayliss, BrianZ. I read the discussion on the bleeder screw.  I can see that I better not touch it!

Sharon_is_SAM

What is weird is that there is NO water - hot or cold- coming from the hot water tap.  It has to be the mixing valve.

Verna

My 2021 T@B 320 with the same black mixing valve had no water coming from the faucets. I figured if I turned the mixing valve a bit, a bit more was better—-WRONG!!  I had to turn the missing valve back all the way to the negative, then towards the positive,stop at the stop,  unscrew, lift the black plastic top over the stop, tighten screw, move a bit, and then I had hot and cold water and pressure on both. 

RetireeBC

Thanks Verna.  It is interesting that you also had the situation of no water. So instead of increasing hot water I should be reducing it? I've increased it thus far so if I understand correctly, I will need to reverse the increases I made and then reduce the temperature even further - moving to the negative. Re-reading your post I think I may have misunderstood. 
 

RetireeBC

I had further communication with NuCamp today. I answered specific trouble shooting questions and provided pictures as requested.  It's great that they're looking into it. I'm hopeful that they will uncover something to explain this situation; unless we figure it out first!

Cheers.

RetireeBC

Sharon_is_SAM said:

What is weird is that there is NO water - hot or cold- coming from the hot water tap.  It has to be the mixing valve.

I'm thinking that as well. 

Verna

@RetireeBC, turn the mixing valve to the negative, making sure you go over as many “jumps” as you did to make it the setting it is now. I was two “jumps” beyond the beginning. (Jumps are where you have to loosen the screw and lift the knob over the little jump—I’m describing the process as best I can.)

Then, I turned the knob towards the plus to the first jump. Loosen the screw until you can get past the jump, tighten the screw and now turn the knob less than 1/2”. That was my “sweet spot” where I got hot water and pressure on both hot and cold. Don’t go any farther. 

If the mixing valve is defective, you should still have the same as before and you need a new mixing valve. If you moved the mixing valve too far as I did, and the mixing valve is NOT defective, it should work perfectly. 

You have to ask me if you don’t understand….

RetireeBC

Thanks for the detail Verna. I think I've got it. 

It's looking like the valve is the problem.

Bye for now.

RetireeBC

Good News.  Problem solved! It turns out that an RV technician installed a check valve backwards on the hot water outflow and cold water inflow when I took it in for a small leak a few weeks ago.  It didn't occur to me that a simple leak repair by a qualified technician would be the problem until NuCamp tech support asked me to look at the arrows on the valves that show the direction of water flow.  I didn't know there were arrows, but sure enough, they were backwards.

Thanks to all for your input and ideas.  It's been a learning experience.

Sharon_is_SAM

Oh brother!  No one saw that coming!

stepheng

We had a hot water issue on last trip (Alde 3010 + LK550 mixing valve). We used our shower at 6000' and hot water worked fine .  Later in the trip we only got a short burst of hot water then cold.  I felt the line going from the Alde to the mixing valve and it was hot.  Water line out of mixing valve was cold.  Tried adjusting valve to increase water heat but still no hot water.  We were at 9100' and wonder if there is an altitude issue (can't think why this should be an issue as the mixing valve should only be temperature sensitive).  Now back home at 1500' and all works fine.  Any ideas or suggestions?

stepheng

Found there is a repair kit for the LK 550 that replaces all the internal parts so there is no need to remove the housing. Anyone know where we can get LK parts here in the US?

stepheng

Can't find repair kit in US.  Contacted Manufacturer and they won't sell repair kit to individuals.

stepheng

Looking at using a Taco 5000 series mixing valve.  Will require a little re-plumbing as the mixed output and cold input are reversed from LK550.  Does anyone know if the hot water line from the Alde that goes to the push-in connector is US or metric? 

Glider11

RetireeBC - Where are those water flow arrows?  Are you looking at a chart that was sent to you? thanx. 

RetireeBC

They are on the check valves that were installed on one side. The arrows were difficult to see.  I had to use a mirror to find them.  I've attached a picture to illustrate. You may have to zoom in on the picture.

mhyatt

Well I can say that on my 5 year old Tab CS, the mixing valve has acted up or failed.  Our last trip (just a few days ago) ended with no hot water at the taps.  The Adel is working perfectly.  Some troubleshooting indicated that adjustment of the valve was of no use, so I am replacing it, though may select a different brand based on input from other RV owners.  I figure the valve gets used 4 to 6 months of the year, we camp 5 to 8 times a summer for 4 to 5days at a time - I would say based on that level of minimal usage the device is not that robust.  I figure a 10 to 12 year life with moderate usage would be a more than acceptable life cycle.