"Thermostatic" Mixing Valve turns off hot - Valve replaced

DougWW

Greetings everyone!

We have just picked up our new 2021 T@B 320S BD and are in the process of dewinterizing.

It seems this pretty red-capped valve turns off the hot water. I tried it first with the factory settings, got a bit of warm water and then nothing out of any of the hot taps. Adjusted it, tweaked it, checked the valve settings and the Alde... no hot water.

Let it cool down while I was head-scratching, and I've got warm water for a few seconds then it shuts off. 

I have cold water everywhere, and if I turn off the Alde completely I can have cold water out of every tap everywhere. But warm that water up to about 35C and it slows to a trickle and STOPS!

I'm at my wits end, and a 1 1/2 hour drive back to the dealership.

Any thoughts? Thanks!

Sharon_is_SAM

If you have completed dewinterizing, is the Alde bypass set at normal?  Did you fill the Alde tank?

Here is a thread that may help.  Check out poster “Clear”.

https://tab-rv.vanillacommunity.com/discussion/12718/new-thermostatic-mixing-valve

DougWW

Sharon_is_SAM said:

If you have completed dewinterizing, is the Alde bypass set at normal?  Did you fill the Alde tank?

Here is a thread that may help.  Check out poster “Clear”.

https://tab-rv.vanillacommunity.com/discussion/12718/new-thermostatic-mixing-valve

Hi Sharon, 
I've been through that post, but thanks for the reference.
The bypass is set to normal. The Alde tank is full and heating works well and normally.
I can get a high temperature of water in the boiler, but it gets no further than the thermostatic valve.
Frustrating.

...Doug

Denny16

You need to adjust the valve to allow for hot water temp you want.  You remove the cap and use it to turn the valve under the red cap.  There is a post here about how to do that.
cheers

Sharon_is_SAM

@DougWW - check out backpacker47 comment here:  https://tab-rv.vanillacommunity.com/discussion/comment/165156#Comment_165156

Not sure if you saw this:

https://tab-rv.vanillacommunity.com/discussion/13243/low-hot-water-pressure-with-new-speedfit-thermostatic-mixing-valve/p1?new=1

DougWW

Denny16 said:

You need to adjust the valve to allow for hot water temp you want.  You remove the cap and use it to turn the valve under the red cap.  There is a post here about how to do that.
cheers

Thanks for the thought... I'm not convinced that plastic nut is up to the task of adjusting that valve. I've been using a small socket instead.

DougWW

Hi Sharon,
I'm out to run through Backpacker47's suggestions this morning. No response from the dealership (surprise?) as yet. There seems to be some consensus on starting wth the valve at minimum temperature. But if the valve is shutting off, supposedly because of temperature, then this doesn't hold a lot of promise. I'll report back.

Sharon_is_SAM

@DougWW - can you post a photo?  Any possibility something is not connected correctly?

Denny16

A dealer will tell you to start at the minimum to prevent scalding water burns, it’s a liability issue.  Also nüCamp has the valve set low for the same reason.  To get useable hot water yiu need to adjust it to up, but I would go in small increments to be safe.
cheers

rhyno

@DougWW try fully opening and closing the valve back and forth. This helped with ours when we first got it and had low hot water pressure. That, and we had a bunch of debris in the hot inlet of the mixing valve...but your issue sounds a bit different. With ours we had a hot tap open while adjusting and it never slowed to a trickle nor stopped.

https://tab-rv.vanillacommunity.com/discussion/13243/low-hot-water-pressure-with-new-speedfit-thermostatic-mixing-valve#latest

DougWW

My problem is not the temperature of the hot water, but the flow of the hot water. It's been a long day, partly in contact with NuCamp and partly with the dealership. So far the problem remains.

To clarify, the symptom is the hot water supply. When the trailer is COLD, as in Alde turned off, we have normal supplies of water running through all 3 hot water taps. The water is cold obviously, but the supply is similar to the cold water supply. When cold the Alde control panel reports the water is 32C or less usually.

When the Alde temperature is up to normal running temperature or about 48C (similar to our previous 2018 T@B 320), and I turn on hot water the flow starts normally momentarily and within 2 or 3 seconds the flow is reduced to a few drips at best. 

Going with the T@B manual, I have experimented with the temperature mixing valve from minimum to maximum. There is no water flow to measure temperature from.

If I cool the Alde, then flow through the hot tap returns.

The dealership felt it may be a one-way valve between the Alde and the mixing valve. I took that apart and that valve is clean and operational. While it was apart I ensured that water was going into the Alde and that it was full. The system was reinstalled with attention to the flow direction through the one way valve.

I have traced the waterlines on the hot side from front to back. As I get no hot water flow at the outside shower, the problem cannot be with the piping of the trailer.

 I am convinced the problem is with the hot water mixing valve. It seems to assume the water is too hot (at any temperature above about 35C) and does not do any mixing at any setting of the red-capped adjustment screw.

What would you suggest?  Thanks.

Sharon_is_SAM

Reduced flow could be a blocked filter or a reversed valve.  The TMV is supposed to work by allowing a set volume of water, so maybe there is a problem with the outlet for the cold water through the mixer.  When you just run cold water, it doesn't go through the mixer.  I say ask for a new mixing valve.  

Here is another 320.  Yours looks the same.


Here is a picture of a 400 by @Pymbur who had problems with limited hot water supply in the shower.  

Denny16

I agree, sounds like the mixer valve is defective.  From what I understand the mixer valve has a safety flow cutoff, if the cold water supply does not supply enough flow to mix the hot water down, then the hot water is shut off to prevent scalding injuries.  So when the hot water enters the valve, it is just shutting down the hour water Flo, as it is not detecting a cold water flow.
cheers

DougWW

So to provide a small bit of closure here, we have an appointment for the trailer on Wednesday.

Since we can get cold water out of the hot taps when the Alde is off, and nothing when it is mid-warm to hot I'm convinced ti is the mixing valve that is failing. The dealership isn't so sure, but will take a look at it next week.

I've never heard back from NuCamp... they were going to get back to me, but no response by phone or e-mail. 

...Doug

DougWW

Now we have the trailer home and tested. The dealership replaced the hot water mixing valve, and everything works just fine now. We did a short trip and the trailer has been "declared ours" by my wife.

Thanks everyone for your comments and ideas.

...Doug