Tankless system goes cold periodically

[Venice230]

I have a tankless system. About once every four weeks, the system goes cold for 20 seconds. There is a temperature blend valve that looks corroded on the outside. I am guessing this may be the issue. Also, what is this valve called? Any suggestions would be appreciated.
Thanks

Rinnai system
RL75i
REU-VC2528FFUD-US (A)

 

[GReynolds929]

That looks like the old Microsoft screen saver, did the guy charge by the elbow?
That TMV looks like it's had a slow leak for a while, I would definitely replace it. I would have recommended replacing or removing it when the water heater was changed. I think they're pointless on a tankless and cause nothing but problems, but they're required by code in some areas.

 

[Venice230]

That looks like the old Microsoft screen saver, did the guy charge by the elbow?
That TMV looks like it's had a slow leak for a while, I would definitely replace it. I would have recommended replacing or removing it when the water heater was changed. I think they're pointless on a tankless and cause nothing but problems, but they're required by code in some areas.

The house built in 2005 and I am not the original owner. I am assuming there was a regular tank when new and was replaced with tankless sometime after but just guessing.

 

[MrInfoPhilly]

Replace the thermostatic mixing valve., Watts
https://www.supplyhouse.com/Watts-0559119-3-4-LFMMVM1-UT-Lead-Free-Mixing-Valve-Threaded

thats a decent one with integral check stops

 

[Venice230]

Replace the thermostatic mixing valve., Watts
https://www.supplyhouse.com/Watts-0559119-3-4-LFMMVM1-UT-Lead-Free-Mixing-Valve-Threaded

thats a decent one with integral check stops

Thanks for the info. Wow, those things are expensive. I see a lot of Cash Acme at the big box stores which are considerably cheaper. Is this a case of you getting what you pay for?

 

[MrInfoPhilly]

Thanks for the info. Wow, those things are expensive. I see a lot of Cash Acme at the big box stores which are considerably cheaper. Is this a case of you getting what you pay for?

The mixing valve link i provided has multiple ASSE certifications., Activates at 0.5gmp., and is extremely accurate for temperature., also has anti-scald feature. Its my Go to mixing valve.

My $0.02

 

[Twowaxhack]

I wouldn’t use a mixing valve with that tankless.

Set the heater at 120 and remove the mixing valve.

 

[Venice230]

I wouldn’t use a mixing valve with that tankless.

Set the heater at 120 and remove the mixing valve.

Can you explain further? You state "that tankless." Are you saying this specific tankless does not need a mixing valve, or generally, all tankless do not need a valve?

Also, we find 120 degrees too cool for our liking and have it set to 135. So, should we stick with a mixing valve because of the higher temperature?

For more background, we live in the Sarasota, Florida area, so I need to consider the plumbing code also.

Thanks

 

[Twowaxhack]

Can you explain further? You state "that tankless." Are you saying this specific tankless does not need a mixing valve, or generally, all tankless do not need a valve?

Also, we find 120 degrees too cool for our liking and have it set to 135. So, should we stick with a mixing valve because of the higher temperature?

For more background, we live in the Sarasota, Florida area, so I need to consider the plumbing code also.

Thanks

Yes

 

[breplum]

With a normal, modern tankless WH I've never seen a mfr. recommend, nor had customer need a mixing valve. Tankless are designed to hold temperature properly when set and drawing min. gpm.