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[SperleFarms]

Looking for some advice on domestic hot water temperature….

My OWB water temperature set point is 190°.  I have less than a 1° temperature drop over approximately 175’ run of ThermoPEX.  I haven’t measured the water temperature out of the T&P valve on my hot water heater, but it’s very hot.  Needless to say the plate heat exchanger is doing it's job!  My problem is the water temperature at the faucet, all of them.  Again I haven’t measured this temperature, but I would describe it as a little better than luke warm.  In my opinion the only thing standing between me and nice hot water is the Honeywell AMX Series mixing valve.  The valve was installed per the manufacturer’s instructions, and I’ve even pulled it a few times thinking it was dirty or clogged with some debris.  Does anyone have any advice, or experienced something similar?

I’ve attached a few images for reference.

[Fourced]

I could be wrong, but I do not believe you can use a plate exchanger in that configuration.

You have it plumbed like a sidearm. Sidearms use gravity flow, plate exchangers use actual flow.

[RSI]

Yeah, I don't think they work very good that way.
Have you held your hand on the pipe coming out of the tank into the mixing valve? If the plate is working at all there you shouldn't be able to keep your hand on that pipe for more that a second with a faucet running.

If that is the problem the best / cheapest fix would be to put a small pump right above the plate.

[boilerman]

I have the same set up on my electric water heater with a plate and it work great. I go into the anode rod port on top rather than teeing into the pop off port. Are you sure you are not air locked on your domestic side? You might try bleeding more air off that bleeder elbow I see in your picture. I've heard of some gas water heaters that just won't thermocirculate and a pump like a bronze 006 taco put on the domestic side will circ the water and it works.

[RSI]

Well, that is why I said to see how hot the outlet pipe is.

has it ever worked? If it did and you have hard water the plate is most likely plugged. I have seen sidearms with a straight through 3/4" pipe plug up solid.

If it isn't plugged and the water coming out of the tank isn't hot then a pump right above the plate will fix it and give way more hot water than without can make.

[Scott7m]

Why would you want to use another pump?  Just something else using 5 bucks a month of electric, looks to me like a sidearm should have just been used to start with, I don't see the benefit of that plate installed that way vs a side arm

[RSI]

If you put the pump on a thermostat it will use less than a dollar a month.
Cheapest way to get it working right.

[Scott7m]

Yea if it was on a stat, but what were the benefits of doing it that way vs a side arm?

[RSI]

Not having to buy a sidearm and more hot water capacity
The water is only hot at the top of the tank with a sidearm unless there is a pump on it. With a pump the whole tank gets hot.

[Scott7m]

So you think a 10 plate installed the way it is there is better than a sidearm? 

[RSI]

With a pump it is. Without probably not. With a pump it will give way faster heat recovery.

[Scott7m]

Yea I agree with a pump, but not the way it was.. A pump is the cheapest way to fix it now, but initially I would think a side arm woulda done well

[RSI]

Yeah I agree on that.
Too many bends to get good natural flow on that setup.

[Scott7m]

Yea...  That was my thoughts

[SperleFarms]

Let me clarify a few things….

First, the plate was used due to the extremely close proximity of the hot water heater and the gas furnace.  In order to use a sidearm I would have needed to move the hot water heater, thus re-plumbing and re-ventilating the unit.  I didn’t want to open a can of worm so to speak, so we used a plate.

Second, the plate seems to be working extremely well.  The piping between the plate and the T&P valve is EXTREMLY hot, as is the nipple coming out of the top of the hot water heater below the mixing valve.  Touch these for more than half a second and they’ll blister you hand, believe me I know. 

Third, I’ve drained several five gallon buckets of water from both the T&P valve and the drain at the bottom of the tank.  The water is scalding hot, bucket after bucket after bucket.