Taco 5000-2 Mixing Valve - Hot Water Temp Fluctuates

JustinS

Good morning to all

Recently, we've noticed that our hot water temperature in our kitchen seems to be fluctuating more than usual.

We'll be using full hot water and suddenly the temperature gets much hotter, to the point of being too hot to touch.

We took a kitchen cooking thermometer and measured the temp, seeing it fluctuate as high as 131F before settling back down closer to 120F. The DHW tank is set to be around 136.

The mixing valve is a Taco 5000-2; I tried adjusting the temp using the plastic cap but that didn't work, as the cap deformed.

Any thoughts on what might be the issue?

Thanks in advance!

Joe Mattiello

hi Justin
is there a recirculation system where 5000 series valve installed? normally what happens is when there is no load, or no one is using hot water, you experience temperature creep. when you use hot water, the temperature should stabilize. Taco introduced a recommended piping diagram to minimize temperature creep. For your reference I attached a document I found in my C-drive; do they still call it C-drive? lol
Anyway, hopefully this helps, and if you have additional questions or concerns, Taco Tech support technicians are available at 401-942-8000.

GroundUp

I have found that the 5000 valves need more of a temperature differential from the hot (or cold) side to the mixed side to operate properly. That 16 degree drop from 136 to 120 is not enough, so it will fluctuate. I've installed 6 or 8 of those 5000 mixers on radiant systems and every single one did the same thing but due to the differential on the cold side. I could remedy it to an extent with flow rate, widening the delta T to make it work right, but then the flow rates were not correct for the job. I've since gone back to Honeywell and Webstone because they work

JustinS

Joe Mattiello said:

hi Justin
is there a recirculation system where 5000 series valve installed? normally what happens is when there is no load, or no one is using hot water, you experience temperature creep. when you use hot water, the temperature should stabilize. Taco introduced a recommended piping diagram to minimize temperature creep. For your reference I attached a document I found in my C-drive; do they still call it C-drive? lol
Anyway, hopefully this helps, and if you have additional questions or concerns, Taco Tech support technicians are available at 401-942-8000.

Hi Joe

There is a recirculation system but it has been disabled for 5+ years now and I don't believe that it has mixing valve, just hot water.

I should have mentioned this earlier but we've been in the house for almost 7 years now and we've never had this sort of fluctuation before. The DHW tank has been set to ~136F for several years so I don't think that's a factor (aside from why there's such hot water available).

Intplm.

@JustinS If this has not been an issue before and the mixing valve has been reliable up until now, I would say that it's time to rebuild the valve. They most likely make a replacement thermostatic mixing valve cartridge.

The fluctuation of temperatures that you have mention tells me the the thermostatic element within the valve is no longer functioning properly.
It's time to rebuild or if it is easier, replace the mixing valve.

Larry Weingarten

Hi @JustinS , For fun, why not try a cross connection test? This is just turning off the cold supply to the water heater and opening up a hot tap. If water flow stops in a few seconds, there is no real problem with cross connection. If it keeps running, that could be another problem to hunt down and fix. Troubleshooting gets interesting when more than one thing is misbehaving!

Yours, Larry

JustinS

Larry Weingarten said:

Hi @JustinS , For fun, why not try a cross connection test? This is just turning off the cold supply to the water heater and opening up a hot tap. If water flow stops in a few seconds, there is no real problem with cross connection. If it keeps running, that could be another problem to hunt down and fix. Troubleshooting gets interesting when more than one thing is misbehaving!

Yours, Larry

Hi Larry

Could you tell me what this test would reveal? thanks

Larry Weingarten

Hi @JustinS , So far, it's been assumed that it must be the mixing valve that's at fault. A cross connection would give you similar problems, so doing the test will hopefully rule out that possibility. The test is simple and quick to do. It would be a shame to replace the mixing valve and still have the problem.

Yours, Larry