Radiant in floor issue

dpetrocik

this is my basement in floor heat zone on my system switched on and off by a wall thermostat and it’s own zone valve. The rear of the system works fine and also runs on zone valves. In trouble shooting l, I tuned off all other zones and just let this zone call for heat. I closed all 6 loops and opened one at a time (5-10) minutes until hot water was entering and warm water was returning). All loops did this although a couple took longer than others which I will assume means a longer loop. Problem is if I crack open all 6, the system has trouble keeping up. Hints, tips, suggestions? Thanks!

dpetrocik

Oops, anyway I can move this post to radiant heat? That would probably be helpful.

Intplm.

What's the pictured mixing valve being used for? If it is being used to decrease temp to your zones it may be faulty and need replacing.

dpetrocik

Yea, it looks like it takes the return and mixes it with the incoming hot water from the boiler. I inherited this when the house was purchased. 

Intplm.

The mixing valve is where I would start. They are built with an internal t-stat element. The element is probably bad.

Zman

If you turn the knob on the valve does it get warmer?
Installers often use high flow resistance valves which make things worse. If you replace it, try to find a replacement with a COP rating >3.

dpetrocik

Also, how does one adjust these without knowing the pressure? I may just breakdown and buy a new manifold and mixing valve for it. As of right now I open the return line all the way and then tried to adjust from the supply line. But it’s like going at it blind...maybe I’m also doing this wrong haha. My first time dealing with in floor heat

GroundUp

Slow down. Define "keeping up". Is that zone not meeting setpoint of the thermostat? What is the water temp leaving the mixing valve? Pressure is irrelevant, all you need to know now is the temps leaving and entering the floor after some run time. Open all loops wide open and start there with temp measurements.

dpetrocik

Exactly. Has a tough time reaching the set point. I think part of the issue is a lot of the time that zone doesn’t call for heat because it stays warm downstairs so the floor and water lines cool way down and then when it finally calls for heat it’s not just the water that has to be heated but the entire floor has to heat up. I can get the floor warm and then it’s fine but it takes some work on my end. I have no clue what the actual temps are because they didn’t install a gauge anywhere near the mixing valve or manifolds. Only temps I know are on the boiler itself which is set 160/180 at the moment. The picture is all I get to go off of as far as the mixing valve goes. I just cranked the thermostat to kick on the floor heat and opened all the loops fully. Drops the boiler temp to 104/106 and it is running constantly until the water/floor heats up which takes a long time since the floor zone hasn’t kicked on since yesterday probably. I know for a fact the boiler is undersized but with the floor the only thing running I’d assume it can keep up. Floor area is about 2000sq ft and the boiler is 60k btu Weil McLain (2015) 

**if the floor would stay warm it probably wouldn’t even be an issue.

GroundUp

Grab the copper pipe entering the supply manifold when the boiler is up at 160+. Can you hang on to it or is it too hot? Sounds to me like your supply temp is FAR too hot and is drawing all your BTU at once, effectively overheating the slab and causing it to flywheel. That boiler can NOT tolerate 104 degree temps, you will destroy it unless something gets changed soon. Getting that supply water temp dialed in is step one. It should be around 100 degrees to start, and can be tuned from there

dpetrocik

Looks like the lowest the supply temp will go with the mixing valve is 120, should I replace with a lower temp valve? And yes, the supply manifold gets pretty damn warm if the boiler is up to top operating temps. Even with the mixing valve all the way down (assuming it’s working that’s still 120 degrees going in...

dpetrocik

After touching pipes...I think the mixing valve is shot. If I touch all 3 they’re all the same temp. Even the return “cold” line coming in is hot which I’m guessing means the valve is compromised letting hot water flow backwards! 🤦‍♂️ Looks like my next day off I’ll be throwing a new mixing valve in and go from there! 

Zman

When the cold slab drags your boiler down that low for a long period of time, the condensate which is formed will eventually damage your boiler. I agree with @GroundUp that you are likely over/under shooting your target temp which is making the temps fluxuate and is costing you efficiency.

If this was mine, I would install one of these and be sure to install the outdoor sensor and boiler return sensor. It will fix both of the issues and make your system more comfortable.
https://www.supplyhouse.com/Taco-I075C3S-1-3-4-3-Way-Setpoint-I-Series-Mixing-Valve-w-Sensor-5204000-p?gclid=CjwKCAiArIH_BRB2EiwALfbH1NYQt0zEVGWvK9pxxP-ugNEHRAk67el66t7GZP4_-I3mpkQqaggFYBoCmXQQAvD_BwE

Intplm.

^^^^^^^^^^^DO THIS.^^^^^^^^^^^^^^^

dpetrocik

Sounds like a plan. Thanks!

Dave H_2

There may filter screens on the mixing valve, and yes, the element may not be opening the way it once did.
Yes, the i-Valve is a good choice to go

Dave H.

dpetrocik

Update: new mixing valve installed and it seems to have done the trick. The internals on the old one we’re definitely shot. It also just had 3 rubber washers and no screens. The new one came with 2 screens and then the washer for the mix port. Thanks again for the help!

Intplm.

@dpetrocik That's good news, And thank you for posting the end results.