Not reaching design temp

IPH

Installation near Red Deer Alberta
B1KE 199 Combi

Building is a shop/barn/inlaw suite. 3 bays that are 20'x56' with the middle bay being higher and having a 20'x22' messanine. 

ICF footings 4' down with 3"foam insulation on a 4" slab
R20 insulation in the walls and r40 in the attic

Each zone is run by a grundfos 15-58 and controlled by a tekmar

The 3 slab zones are set to 110f with mixing valves while the messanine is at 150f - the boiler set temp 

All zones are supplied after the low loss header

The outer bays have been consistently hitting set temps(thermostats) of 70 and 50. The middle bay however is set to 70 and is only hitting 65

The outside temperatures have been all over the place since the install. In talking with the system designer we are both pretty confident we have enough btus available as the boiler rarely modulates above 30% and the outer bays are having no trouble. 

The suspicion is flow but I have been seeing about 25 degree temperature difference on the supply and return of the troubled zone which makes it seem the heat is going out to the slab. 

Any ideas to further troubleshoot the situation? 

kcopp

What size tubing and how long are the loop lengths?
Why the mix valves? is the whole job just the slab or are there other high temp zones?

hot_rod

Do you have access to an infrared camera? You could assure all the loops are warming. Or are there flowmeters at the manifold for each loop?

IPH

5 loops of 1/2" pex approximately 250' each. The messanine zone is staple up so its run at higher temp. kcopp said:

What size tubing and how long are the loop lengths? Why the mix valves? is the whole job just the slab or are there other high temp zones?

IPH

hot_rod said:

Do you have access to an infrared camera? You could assure all the loops are warming. Or are there flowmeters at the manifold for each loop?

Yeah I took a look at it after I had the system on for about an hour. I could see the lines warming but it was slower than I would have expected. 

No flow meters on the manifold

IPH

LRCCBJ

IPH said:

The suspicion is flow but I have been seeing about 25 degree temperature difference on the supply and return of the troubled zone which makes it seem the heat is going out to the slab.

A 25° DT is not helping you in this regard. The average temperature of the problem zone is 12.5° less than the SWT. Ideally, you'd want to flow sufficiently to obtain a 10°DT. I suspect the mixing valves are your problem here. They typically have quite a bit of flow restriction.

hot_rod

Even if those are low Cv mix valve, like a 2.7Cv with 5 loops at .7 gpm per the pressure drop is fairly low.

Some of those mix valves, if it is an ASSE 1070 or dual listed valve, have fine strainers and checks on H&C ports. Check to see if so, I would remove the check and strainers.

The delta T will be wide on cold start up, and close down as the floor warms, so check them delta as that zone is about to shut down, it shouold be at or close to design, typically 10- 15 ∆

IPH

Even if those are low Cv mix valve, like a 2.7Cv with 5 loops at .7 gpm per the pressure drop is fairly low. Some of those mix valves, if it is an ASSE 1070 or dual listed valve, have fine strainers and checks on H&C ports. Check to see if so, I would remove the check and strainers. The delta T will be wide on cold start up, and close down as the floor warms, so check them delta as that zone is about to shut down, it shouold be at or close to design, typically 10- 15 ∆

I was picking my dad's brain and he asked if they had strainers. They do so that's what I plan on checking tomorrow. Is it worth taking out the checks if the other two zones are the same size and having no struggles? The 25 degrees was on cold ish start. So we will see how it goes. 

IPH

Hot side of the mixing valves was almost completely choked off on all 3. Seems like them coming off the vertical ended up being a sediment trap. 

I didn't flush the system on start up because of the freezing temperatures so it got glycol right away. Lesson learned. Also putting in a strainer

Was surprised at the amount of stuff in a system that is mostly pex and the rest copper on the wall. 

hot_rod

That system needs to have a cleaner run for a day or so, then a good full volume power flush. That is too much crud in a system with sensitive valves like thermostatics.

Those mixing valves may lock up with crud like that getting into, now with strainers removed.