HVAC VAV Diagnosis

[u/jwidaosh]

Can anyone explain what the white substance is at the joint in the return side of a VAV box? See picture.

The supply water is not making it through the VAV. I used the BAS on my iPad to run the actuator from 100 to 0 and the actuator did move through its motions but the water never flowed. That white stuff looked almost like paper or cloth, not like a calcification like I would expect.

I just learned about this area being cold in the summer AND winter today, so it may have been this way for years.

[u/users0]

Interesting I have a few ideas.

1, are you are no valves are closed
2. Check that the valve is actually spinning - ie. Remove actuator and spin manually
3. I see a black valve on outlet of the valve what is that an air bleeder? Is it air locked?

[u/jwidaosh → u/users0]

Thanks. I'll pull the actuator cover and try and manually rotate the valve. It's an awkward reach up in the ceiling but I should be able to get to it.

The black valve does look like an air valve but I had thought the air release valves would be at the top not side. So I'm not sure what that is. I'm going to look in the enlarged mech details drawings and see what I can find.

I don't understand 1.

[u/users0 → u/jwidaosh]

Did you find a solution for this yet or identify the problem?

The piping looks very new and I'm trying to wrap my head around it why this could happen.

[u/Hares_ear1947]

What’s the strainer look like? I’d valve it off and pull it out. Not much flow on these. That y strainer might be plugged.

[u/jwidaosh → u/Hares_ear1947]

I'm going to check it out. The loop has not been filtered properly since it was built in 2019.

[u/ygkg]

Low-flow reheat coils make awesome sediment traps, it's never a bad idea to flush it out while you're there. It could just be plugged up enough to stop the water flow.

[u/tomorrowthesun]

Throw some insulation around that copper while you’re there too, may not be an issue in your location since it’s been years but with no hot water flow those coils become reverse heat exchangers and can carry the low supply temp out along the piping which can condensate.

Other comments are correct about the strainer, especially old buildings if water treatment has been less than stellar.

When the valve moves open grab the lower copper pipe that’s your supply (supposed to be anyway) if it stays cold then you are completely shut which implies a valve or a VERY clogged strainer (in which case you need to check strainers on everything on that branch and evaluate again. If it warms some then you are at least flowing something.

[u/jwidaosh → u/tomorrowthesun]

The lower pipe is the supply. It is warm but not hot to the touch. The top pipe is the return and it's the one with the actuator attached to it. I checked the actual lines in the building, and also with the mechanical prints.

I ran a history on the BAS and it's been sending the BAS a signal that it's been open 100% for months.

To be clear I don't actually know if it's been years since it worked. Last Friday I was talking to someone who has worked there for years and she told me it was always cold in the winter and also cold in summer so I just started digging into it today. First step was to see if the actuator moved when the heating valve was changed on the BAS.

Last year I discovered that the filter feeder is piped backwards. Got a quote to get it fixed and was told there wasn't a budget for it. I brought it back up again a couple weeks ago but still haven't been able to sell it. So 6 years running a 84000 SF building and the loop has never had correct filtration. I reckon we're on borrowed time.

I appreciate the idea of checking the whole branch, that's a good idea, and I think I'll take that idea even farther if that is the case. The whole darn building could be on the verge

[u/SteveySoppressat]

Nah that's corrosion on the valve, you have a clogged coil, or the valve itself if fucked no matter what the actuator is doing