First Operations Hot Water Coil Freeze Protection

[Rondelli]

Wondering if anyone knows of or has heard of First Company hot water coils freezing causing copper fins ruptures or bursts resulting in above ceiling air handler failure, not to mention, flooding. As of new year, units come standard with freezestat (used to be optional).

 

[atlas06]

Looks like the low bid won the job, you get what you pay for.

 

[cmillburn]

I haven't heard anything specifically, but where did the cold come from? The plenum or outside air ducts?

 

[atlas06]

It appears that you are using a residential grade unit (a very low grade residential unit) for a commercial application.
I'll take a guess:
Are you cycling the fan? you may be running the fan continuously and may have gotten into stratification of cold air not mixing well with RA.

 

[Rondelli]

The cold is supposedly coming from the plenum. And the units are being used in low income apartment units in a residential application. One failure occurred after the unit was started up, ran for 5 day period and then shut down until occupancy. The copper tubing inside the unit's coil section burst.

 

[Rondelli]

Also, the unit's location is in the temperate bay area foothills--Dublin, CA. Low temp. in these winter mornings is approx. 37-42 degrees.

 

[absrbrtek]

How is the 37-42F air freezing the coils? I don't see the coil being the issue. JMHO

 

[Rondelli]

We are looking at copper tubing inside the coils bursting--the unit's were plumbed with pressure relief valves, etc. and the copper inside the unit keeps bursting. Theory is the calibration may be wrong on the copper tubing making it too thin? Don't know yet but we have people looking into it.

 

[lilliput1]

Relief valve will not protect frozen coil from bursting because tube failure will be caused by water expanding when frozen. We typically use a circulator pump to circulate water in the coil when outdoor air is 40°F and below. The circulator gpm is a fraction of the coil design flow gpm. The HW preheat coil control valve control must be active even if the unit is shut down (control valve operated to maintain 50°F downstream of the heating coil).

 

[RossABQ]

What is the exact nature of the "bursting"? Did an elbow blow off, or did the actual tubing "fishmouth" in a straight section. This doesn't sound like a freezing problem.

 

[MPcontrol1]

i recently had a problem with frozen coils that broke when we had an unusual nights here in Fl. Alot can contribute to the coil failures such as ex fans running all the time creates pressure differences therefore depending on how well its sealed (the building that is) it will suck in the cold air. Also there should have been some kind of freeze protection in the program in the control system so when the temp reaches a certian point the pumps would operate and the valve will open therefore moving water. But in your case it would be hard to say but it wont take much for the coils to rupture. Protect them as much as you can becasue they can do alot of damage

 

[Rondelli]

Thank you for the information. We'll keep all these responses for reference should we have additional ruptures.