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passandscore
20-07-2013, 03:52 AM
Hey guys,

I responded to a arena that had a high level occur in the chiller. After getting the plant back online I started to investigate and came across the following. There are 3 sources in which liquid can enter the chiller.

1) Liquid line solenoid
2) Liquid condensate from the snow melt pit heat exchanger
3) Liquid condensate from the underfloor heat exchanger.

The attached pic refers to #3, the underfloor. I have ruled out the others. You can see from the pic that there is a Phillips float valve and the outlet is frosted (right back to the chiller). Normally the valve opens only when the float is full enough to lift the needle off its seat. It closes shortly after. This is not happening! I can see liquid boiling off in the sight glass and the float is cold, plus the heat exchanger itself is sweating. If the check valve is leaking is it possible for the liquid to pass backwards through the float? If not then it has to be a faulty float. What would be the ideal way to confirm that?

Any thoughts?

PIC - http://passandscore.weebly.com/, float valve is fig 7 from the download.

RANGER1
20-07-2013, 11:02 AM
passandscore, If in doubt rip it out.
Suggest order new needle & seat but need a bit more info on how the whole thing works!

passandscore
20-07-2013, 01:11 PM
The system operates as follows. Primary Refrigerant - Ammonia. Secondary Refrigerant - Brine. Discharge ammonia vapor enters the top of the heat exchanger, condenses and enters the bottom of the float valve. The line on top of the float valve is just a vent line back to the top of the heat exchanger. Once there is enough liquid in the float it will open, allowing the liquid to travel through the outlet and back to the chiller entering at the same point that the regular liquid makeup would, in the bottom. As for the brine, it is pump circulated through the tubes in the heat exchanger, picking up heat and transferring that heat to the underfloor.

Before i rip anything out I am looking for a simple way to confirm a faulty float.

HVACRsaurus
20-07-2013, 01:59 PM
Hi,

Close valves top & bottom of Phillips float - that will stop feed to accumulator..

But,

a) Under normal conditions liquid WILL condense because the underfloor glycol temperature is less than saturated condensing pressure

b) line is usually insulated for reason a)

c) during low load the underfloor glycol might condense more liquid than the accumulator can "consume"

d) if the float is leaking...... What should pass through....... Gas!

e) if condition c) exists inhibit underfloor pump during low load.

RANGER1
20-07-2013, 10:21 PM
passandscore, If in doubt rip it out.
Suggest order new needle & seat but need a bit more info on how the whole thing works!

I didn't mean to be smart by saying "if in doubt rip it out", but I thought you answered your own question by saying you eliminated other 2 possible reasons.
You are only giving us the local problem of the Phillips float, we or I would like to know how the whole system works.
HVACRsaurus is right about float, but if you could be sure level in heat exchanger is low so you know float should not be feeding, then observe. Is there a place to connect a gauge on float to see if pressure drops when float gas & liquid are isolated.
The non return valve should not leak & back feed if pressure is lower than float pressure.
Liquid would sit in this line for awhile after float needle & seat closes.
It would be surprising if this float on its own can give a high level as its only 1 of 3 heat exchangers on discharge of compressor.

- Is it critical charge
- can you isolate other 2 sources of liquid makeup & observe. How did you eliminate them.

Segei
20-07-2013, 10:43 PM
How do you control brine temperature?

RANGER1
21-07-2013, 02:00 AM
passandscore, when was the last oil drain on chiller. Could control column be sluggish because of oil build up?
If there was liquid being condensed in H/E it has to return to chiller no matter what. Normally draining this line direct back to liquid receiver would be ideal (if it were mounted above liquid receiver, no float required).

passandscore
21-07-2013, 02:51 AM
The system is not critical charged. This is a 2 sheet facility. They have 2 chillers piped identically. The other sheet is now offline and valved it for the season. When both chillers where online I isolated all the liquid feeds to the chiller in question, therefore pumping it out. Once it was pumped out I would de-energized the liquid line solenoid and open the isolation valve corresponding to that valve. Then I just wait to see if it is passing by. The chiller has a Hansen Level indicator so it is easy to determine. I then isolated that solenoid once again and did the same thing to the snow melt and underfloor solenoids on the discharge side of there respected vessel. No solenoids proved to be the problem. I focused on the float valve simply because it had excessive frost build up. Perhaps no components are at fault? Perhaps it is a problem like HVACRsaurs stated regarding low load. I'm still trying to understand that completely. Care to elaborate?

The system is sensing return brine temperature and it has a cutout set-point of 3c with a 1c deadband.

The oil pot is completely iced-up so I would venture to say it was drained recently. I will check the piping to the column to see if oil can get trapped in there. If so it is certainly a potential problem.

RANGER1
21-07-2013, 07:06 AM
Hi,

Close valves top & bottom of Phillips float - that will stop feed to accumulator..

But,

a) Under normal conditions liquid WILL condense because the underfloor glycol temperature is less than saturated condensing pressure

b) line is usually insulated for reason a)

c) during low load the underfloor glycol might condense more liquid than the accumulator can "consume"

d) if the float is leaking...... What should pass through....... Gas!

e) if condition c) exists inhibit underfloor pump during low load.


Possibly liquid can condense after leaking float slowly increasing level as well as ice melt topping up chiller with its condensate.

Can only try to eliminate by installing new needle & seat, inspect non return valve while lines are empty.
One more high level call out may cost more.

Josip
21-07-2013, 02:13 PM
Hi, passandscore :)


Hey guys,

I responded to a arena that had a high level occur in the chiller. After getting the plant back online I started to investigate and came across the following. There are 3 sources in which liquid can enter the chiller.

1) Liquid line solenoid
2) Liquid condensate from the snow melt pit heat exchanger
3) Liquid condensate from the underfloor heat exchanger.

The attached pic refers to #3, the underfloor. I have ruled out the others. You can see from the pic that there is a Phillips float valve and the outlet is frosted (right back to the chiller). Normally the valve opens only when the float is full enough to lift the needle off its seat. It closes shortly after. This is not happening! I can see liquid boiling off in the sight glass and the float is cold, plus the heat exchanger itself is sweating. If the check valve is leaking is it possible for the liquid to pass backwards through the float? If not then it has to be a faulty float. What would be the ideal way to confirm that?

Any thoughts?

PIC - http://passandscore.weebly.com/, float valve is fig 7 from the download.

I should understood your explanation how that plant works, but unfortunately I don't ... is it possible to post the schematic scheme of the plant?

... or maybe another photo where we can see chiller and complete piping from float valve to the chiller ...

but ... according to your photo and attached manual for float valve (see Figure 2 and Figure 7) ... seems float valve is installed wrong ... the flat side of the float would be on the bottom and the belly on the top on your photo installation is opposite ... maybe I am wrong ... I suggest you to open that valve and check when is open and when is closed ...

This float is a high pressure type then the system should be with critical charge i.e. whatever condensate within heat exchanger/condenser will enter into chiller ... from your photo this condenser is S&T type equipped with float seems like critical (refrigerant receiver is not mentioned and not visible on your photo) charged system

If the float is a low pressure type it should be installed near to chiller at the requested level of the refrigerant within chiller ... system can be overcharged because the excessive refrigerant will remain within condenser (not too much-to not reduce pipe condensing area) or within HP receiver - where we can accumulate much more refrigerant ...

Best regards, Josip :)

passandscore
21-07-2013, 04:16 PM
I will try to get a piping schematic of the plant.

The room is small and over filled with equipment so there is no way to take a photo(s) that wouldn't just confuse the matter further.

It does appear that the float is installed incorrectly. Good eye! I will be fixing that as well as replacing the needle and seat assembly.

The float is a high-side model but used like an oil drain application. There is a liquid receiver that supplies both chillers. The underfloor heat exchanger in the photo is a shell & tube model where the discharge gas condenses and the float opens as it gets full allowing the liquid to enter at the bottom of the chiller.

Josip
21-07-2013, 07:59 PM
Hi, passandscore :)


I will try to get a piping schematic of the plant.

The room is small and over filled with equipment so there is no way to take a photo(s) that wouldn't just confuse the matter further.

It does appear that the float is installed incorrectly. Good eye! I will be fixing that as well as replacing the needle and seat assembly.

The float is a high-side model but used like an oil drain application. There is a liquid receiver that supplies both chillers. The underfloor heat exchanger in the photo is a shell & tube model where the discharge gas condenses and the float opens as it gets full allowing the liquid to enter at the bottom of the chiller.

When you check a float valve assembly don't forget to check non-return valve above.

Even if you have a liquid receiver I believe it is only to refill the system from time to time when need refrigerant ... I assume there is a liquid line from that receiver to chiller ... maybe that one with solenoid valve, but also should be with stop valves before and after solenoid valve ... this solenoid maybe leaks ... then you charge your chiller from two pipes ... liquid from condenser and liquid from receiver controlled by solenoid valve what is not good i.e. hard to control

... but scenario can be different at all .... this is my imagination ... I can be wrong ... if you have a level switch (like Danfoss 38E or some Parker type) beside chiller then I can be right .... if you confirm about level switch then I will tell you my imagination ...

Best regards, Josip :)

RANGER1
22-07-2013, 10:25 AM
josip good pick up on float, sometimes the obvious is overlooked.

I wonder if spare plant has same incorrect installed float if we are understanding this correctly!

passandscore
22-07-2013, 12:59 PM
I will be checking both floats on both plants today. The other plant is offline for the season the the valves are isolated so at this time one rink cannot affect the other. Different story when they are both online though.

passandscore
23-07-2013, 01:44 AM
Problem solved - I determined that the column that houses the level probe had oil in it. After removing the oil and re-calibrating the controller I was able to maintain a more accurate reading/level.

As for the Phillips float I contacted Phillips directly and confirmed the orientation of the valve. It turns out that it is installed correctly I had just been supplied with the wrong manual. It was not a 270 series but a 700H. A legible data plate would have helped! These valves modulate, always keeping a flow through it as long as there is liquid present, hence the frost.

Good to know!

Josip
23-07-2013, 09:31 AM
Hi, passandscore :)


Problem solved - I determined that the column that houses the level probe had oil in it. After removing the oil and re-calibrating the controller I was able to maintain a more accurate reading/level.

As for the Phillips float I contacted Phillips directly and confirmed the orientation of the valve. It turns out that it is installed correctly I had just been supplied with the wrong manual. It was not a 270 series but a 700H. A legible data plate would have helped! These valves modulate, always keeping a flow through it as long as there is liquid present, hence the frost.

Good to know!

Good ... lesson learned ...

So you have a level probe i.e. level switch and feeding to the chiller is directly from receiver via solenoid valve controlled by level probe ... what was my imagination ... level probe was not mentioned before so we were guessing all feeding liquid is coming from condenser via float valve ...

... then if the float valve is 270 series it will be installed correctly ((in this case always closed without liquid (I was thinking it is installed in this position intentionally) and when liquid comes rise the float and release liquid to the chiller)) draining surplus liquid from condenser to the chiller plus additional feeding up to the requested level within the chiller directly from receiver ...

... anyhow it will be good if you can post piping scheme ....


Best regards, Josip :)