hand exspansion valve settings

[chilldis]

the company I work for has contracted with some "experts" to help fine tune our ammonia system for energy efficency. they have told my supervisor (who has no education or experience in refrigeration) that all our hand exspansion valves should be set at 1 1/2 turns open. I have valves set at 1 1/4 turns to 2 1/2 turns depending on the coil. the frost patterns are even and the temperatures in the rooms are consistant. anyone out there have any thoughts on this subject?

[Andy]

the company I work for has contracted with some "experts" to help fine tune our ammonia system for energy efficency. they have told my supervisor (who has no education or experience in refrigeration) that all our hand exspansion valves should be set at 1 1/2 turns open. I have valves set at 1 1/4 turns to 2 1/2 turns depending on the coil. the frost patterns are even and the temperatures in the rooms are consistant. anyone out there have any thoughts on this subject?

Hi Chilldis

I would think the settings would be different for every coil. 1 1/2 turns might be a starting point, but only that.

Kind Regards Andy

[chilldis]

thanks Andy, that validates what I have been saying to my supervisor since this came up

[US Iceman]

Using 1-1/2 turns open is a good starting point to help commission the system. If anything, you could start with the valves slightly open more on the coils at the highest elevation or those furthest away from the pumps. The coils closest to the pumps might be less open, since the pressure will be higher when you are closer to the pumps.

The frost pattern method is a good way to adjust these after the system has stabilized because it is difficult to adjust for zero superheat on the evaporators.

When someone starts spouting off general adjustments for all things you might want to question them closer. It's easy to also sell energy saving projects by stating general statements, like get the suction pressure up and the discharge pressure down. Both are fairly easy to do, but might not work depending on the actual system operation also.

[Segei]

There are so many energy efficiency "experts" around. They can claim anything as energy saving measure.
I found simple way to adjust bottom feed overfed coils. Majority of these coils have BPRs(back pressure regulators) for defrosting. During cooling mode these BPRs show liquid pressure after expansion valves. Usually, this pressure should be 5-10psig higher than suction pressure. So expansion valves can be adjusted accordingly.

[chilldis]

thanks for the feedback, I really do appreciate it.

[Magoo]

Clients pay mega bucks for these desk jockey experts. I had several clients come back with their suggestions, and reply by saying turn everything off and really save some money. Client then drops into the reality groove.
magoo

[US Iceman]

That's very true magoo. A lot of these characters have not actually worked on a system or even designed one, but they insist on telling people how they should work.

[nh3wizard]

Like what most everyone has said, 1 1/2 turns is a good place to start, you will still have to visually check the unit to see how it is performing.

[jromine]

You want to make sure the entire evaportator is frosted and 1-1/2 turns is a good starting point. To dial it in you should measure the air temp across the coil with a device that will measure tenths of a degree. Adjust the HEV in 1/4 - 1/2 turn increments (then wait 1/2 - 1 hour) to get the maximum air temp difference across the coil. Once you stop getting increases, back down to the last increase in temp and open 1/4 turn past that setting.
As operating conditions change (summer vs winter) the expansion valve adjustment will also.

[Grizzly]

You want to make sure the entire evaportator is frosted and 1-1/2 turns is a good starting point. To dial it in you should measure the air temp across the coil with a device that will measure tenths of a degree. Adjust the HEV in 1/4 - 1/2 turn increments (then wait 1/2 - 1 hour) to get the maximum air temp difference across the coil. Once you stop getting increases, back down to the last increase in temp and open 1/4 turn past that setting.
As operating conditions change (summer vs winter) the expansion valve adjustment will also.

It is a good idea to check the date of the post before replying.
Your good advise may be a little late.
Cheers Grizzly

[chilldis]

advice, even a little late, is still a good thing. thanks for the feedback.

[Segei]

You want to make sure the entire evaportator is frosted and 1-1/2 turns is a good starting point. To dial it in you should measure the air temp across the coil with a device that will measure tenths of a degree. Adjust the HEV in 1/4 - 1/2 turn increments (then wait 1/2 - 1 hour) to get the maximum air temp difference across the coil. Once you stop getting increases, back down to the last increase in temp and open 1/4 turn past that setting.
As operating conditions change (summer vs winter) the expansion valve adjustment will also.

I don't think that it is practical. If you have 100 coils, it takes time to adjust them twice per year. What is the difference between summer and winter coil operation?

[desA]

advice, even a little late, is still a good thing. thanks for the feedback.

Agreed. I'm new to RE & find this kind of practical information very valuable.

Thanks to the kind advisers on RE.

[jromine]

Segei,
The difference to be concerned with is the operating conditions of the system. Typically the system operates at significantly different pressures between winter and summer.
I agree, it may not be practical to adjust all if you have a large number of coils (and limited staff), it may be best to find the happy medium. On the other hand, you may be able to record the settings after one annual cycle and just make the adjustments seasonally. The main point was just giving guidenace on how to find the "right" setting...just my opinion.

[US Iceman]

Typically the system operates at significantly different pressures between winter and summer.

Why?

The evaporating pressures should exist within a defined range depending on how much you let your suction pressure float (or minor adjustments to BPR's - which I don't care for).

So if the evaporating pressures stay within their prescribed range then the only factor that change the hand expansion valve capacity (other than adjusting it) is the liquid feed pressure to the hand expansion valve.

If you use a pumped liquid system (mechanical pump or gas powered) or a control pressure system the liquid pressure is relatively stable all year long.

Hence no need to adjust the hand expansion valves once they are set during commissioning.

[chilldis]

very true Iceman. in my experience once a HEV is set ( or reset to keep the paperpushers happy) it should do the job no matter the season. I do vary my suction pressure by a few pounds from season to season. this whole thread started when I asked what other techs do to set a HEV, I think I have got the answers I was looking for, thanks to all.

[josei]

I w´d apprecciate that anyone out there can talk about why and how [procedure] to do this kind of system adjustment. [Fine tune of ammonia system for energy efficiency.].

Thanks.

J.I.M.

[Segei]

I w´d apprecciate that anyone out there can talk about why and how [procedure] to do this kind of system adjustment. [Fine tune of ammonia system for energy efficiency.].

Thanks.

J.I.M.

Adjustment of HEV isn't energy savings. This is regular commissioning.
Energy savings require 2 steps.
1. Determine optimum set points.
2. Implement these set points.
Very often we don't know the optimum set points and sometimes we don't know how to implement them.

[US Iceman]

The adjustment of hand expansion valves is a one-time requirement. The valves should be set so that a sufficient supply of liquid is provided to the evaporator so that it can achieve it's catalog rated performance. This is not efficiency related.

Think of efficiency as a ratio. A common ratio is COP. Here in the US we use kW (power)/Ton of Refrigeration (for compressors). Other ratios can be defined as needed to explain operating data of any specific component (one where electricity is used in relation to something else, i.e., air flow, liquid flow, etc.).

[Segei]

The adjustment of hand expansion valves is a one-time requirement. The valves should be set so that a sufficient supply of liquid is provided to the evaporator so that it can achieve it's catalog rated performance. This is not efficiency related.

Think of efficiency as a ratio. A common ratio is COP. Here in the US we use kW (power)/Ton of Refrigeration (for compressors). Other ratios can be defined as needed to explain operating data of any specific component (one where electricity is used in relation to something else, i.e., air flow, liquid flow, etc.).

We have to take all these ratios and estimate system efficiency. Certain combination of variables will give us optimum system efficiency.

[sterl]

If the evaporators were built for recirc duty and the unit has a guage connection near the liquid header: Close the HEXV COmpletely. Read pressure. Open the HEXV unitl the gauge gains pressure representing the delta-p of MFRS Spac.

[sterl]

Note that will not work with both Gauge and HEXV close to each other and well above the evaporator....

The seasonal gain topic exists only for devices like air handlers which encounter more than 3-times the load at 35 C as at 25 C outdoor temperatures. Other than flooding return pipes: Theres no essential or continuing efficieny to be gained by tuning HEXV's on recirc units. On Liquid Makeup there is some gain in terms of control regularity and moving parts on controlled devices (slide valves, unloading solenoids)...So it could be of some effect on vessels for medium temp duty; the process , minus 40 loads don't know how hot it is outdoors.

[Magoo]

Go back to the basics and check what the pumps, for example are pumping to satisfy the refrig load, against pump curves, one or many evaps., what ever. Double check the compressor performance, you can only get the max from compressor.,with a system balance, the fine art of trimming HEV's come from evap outfeed temps., the compressor dicatates the efficiency factor.

[Magoo]

There is an old saying in NZ about consultants, that rings very true.
Consultants "are the ones that come out of the hills after the battle is over, and kill all the wounded ".
magoo

[US Iceman]

There is an old saying in NZ about consultants, that rings very true.
Consultants "are the ones that come out of the hills after the battle is over, and kill all the wounded ".
magoo

Very true...

The version I have heard is: A consultant is someone that comes from out of town!

They only get called after everything else has not worked.