TXV's To Adjust or Not to Adjust - That is ....

[Refrigerologist]

[quote=philfridge;100895]

Many engineers' in this industry say "you should never adjust a TXV superheat setting as they are factory set".

This is correct and if you select the right size orifice no adjustment is required . Its all about knowledge and experience , however not everyone knows how to select the correct size orifice they then start messing with the t.e.v ?? why o why just leave them valves alone and get some training

If you read some of my previous posts you will see that I completely disagree. Valve superheat should always be checked and adjusted as per individual system requirements. As I have said, if we are not to adjust the valve then the manufacturer would not bother to fit an adjustment screw I would suggest you look at a selection catalogue for, say Danfoss valves, it will show that an orifice will provide different capacities at differrent conditions and the valve cannot be factory set to cover all of the possible conditions that the valve will need to cover!

[philfridge]

[quote=Refrigerologist;101113]

If you read some of my previous posts you will see that I completely disagree. Valve superheat should always be checked and adjusted as per individual system requirements. As I have said, if we are not to adjust the valve then the manufacturer would not bother to fit an adjustment screw I would suggest you look at a selection catalogue for, say Danfoss valves, coit will show that an orifice will provide different capacities at differrent conditions and the valve cannot be factory set to cover all of the possible conditions that the valve will need to cover!

Like i said you do not need to adjust the valve if you know what you are doing with orifice selection . As you mentioned Danfoss valves these are preset at 2 1/2 turns out and this does not need any adjustment in my experience

[750 Valve]

[QUOTE=philfridge;101154]

Like i said you do not need to adjust the valve if you know what you are doing with orifice selection . As you mentioned Danfoss valves these are preset at 2 1/2 turns out and this does not need any adjustment in my experience

I completely disagree, comparing a danfoss tuae valve which has 9 selectable orifice sizes to say a sporlan balanced port valve (SBF series) which has only 5 - leaves a lot of room for mismatching evap load to valve capacity with the sporlan valve. If you believe EVERY single valve will keep 6K superheat then maybe you need to set up some more evaps... distributor and coil design have a big influence on how a valve behaves as well - this is why every valve should be evaluated for its performance and adjusted if necessary to keep a stable superheat.

I commission supermarket cases nearly every day (or night ) and have been doing so everyday for nearly 8 years straight now and I cannot tell you how many of the same cases with the same evaps, distributors and txv's I come across... if you think they all behave the same as far as superheat control you have another thing coming. I use an Einstein or RMCC in a suitcase and setup probes to log and graph their performance, there are differences in their factory setting to say the least, Alco valves are the worst as far as differing behaviours for the same given conditions, then sporlan and I'd have to say Danfoss are probably the best as far as consistency goes.

I'd love to just start them up and skip the whole txv logging and adjusting but unfortunately the supermarkets over here have consulting engineers that will randomly check superheat in each store on handover - if its not between 4 to 6k you will be made to do them all again .

[Refrigerologist]

[quote=750 Valve;101205]

I completely disagree, comparing a danfoss tuae valve which has 9 selectable orifice sizes to say a sporlan balanced port valve (SBF series) which has only 5 - leaves a lot of room for mismatching evap load to valve capacity with the sporlan valve. If you believe EVERY single valve will keep 6K superheat then maybe you need to set up some more evaps... distributor and coil design have a big influence on how a valve behaves as well - this is why every valve should be evaluated for its performance and adjusted if necessary to keep a stable superheat.

I commission supermarket cases nearly every day (or night ) and have been doing so everyday for nearly 8 years straight now and I cannot tell you how many of the same cases with the same evaps, distributors and txv's I come across... if you think they all behave the same as far as superheat control you have another thing coming. I use an Einstein or RMCC in a suitcase and setup probes to log and graph their performance, there are differences in their factory setting to say the least, Alco valves are the worst as far as differing behaviours for the same given conditions, then sporlan and I'd have to say Danfoss are probably the best as far as consistency goes.

I'd love to just start them up and skip the whole txv logging and adjusting but unfortunately the supermarkets over here have consulting engineers that will randomly check superheat in each store on handover - if its not between 4 to 6k you will be made to do them all again .

The quote at the head of your post is not one of mine. I believe valve superheat should be checked and adjsuted, if it is required, for every system on commissioning. In other words you will get no argument from me I will also add that I too find Danfoss valves to be the best and most consistent.