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I've got an RTUA 70 with the exact same symptoms.

At start up, only with circuit #2, EWT at sensor drops quickly while LWT sensor doesn't change much, and it will lock out.

There are no provisions at chiller barrell for measuring pressures. I just found the curve for the chilled water pump and am going back to take those measurements, but I have a feeling I will find the flow to be within specs, maybe even above specs.

Pumps from and back to an open tank. There is a filter device in the line, but when I asked the maintenance man about it he said there were no bags in it, haven't been for years. The water in the tank looks like the creature from the black lagoon would be comfortable in it.

I'm guessing at this point that the chiller barrell is fouled, or the baffles are damaged in some way. The 1/4 inch nipple off the top of the barrell on the outlet side, used for an air vent, was plugged with crap.

Sensors read identical when neither circuit is running and temp stabilizes thru barrell.

Is it possible that the LWT sensor may be covered in crud, slowing it's response time in relation to the EWT sensor?
Or could a problem with the EXV or unloaders cause this on start up, maybe especially at colder ambient?

Is there anything else, not flow related, that would cause this?

Originally Posted by graham

...But what if you dont like chocolate ??????
Why not tomato soup ????
Or strawberry yoghurt ??

perfectly acceptable buddy!

but as was mentioned before...you just need to specify...like 'feet of head' or 'feet of water' or 'feet of pudding' or 'feet of tomato soup'

from now on...let us all convert all densities into the density of chocolate pudding and confuse the crap out of everyone!

But what if you dont like chocolate ??????
Why not tomato soup ????
Or strawberry yoghurt ??

UPDATE

I added some details to my profile....if anyone's interested...thanks

FOUND IT...sorta!

Density of water: 62.43 lbs/ft^3

Chocolate pudding: 59.631 lbs/ft^3

from now on...let us all convert all densities into the density of chocolate pudding and confuse the crap out of everyone!

Originally Posted by jayguy

or pudding. it could be be pudding. what IS the specific gravity of pudding? i suppose that it would depend on flavor and whether it was made of whole milk or skim....google time!

I don't think flavor plays a factor but milk on the other hand changes everything. Now I'm hungry for some pudding. Thanks jayguy

Originally Posted by Phisher

"ft. of head" of what liquid? If the liquid is not water, then you must factor the specific gravity of the liquid...

or pudding. it could be be pudding. what IS the specific gravity of pudding? i suppose that it would depend on flavor and whether it was made of whole milk or skim....google time!

workinschlep,
Just a word of advice. Guys on this site like to check profiles for credentials before responding to posts. Update your profile and get your post numbers up so you can apply for pro membership.

Originally Posted by workinschlep

That is something I hadn't considered...thank you..I just found this sight and found it pretty interesting.

No problem. Welcome to the site. I learn more on this site then I do in training classes.

Originally Posted by Phisher

"ft. of head" of what liquid? If the liquid is not water, then you must factor the specific gravity of the liquid. The term "head" was adopted as the industry standard when referring to pumps. I posted the flow chart from the RTAA IOM. I'll let you read it for yourself.

That is something I hadn't considered...thank you..I just found this sight and found it pretty interesting.

Originally Posted by workinschlep

Its actually "ft. of head".......pd times 2.31 equals ft. of head....which allows you to find gpm....Mike

"ft. of head" of what liquid? If the liquid is not water, then you must factor the specific gravity of the liquid. The term "head" was adopted as the industry standard when referring to pumps. I posted the flow chart from the RTAA IOM. I'll let you read it for yourself.

FT. of water?

Originally Posted by Phisher

Your right it is "ft of water" not psid. Not the first time if spoken without thinking first.

Its actually "ft. of head".......pd times 2.31 equals ft. of head....which allows you to find gpm....Mike

Originally Posted by sds5150

It still wonder about the internal design of the evaporator. It is strange that Circuit 1 would work, but not circuit 2.

Phisher nailed it. Circuit 2 is closer to the EWT sensor, therefore with low flow the temp drops there first.

I open my trane evaporator and metal baffles are both European and American (ertab, ertwb, RTAA)


Read page 120 of the IOM it clearly states that the evaporator is constructed using steel. copper and POLYPROPYLENE components .
Last time I checked polypropylene was a plastic unless I was absent from science class that day ????

20# entering pressure sounds low to me. Where are your pumps located in relation to the chiller? How many floors is the building? Have you checked the water makeup to make sure it's working? Did you use the same pressure gauge for the entering and leaving pressure readings?

I open my trane evaporator and metal baffles are both European and American (ertab, ertwb, RTAA)

Longtime lurker here; sds, I see in your first statement you mention automotive plant. Is this chiller on an open sump? Is there an open tank somewhere in the chilled water system, or any other way for process debris or material to get in the chill water? If so, the chiller barrel could be acting as a strainer and be clogged up with that material. This would affect water flow rate and heat transfer. Flow decreases and pressure drop increases ( think of shutting a valve ). Heat transfer decreases due to insulating effect of material on tubes and maybe even covering some tubes and preventing water from flowing over them. This could also happen if there have been recent additions or repairs made to chill water system and debris was introduced ( this is less likely to cause this much of a problem ). If this is not an open sump.... never mind . I would look at Graham's last post. I have never seen that , but from previous posts I wonder Graham has?

I have my profile photo trane evaporator

Has this evaporater ever seen "hot water " temps over 125degrees F will deform the plastic baffles and the heat transfer goes for a S?&$ and your evap temps will take a dive .

give me your email, I send the photo of the evaporator before assembly