I have a 40ton chiller on an office building… mid 60’s vintage… cold water a/c boiler/hot water heat…
for the most part for it’s age it’s not alot of trouble… and the electric bill is always cheaper than i think it should be for the building size (very well sealed building and alot of concrete mass)
had the chiller pump leaking (the pump that pumps water thru the cooling tower and thru the compressor coils) when this pump screws up (stops pumping) the compressor will get hot and it then blows a pop off valve releasing it’s r-22 charge… all of it… so i try to take care of the pump…
not knowing a ton about this system but have’n kept it up the 6-7 yrs i’ve owned the building i can only base it performance on what i’ve known /learned in those years…
i write down the high & low pressures everytime we check em… so the only norm i know is based on this info… i have had “professionals” service it also, seems they knew as much or as little as me…
anyway after replacing the seals in the pump… it was still leaking a bit… watching the pump wind to a stop… Mike (the all things guru that works with me) spots that the pump is turning backwards… only knew this because he knew how the vanes in the pump were… i’d have never spotted it… anyway i’m not there so he calls me and i tell him to reverse 2 wires (3ph) and see what happens… yep… spins in the correct direction…
he calls right back… says this thing has never been this quite and smooth… the presures have never been in these ranges… and the water temps coming out of the chiller have never been this low…
have no idea if it’s always been this way… if the pump was replaced at some point and wired with the wrong rotation… i do know it’s been this way for the years i’ve owned it… no way do i see that anyone would have ever spotted it unless the pump just died and even then they wouldn’t have known the old pump ran backwards… we’d just think WOW that new pump sure makes a difference…
if the pump hadn’t leaked a little after we rebuilt it mike would have never spotted it… i know i wouldn’t have because i didn’t even know/remember which direction the vanes in the pump went… have to wonder how many things like this are never found out…
anyway… i hope i get calls about the building being too cold…
p
Replies
There are lots and lots of those kind of problems on anything that is "one shot" design and build.
Now a similar problem might have been in a car, but with the thousand made sooner or later someone finds the problme and then they go back and check the source.
I used to design control systems for rual water distribution systems.
We had a master program and then a customization scheat that defined each tower, each pump station, each monitor point. The parameters to be measured at each site, what combination of pumps that there are. What controls the pumps and in what sequence they run. What signals are used for inhibits of the pumps such as low water cutoffs, etc.
Literely millions of combinations and ALL of them have not been tested.
And from time to time the new features are added to the main program.
Had one location that they added a couple of new remotes and required a new feature. In testing it out I found that a feature that had been at the location could not have worked as designed for the last 8 years. But no complaints. And the fest that I could find that was the only location that used that combination.
So the question was do we leave it alone because now that it he way that the customer thinks that it should work. Or "fix" it and maybe have some other side affect.
BTW you should add some safeties to the compressor.
An overtemp or overpressure cutout. Or waterflow switch inhibit.
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
I'll second the flowswitch. Even a pressure switch on the water side. Lot cheaper than new freon.
man thanks for input... over the years (40) it looks like 100 different people have worked on this unit.... many many types of controls and management systems have been added and disconected ... I guess i should have before this taken the time to remove all the junk that was "sold" to previous owners and get it back to basics...
i too would think there has to be other safeguards inplace so that it wouldn't blow it's charge... I assume they have been bypassed... it's a old carrier unit... with a maurby ? water tower... I am and have been on the lookout for a newer system that has been removed for whatever reason just so i have one when i really need it...
thanks again for the input
P
I think your tower may be a Marley. Good units still produced today.
Mike L.
i've got a building wired 3 phase. the other day the elec. pole blew down and the electric company came out and put the new pole up.what surprised me was that they were unsure which wire goes where and was concerned about the phasing.had to get a electrician there to confirm they were right.
i wonder if there has been work done at your service entrance at some time and they got it out of phase?
now just so were all clear i have no idea what all this phasing krap means other than if it's wrong things spin backwards,but just thought i'd throw it out there.......... larry
hand me the chainsaw, i need to trim the casing just a hair.
Good catch on the pump rotation, you should check rotation on ALL of you 3 phase equipment after that one. Like a pump, a fan running backwards will still move air, just not enough of it.
You really need to put a manual reset (so you will go look at the problem and fix it) high pressure safety on your chiller. It is piped to the discharge side of the refrigeration circuit and wired into the controls to interrupt the coil voltage to the compressor contactor. WAAAY cheaper than a full charge in your chiller. If you get a combination high/low switch or a second low pressure safety, (both will need a second connection to the suction side of the refrigeration circuit) you will be able to have your unit shut down on a loss of charge without risking your tube bundle (you just think the freon was expensive).
There may already be a high pressure switch on the unit that may have been bypassed since the backward pump ritation would cause higher head pressures and consequently, frequent trips of the switch. It would have been easier to bypass the switch than troubleshoot the real problem.
Edited 7/24/2007 6:17 pm ET by Bender
What brand is your chiller? I had a pair of Carrier 125T units, installed in 1968, that did a nice job unmtil they were replaced in 2001. We replaced them because of added heat load in the building, and they could no longer keep up ... they were running at 100% from March through October. We put in some larger 2-stage units, and we could run at partial load and still keep the building cool. The compressors were not evenly split, so it wasn't as simple as running at 25% or 50%, there was some odd percentages. But now we had redundancy!
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