40 degree outside air, need to turn chiller on

[krptonicx]

Just started new job 2 months ago,,worked in residential for 10 years,this is my first industrial/commercial job..All greek to me,but im learning a lot everyday.Dont understand one thing though,why the hell do i need to turn the chiller on when its 40 degrees outside...Always thought economizers were invented to give free ac when needed...if i dont turn off the 5 million btu boiler when its 40 and turn on the chiller,,the building gets in the lower 80's,just doesnt seem right to turn on the ac at 40....its been like this ever since it was installed,my guess is low-bid install...any feedback?

[maxster]

with 40F OA you should be mixing that with RA and dumping some of the same return,the space sounds like it has a good interior load once the day gets going with people and lighting loads ETC.if your AHUs are setup for econo the coils should be drained of the chilled water for the winter,and your AHUs should be setpoint controlled on the heating coils from DA or even RA...are there heating coils in the same chilled water AHUs.

[jayguy]

welcome to commercial/industrial world! mother nature still works the same in this world as it did in the resi world...mistakes just cost more and make bigger bangs we also have a lot of dumb installers, techs and engineers in this world...and some great ones too. keeping that in mind, you may be correct...someone may have messed up...investigate it. at the very least, you will learn something and the customer will be greatful that you check out everything.

you may have an interior space that needs cooling year round. you may have a space that has humidity concerns. if you can not get the proper amount of air to the space with the correct air properties, you may have to mechanically condition it.

[snipe70e]

If your building is just office space and you have an operating eccon system you should not need mechanical cooling.

If you have data centers of process areas then they may dictate other operations.

[big johnson]

Just started new job 2 months ago,,worked in residential for 10 years,this is my first industrial/commercial job..All greek to me,but im learning a lot everyday.Dont understand one thing though,why the hell do i need to turn the chiller on when its 40 degrees outside...Always thought economizers were invented to give free ac when needed...if i dont turn off the 5 million btu boiler when its 40 and turn on the chiller,,the building gets in the lower 80's,just doesnt seem right to turn on the ac at 40....its been like this ever since it was installed,my guess is low-bid install...any feedback?

What are your mixed air dampers doing on your air handlers? Is your economizer working? What's your discharge air set point? What is your discharge air temp with economizer running? Your dampers are not modulating to mix outside air so you have to run the chiller. That would be my first approach.

[acjourneyman]

Put it this way, if the mechnical engineer was experienced, good and not just out of school you should not need a chiller at 40 deg.Problem is there is alot of lousy engineers out there and that is where we come in, to fix there problems.I have walked on lots of jobs and heard, your controls suck, your AHU's can't keep up , yada, yada yada, and I always say, the best equipment in the world can't fix the worst engineereing in the world, simple as that.

[Airmechanical]

Put it this way, if the mechnical engineer was experienced, good and not just out of school you should not need a chiller at 40 deg.Problem is there is alot of lousy engineers out there and that is where we come in, to fix there problems.I have walked on lots of jobs and heard, your controls suck, your AHU's can't keep up , yada, yada yada, and I always say, the best equipment in the world can't fix the worst engineereing in the world, simple as that.

very well written journeyman!



.

[snipe70e]

Put it this way, if the mechnical engineer was experienced, good and not just out of school you should not need a chiller at 40 deg.Problem is there is alot of lousy engineers out there and that is where we come in, to fix there problems.I have walked on lots of jobs and heard, your controls suck, your AHU's can't keep up , yada, yada yada, and I always say, the best equipment in the world can't fix the worst engineereing in the world, simple as that.

Boy ain't that the truth

[dan sw fl]

..... this is my first industrial/commercial job.

... , why the hell do i need to turn the chiller on when its 40 degrees outside. economizers were invented to give free ac when needed.

its been like this ever since it was installed, my guess is low-bid install.

any feedback?

What type of industry?
What are the internal gains?

Is an economizer currently installed?
If not, is it reasonable to plan an upgrade and retrofit the unit to reduce the ever increasing operating costs?

If yes, How is the economizer set-up?

Like big johnson states
Your dampers are not modulating to mix outside air so you have to run the chiller.

Fix might be relatively simple, if someone knows the current control scheme.

[chillerout1]

do you have a water side economizer for the chilled side ? you will have a large plate heat exchanger and valves in pipe to bypass chiller and cool water using the cooling tower

[tex~n~oz]

You are probably right about the low-bid... but it doesn't go back to the installer as he's usually just installing as per engineering plans. You can't really drop it in the lap of the engineers either as they have been given a budget to stay within. It goes back to the bean-counters who get a pat on the head and a huge bonus from the big boss when the project comes in at $500K under projection. Everyone forgets to tell the boss that he's going to lose his shirt on inefficiencies by running chillers at 40.

Contractors report to engineers
Engineers report to planners
Planners report to bean-counters
Bean-counters kneel under the bosses desk and work to please...

Once again, if the boss would just talk to the engineers, he'd be clued in, but because he can't be bothered, he pays in the end as everyone's had a dash for savin' cash in between.

IMO the only people who aren't influenced are the engineers and contractors. It's to their benefit to make a larger, more complicated install as they get paid more.

I just commissioned a multi-chiller install that assuredly cost millions yet didn't have a single air-purge valve on any chilled water line. Why? Because they cost too much money and they will be added as a "variation" later if they absolutely have to have them.

Tell me where that came from?

[big johnson]

It appears that krptonicx has left the building leaving the rest to rant and rave about design engineers.

[dan sw fl]

IMO the only people who aren't influenced are the engineers and contractors.

It's to their benefit to make a larger, more complicated install as they get paid more. << ... Tell me where that came from?

Original design engineering is based on a fixed fee.

Of course, it may be quite different in the land of OZ

[esornivram]

Original design engineering is based on a fixed fee.

Of course, it may be quite different in the land of OZ

it can also be cut during build, and many things could have been left out. ran into this in an new city hall being built, they cut out controls, water by pass valves, and improper water flow thru chillers, resulted in fllod back and took out all the compressors, 400 tons worth.in less than 14 months of ops

[tex~n~oz]

It's my understanding that the engineering firm charges a commission based on winning bid, not to include any later variations, on top of a previously agreed upon fee.

That's my understanding and it would make sense.

The more complicated the system, the more liability on the engineering firm, the more man hours to design, the more money they get on the bottom line.

[krptonicx]

basically,from what i can gather,its just a low bid installation..Its state of ct office buildings..I am gunna have one helluva time doing any repairs on these unites,they are literally shoehorned in above the drop ceiling.I changed the filters on the 67 fan coils in one building,and literally had to fold up the filters like accordians to get them in there...Never seen anything like it.

[allank]

Does the chiller short cycle

[crab master]

We have a system that we have to run the same way. Fan coils with heating and cooling on each floor and the only outside air available is the minimum outside air intake required for each floor. Sun comes up and its around 40 degrees OAT, the solar load is enough that we have to bring on the chiller. No water side economizer either.

[tex~n~oz]

basically,from what i can gather,its just a low bid installation..Its state of ct office buildings..I am gunna have one helluva time doing any repairs on these unites,they are literally shoehorned in above the drop ceiling.I changed the filters on the 67 fan coils in one building,and literally had to fold up the filters like accordians to get them in there...Never seen anything like it.

When I was in service, I had a building with almost the same set-up. Water-source heat pumps just stuck anywhere they could find a place to stab em. Of the 150 units, there were about half a dozen that never did get a filter change as they couldn't be gotten to without dropping the whole unit.
Sounds like they've done the same thing with your fan coils...

It took years, but I finally found out why.... Cheap as hell to buy, install and duct with flex. The engineers didn't care if you couldn't get to the filters.. Not their problem and by the time it was a real issue, the job was signed off and paid for.
It costs just a fraction to put these types of systems in place as compaired to a properly designed system with central AHUs, VAVs and metal ducting, economizers, etc.

Don't shoot the installers, it was the bean-counters behind the smoking gun on this one. They wanted CHEAP and you got it.

Be thankful for small blessings though.. No compressors or reversing valves to change out while balanced over someone's desk; while you're holding a hot torch in a small dusty cabinet with a mirror in your teeth to see what you're doing.

I had almost forgotten about that miserable migraine of a place....... It was a mental hospital and more times than not, I just wanted a room at the end of the day.