Original message
| Zzz
 |  "enthalpy"
, posted Sun 5 Aug 10:23  
How can i learn more about enthalpy controls and diagnostics. I know how they operate just need more on fixin em.
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Replies:
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| kimmy
| "Re(1):enthalpy" , posted Sun 23 Sep 22:26
Enthalpy controls work on outside air and inside air.
If it is humid the A/C works.
If it is not humid the outside air cools.
Any questions will be answered. Eventually.
30+ years in the HVAC/R trade.
Started when equipment was repaired not replaced.
Still feel the same way.
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| | Zzz
| "Re(2):enthalpy" , posted Wed 26 Sep 23:40
thanx for the usles tidbit
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| Zzz
| "Re(1):enthalpy" , posted Tue 21 Aug 09:48
What Are the Options?
To increase the likelihood that an economizer will not turn from an energy saver to an energy waster:
1. Specify upgraded components, such as stainless-steel dampers, direct-drive actuators, and enthalpy control.
Stainless-steel dampers resist corrosion much better than the galvanized-steel and aluminum dampers typically used in economizers. Though stainless-steel dampers cost about twice as much as galvanized-steel dampers, they are cheaper than the total cost (including labor) of removing and replacing a failed damper. Unless a building is near sources of marine or industrial corrosion, however, this extra cost is probably not justified.
Direct-drive actuators have fewer moving parts between actuator and damper, and therefore fewer parts that can fail. They are also much easier to install than typical linked actuators. Since their introduction in the 1980s, a company named Belimo has dominated the market, but increased competition is narrowing the price gap between direct-drive actuators and the more failure-prone linked actuator. In many cases, direct-drive models now cost the same as or less than their linked counterparts.
In a relatively dry, mild climate, a drybulb control system that simply measures outdoor air temperature is sufficient. In more humid climates, enthalpy-based controls, which account for both drybulb temperature and humidity, are best. Modern sensors that use solid-state electronics to measure enthalpy are much more reliable than older-technology sensors.
2. Test economizers right from the start and at least twice a year thereafter. Here are three testing techniques:
Observe the damper position. Stand next to the outside-air damper with a handheld thermometer, and compare the damper position with the lockout and high-limit settings. If the damper's position is inconsistent with the settings on the controller, either the controls are malfunctioning or the damper is stuck. For the same reason that a broken clock tells the right time twice a day, it is impossible to know from a single observation whether a damper is functioning properly or just happens to be frozen in a position that is momentarily consistent with the controls. For this test to be effective, it must be repeated under a range of outside-air conditions.
Fool the economizer controls. To test drybulb economizers, wait for a cool day when the economizer damper is open, and then warm the outdoor temperature sensor with your hands or an electric hair dryer. When the measured temperature exceeds the lockout setting, the damper should move to its minimum position. If the economizer has enthalpy controls, lightly spraying the enthalpy sensor with water from a spray bottle will temporarily raise the humidity of the air, which should trigger a reaction from the system. If the system does not behave according to its control settings, either the sensors are inaccurate or the economizer controller is malfunctioning.
Install temperature dataloggers. For a detailed look at how individual economizers operate over time, diagnosticians can install portable devices that measure and log temperature. Typically, these devices are installed in the outside-air, return-air, supply-air, and mixed-air streams for two weeks. The collected temperature data may then be downloaded and diagnosed using simple spreadsheet software.
3. When all else fails, lock the economizer in the minimum-outside-air position.
Some economizers cannot be cost-effectively maintained in working order. They may be:
located in an especially corrosive environment,
made from seriously inadequate materials,
even in top condition, capable of producing only inconsequential energy savings,
installed in a building with undersized outside and exhaust air openings, or
serviced by unmotivated technicians.
Regardless of the reason, if an economizer repeatedly fails and it is prohibitively expensive to repair it, the best solution is to lock it into its minimum-outside-air position. Although you don't get the benefits of the economizer's potential energy savings, you do guard against its becoming a significant energy waster.
"This is the best I could find so far, more knowlege is required."
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| timlaw
| "Re(1):enthalpy" , posted Mon 20 Aug 18:25
what brand names do you need repair infromation on?
Tim Law
Chief Technical Officer
Tudi Mechanical Systems
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| | Zzz
| "Re(2):enthalpy" , posted Tue 21 Aug 00:55
honeywell seems to be the most popular around here I would expect diagnostics would be pretty much the same on all though.
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| fitter597
| "Re(1):enthalpy" , posted Sun 5 Aug 16:50
The Union offers classes on economizers which get into great detail on enthalpy's and how they not only sense temp but humidity as well.
Pipefitters Local 597
" We do it right the first time"
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| | Zzz
| "Re(2):enthalpy" , posted Sun 5 Aug 21:22
If I was in the union that would be gr8. Don't think they'd let a non-member take it but thanx
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| | fitter597
| "Re(3):enthalpy" , posted Sun 5 Aug 21:39
carrier holds classes for that I think, check with the local suppliers
Pipefitters Local 597
" We do it right the first time"
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