Learn more about Top 10 temperatures you should know about water chiller systems. The temperature of the water chiller system has a normal temperature range, beyond this range is not normal. These abnormal factors may be the fault, maybe adjusted incorrectly, but it is necessary to analyze the cause, and timely processing or inspection. These temperature points are difficult to measure with a thermometer, generally can only be estimated by hand, and then judge whether normal.
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1. Exhaust temperature:
What affects the Exhaust temperature?
In summer, the exhaust temperature of the compressor is relatively high, hands can not touch.
Exhaust temperature is too high:
The compressor suction temperature is too high, or condensation temperature is too high caused by, must cause attention.
Exhaust temperature is too low:
the hand-touch exhaust pipe is not hot, which means the suction temperature is particularly low, The compressor may run wet stroke or system working fluid is a relatively small operation state. The compressor wet stroke is easy to damages the valve structure, the refrigerant in very few circumstances operation, will affect the motor winding heat dissipation, accelerate the aging of insulation material.
2. Compressor housing temperature:
Impact of casing temperature changes on compressors and refrigeration systems The temperature field of the enclosure of a fully enclosed compressor casing can be divided into two parts:
The upper casing is affected by the inhalation of steam, the temperature is relatively low, and it is in the range of slightly hot or slightly cool. It is estimated that there is condensation water on the surface of the casing around the suction pipe at around 30 °C. The heat generated by the motor in the lower casing and the frictional heat carried by the frozen oil is mainly taken out of the casing by the steam.
Why happen for excessive shell temperature?
the surface temperature of the shell exceeds the normal range, mainly because the suction temperature of the refrigeration system is too high (above 15&#;).
Excessive hot steam into the compressor, absorption of heat in the housing, the steam temperature is higher so that the temperature of the housing rises.
The temperature of superheated steam rises very high, the temperature of the housing also rises very high, adverse to the cooling of the oil, which will affect the lubrication of the moving parts, accelerated wear, or severely make the bearing hold the shaft (bite). Still can cause exhaust temperature to rise additionally
Why affect the case temperature?
the surface temperature of the case is lower than the normal range. because the suction temperature is too low (less than 15 ° C). It is good for cooling both the refrigeration oil and the motor windings, but the cooling capacity is reduced. When the inhalation temperature is extremely low, most of the casing will be dew condensation, and there is a danger of liquid hammer. This is a fatal blow to the compressor, and special attention should be paid. At the same time, a large amount of refrigerant is dissolved in the frozen soil, which is not conducive to the lubrication of moving parts.
3. The condensation temperature:
What is the normal temperature condition of the condenser?
The first half of the heat pipe is very hot, and its temperature has a slow gradual decline in balance. The thermal sensitivity of the rear half of the heat pipe is greatly reduced compared with the first half. Because the refrigerant in the second half of the pipe has gradually liquefied, and the condensation temperature and the supercooling temperature have been reached.
What are the anomalies?
One is that the first half is not too hot, and the second half is close to normal temperature (ambient temperature), because the compressor absorbs the wet steam refrigerant or the refrigerant amount is insufficient.
The other is that the entire condenser is very hot due to excessive refrigerant charge or low ventilation, or high ambient temperature.
4. Condenser Shell temperature:
Water Cooled Condenser :
The shell of a shell-and-tube condenser is normally relatively hot in the upper half and warm in the lower half. The abnormal condition is that the whole Shell is not too hot, the reason is not enough refrigerant.
Another situation is that the whole of Shell is very hot, which is due to insufficient cooling water or poor cooling effect (scaling in the pipe).
Casing Condenser:
Under normal circumstances, the casing surface is very hot, as it is too small cooling water or poor cooling effect; the other is the entire casing surface is not too hot, its reason is the insufficient refrigerant.
Air-cooled condenser:
Air-cooled finned condenser fins are normally relatively hot in the upper half and warm in the lower half. The abnormal condition is that the whole fin is not too hot, the reason is not enough refrigerant.
Another situation is the whole condenser fins are very hot, this time can look at the air-cooled condenser surface is not a lot of dust, if too much dust, you can use high-pressure water rinse fins.
5. The Temperature profile of the reservoir:
Under normal circumstances, the suction tube feels cool to the touch of the hand and is covered with dew. The reason is the condenser cooling difference, high condensation temperature, or refrigerant charge too much.
6. Liquid tube temperature and filter temperature status:
Liquid Piping temperature status: under normal circumstances, the liquid piping is warm. Under abnormal circumstances, the liquid tube is relatively hot. The reason is the condenser cooling difference, high condensation temperature, or refrigerant flow too much.
Filter temperature condition: The basic condition is the same as the infusion tube, but it has a prominent abnormal phenomenon, that is, the filter may be cool, the reason is that the filter mesh is blocked by sludge, so that the filter is blocked, when the refrigerant flow filter screen, throttling occurs, that is, a part of the liquid gasification endothermic, so that the filter cool, serious condensation. Another abnormal phenomenon is the filter is not hot, and the ambient temperature, the reason is a completely blocked filter, the refrigerant can not flow.
7. The temperature of the suction tube
Under normal circumstances, the inspiratory tube feels cool to the touch of the hand and has dew on it. Abnormal circumstances: breathing tube cold, Dew too much, resulting in large-scale Shell dew. The suction tube is not cold, not dew, Shell is very hot. The reason is that the refrigerant flow is too small or the amount of refrigerant is insufficient. The result is an increase in exhaust temperature and a decrease in cooling capacity.
8. The temperature of the thermal expansion valve and evaporation temperature
Thermal Expansion Valve (including electronic expansion valve): normally, the lower part of the expansion valve body is very cold, and there is dew, refrigerant flow sound is very dull. In abnormal circumstances, one is the valve body is cold, more surface dew, or even frosting, the flow of refrigerant sound larger (gas flow). The reason is that the filter screen is blocked, or power box refrigerant leakage, the valve hole closed.
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Capillary temperature: under normal circumstances, capillary cool and knot dew, there is a liquid flow sound. Under abnormal conditions, first, the surface is very cool, but also dew, but the sound of the flow is louder, is the gas flow, its reason is insufficient refrigerant; second, the surface is not cool, not dew, can not hear the sound of the flow, its reason is the filter plug or capillary plug.
Evaporator temperature status: under normal circumstances, the outside surface of the evaporator is very cold, its condensation dewdrops constantly dripping down, in and out of the air temperature is larger, usually, t can be 12 ~ 14 °C. In abnormal conditions, the evaporator surface is not too cold, dew is not much or not dew. You can hear the refrigerant flow sound very loud, in and out of the temperature difference is small. The reason is insufficient refrigerant volume, or expansion valve opening is small.
9. Environmental temperature requirements for outdoor water chiller systems
According to the National Standard, the water chiller unit should run normally when the ambient temperature is below 35 °C. and can reach the refrigerating capacity and other indexes of the product nameplate. When the ambient temperature is in the range of 35 ~ 43 °C, the air-conditioning unit can run, but it can not guarantee the refrigerating capacity of its chrome brand, it has been running at full load, this is the condensing temperature, the pressure, the exhaust temperature are quite high, if the indoor unit has more heat, it's possible for the electronic protector to act, cut off the power and stop the operation. When the outdoor temperature exceeds 43 °C, the air conditioning unit is in overload operation, which will lead to the action of the electric protection device, cut off the power supply, stop the operation.
10. Requirements of indoor air-conditioning temperature
Indoor normal constant temperature value should not exceed 30 °C as well. If the temperature exceeds 30 °C, the air-conditioning unit may be operating under overload conditions, the refrigeration system condensation temperature and exhaust temperature will rise, which may also cause the electric protector action, cut off the power supply, it is disadvantageous to the operating life of the air-conditioning unit.
The heat pump system and water chiller system are the same, whether the normal operation of the heat pump, the main check four-way reversing valve work. Commutating valve, you can hear a relatively loud gas flow sound and the impact of solenoid valve thimble sound (Electromagnetic Field Suction Valve Center), when the solenoid valve in the process of commutating can not hear the two sounds, the solenoid valve may malfunction.
From the above information, you should know-how is important for the temperature of water chiller systems.
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I get emails from time to time with questions that stem from the articles or the podcast. This was a great question, but I was not the best person to answer it.
I reached out to Jeff Neiman, our resident HVAC School chiller tech, and he answered it. Here is the question:
Hello Bryan,
Thanks for all the good material you provide. I mostly work on the commerical building side of HVAC where chilled water is used as cooling medium and cooling towers provide condenser water. We have chillers as well as heat pump and air cool splits throughout facilities. Most of your diagnostics and troubleshooting methods are for air cooled units. Can they be applied to water cooled evaporators and water cooled condensers? My thinking is yes and no, because with cooling tower 85 supply and return 95 is maintained and 45 supply and 55 return chilled water is provided. Since there is not much change in these temps as opposed to outdoor ambient temperature there won't be much pressure change in condenser. And as long water is regulated at proper flow to evaporators and condenser then all should hold steady. Do you have any input on this? I'm in NYC. Went to 2 year hvac school and worked almost 3 years in field starting out as a helper in service van as experience and learned as much then got into the building side for about 8 years now. I like listening to your podcast and reading your material as it keeps me refresh with field work as the building side is a little different but the basics and fundamentals are the same. Thanks!
&#;Anand
Hey Anand,
The answer is yes.
Some of the measurements can be applied to chillers as well. Just some of the verbiage is different, and the values differ.
The numbers for chilled water (44 out 54 in) and condenser water (85 out 95 in) are industry-standard values at full load conditions. Most chillers, regardless of manufacturer, will have a 10°F delta T on the cond and evap. Machines that operate outside of those ranges are chillers that were ordered specifically to provide a lower temp or larger delta T.
Many people look at the compressor motor RLA% as the chiller capacity, which is not accurate. Chiller capacity is measured by the evap delta T. If the chiller is designed for 10°F (5.5K) delta, is currently providing 44°F (6.66°C) water, and the return water is at 49°F (9.44°C), the delta T is 5°F (2.75K). So, that chiller is currently running at 50% of its total capacity.
Subcooling is still measured the same, although the reading that you get will change as chiller capacity changes. At low loads, your subcooling will be lower and will increase as capacity increases.
Suction superheat is a value that I really don't look at because the reading on a flooded type of system will usually be very low or even 0. Rather, discharge superheat (discharge temp &#; cond sat temp) is a more accurate reading and will be a direct result of your suction superheat. When there is high suction SH, there will be high discharge SH and vice versa. Again, this value will change as chiller capacity changes.
However, if the chiller is a DX type, the suction superheat is just as valid as on a residential system.
One of the values described in the podcast was temperature difference (supply air temp &#; coil temp).
In regards to air handlers with chilled water coils, you can do the same thing. Measure your supply air temp minus the coil leaving water temp. This will tell you how well the heat transfers to the water from the air going across the coil.
In chiller lingo, this measurement is called the approach.
There are two different approach temps that I look at on a chiller:
Approach values should range in 0 &#; 3°F (0K &#; 1.65K), given that your flows are correct.
Just like on air-cooled units where proper airflow is needed across the evaporator and condenser, you need to verify that you have proper water flows.
In air-to-air applications, you measure static to identify airflow issues. In water applications, I measure the pressure differential across each barrel. If I know my design pressure drop on the evap and cond, I can compare it to my actual to know if my flows are proper. However, keep in mind that most chiller manufacturers will give the design pressure drop in ft/hd. You will need to convert your real-time reading to ft/hd to accurately compare if you are using a gauge with a psi scale.
Even if your water temps stay pretty constant while in operation, your pressures will veer off as problems arise, and your approach values will increase.
The chiller will always try to maintain at 44°F (6.66°C) chilled water out (or whatever the setpoint is) as long as it can do so.
The refrigeration cycle doesn't change. Stick to the basics, and don't overthink it.
When running a building, try to get your condenser water as low as possible when running, but stay above 65°F (18.33°C).
Anytime you can provide condenser water lower than the design of 85°F (29.44°C), you will lower your condenser pressure and lower the lift (cond pressure &#; evap pressure). This will result in less work the compressor has to do and lower KW. This is a common method called condenser relief.
&#;Jeff Neiman