I'm currently using a 7W C9 Christmas bulb, one of the big old traditional ones. I've quit using them outdoors and have bulbs leftover, and they happen to fit the fixture I have.

I've used a little duct tape to hold the sensor closer to the bulb. They're held slightly apart by a small block of wood. Wrapping them completely would make me nervous. I've considered wiring in a resistor held next to the sensor but frankly the light comes in handy. Easy to spot across the dark basement.

That is helpful, so thank you.

Regards,
Pete

 

Actually, the idea of heating the temperature sensor is the best one yet, because it does not connect into the control system at all. It just adds a bias heat source. So you have little chance of breaking the system I like that a lot.

Yebut said approach may well 'break the system' (specifically, degrade the lube with subsequent compressor damage) owed to prolonged sub-design evaporator temp operation - nor is the described 'kludge', cleverly non-invasive though it may be, likely to 'help you' with warantee, service contract nor insurance claims (should said underwriter{s} opt to thoroughly investigate the failure mode) -- Ya see, POE (i.e. Polyolester [sic] lubricants) 'tell tales' of past thermal 'aberration'.... -- Quoth the raven

But hey! Please don't get me wrong! -- While a strong advocate of re-purposing' where same may be practically realized - a (long term) positive outcome seems most unlikely here...

Sincerely, Best regards
HP

 

Certainly operation at a lower temperature may lead to problems, but consider that this is not an extreme excursion, rather just 15 to 20 degrees, at most. So certainly there might be a problem, it is more likely not to be a pproblem.

 

Certainly operation at a lower temperature may lead to problems, but consider that this is not an extreme excursion, rather just 15 to 20 degrees, at most. So certainly there might be a problem, it is more likely not to be a problem.

Where 'metering' is via an 'expansion valve' I tend to agree -- but then many (most?) 'window units' employ 'capillary tubes' (which being especially lubricant viscosity, temperature, pressure critical). -- In any event, given the negligible cost of said machines (typically ≤$ 800 USD Re: units featuring 12,000 through 20,000 BTU thermal transfer capacity), it won't cost him much to experiment!

Hey! @#12 -- Your input here (being, as you are, a refrigeration/HVAC professional, would be most helpful)!

Very best regards
HP

 

Unfortunately I did neglect to consider the effect of reducing the temperature upon the viscosity of the lubricant. One of those unintended secondary results that I often point out to other folks. My error indeed. If that effect has a negative result it will show up as a reduction in efficiency, and add to the power consumption so that the total power required would be more than anticipated by just the additional heat removal energy requirement. Much simpler to understand than to measure.

 

Unfortunately I did neglect to consider the effect of reducing the temperature upon the viscosity of the lubricant. One of those unintended secondary results that I often point out to other folks. My error indeed. If that effect has a negative result it will show up as a reduction in efficiency, and add to the power consumption so that the total power required would be more than anticipated by just the additional heat removal energy requirement. Much simpler to understand than to measure.

...and therein lies the bane of 'modern' systems of all description -- to wit: inflexible of application, inimical to modification and without repurposable components/subsystems...
Seems we've descended from an already far from ideal (albeit often 'workable') 'elastic band and duct tape' world to one of indivisible 'blocks' and 'modules' -- Life's tough <<tears>>

Very best regards
HP

 

...and therein lies the bane of 'modern' systems of all description -- to wit: inflexible of application, inimical to modification and without repurposable components/subsystems...
Seems we've descended from an already far from ideal (albeit often 'workable') 'elastic band and duct tape' world to one of indivisible 'blocks' and 'modules' -- Life's tough <<tears>>

Very best regards
HP

This is the area where experience and insight come in to the picture. Knowing what the viscosity versus temperature curve of the particular compressor oil shows would be very useful.
In a much broader thought, that experience and insight that some folks possess is why some employees are far more valuable than others. I see efforts like ISO 9000 and it's ilk as working to reduce all jobs to menial labor to avoid the need for anybody to have any skill or insight.

 

Not sure that 60 deg. Fahrenheit is the lowest temperature that room air conditioners are normally designed to cool to, but assume that that is correct. What I want to do is, in a simple way, to make the conditioner's compressor not stop running until after a "room" temperature of about 40 deg. Fahrenheit has been reached.

In other words, the room (window) air conditioner will be used to make a walk-in refrigerator.

Assume that the air conditioner has a thermistor-type room air temperature sensor. A thermistor can be either postive or negative temperature coefficient (ptc or ntc). Another given is that the temperature setting of the air conditioner (the desired room temp) is 60 deg. F.

If the temperature sensor is a ptc, then I would connect a rheostat in series with the thermistor. In that way, assuming a correct resistance value of the rheostat, resistance of the thermistor is less than normal when the compressor is shut off as room temperature reaches 40 deg. F.

If the temperature sensor is ntc, then I would connect a rheostat in parallel with the thermistor. Where the resistance of the rheostat is correct, then resistance of the thermistor must be greater than normal before the compressor is shut off and room temp. again equals 40 deg. F. Given a 40 deg F. room temperature, the total resistance of the thermistor in parallel with the resistor is equal to the resistance of the thermistor with respect to room temp. equal to 60 deg. F lacking the rheostat connected in parallel with it.

These two different possible circuits are shown in the drawing below.

Over the past two days I have been trying to understand the workings of air conditioners, but I have previously done very little with them. So I'm looking for advice from anyone who is experienced with them as to whether or not what I have in mind is practical and not cause damage to an A.C. .

View attachment 179495

Um... stop. Wait. Understand what you are doing. HVAC systems are rated to cool to a specific level (and not below) that, based on factors like: air volume, humidity, etc. If you cool too far, and don't sufficiently keep the coils heated, they will freeze and you will break your AC. You got $6K sitting around for repairs?

 

Um... stop. Wait. Understand what you are doing. HVAC systems are rated to cool to a specific level (and not below) that, based on factors like: air volume, humidity, etc. If you cool too far, and don't sufficiently keep the coils heated, they will freeze and you will break your AC. You got $6K sitting around for repairs?

Year-old thread! It either blew up or not by now.

 

Um... stop. Wait. Understand what you are doing. HVAC systems are rated to cool to a specific level (and not below) that, based on factors like: air volume, humidity, etc. If you cool too far, and don't sufficiently keep the coils heated, they will freeze and you will break your AC. You got $6K sitting around for repairs?

Interesting Assumption. I have seen home AC systems with the evporator frozen into a block of ice because dust caught the water and it froze. It did take quite a time to thaw but then the system worked just fine for severl years, still working today. So freezing outside does not mean freezing inside,

 

Um... stop. Wait. Understand what you are doing. HVAC systems are rated to cool to a specific level (and not below) that, based on factors like: air volume, humidity, etc. If you cool too far, and don't sufficiently keep the coils heated, they will freeze and you will break your AC. You got $6K sitting around for repairs?

There are many people currently putting this into practice. See below the link to a company that sells a controller to make a room air conditioner cool a room to below 60 deg. F. Their controller allows the air conditioner to cool the room to close to freezing temperature by including a sensor that detects when the fins are developing ice.

https://www.storeitcold.com/

Storeitcold recommends removing the air filter in front of the cooling fins and periodically cleaning the fins with I presume a vacuum cleaner. With my neighbor's walk-in cooler cooled by a window air conditioner, I think I was able to get the room temperture to 45 deg. F. This did not by any means destroy the air conditioner.

-Pete