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Posted by Zyp on March 1, 2008, 4:14 pm
.p.jm@see_my_sig_for_address.com wrote:
>
>> Marc O'Brien wrote:
>>>> Marc O'Brien wrote:
>>>>> On Feb 26, 3:30 am, .p.jm@see_my_sig_for_address.com wrote:
>>>>>> wrote:
>>>>>>> Tony wrote:
>>>>>>>> Taken in consideration what stormin and zyp told you
>>>>>>>> I believe that EPR valve are still being made
>>>>>>>> tony
>>>>
>>>>
>>>>>>>>>
>>>>>>>>>> I poped back in to see how this cellar cooler system was
>>>>>>>>>> doing after my repairs.
>>>>
>>>>>>>>>> It's iced again but this time the full charge still exists,
>>>>>>>>>> subcool remains sufficient.
>>>>
>>>>>>>>>> It's design saturated evaporating temperature is about 4 deg
>>>>>>>>>> C, however, surely, due to an inefficient compressor the
>>>>>>>>>> lower evaporator circuit freezes?
>>>>
>>>>>>>>> Add a hot gas bypass and solenoid.
>>>>
>>>>>>> For the first time in how many month's, I actually understood
>>>>>>> what Tony said. An EPR valve might help here.
>>>>
>>>>>> At the risk of short cycling. I always hesitate to look at
>>>>>> 'solutions' that involve re-engineering the system.
>>>>
>>>>> Indeed, keep it simple stupid. The irony is that one has to know
>>>>> an aweful lot more each time one wants to further simplify
>>>>> something. Like the saying "Sorry my letter to you is so long but
>>>>> I didn't have the time to write a shorter one".
>>>>
>>>>> An EPR reduces evaporator volume flow which is precisely not what
>>>>> you want if your problem is already too little evaporator volume
>>>>> flow.
>>>>
>>>> I'm not sure his problem stems from evaporator flow. It seems to me
>>>> that when the fixture temperature is just above freeze point, and
>>>> the evaporator is below freeze point, you're getting frost no
>>>> matter what you do. At least an EPR could keep the evaporator from
>>>> reaching that point. [Albeit - it is already a case of
>>>> refrigeration effect being lost because of the saturation
>>>> temperature and flow.] Perhaps just simply execute a defrost every
>>>> 3-4 hours for 20 minutes would be sufficient. It depends on his
>>>> load for the fixture, no?
>>>
>>> I have a full charge but I am not getting even frosting. The room
>>> temperature at the time of frosting was 16°C.
>>>
>>> I happen to be popping in again tomorrow for another un-related
>>> reason and will experiment further.
>>
>> You shouldn't see frosting on a Medium temperture coil at that [16º
>> C]fixture termperature, but if it is set up as a high temperature
>> coil, then you would.
>>
>> Can you tell me what the application is? High or Medium
>> termperature?
>
> And the delta across the coil.
>
>
> --
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>
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If it's a Medium Temperature application [cooler] which should try to
maintain somewhere between 35º F and 45º, the delta from saturation to
fixture should be about 20º. Which would allow for frosting and usually
most coolers [because the product temperature is above freezing] would allow
for random defrost.
--
Zyp
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