HP Switches (Manual or Auto)

Hi Guys,

31 degree's on Friday so i have spent the last 3 days travelling around resetting manual HP Switches. Whats the feeling in the trenches, Manual or Auto. The way i see it is:-

Manual: FOR:- As soon as the system goes HP it shuts down until someone physically goes to look and reset it.
Against:- As above, loads of calls

Auto: FOR, any temperary problem, high ambient ect will not shut the unit down permanently only until the pressure drops and then restarts
Against: If there is a genuine fault, Cond fan u/s for example the compressor will keep cutting in and out at high head pressure until it goes BANG !!!!!!

Personally, i think i would edge towards the auto switch but what are everbody elses feelings

Regards

Fatboy

There is no question in Canada where we have laws that spell that out.
The code reads in part:
"...provide the compressor with protective devices that will automatically prevent the supply of energy to the prime mover of the compressor when an abnormal condition occurs during the compressor's operation, including,
(a) a high pressure limiting device in the compressor discharge line"
that
"(a) not be capable of automatically restarting the plant... and
maintain the visual warning until the abnormal or unsafe condition is rectified. O. Reg. 219/01, s. 39 (7)."
and that such controls
"... are independent of other control systems, are hard wired, regularly tested under operating conditions and calibrated as required..."

Brian Inman

Hp switch cuts the system = problem . . . if it's atomatic , the problem will not go just by restarting automaticly the system , if that's the case waawwwwww (i like that , if the system fixes itself automaticlly) . . .
I'm against automatic switches although manual switchs cause us a load of phone calls it really protects the compressor . . . . so going to reset an hp switch and fix a little problem is more confortable than changing a compressor lolol

Another question then - why do they make the switches with the choice of auto or manual ?

From the simple reason that also here you get different opinions.

Personally/ I prefer the manual reset but always connect the warning red lamp to the high side.

Chemi :)

Quote:

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Originally Posted by frank

Another question then - why do they make the switches with the choice of auto or manual ?

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To name one application,auto-reset is often used for cycling condenser fan/s.

High pressure switches are not soley made for the fridge or a/c trade, hence the choice of manual/auto.

Quote:

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Originally Posted by frank

Another question then - why do they make the switches with the choice of auto or manual ?

---

Hi Frank, auto hp switches are also required on some types of cascade systems, they are used on start up when the standing pressure of the low side refrigerant is high. cheers dill.

Hi to all.

Here in Denmark we always use manual reset for high pressure, but
i do know of this problem. The cooling unit installed in the country
must always take acount to the ambient temperature, this means
that the SOT temperature for the unit is calculated to low.

SOT temperature = Safe operation temperature.

The problem is only caused for one thing ( $ ) :)

Regards
Carlo Hansen

Hi Guys,

I had noticed recently that all the new units coming from Hubbards all come with Manual Resets.

i just wish the designers would realise that the ambients in the uk do go over 30 degree's sometimes. It amazes me that even on refits costing hundreds of thousands of pounds that the condensers can't cope in a heat wave.

Regards

Fatboy