limit or operating switch

[maurice]

Need a little education on a switch.
This is not the exact one but very similar. It is installed into a ptac unit with resistance heat. The company wants to sell me a entire coil assembly but the problem is just the switch. So I am looking for just the switch. Heres the link: http://www.hvacpartstore.com/product_de ... ucts_id=49
Question: What does the numbers on the label mean: L145-40F?
Thank you.

[Robert]

Hi,

L = Limit

145 = Cut-out temp (shuts down system at 145*)

145 - 40 = 105 = cut-in temp (system comes back on once cooled to 105*)

F = Farenheit



Thanks,
Robert

[maurice]

Thank you for the reply.

Another question....the L145-40 is at the top or beginning of the coil and there is another at the bottom or end but it is labelled L160-40F. Is this the high limit switch and the first one is the operating switch?

Could you explain to me how these work with the thermostat? If the operating switch opens and closes with temp. What does the thermostat operate then?

Questions clear as mud?

Thanks for your help.

[maurice]

These switches are on a PTAC (packaged terminal air conditioner) unit with electric heat coil.

In heating mode:
Does the switch turn the blower on at 145* then when it drops 40* to 105* shuts it off?

The other is the high limit. Turns the blower on to cool the coil down if the operating switch fails. Is this correct?

[Robert]

Hi,

No, both of those are safety limit switches. IF the blower does not come on or for any reason the cavity reaches the 145 or 160 temps, the power is shut off to the element coils until the cavity cools back down to 105 or 120.


As long as that doesn't happen, they remain closed and power just passes through them.


The elements are controlled by either a sequencer or contactor and they are energized by the thermostat.


Clear as mud your way ? :>)



Thanks,
Robert

[maurice]

AHHHH!

I understand now.

The mud is cleared away.

Thank you for taking time to help me out.

God Bless.

[Robert]

Hi,

You're very welcome, it was my pleasure.


Take care and God Bless,
Robert