HVAC / Electrical

[Eddie702]

2 refrigerant lines run from the outside condenser to the inside mini split indoor unit on a typical system with one head. One is the suction line that runs about 40 degrees in cooling mode and the liquid line that runs about at the ambient outdoor temp (roughly)

When the system reverses (in a heat pump) now the bigger line that was the suction in cooling is now the compressor discharge line in heating and gets very hot. The indoor unit is now heating and the liquid line (small line) remains the liquid line although the flow in it is reversed.

 

[kwired]

Only by people who don't know what they're doing. Any opportunity for the hot liquid to lose heat would be a good thing.

unless it is a heat pump, then you may want to hold as much heat as possible until you reach the indoor coil when in heating mode. But I haven't encountered one that is hot enough to damage 90C conductor insulation on your average heat pump. Commercial/industrial refrigeration applications maybe they could be that hot.

 

[kwired]

2 refrigerant lines run from the outside condenser to the inside mini split indoor unit on a typical system with one head. One is the suction line that runs about 40 degrees in cooling mode and the liquid line that runs about at the ambient outdoor temp (roughly)

When the system reverses (in a heat pump) now the bigger line that was the suction in cooling is now the compressor discharge line in heating and gets very hot. The indoor unit is now heating and the liquid line (small line) remains the liquid line although the flow in it is reversed.

How hot will depend on outdoor ambient temperature and how much heat there is for the outdoor coil (now the evaporator) to gain. It can be too hot for you to hold your hand on but likely not hot enough to be damaging to a conductor inside an adjacent raceway with 90C insulation on it, especially if that closeness is only for a little bit as it passes through a roof or wall then they gain more separation again.

 

[drcampbell]

... When the system reverses (in a heat pump) now the bigger line that was the suction in cooling is now the compressor discharge line in heating and gets very hot. The indoor unit is now heating and the liquid line (small line) remains the liquid line although the flow in it is reversed.

This is correct. Please disregard my earlier brain fart.

It's still a good idea to keep some distance, and/or thermal insulation, between refrigerant lines and electrical lines .

 

[kwired]

18 AWG CL2 thermostat cable is zip tied to line sets all the time for domestic units and never seen one that had been subjected to too much heat other than maybe some HVAC tech not paying attention when brazing a line fitting.

 

[ggunn]

18 AWG CL2 thermostat cable is zip tied to line sets all the time for domestic units and never seen one that had been subjected to too much heat other than maybe some HVAC tech not paying attention when brazing a line fitting.

I think that the point was that if the conductors were sized so as to get up near the temp limit for the insulation when carrying the maximum current, then strapping them to a hot refrigerant line might push them past it. There is no current to speak of in a thermostat.

 

[ramsy]

I think that the point was that if the conductors were sized so as to get up near the temp limit for the insulation when carrying the maximum current, then strapping them to a hot refrigerant line might push them past it. There is no current to speak of in a thermostat.

Seen extension cord for T-State control, strapped along the HVAC refrigeration line, but couldn't find a code reference that prohibited it.