Amer. Std. Defrost Question

[Unclev]

I have a fairly new amer std heritage 15 heat pump with a tcon803 stat. This is the first winter it has seen. Is it normal when in defrost mode to shut off when the indoor stat temp is satisfied? This has happened twice this cooling season. 99 % of the time it will totally complete the defrost cycle, the outdoor fan will restart and resume heating. Thanks for all the great advice and happy new year to all. Uncle V.

[SBKold]

Your post is a little confusing but here goes....

Yes if the thermostats shuts call for heat off during a defrost the unit will shut down.

When the next call for heat comes it will resume defrost cycle (no fan) until cycle is completed.

This should never happen during cooling.

[Unclev]

Thank you for the reply! I am comparing this Amer. Std. to my old York system which also had electronic demand defrost. My old York system would always 100% of the time call for defrost and finish the defrost cycle and start heating again. It would never stop the heat pump "during" the defrost cycle. This system has stopped twice now during defrost mode and when it came back on 10 minutes later was in heat mode. It almost seems that the stat becomes satisfied and it does not care what mode it's in it just turns off because the temp has been satisfied. I'm OK with that as long as it is normal operating conditions for this brand of heat pump & Stat.

[Chuck]

Yes, it is normal. And since it has a true demand defrost, it will defrost again (if needed) if a defrost cycle was cut short.

Do you sit and watch it 24/7? Lol. Or how can you be sure the York never did it?

[SBKold]

If it shuts down during a defrost it should resume the defrost the next time the thermostat calls for heat.

If it doesn't and the unit comes on back in heat (fan running) then its not correct.

[BaldLoonie]

If the sensor says the coil is clear, maybe it won't start back up in defrost.

[beenthere]

Thank you for the reply! I am comparing this Amer. Std. to my old York system which also had electronic demand defrost. My old York system would always 100% of the time call for defrost and finish the defrost cycle and start heating again. It would never stop the heat pump "during" the defrost cycle. This system has stopped twice now during defrost mode and when it came back on 10 minutes later was in heat mode. It almost seems that the stat becomes satisfied and it does not care what mode it's in it just turns off because the temp has been satisfied. I'm OK with that as long as it is normal operating conditions for this brand of heat pump & Stat.

What York unit did you have. The outdoor unit doesn't have a way to keep the indoor blower running when the stat stops calling for heat. So your York probably did shut down during defrost cycles sometimes. Just you never noticed it.

[kdean1]

If the thermostat is satisfied and the outdoor coil is clear, why does it matter if it shuts off?
"If it ain't broke, don't fix it."

[SBKold]

If the sensor says the coil is clear, maybe it won't start back up in defrost.

Because usually it won't warm enough to reach termination temp without short continued defrost.

[Unclev]

Thanks to all the great info! My old (1992) York was an EFH series with a single speed indoor blower. I am positive that when it went into defrost the indoor blower motor was on. I know this for a fact because the aux heat never came on to temper the air when in defrost mode thus blowing cold air. I think that is why it always would finish the defrost cycle in it's entirety because at that point the indoor air was now way colder and the stat saw this and continued to heat until it finally shut off. With my new Amer. Std. it now has staged aux. heat so when in defrost mode stage one kicks in and the indoor air is now warm not cold like the old York. It would now make sense if the stat gets satisfied during defrost it will shut off. Thanks for all the great info. Now it all makes sense!

[beenthere]

LOL, no aux heat would tend to make it complete its defrost cycle every time.