Not heating - Dryers

If it's a heat pump, it means you either bumped the heat up to a temp that the heat pump cannot reach quickly OR it's so cold out that there is no heat for the heat exchanger to pull from the air outside.
Both conditions turn on the heat strips in the air handler. The heat strips are your 'auxiliary heat.'

If it is a heat pump if the ambient I door temp is not than 3 degree s lower than 66 it utilizes the aux heat ( heat strips) to help the unit achieve your desired temperature set point faster. Also the heat pump does need help if trying to overcome really cold temperatures. Once set point is achieved the heat pump should be able to keep the home at the set point without aux heat. But the flashing may just be to let you know that the heat strips are in use at the current time. See if when the temperature gets close to your set temp if it goes away. If not a heat pump it may always flash to just tell you heat strips are in use. Some homes mostly trailers only have heat strips but on heat pumps heat strips are there to help heat pump get to your desired temp. But when your heat pump can maintain the temp without the strips is where it saves power. Also heat pump thermostat hVe emergency heat settings. This scares alot of people but if your heat pump isn't working and you have to switch it to emergency heat until you can get it fixed,. That means that the system is only using heat strips and not utilizing heat pump at all. Power bill may be a little higher but remember, most trailer homes only have heat strips and if you do not use emergency heat in this situation your heat strips will only heat home 3 degrees below set point on thermostat to allow heat pump to bring it up the other 3 degrees. If heat pump isn't working correctly you will always be 3 degrees colder than what you set you thermostat at. Maybe too much info but it's prolly just your aux heat on helping system achieve the desired temp you set thermostat too.

If you have an air to air heat pump, in colder temperatures, the heat pump will not heat as well as it would in warmer outdoor temperatures making it run longer. the digital thermostats work off of a built in algorithm that kicks on the auxiliary heat when the heat pump runs to long so that it will satisfy the thermostat quicker. This can be tied to the Emergency heat @ the thermostat energizing a few heating elements, or just energizing a separate element from the emergency heat. I always recommend on an air to air heat pump to run the emergency heat when you have consistent Outdoor temperatures below 20 degrees F because you will cycle the heat less by getting hotter heat making life more comfortable, and it costs about the same as running the heat pump since @ those temperatures, it will run all the time.

If the compressor is off and the heat coil is on - this is normal for the "E" or emergency heat setting. Check for proper connections between the Heat-pump, furnace(heat source) and the thermostat and that the thermostat is capable of controlling a heat-pump with secondary/emergency heat units. Thermostats designed for this have 4 settings: Cool / off / heat / E(emergency heat). in the "heat" setting, both the Heat-pump and Aux heat work together to maintain temperature. In the "E" setting, only the Aux heat source is used. The "E" setting should only be used in extreme cold - when the Heat-pump can no longer produce heat.

Is it a heat pump? Is it a heat pump stat? Is ambient temp high enough to allow heat pump to run?

If your thermostat has an emergency heat setting this means you have a heat pump system.
Yes you need to set the thermostat to heat for heating the house.
The emergency heat setting should never be used unless your outside unit is not functioning.
The emergency heat setting overides the heat pump (the outside unit will not be energized).
The emergency heat setting will run the auxillary heat (heat strips) only.
When the thermostat is set in the heat position the heat pump will run to heat your house.
If the heat pump can't keep up (extreme cold) then then the auxillary heat will kick in to augment the heat pump until it satisfies the thermostat settings. If your room temperature gets 2 degrees below your thermostat setpoint, your auxillary heat will kick on. Example, say you are going to be gone a couple of days and you turn your heat down to 60 degrees. When you return and it is 60 degrees in your house, you turn the thermostat up to 70 degrees. Since you are turning the temperature up 2 degrees or more (10 degrees in this case) from the 60 degree room temperature then the heat pump will come on and the auxillary heat strips. The unit will continue heating like this until the temperature in the house gets to 69 degrees and the heat strips will turn off and the heat pump will continue to run until the 70 degree setpoint is reached.
Hope this helps.
SeagullAC

It stands for Emergency Heat. (Back up heat) . Normally you will find it on heat pumps. It's used manually when the compressor goes out on a heat pump. It's used automatically by the unit when it's so cold outside the heat pump can't keep up. This happens when there is not enough heat in the air to draw heat from. This happens at around 23 degrees. I hope this explains what emergency heat is and what it's used for.

Economy Mode = EM
Auxelary Mode = AUX
in em mode heat pump does most of the work in aux either an electric heating element is used or gas depending on if it is gas or all electric

Sorry, neither of these answers are completely correct.
You have a heat pump (or the wrong thermostat). Let's assume you have a heat pump.

In air conditioning mode, it works like every air conditioner you have ever had, but...

In heat mode, it reverses its operation. Have you ever felt the air coming out of the outdoor unit of your A/C unit? It's hot, isn't it. And the air coming out of the indoor unit (out of the registers) is cold. Now for a heat pump to produce heat it simply runs the air conditioner in reverse and the heat comes out in the house and the cold is released outside. Neat, huh!

Here's the problem with heat pumps...when it is really cold outside the heat pump can't produce enough heat to heat your home. So it has an additional heat source called "Auxiliary Heat". This heat comes on automatically when the house doesn't get warm enough. The source of this heat is based on the region of the country you are in. North/Northeast generally have oil heat, other regions have gas, and still others have to use electricity to heat. In Texas, we usually use electricity as the supplementary heat on heat pumps. VERY EXPENSIVE!

Now the "Emergency Heat"...this is exactly as stated in Solution #2. This is manually turned on by YOU at the thermostat when your heat pump fails. This turns on the auxilliary heaters and turns off the heat pump (remember, the reverse air conditioner). Again, this can be quite expensive to run if your heat source uses electricity! Gas and oil may be cheaper. The emergency heat is only designed (normally) to keep the house livable (not comfortable) until the Heating Tech can get out to you and fix your heat pump.

Something else you should know. It is normal for a heat pump's outdoor coil to frost up during heating mode. It will detect this and go into DEFROST mode and melt the frost off the coil. While it is doing this, it will turn on the auxilliary heater to keep the air blowing in the house at a reasonable "warm" temperature, but it will not be as hot as normal. In fact, heat pumps produce a lower temperature heat than traditional heaters. So the air may feel cooler during heating than you are use to anyway. This is normal and is not a sign of a problem.

So what do you do: Set your thermostat to the temperature you want and set the controls for HEAT/COOL and FAN-AUTO/ON and leave the EMERG HEAT off unless your heat pump breaks.

As always, keep your filters clean and your outdoor unit's coils clean and free of debris.

Hope this explains your question for you!