We need wiring for heat strip install on Coleman Package Unit Model PHP036H1321A --- HELP!

Look on heater strip to determine wattage . Most heater strips are 5000 watt . You can buy a kit to restring heater (just pull out burned wires and install new ones from kit for a good as new heater and much cheaper )

Probably a bad limit switch on the strips or the heat sequencer/relay is falling out after continued amp draw. I would lean toward the heat relay/sequencer. Havent heard of any problems with coleman limit switches. These units were prone to get water inthe electrical compartments due to the evap coil being right above it. Check to see where the power break is starting at the strips and working backwards throught the circuit. That will tell you for sure. Make sure you have 24v going to the heat sequencer too.

There should be an overload protection device in series with the low voltage wiring(t-stat wiring) Is it resting on the heat strip or too close to it? It is a saftey device to shut off the heat strips if the fan quits or a fire in the heat strip section. check that or by pass it, if it stays running then ur thermal protector is bad, couple bucks at the parts house.

Hi, yes you can use the same thermostat if you are replacing the unit that has the same sequence of operation. What I mean is, if the old unit is a gas fired furnace and outdoor condenser split system for the a/c you can use the same controls, or if its a package unit. Now, if you are installing a heat-pump unit in place of a gas fired central unit, you will need to pull more stat wire and buy a heat-pump thermostat to make it run.
Shastalaker7
A/C, Heating Contractor

I see what you see also in the manual. The difference is the Heat Strip package that part is optional and the 600212-001 with the optional heat strips becomes the new 600315-001 I talked to Dometic Duo-Therm and the models are the same but they both are not heat pumps but the new heat strip package comes on when told to go into heat mode when you change the thermostat to heat. The part you purchased will fit both model numbers you listed for your roof top air conditioner. Thanks, Sea Breeze

Hi, sounds like you could have a couple of problems. If the breaker is tripping when the strips are calling, they are drawing more amps then they should. The data plate on the unit will tell you the Amperage rating of the heat strip package that is installed and should match that of the breaker. Since the breaker was replaced I would recheck how tight the wiring is at the breaker as they will lossen up do the the heat they are pulling. Make sure they are tight both at the breaker and at the strips, just turn the breaker off and check this. Also, the strips should energize when the thermostat needs them to help out the heating cycle. It is good you can manually turn them on, but you shouldn't have to. I can not guide you through the process of checking T-stat operation as I would need to be on site to see how they wired it at the unit and stat.If it has always worked this way then this is most likely the way the installer wired it. If not, you will need to have the stat checked out. I would consentrate on solving the breaker problem. Just look at the data plate for the strips amperage and see if it matches the breaker amps. Tighten these connections and I bet this will solve the big problem. If you had a clamp around amp probe and with some help from me I could guide you on how to do an amp check to see if its the strips, wiring, or breaker by doing a amperage check. Tighten up all the connections and keep me posted for more help. I will be here to help you solve this.
Good Luck,Shastalaker7

Hi, like most of the RV roof tops, they will have a manual showing the type and wattage of heat strips you're system calls for. It comes as a unit, pre-wired to fit and set in place. You should have no problems installing a heat strip kit, but make sure you get the right one that the unit calls for as they do make several models. Very self explanatory. Also, be sure that you're system calls for a heat strip package?? Good Luck, and if you need more help please contact me. Very easy to set in place and plug in. Sincerely,
Shastalaker7

couple screws its simple they set in front of blower and plug in

If you are calling for heat and the thermostat is set for 2 degrees higher than room temp, the heat pump and strips come on.
When the room temp and stat temp are less than 2 degrees the strips turn off.
That is, unless the installer wired the t-stat for the strips to stay on.
If they are coming on in the air/cool mode then you have a bad heat relay or a t-stat wire shorted.

Wiring diagram is normally included and fixed to the inside cover of the electrical end cover of the control compartment. Instructions for wire size required and fused disconnect should be on the unit name plate.