Question re. Carrier dual fuel Heat Pump.

[Volfandt]

I have a Carrier dual fuel Weathermaker Puron 38YXA Heat Pump with a Weathermaker 9200 58MXA Gas furnace and I'd like to "coon tune" this setup to run alittle longer in heatpump mode before it switches over to the gas furnace.
I was told by the installation/servicing dealer that it couldn't be adjusted down, that it is set to kick the furnace on at around 35 degrees and that is it! Set in stone! I even contacted Carrier's customer service with this request and they referred me to my local dealer because they indicated that they were not staffed to handle technical support questions to endusers......
The dealer did a very good job and has responded in a timely manner for the only service call I've needed thus far but, I don't think they know the full capabilities of these units. They were the lowest price....

From what I've read here lately, it would seem that I could realize some substantial savings if I could change the furnace "on" temp down to 30 degrees or so.
The warmth of this setup is outstanding for the 3 yrs I've had it but with the cost of natural gas and it's ever escallating price, it's almost as if I'm burning dollar bills for heat!
I have the owners and installation manuals and troubleshoot and repair electronic and electro-mechanical telecomminucations devices for a living so I can be considered dangerous. /forums/images/graemlins/grin.gif
The units do have 7 yrs left on their warranties so I don't want to get to "jiggy" with it /forums/images/graemlins/grin.gif if'n you know what I mean.

All comments, suggestions, opinions appreciated.

Volfandt

 

[Volfandt]

Bump

Volfandt

 

[thcri]

Volfandt,

I am a Carrier dealer in Minnesota. 35 seems a tad bit high. Tell me what controller are they using to make the switch over. You must have some kind of outdoor stat or controller with a model number on it. In some cases it may even be your utility company making the switch over.

murph

 

[dummy]

On my setup, there is a separate thermostat on the outside unit which controls when the "dual fuel" kit turns on. It is a simple screwdriver adjustment to change temp. settings. Attachment for illustrative and comparative purposes. Dual fuel

 

[Volfandt]

Thanks for the replys.
thcri, my outside unit does have an outdoor thermometer. I can depress the temp control up & down buttons simultaniously and get the outside temp to display in the inside controller thermostat's LCD display.

dummy, my dual fuel setup doesn't have an outboard dual fuel kit like what you linked. If mine has one, it must be integrated and integral to either the inside or outside unit.

The bottom of the furnace houses the main processor and there is a small window where one can observe the blinking "heartbeat" LED. I'm going to assume that any adjustment to be made will be in there, or possibly in the outside unit. With the exception of the thermostat theres no additional outboard controllers, panels or junction boxes.
The controller/thermostat is wired directly into the furnace and another low-voltage multi-conductor thermostat wire runs from the furnace to the outside unit.

 

[bmac]

Just today I had a discussion about a Trane dual fuel heat pump with my HVAC subcontractor. He said this unit has an outside thermostat that I can set to any temperature I want for the gas heat to kick in. Or, if I want, set it so the furnace never kicks in (don't know why I would ever want that to happen unless propane became prohibitively expensive).

 

[thcri]

Get me the model number of each of the pieces of equipment. The board you are talking about is the board for the furnace only. There may be a board in the heat pump section and sometimes there is a board up in your rafters with just an prope sticking out. But the board in the little glass is for the furnace section.

murph

 

[Volfandt]

Heat Pump inside unit model#: CD5A036017AAAA

Heat Pump outside unit model#: 38YXA036--321---

Furnace model#: 58MXA080-F-1--16

I've traced the low voltage wireing out and there is no other devices wired in between the inside unit and the thermostat nor between the inside unit and outside unit.

Thanks
Volfandt

 

[thcri]

I will try and look up them numbers sometime today. I am very familiar with the furnace and air handler but not the outdoor unit. I will get the options and wiring diamgrams out and see what actually converts this unit.

murph

 

[Volfandt]

Murph, I did some more research and have found out that the programmable dual fuel thermostat also handles the conversion so an interface kit is not required.

The Balance Point Temperature setting (BPTS) and Auxiliary Heat Lockout setting (AHLS) are all programmed via putting the dual fuel thermostat into configuration mode.
I downloaded the Installation, Start-Up and Operating Instructions pdf from the Carrier website and it is explanatory enough to make me a thoroughly dangerous man /forums/images/graemlins/grin.gif

The default balance point temperature setting (BPTS) = OF, which means heat pump operation is allowed at all outdoor temperatures.
It can be set at 5 degree increments from 5 to 55 degrees & OF.

The default Auxiliary Heat Lockout setting (AHLS) = OF, which means the furnace can operate at all outdoor temperatures.
It can be set at 5 degree increments from 5 to 55 degrees & OF.

I've just started reading up on it and haven't actually checked the settings but I'll bet a dollar to a donut that it's set to default.

A couple questions if you don't mind.
1) If'n my cipher'n is correct, I'd say that I would want to leave the BPS setting at default. That way the HP will work up until it can't keep up with the demand and the aux heat takes over. Correct?

2) It looks like I can set the outside temp at which the furnace is allowed to come on by setting the AHLS.
It is setable in 5 degree increments from 5 to 55 degrees.
So if I set this to 25 or 30, the furnace won't kick in until the outside temperature drops down to or below this setting, is this correct?
According to the manual, selecting emergency heat will overrride this setting and I'm also going to assume that defrost does also.

3) My thermostat is located directly above the main return on an inside wall in my hallway (where my original hp thermostat was). Is it all right above the return or should it be relocated?

I verified that I'm set up for dual fuel by powering down then powering up the inside unit and seeing the thermostat display DF before it went to it's normal display.

Thanks
Volfandt