short cycleing furnace

[torchkeeper]

My g6rc nordyne short cycles. Say thermostat reads 63 we come home set it for 68. Furnace fires fine. But only raises the house a couple degrees. Furnace fires back up and does same thing over and over till thermostat reaches 68. Should I be looking to thermostat or supply air limit switch? Or am I way off? Live on shore of Lake Ontario, still running furnace now and then.

[BryanS]

Is this gas or oil furnace? Might be tripping a limit switch. Like a hi temp switch maybe not getting enough airflow and overheating. Or maybe it could be a pressure switch issue. I've worked on very few gas furnaces. I'm sure someone else could give you better advice that actually works on this kind of equipment more often.. I only mess with them when friends or family call me up

[torchkeeper]

Sorry, forgot to mention . Propane  fueled unit.

[torchkeeper]

Pressure switch and air supply limit switch were replaced over winter and nothing Sq.. Ft.

80,000 btu. 92+ heating 1500 sq.ft. cape chalet.

[BryanS]

Cool. If for some reason you had a a clog at say your evap coil the heat would build up and trip the hi limit. It could be the thermostat. Personally if I suspected the thermostat, I would jump it out, and see if the unit reaches the set point without shutting down. Obviously, if it stills shuts down, then it isn't the thermostat. The first thing that comes to my mind causing the unit to shutdown, then starting back up once it has cooled down is a limit tripping.

[torchkeeper]

I am going to open evap. coil box and check. Never thought of downstream ! That`s why I rely on you guys. I`ll post as soon as I get it open. Thanks again.

[m_west5]

What do the diagnostic lights on the circuit board indicate?

[torchkeeper]

no codes ever while it does this . constant red and steady yellow while flame is present.

[m_west5]

Sorry, forgot to mention . Propane  fueled unit.

Was it always setup for propane? Or was it on NG?

[m_west5]

Pressure switch and air supply limit switch were replaced over winter and nothing Sq.. Ft.

80,000 btu. 92+ heating 1500 sq.ft. cape chalet.

By this, do you mean the pressure switch and air limit were replaced and these did not fix the problem? Correct part numbers (especially limit)? Did the technician offer any other solution?

[torchkeeper]

always propane, both were replaced. I will have to check limit switch to see if it was replaced with correct temp replacement. It was different color coveings over the two stand-off legs to switch disc?  I opened cover to A coil but ,it only gave  me access tp downstream side /top . Looked clean as unit has always had electronic air cleaner attached. I have to open the other panel  to really see the side facing furnace. As  I imagine that would be the side catching dust from return air. Furnace has filter though? I was out of town when these were replaced , so I didn`t speak to service. Wife was here.

Thanks for the continued help.

[torchkeeper]

As I said  earlier cape with 23 foot vaulted ceiling, 2 68 inch 5 blade fans to help in winter. I realize the heat will always go up. Should I go up in size to a 120,000 btu ? Or will it just burn more propane and not add more temp. rise in house. Home is only 4 years old. 2x6 side wall insulation and r-39 in vault and upstairs bedroom ceiling.

Heat is more of concern than A/C. Here on the lake shore we stay cooler than across the road.

[m_west5]

always propane, both were replaced. I will have to check limit switch to see if it was replaced with correct temp replacement. It was different color coveings over the two stand-off legs to switch disc?  I opened cover to A coil but ,it only gave  me access tp downstream side /top . Looked clean as unit has always had electronic air cleaner attached. I have to open the other panel  to really see the side facing furnace. As  I imagine that would be the side catching dust from return air. Furnace has filter though? I was out of town when these were replaced , so I didn`t speak to service. Wife was here.

Thanks for the continued help.

Check limit, specification should be printed somewhere on part. Do you still have old part to compare?

[m_west5]

As I said  earlier cape with 23 foot vaulted ceiling, 2 68 inch 5 blade fans to help in winter. I realize the heat will always go up. Should I go up in size to a 120,000 btu ? Or will it just burn more propane and not add more temp. rise in house. Home is only 4 years old. 2x6 side wall insulation and r-39 in vault and upstairs bedroom ceiling.

Heat is more of concern than A/C. Here on the lake shore we stay cooler than across the road.

Should not be necessary. Did it work sufficiently when new?

[torchkeeper]

Found box for replacement air supply limit and it is correct value.Opens at 250 closes at 210. The 80,000 btu have the highest opening temp of all the nordyne g6 models. Even higher than 100,000, and 120,000 ? Thinking a coil may be restriction? It was a separate attic unit in house we moved it from. We just moved them from house we demoed a 100 feet away. Had no way to put in ceiling vent for a/c as this is a new build modular. So we put coil box in line with furnace. Did I make a large mistake? Coil cabinet and furnace cabinet same outside size. They married right together.

[BryanS]

Where is this located now? The other one came out of an attic you say so I'm just wondering if you got it in a basement now standing upright. Coil could be in the wrong position for the application you are using it for now.

[BryanS]

Most furnaces have a temperature rise indicated on the model tag. I believe you can check temperature before the furnace and after to see if you are within range. You need to drill a hole into the ductwork and have an accurate temperature probe. I believe that would tell you if the furnace is working within specs. I want to say if airflow is to low then the temp rise would higher than rated. If airflow is to high the temp rise is to low then the air flow is to high. Maybe someone can correct me if I'm wrong. It's been 4 years since I went to school for HVAC.

[torchkeeper]

Both units are horizontal, coil was that way in attic and furnace is vertical or horizontal option . they are both horizontal hanging from floor joists. The coil is pointed with < heat/blower coming from open side of v . top/point is aimed downstream.

It`s been 42 years since I went to school!!!

[m_west5]

Found box for replacement air supply limit and it is correct value.Opens at 250 closes at 210. The 80,000 btu have the highest opening temp of all the nordyne g6 models. Even higher than 100,000, and 120,000 ? Thinking a coil may be restriction? It was a separate attic unit in house we moved it from. We just moved them from house we demoed a 100 feet away. Had no way to put in ceiling vent for a/c as this is a new build modular. So we put coil box in line with furnace. Did I make a large mistake? Coil cabinet and furnace cabinet same outside size. They married right together.

Perhaps. Anyway to take and post some pictures?

Also, can you clarify on the "had no way to put in ceiling vent for ac" please?

Edited May 19, 2014 by beam current

[torchkeeper]

New camera on order, It`s a modular so all sheet \rock ,wiring and plunbing,  cabiniets, toilets come pre-installed. Has a loft second floor, flooring and insulation already down. Roof is hinged and crane does a lift ,kneewall hinges down and second half of roof folds over again.! You know I have all set - day photos on card from old dead camera. Tomorrow I will see if I can get some uploaded.

Thanks for hanging in with me guys. What fun would a simple problem be !!!

[torchkeeper]

Got a quote for a Finnish ,soapstone fireplace,Tulikivi. Do a search,they are over a 1000 years old tech. Damn  impressive, if I do the support from first floor to basement. Of course I need to add 12-18 inchs of re-bar filled concrete, after installation I`m only out 25 to 30 grand! Only burn 2 times a day . Wish I hit a lottery!!