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I have A Trane Model TWE030 that is giving me intermittent problems.  I Oct. when I first tried using the heat function everything worked for a couple of days.  Then the fan would not come on.  Called the technician and he removed the big cover panel, when he went to remove one of the little covers inside the fan started as soon as he put a screw driver on it.  After repeated attempts to get it to repeat the no start, no luck.  It started every time. Although he did not say as much, I suspect it is an intermittent relay as that appears to be what is under that small cover.  Today the fan would not come on again.  This time I removed the big cover and as before the fan started when I removed the small cover.  If it is a relay problem, how do I identify the relay ?  How do I convince the Tech. to replace the relay when it is intermittent and does not show up for him.  The unit is 5 years old and I have a 10 year insurance program on it.

Thanks in advance

Tom

It sounds like a faulty relay.  The vibration from removing the door is probably causing the relay to close as it should.

Look at the wiring diagram below.  The red arrow is pointing to the fan relay.

The technician should replace the $10 part and avoid repeat calls.  Otherwise he is losing the company money if his insurance plan is covering the service call costs.

As a technician I would sit there cycling the system until it happened again.  Mind you it's a very simple system so replacing a sequencer or fan relay in an electric furnace is a no brainer when you're facing intermittent problems.

Thanks for the reply.  Tech came yesterday and fortunately was able to get the unit to go "on" and "off" by wiggling the fan rely.  Changed the relay and everything appears OK.

Tom

I have a Trane TWE030 air handler as part of my electric furnace, heat pump installation.  It is equipped with a 5" pleated filter which I change every 6 months.  Is this the proper interval.  The reason I ask is when the tech was here to replace the fan relay he seemed very interested in the filter condition.  Due to communication problems, he was French and spoke little English while I am English with little French, I was not able to understand his concerns.  A couple of hours after he left his office called and questioned when I changed the filters.  I explained I change them every 6 months and was due to change it at the beginning of Feb.  I guess by their records I had only purchased 1 filter from them.  I also told them I buy them on line as the are half the price for the same OEM filter.  Could the filter condition contribute to the Fan Delay Relay having to be replaced ?  I have a 10 year insurance policy on parts replacement so I wonder if they are looking for an excuse not to cover the cost of the relay. 

Tom

I suppose a very dirty filter could cause the motor amps to increase and cause the wire terminals to overheat and damage the fan relay, but I don't believe this is what caused your relay to fail.  A 240V motor has low amps and the motor would have internal overload protection.

I use a 5" MERV 16 filter that claims to be good for 12 months but I change it every 6 months.  How long the filter lasts depends on the environment, are there smokers, animals etc...?

You will notice reduced airflow from the supply air vents and noises from the return air vents when the filter is really dirty.  Sometimes a dirty filter can cause your furnace to cycle on limit (overheat) which kills the efficiency of the furnace.  Usually the furnace room will be much hotter than the rest of the house when this is happening.  This type of short cycling could cause the fan relay to fail prematurely because it's opening and closing more often.

Some high efficiency filters are bottom loading so it's hard to tell when they are plugged with dirt and dust.  Don't try to vacuum the filter, it's best to replace them.

There might be some literature on your filter lifespan if you Google the filter model number.

When the Tech was here replacing the fan relay he also put a clamp like devise over the large Red wire and showed me a reading of 85.1.  At that time I did not know what the reading meant or was and as he spoke little English I got no explanation.  After looking around on line it now appears he was reading the AMPs on that wire.  I think 85.1 is high in this case but I don't know.  The outside temp was around -23C so the unit was in the heat mode with the fan running.  Is this reading high??  Could a dirty filter cause the reading to go that high.  I think if he was only reading the AMPs to the fan motor it would be much less.  I know squat about electric furnaces and have about the same knowledge of electricity.  Thanks.

Tom

What is the double breaker size in the panel?  I think he may have been reading 8.5 Amps.  85 Amps should cause the breaker to trip.  Did the technician measure the Amps with the filter removed?

Your furnace probably has a 1/3HP fan motor.  It will have a rating plate on it that specifies the FL (Full Load Amps) and LR (Locked Rotor Amps).

The FL rating should be between 2 and 3 Amps depending which speed is running.  8.5 Amps seems high, but I would have a look on the motor itself and double check the ratings.

The house panel has a 100AMP Breaker for the furnace/heat pump and the furnace itself has two 60 AMP breakers.  He only did the reading with the filter installed.  None with the filter removed.  Unfortunately I don't have an AMP meter to check it myself.  The motor is 1/3 HP with a FL of 2.1 AMP.

Tom

Maybe the fan capacitor is bad.  It's labelled CF on the wiring diagram.  Otherwise a restricted filter or undersized duct work might be causing the increase in Amps.  The motor itself might be siezing up.  Have you tried turning the blower wheel by hand to see if it spins freely?

You'd need a multimeter to test the capacitors microfarads.  It's a inexpensive part though and a good place to start.  Just make sure the replacement capacitor has the same microfarad and VA rating as the old one.

Have you noticed an increase in your hydro bills?

I finally got my own ammeter and checked the furnace today.  It is around freezing so any heat is coming from the heat pump.  With the fan running I checked the load on the red wire going directly to the motor  2.7 AMP and also the black wire which also read 2.7 AMP.  I also checked the big red wire going to the 60 AMP breaker and it also read 2.7 AMP.  I think that is the wire the tech checked when he was here.  Where he got a reading over 8 AMP is beyond me.  I took out the 6 month old filter and still got 2.7 AMP with no filter installed and checked the fan rotation which was quite easy to turn so all seems OK to me.  Put in my new filter and everything seems fine.  I think the old fan relay just decided to pack in without much outside influence.

Thanks for all the help and suggestions.

Tom

It sounds like everything is running as it should.