Nortron Furnace

[lonestarheir]

You may have two of them, but they may be using one of them for something else, with out being there - don't know for sure. It looks to me that the seperate two wires are on top, from the pic anyway. It is hard to tell with the angle of the pic.

__________________________________________________

Brandon
- Have you changed your filter this month? -

[imeduc]

--------------------------------------------------------------------------------

I got one other question? if I can be so bold, is there a fast way to test each element ?

For what .Are they good ???? Are do they come on???? Pull the wires off both side of the element and ohm them out that will tell you if they are good. Turn the heat on and Amp each one will tell you if it came on.

ED

My mistakes dont define me they inform me.

[LazyPup]

The basic logic for this heating unit is relatively simple although it does have some very nice add -on features.

When you examine the schematic you will note that there are primarily two types of control components, sequencers and relays.

Inertia is the physical law which states that a body at rest tends to remain at rest, or a body in motion tends to remain in motion unless acted upon by an outside force. When a motor is off and standing still inertia tries to keep the armature at rest, therefore when a motor is started it requires an initial burst of energy to overcome inertia before the armature can begin to rotate. The burst of energy required to start a motor is known as the “Locked Rotor Amperage-LRA). Once the motor begins turning it then draws “Full Load Amps- FLA” which is the amount of energy required to maintain the motor in motion.

Purely mathematically speaking 746 watts of electrical energy equals one horsepower of mechanical energy, therefore we could say that a 1/4HP electric motor should draw approximately 746 / 4 = 186.5 watts. While that is the theoretical wattage draw, in the real world there are other energy losses in a motor, such as hysterisis losses which are stray currents that float through the motor windings and dissipate energy in the form of heat and frictional losses to bearings or other components within the motor. Normally under full load a motor will draw about 110 to 125% of the theoretical FLA therefore a 1/4HP motor will typically draw about 186.5 x 125% = 233 watts.

The mathematical formula for watts is
P=E x I
where P= Watts (Power), E= Electromotive Force (volts) and I = Inductive Force (amps)

We could then use the formula I = P / E.
223watts / 220 volts = 1.05 amps

LRA (locked Rotor amps) is typically 3 times the FLA therefore while it only requires 1.05 amps to run the blower motor it would require 3.15amps to start the rotation. Fortunately the LRA draw only occurs for a fraction of a second until the rotation begins.

Typically residential electric furnace heating elements are made in 5KW, 7.5KW, 10 KW or 15KW increments. One KW = 1000 watts.

5KW elements are the most common so for the purpose of illustration let us use the 5KW element. Under normal load a 5KW element draws 5000 watts. Again using the formula A = P / E we can then compute the amp draw of each element as 5000w / 220v = 22.7Amps.

Here again, the 22.7amps is the amount of current required to keep the element operating at its rated capacity, however during the initial start up the Tungsten or Nickel heating element is cold (Ambient temperature). The physical resistance of the metal decreases with increase in temperature. When the element is cold it has maximum resistance and requires a surge of power to physically heat the resistance element metal to its normal working temperature. Once it arrives at working temperature it only requires the amount of energy required to maintain that temperature, which is equal to the amount of heat energy being radiated from the element. Here again, the initial start current is approximately 3 times the run current, but it only requires the start current for a second or two until the element reaches working temperature.

The problem is that if all the components in the system, the fan and all heating elements were to start at the same instant the electrical demand would be 3 times the normally operating current for the system. Even though this start up current only lasts for a fraction of a second, it would place a severe load on the primary electrical service panel and main breaker.

In order to prevent that surge load on the electrical supply a heater uses ‘Sequencers” to effect a time delay between starting the different components, thereby spreading out the initial load. ( I have prepared the attached illustration to show the sequencer function)

If you examine the illustration you will see that a sequencer has a small heating element in the base and the switching stages are actually small thermostats that close on temperature rise. The heating elements are then connected in series through the small thermostats. When the house thermostat calls for heat the 24v signal voltage heats the heating element in the base of the sequencer. As the heat from the control heating element rises in the sequencer the first stage (lowest thermostat) will close in approximately 30 seconds and turn the first heating element on. The heat from the control heater continues to rise keeping the lower thermostat on while heating the upper thermostat which will then turn on in approximately 90 seconds from the time the control signal was applied. When the House thermostat is satisfied it turns off the 24v control voltage and the sequence begins to cool down again. In this case the upper thermostat cools the quickest, which opens that thermostat and turns off the second heating element. As the sequencer continues to cool the lower thermostat will again open and cut off the power to the first furnace heating element.

In your furnace the control voltage goes through the middle sequence and on to the upper sequencer. In this configuration, while the bottom sequencer is staging the first two heating elements at 30 and 90 second intervals, the control heater in the top sequencer is not activated until 90 seconds has elapsed. The top sequencer then delays the start of the top furnace heating element another 30 seconds.

The control circuit for the upper sequencer is also run in series through the “Energy Saver” switch. When the energy saver is turned on the upper sequencer is disconnected so the furnace only uses two of its three available heating elements. This effectively reduces the energy requirement by 1/3, but it also decreases the amount of heat the furnace can generate by 1/3.

The Summer/Winter switch controls the fan motor only. In the summer mode the fan can be used as a whole house circulation fan without the heating unit coming on. In the winter mode the fan will only operate when the heating unit is on. This switch basically functions in the same manner as the FAN/AUTO switch on most house thermostats. When the Summer/Winter switch is in the Summer position it operates the fan motor in a manual mode in the same manner as FAN would on a normal thermostat. (This could also be the reason your fan motor is staying on even when your thermostat is off.)

The Mild/Cold switch on your furnace selects fan speed. I have not traced that portion of the circuit yet but I presume in the cold setting the motor is running in low speed which would allow the air to heat more before it is expelled from the furnace.

[sdavidson]

OK, I changed both relays today, furnace sounds alot better. meaning it doesn't chug, but still doesn't turn off ? meaning it goes into like a low setting.. I hear the fan is still on, and the air is not hot, but it still seems on... I am going to change my thermostat tommorow, just wanted to know if anyone had any ideas about perhaps the sequencers doing it ?

Thanks

[sdavidson]

ok, I changed the Relay's today, both of them.. and it is way quieter, not chugging along, but I noticed it still doesn't completely turn off ? you think I have something else going wrong with it ? perhaps a sequencer ? or even worse motor ?

[smokinsiggy]

been housesitting, for my neighbor. , he has nortron wood/electric, we have similiar problems, fan runs continuosly, electric 240v-24v . noticed today that the fan not only stays , but the electric heat coil stays hot , no response from 2x stats. i will need to go get the model # . my major question is: where does one find parts for this unit in lower mainland bc , canada. educated guess this old dog should be @15-16 yrs old ??????? barely used on electric been buggered for long time.[?] found today likely fan relay and obviously more issues. please reply ASAP need to go get more firewood at this rate. lol

[Fitter597]

this is very simple, find the w wire leading from the stat to the machine, it is to serve two purposes, 1 fire the relay to send power to the sequencers and 2 fire the relay for the fan motor, electric heat fires the fan at the same time it does the sequencers (heating elements)you have two relays on the bottom i see, one is for the sequencers one is for the fan, your fan relay must be wired hot, to run the fan all the time, i think it is the one on the left seeing the wires run to the bottom section of the machine and to the motor, the two top wires should be the coil for the relay 24 volt relays i'm guessing? Now see where the W wire from the stat goes to? it should go to both relay's, i'm thinking it just goes to the right one and the left one is getting straight hot signal from the transformer. follow the W wire from the stat that is the answer.

[Fitter597]

i just noticed something else....you have red and blue wires on the left relay, those are speeds for the fan motor, i wonder if your w wire is wired right and you have those other speeds hooked up on the normally closed switch of that relay? so that when you stop the call for heat the relay powers off and the normally closed switch runs a lower speed on the fan? you should have 4 wires on the motor, red, blue, black, and common, white or yellow, tell me what the colored wires go to, and let me know if you have a/c or not. if not, disconnect the red and blue and try running the heat, if the fan works normal, tape them wires up.

[JCforever]

nortron electric furnace 21b 20h

Hello,my nortron 21 b 20h electric furnace, on automatic sometimes it heats but fan wont wont always go on, and other times no heat no fan...when i swich to on fan works always but, sometimes does not heat, other times it does.
Can this be a faulty sequencer ?? the one that has two on the same plate...
Thanks for your help
JC

[HayZee518]

check for power on the load side of the sequencer. one side of the elements will be tied to the other hot side. the sequencer coil will be 24 volts. when its calling for heat if you have voltage at the sequencer coil but nothing happens, then the coil is burned out.

[JCforever]

Thanks, will try this in the morning, now I have the thermostat on ON, fan is going and I have heat, but if I put it on automatic, no fan , no heat..but sometimes the elements heat but fan wont go on, and some times it will work normal for a short period...could a faulty sequencer be intermitent ?

Thanks , will let you know tomorow.
JC

[HayZee518]

I imagine anything is possible. Can you post a schematic for the furnace? I can tell better of the operation with something to look at and better to give you some idea of what to look for. A common "ladder" diagram would be ideal.

[JCforever]

Nortron 21 B 20 H

Hi, it is like the picture you have posted on # 7 on page 1, exept that it was installed with the elements on top.
Think I will change the sequencer that has two on the same plate, they go for 76.00 here, my guess would be this could be the problem, then i'll seefrom there. The problem is intermittent, makes it a bit more difficult to find.
Thanks JC

[paul52446m]

The other relay might be for air con. Try just tapping the fan relay and see if it goes off.
Are you sure one of the heating elements is not staying on to? That would make the fan stay on. Later Paul

[JCforever]

Nortron electric furnace

Thanks everyone, I changed the plate with the two sequencers , and everything is back to normal..it fires up the first elements and starts the fan.

Just saved at least $125.00 for service.

Many thanks to Hay Zee 518 and to Paul
JC