Wall Furnace

JackFre

www.ductlessheating.com It is the best wall furnace in the business. DV, 81-84%, highly reliable, simple install. Excellent vent system, modulating gas valve and blower. Cool to the touch...etc!

Darin(in Michigan)

Wall Furnace

Does any one manufacture a wall furnace(
Empire, Williams, etc.) that does NOT have that rediculous ECO switch and still have a reliable control circuit.

Ken_40

ECO means

emergency cut-off(out)

Which particular one are you referring to. A vent hood spill switch? Roll out switch? What?

I'm pretty sure these switches are needed to prevent someone getting killed. Perhaps the lives involved are not worthy of living?

(;-o)

Steve Ebels_3

I think

The fact that Darin mentioned the unit having a "reliable control circuit" would mean that he's not willing to compromise someone's safety.

Darin, I know what you are referring to on the ECO thingy. They are a big time PITA. All of the wall furnace brands that I am aware of currently use this wretched device. The purpose of which I am unsure of. They do nothing that a more "normal" control circuit which contains a thermocouple, high limit and some type of roll out protection does. Many of the wall furnaces I run into are in cabins or minimally occupied homes thereby assuring freeze up situations and late night calls when the weekend folks arrive at 10PM on Friday night.

Unknown

only kind

Only kind I use are the direct vent, sealed combustion type, garage safe and no open flame exposed and less pilot blow out

Steve Ebels_3

Too small

I don't think anything like that is available in the 50K-65K range. That's the input of the wall furnaces Darin is grumping about.

Unknown

ECO is a

Energy Cutoff usually wired into the thermocouple line as a safety in the event of a run away (Passing gas valve). It will shut off at a temp usually above the high limit switch temperature which is designed to be part of the operating system of the furnace.

ECO's are required if not using a dual seated (redundant) gas valve. I would check with Wall Furnace manufacturers to see if they are now using dual seated valves and have eliminated the ECO.

Otherwise you can get a wall furnace which is electric ignition and does not have the same set up.

Steve Ebels_3

Which brings up the question

Why do these type of appliances need an ECO in the first place? Why don't the manufacturers use a redundant type valve on them? Cost?

Unknown

The ANSI standard

for Boilers and Furnaces requires a redundant valve. The ANSI standard for space heaters and wall furnaces does not. And yes they are less expensive.

Darin(in Michigan)

Wall Heaters

Sorry guys, I started the thread and didn't keep an eye on it. Thanks for the input. Yes, I know the ECO is a safety not to be messed with. However I feel that 30 millivolts(the thermocouple output) is not enough voltage to accomodate a less than perfect condition. The way this particular unit is running is that the millivolt reading just after the pilot valve will hold is 22 Mv. After about 5-10 minutes of the main burner being on, the Mv output starts to fall down to about 16 and "PLOOP"... no more flame(pilot or other). There is NO vent spillage and the temp reading at the blocked vent safeguard is 110 degrees with a negative draft as indicated by a lighter. I noted yellow licking in the heat exchanger when the burner was on but because there are no air shutters, there is no way to adjust air/gas mixture. My thinking is that the unit has too well established a draft and it is turning the pilot into a small cutting torch and the MV output falls. I am concerned that if we reduce pilot gas, the pilot will fall out on off cycles. I think MV systems are supposed to use gold plated contacts to insure good conductivity on MV systems. I just can't believe that The manufacturers use such precautions(Hey that costs money) and they are simply too finicky a unit to go in any installation less than the one they dream up in the lab(when you come across the perfect job in the field, let me know. I want to take a picture.) My feeling is they ask too much of that 30 MV signal

Unknown

Thermocouples

Darin it sounds like something else other than an ECO may be the problem. What is the drop out reading on the thermocouple/magnet assembly? What is the make and number of the gas valve? I assume that the 16 millivolts you are measuring is a closed circuit reading? I have included some information I often post for folks concerning troubleshooting thermocouples. By the way systems have been running on these systems for many years and work fine. It is true in recent years manufacturers have had to overload the millivolt circuit because of added safeties. The only time you would typically find "Gold" contacts is on Powerpile Systems and in particular on the #11 MV low water cutoff switch on the McDonnell Miller # 67 low water cutoff.


I am often asked about troubleshooting a thermocouple on gas systems. This will be a permanent reference that will give a step-by-step procedure.

A thermocouple is a device used to satisfy pilot safety on many 24 volt gas systems. The thermocouple is a device made up of two dissimilar metals. They are joined together at the tip (Hot Junction). When heat is applied to that hot junction a small millivoltage is created. This develops because of temperature difference between the hot junction and what is called the cold junction. The flame has to envelop the upper 1/2" to 3/8" of the thermocouple and the tip should glow a "dull red". If the flame is adjusted to a sharp flame it will glow "cherry red" this will cause the tip to be welded and eventually the thermocouple will fail. The flame should be adjusted to a soft blue flame, not roaring or lifting. The normal millivolt output is 25 to 35 millivolts, on some you may even get up to 35.

The other part of this safety pilot system is the electromagnet (power unit). It is if you will the LOAD and we can say the thermocouple is the SOURCE. The electromagnet is made up of a coil of wire and "U" shaped iron core.When the thermocouple is heated and the millivolts generated the coil will be energized and create a magnetic field. The magnetic field will cause the "U" shaped iron core to be magnetized, it in turn will hold open a seat allowing gas to pass through.

When this system malfunctions it typically causes the pilot to go out and the gas will not flow. The first thing that should be done when arriving at a pilot outage situation is to do some visual checks.

1. IS THE PILOT LIT?
2. IS THE PILOT CLEAN? (NOT YELLOW)
3. IS THE PILOT HITTING THE UPPER 1/2 TO 3/8 OF THE THERMOCOUPLE?
4. ARE CONNECTIONS TIGHT?
5. IS TIP DAMAGED?
6. IS THE COLD JUNCTION BEING HEATED BY THE PILOT OR MAIN BURNER FLAME?

Once those things are addressed it is a good idea to take some millivolt readings. It should also be mentioned that many times it is the policy of some to replace the thermocouple on a call and clean the pilot. It is not a bad thing to do, however it is statistically about 85% of the time it is the thermocouple giving the problem. It is the other 15% of the time that taking readings can solve other problems.

You need a multimeter with a DC volt scale as the millivolts generated are DC volts. There are four readings we are going to take they are

OPEN CIRCUIT - this is taken with the thermocouple disconnected and the meter leads attached to the outside of the thermocouple and the other meter lead attached to the tip of thermocouple. The pilot-on-off knob will have to be held manually to take this reading. This measures the output of T'couple the readings must be above 17 to 18 millivolts.

* CLOSED CIRCUIT - This measures the millivolts used by the coil in the electromagnet . A rule-of-thumb is this reading should be roughly half of the open circuit. It is taken using an adapter screwed into the magnet and the thermocouple screwed into the adapter.

CLOSED CIRCUIT LOAD - This reading is taken the same as the previous reading except the burner is now on. With a proper flame this reading should be about the same as the previous reading. With a lifting main burner flame or excessive drafts or chimney pull, this reading may reduce from previous reading (flame being pulled away from the thermocouple). With the cold junction being heated this reading may increase. If the "cold junction" is heated excessively it will break down.

DROP OUT - This is the final reading. It requires the pilot to be blown out. It measures the ability of the magnet to hold under reduced MV input. A good unit should drop out below 6 MV's - normal is 1 to 2 MV's. The allowable "drop out" time is 180 seconds yes three minutes. It is more likely to be a minute and half to two minutes. There will be an audible "click" when the magnet shuts down.

* THE CLOSED CIRCUIT READING REQUIRES A SPECIAL ADAPTER THAT SCREWS INTO THE MAGNET ASSEMBLY TO ALLOW CONNECTION OF THE METER. AN ADAPTER CAN BE PURCHASED FROM ANY ROBERTSHAW DEALER THE PART NUMBER IS 10-038 THERMOCOUPLE TEST ADAPTER.

A normal set of readings

OC- 30 millivolts
CC- 15 millivolts
CC(load) -15 millivolts
DO- 1 millivolt

The best way to be able to diagnose these readings is to use MILLIVOLT CHARTS these can not be displayed here but I can provide them if you e-mail me.

Thermocouples from different manufacturers vary as to their dependability. The only thermocouples I recommend are made by Johnson Controls. The K15 and K16 series are the best. If you are having durability problems then use the K16RA which is a nickel plated high ambient or corrosive environment thermocouple. The Husky (K16) will fit most applications and for those that it does not the Slim Jim(K15) will fit.

To repeat the adjustment of the pilot flame to envelope the upper 1/2 to 3/8 of the thermocouple is important, the flame should be a soft blue flame not roaring which will cause the tip to glow a "dull red" versus "cherry red".

The combustion condition (excessive temperatures) in the chamber is also an issue and this will require a combustion test and draft measurement to insure that excessive temperatures are not being applied to the pilot. In some cases on water heaters it may be necessary to alter the pilot adaptation to get better quality performance. This however should not be done unless you have had proper training.

The possiblity of the equipment operating in a depressurization environment will certainly lead to thermocouple failure. In addition if the equipment is flued together with a "fan assisted" furnace or boiler this can lead to problems. There are solutions to this also but training is required.

The thing that I find is often a problem is the environment in which the equipment is operating. Many times corrosive chemicals and airborne contaminants are being drawn into the air gas mix and a checmical reaction takes place. This again requires attendance at a training session by a professional combustion person to help you to see the various affects this will have.

Last of all the failure to put all the doors and covers back in place on equipment. The failure to do this will cause an alteration in combustion air and the flame stability is affected.

The design of some equipment is also a problem. When there is high demand for heat (very cold weather) the temperatures that are created in the chamber have an adverse affect on the pilot and thermocouple system. The addition of the K16RA thermocouple can offer some assitance toward extending the life of the thermocople in this situation.

Insufficient air for combustion and dryers operating in close proximity to equipment also lead to problems.

Last of all and this is not directed at any one in particular but just plain lack of service personnel and installers knowing what they are doing.

My book "Circuitry and Troubleshooting" addresses many of the things in question here.

Scott Gregg

Rinnai!!!

That little jewel is going to make a lot of people very very happy!

It's the best bang for the retrofit buck I have seen in a long time.

Darin(in Michigan)

Thanks

> That little jewel is going to make a lot of

> people very very happy!

>

> It's the best bang for

> the retrofit buck I have seen in a long time.

Darin(in Michigan)

thanks

Thanks guys. I'll look into hte Rinnai unit and pass th info on. Yes the millivolt readings were taken with the circuit closed. I have the old honeywell graph that shows thermocouple performance and drop out values and use it on jobs like this. Seems to finicky to me. All the values are where they should be cold and start to change after the unit's run a while.

tim smith

Thermocouple

Darin, can the Honeywell thermocouple and install a Johnson controls K16BT-36 thermocoulple. They have better MV output under load and generally last longer. They are a little larger in diameter but usually we have no problem getting them in. Good Luck, Tim.