I have a Munchkin boilder with a 926 control board that has just recently started throwing an F06 error code. I'm in a rural area that is hard to get service. What is the most likely cause? What should I check first? Nothing apparent is wrong. I've disconnected Boiler Out water pipe and then run water through it without a problem. I did get some rust out, but nothing significant. Where should I go next?
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If you have the model number of the Boiler I might be able to pull the service manual on it. We can go from there. Meantime look on the wiring diagram glued to the inside of the service panel for a note explaining the error code.
It is a Munchkin Model 80M manufactured in July of 2001. About 8 months ago I was having trouble with the flame lighting. I completely replaced the wiring harness with the new 926 Control Board. It lights beautifully now. However, I am now getting an F06 error code. Return (inlet) Temperature Exceeded 230 degrees F. It says to check the circulation pump operation. It seems to be working. I disconnected the outlet of the boiler and ran some water through it. Rust appeared, but nothing significant. I've got the manual, but I'm not sure where to go next.
Hello again, use a thermometer to see if the return inlet temp actually exceeded 230F... that would be very unusual if it did, I suspect the temperature sensor at that location
If it shows on the wiring diagram as being a thermistor, it is likely failed, thats a twenty dollar part
Your manual will have a chart showing how many ohms it should read at various temperatures.... you can check it with an ohm meter.
Let me know, we can go from there as necessary,
OK, I won't be able to do this tonight as I have another obligation, but Wednesday should work out. Thank you. I'll let you know.
Hello again, that sounds like a good plan.... post back when you can, no need to respond to this note before then.
Today when I went down, the boiler had the F06 error code. This is typical after a failure. In addition, it blows about a gallon of water out of the over temperature/pressure relief valve, T&P valve on the diagram. Since the water is now cool, it heated up as normal after reset and shut off. The max temperature I saw on the controller was 175. I've also got a temperature and pressure indicator on the boiler out. It got up to about 180 degrees and 24 psi. This could go on for a couple of days before another failure. So, since I can't tell when it will fail next, it is going to be hard to get that inlet temperature at failure.
Is there anything else I should check prior to the next start? Why is it blowing water out the T & P valve? I also went back and re-read the Control Board upgrade kit instructions the I performed about 8 months ago. The thermistors were replaced with that upgrade. I suppose one could be bad, but they are fairly new.
I read the tag on the T & P valve. It said to exercise the valve once a year. I did this and got a lot of rusty water out.
That's it for now. How should I proceed?
Hello again, set the high limit cut out thermostat, a bit lower, from 200F or where ever it is set, about 5 degrees lower.
Set the operating thermostat into the 160F range and the differential on that thermostat to 15F so that the boiler water has to cool to 145F before the burner comes on and cuts off when the water reaches 160F
when you set the operating temperature controller to 180F. what happens when the boiler shuts down its that residual heat in the fire box over heats the water to 200F or so and trips the high limit or causes the TP valve to open
thats a simplified summary of it.
Let me know how that goes, we can proceed from there
OK, I went down tonight and the boiler was still working. It had not yet failed. However, I followed your advice and reset the temperatures. It had been set at 180 degrees with a 20 degree differential. I reset to 160 and 15 as you recommended. I'll have to wait a while to see if it fails again. What I don't understand, however, is why it would have worked flawlessly for 8 months straight and all of a sudden start throwing errors and failing. Do you have any thoughts on that?
Wish me luck.
Hello again, the high limit control is mechanical in its sensor and switch action... those can wear a bit and change calibration a few degrees. thats one factor.
So that if your electronic operating control was set at 180F, very close to tripping at 200F on the off cycle due to residual heat... but still not tripping... then if the mechanical switch wears a bit, it will start tripping.
By setting it lower, to the 160 or 165 F range you preclude such problems.
The other issue is water flow changes through the boiler, as any line strainers get clogged up, or air in the system, reducing water flow, the boiler runs a few degrees hotter... so that on the off cycle the temperature surge due to residual heat in the fire box takes the temperature higher than it did before... tripping the high limit switch.
Let me know if that makes any sense.
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Well, it looks like we aren't quite there. Since this last response, the boiler failed again. It had the same F06 code and a dumping of some water out the PV Valve, but not as much as in the past. Following your previous guidance, I lowered the temperature again, this time from 160 to 150 degrees, still retaining the 15 degree differential. It went a few more days and failed again. Same F06 code. I can't tell if it dumped any water as I did not dump the bucket from the last time, but if it did, it was minimal. I can reset it and it will work for another 2-3 days before it fails again.
This boiler powers not only the hot water tank, but is set up to do readiant floor heat also. Most of the time this functionality is not exploited as it is for the garage and shop area and is used only in the winter. But there is a complex piping and pump system set up. It is controlled by a Taco controller and recently the only demand on the system has been that of the hot water heater.
I don't know if the above is pertinent, but I wanted to give you all of the details I know. The manual says to check the circulator among other things, but it is not installed on this model. Do you have any thoughts on what else to do? Thank you.
Hello again, if each time you lower the temperature it runs for a few days, then the PRV valve is forced to release, that is generally due to slightly leaking valve seat in the city water make up line that feeds water to the boiler.These can be run as sealed systems, if you leave the city water make up valve open and the pressure regulator valve (also called a PRV) can keep adding water until the boiler pressure limit is reached, then when the water heats up and expands, it blows the pressure relief valve on the boiler.Cure is to replace the pressure regulator valve and set it for 15 psig...Look that over, see if you have a PRV in the make up water line..or not, and tell me if the feed valve is open or not.We can go from there.
Well, let's add a few details to this. I'm not on city water. I live in rural Montana and have my own well and all drains into a septic system. There is a pressure tank that regulates the pressure for the whole house. I haven't really noticed any difference in the pressure on any of the faucets. It actually provides pressure to the house and four outside frost free valves.
The way the system is set up is that I have a ground source heat pump that not only provides me heating and cooling for the house, but the residual energy heats a dummy tank of water to 85 degrees. This supplies the input to the boiler. The hot water from the boiler primarily feeds the master bathroom shower, but also pushes water down to another electric hot water heater which supplies water to other needed fixtures. The house is fairly larger. There is a recirculation pump that is on part-time so that hot water is supplied to all of the sinks when it is running. It primarily runs when we are home.
I'm not sure how much of this detail is needed as the issue still seems to be the boiler, but I'm trying to give you an idea of the whole system. If there is a some sort of pressure regulator valve for the boiler, where would it be located and how can I tell if it is bad? Is it co-located with the pressure tank?
Hello, in summary, most boiler feeds have a check valve in them, so that any water that gets into the closed loop, cannot get out unless it blows the pressure relief.You have a complex system, that I cannot see from here...but if the pressure relief is blowing occasionally, thats the problem about 99% of the time... by what exact means depends on the plumbing.Water is getting into the closed boiler loop, its trapped, when it heats it expands and blows the pressure relief.an Expansion Tank is fit into the system to prevent that...within limits... Find that and check the air pressure on the tank, if water comes out, then the bladder in the tank is bad.
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I think you are on to something. I did check the expansion tank and it appears to be good. The pressure indicates about 12 psi. which is the factory default.
On the outlet of the boiler there is a pressure and temperature sensor. The boiler started up while I was down checking. The pressure indicated 24 psi, but I was hearing a mechanical clanking inside of the boiler. This is not normal, but while it was clanking, the pressure indicator varied from 24 psi down to 18 psi with each clank.
I looked around the boiler, and if there is some sort of pressure regulator in the boiler, I cannot see it. Even with the cover off, it is not evident where this component is located. Is it a component that can be changed? Or is it internal to the boiler itself?
Hello again the pressure regulator on the water feed to the boiler, if there even is one, is outside the boiler, and not part of the boiler.. and could be 20 feet away from the boiler.https://lh4.googleusercontent.com/public/mfmIaFAOi6LMTu26hucWiNZYPAOIa11ATnHAm8VIclCTtmoWPRILYD-pz5uLNAZwyeLjdVy66LgMFtMbeOSBSglIwhayKuWJWTaTOGAa8uAjFP4Ly8Ul8gCX00voPtcy0-bkv0HJ3UnpXXWptEEeQxrpOP_l4YSjmGzQXy-nJL2s63MEy5oyA38The clanking noise and the pressure drop from 24 psig to 18 psig is not common.over firing of the boiler without adequate water flow would cause a steam bubble to form then burst... inaquate water flow can be caused by an air bubble in the closed boiler loop restricting water flow.Look the system over for air bleed valves anywhere in the entire closed hot water loop and see if you can let any air out.Various types shown here.https://encrypted-tbn0.google.com/images?q=tbn:ANd9GcSQ_V1NK1qVQa1taXLdCbutRmzRBISCwecnfBVj8f3Rl5y7x3wcthose are *always* located at high points in the system.. or level pipe with a hump in it.If the boiler is over firing it could also be a problem with the boilers electronics water temperature control circuit.You can experment with that while examining the burner box flames closely.. the hgher you set the boiler water temperature above its current temperature the higher the firing rate.As you set the temperature lower, as the boiler cools the firing rate should drop to zero.
After last night's conversation, I found the pressure regulator in the system. I researched it today and found that it has a strainer built into it. So, I cleaned it. After 11 years of continuous operation, it did have dirt and sand in the strainer's filter. After doing this, I started the boiler again. It came up to temperature and ran for one complete cycle without any problems. I did not hear any clanking and all appears fine right now. I'll continue to monitor this, but I'm hopeful. Thanks again for the continued support.
You are welcome Tom, that sand might have also caused the valve seep, if you still have trouble with the pressure going high, replace the valve,..those are not expensive.
It has been a week now without any problems. I think this issue has been resolved. Thanks again for the help.