residential boiler outdoor temperature sensor how to test
EDITED to add additional pictures
UPDATE (second update) SOLVED Thank you, all of you! Special thanks to Bob "hot rod" Rohr. I followed your advice and turned the knobs on the control and the secondary boiler fired up. I turned the knobs back to the former settings and the secondary boiler shut down. The primary boiler was firing while I was doing this. Thank you all for saving me from trying to find another heating company to fix the situation. It turns out that BOTH HEATING COMPANIES WERE WRONG!! The outdoor sensor bulbs are working just fine same as they were last winter, same as they have been for 30 years.
UPDATE (first update): this morning my house was 59 degrees. The heating company that came out yesterday said it would be an additional charge to have the guy come back out because "everything was working fine yesterday". I checked and found that the guy forgot to turn the boiler back on after he shut it off. He also left some papers laying on top of the boiler against the pipe that goes to the chimney with the hot exhaust from the boiler. Maybe it's good he forgot to turn the boiler on so I was able to remove the paper before the exhaust pipe got hot.
I have a HydroTherm residential hot water boiler which has an outdoor temp sensor with an aquastat control. Is it possible to test the sensor and determine if it is working correctly?
The house is a large tri-plex in a Minnesota. I have two boilers and two sensors. One of the boilers heats the house most of the time and the secondary (identical) boiler only heats when the outside temperature is too cold for the main boiler to keep the house warm. Each boiler has a separate outdoor sensor and control.
A heating company came to replace a pressure relief valve and after replacing the valve they looked at other things and said that one of the sensors was working fine and the other sensor was not working. Both sensors were working fine last winter.
I understand that I could put the bulb in ice or dry ice but is it possible to test the ohms or adjust the control and see if the boiler fires. I had a second heating company come out to determine if the sensor was bad and they charged me $200 to tell me that it was not possible to test if the sensor was working or not. The sensor in the image below costs $60 and I could easily replace it myself and wire it exactly the same as the current sensor and set the control the same as the current sensor.
Below is a link to the same sensor and control that I have.
https://www.motionsurplus.net/sensors-transducers/23916-honeywell-l6008a.html
Comments
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What you have is an aqustat used to sense air or water temperature. Is that what you are calling a sensor? It is really an outdoor air control.
The control has 3 terminals R, w, and B.. All it is is a single pole double pole switch that works on temperature. The "R" terminal is the common . It will always be connected to the w terminal or to the B terminal but not at the same time. It will be connected to one or the other depending on the tepm at the sensor bulb and on where the dial is set.
So using this for an outdoor air control for a boiler I would think you would have two wires one to R and one to B. If the outdoor air at the bulb is at 60 and your set to 60 The r & B circuit would open above 60 (to shut the boiler down) and close below 60 to start it up.. it. This is not exact as the control has a differential built in. You can usually here it click when you turn the dial.
You can put an ohm meter across the terminals to check it. Measure the temp near the bulb and the control should work and you should here a click when the dial is sset and turned near the bulb temp
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that would be an odd temperature range for sensing outdoor temperature 100-240 degrees
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream
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Yeah, something not making sense. That control looks brand new with capillary coiled up
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how old is the boiler. I don’t find any info online for that name? Highly unusual.
Honeywell did make a capillary outdoor reset control, back in the 50 or 60’s
It would have two cap tubes going into it.
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream0 -
Thank you all very much for your help and advice. I really appreciate it.
I'm calling the outdoor temperature sensing bulb a "sensor" because that's what the heating guys called it. I describe the "control" as an aquastat because that's what it says on the label inside the cover. The "control/aquastat" is the part inside the house.
The picture is from a brand new aquastat/sensor that I found online. It is the same model number as the one connected to my boiler. I did not take a picture on the old one connected to my boiler.
The boiler was in my house when I bought it 25 years ago. I think the boiler was old back then. Both boilers work great and I will not be replacing them. I think the name of the boiler is ThermoKing but I'm not sure. I will check in the morning and post back with the name and model number of the boiler.
EBEBRATT-Ed, I will attempt to adjust the control and see if the boiler will fire but maybe the secondary boiler won't fire if the main boiler is hot and the outdoor temperature is mild.
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tekmar probably has a control that can do it with a thermistor outside so you just have to run wire outside, not a cap tube and sensing bulb.
it is relatively easy for the tube or bulb to get damaged and for the charge to escape
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ThermoKing makes refrigeration and air conditioning equipment for the trucking and public transportation industry.
Is this an electric boiler ?
Pictures of your equipment and the rating plate may help.
National - U.S. Gas Boiler 45+ Years Old
Steam 300 SQ. FT. - EDR 347
One Pipe System0 -
The Honeywell ODR, cap. tube controls look like this. The have very long cap tubes to reach outdoors. Two sensors.
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream0 -
After this many years it is possible that you have a L6008A cover but not a L6008A control. I have seen this happen. it is possible yopu have a L6007A with the proper temperature range.
If a cover gets lost and a customer a asks about the missing cover, I would look in my truck for a old cover that might fit, even if the label on the inside indicates it is for a different model of the same type control.
The model that you need that has the proper temperature range may no longer be available. If it is available, it would most likely ge a special order and would cost more than $60.00. Not recommended is a way to change the. range by turning the dial past the stop on the control by bending the stop down and turning the dial. then bens the stop back up. The increments and numbers on the dial will no longer be accurate but it will do the job if that is the last resort. I would opt for an outdoor thermometer that was designed just for that purpose. But that is also a more expensive control.
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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If you do need to replace that control, consider an electronic setpoint control. It's digital reads temperature and has a lot more control settings.
Honeywell, Penn, Ranco, Johnson Controls are other brands. Should be less $$ compared to the old technology cap tube controls.
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream
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Thanks for noticing that. I will post another picture of the control that shows the model number.
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Thanks mattmia2, I will look into that. I'm hoping that the existing thing is working fine. I hope the guy did not test it or did not test it correctly because it was working fine last winter.
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hot_rod: sorry, my mistake, I should have checked instead of guessing at the name of the boiler. You are correct, that was not the name. The name is HydroTherm. I posted additional pictures including the boiler(s) with the name on the front. Thanks for catching that.
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Thanks, yes you're right. The correct name of the boiler is HydroTherm. Thanks for the advice about the pics. I just posted additional pictures including the rating plate. It's a residential gas boiler.
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It looks very similar but it only has one copper wire going outside with the bulb on the end outside. I posted a picture with the model number.
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Thank You Ed, I really appreciate your advice. I posted a picture of the control with the model number on it.
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Thank you! If I find a way to test the existing aquastat/sensor/control thing and if it is good, then I won't do anything. If it's bad and I need to replace it, I can replace it with the exact same model and do that myself using the existing settings. If I replace it with a modern electronic control then I might need to find a heating guy in Minnesota who can help me get the settings correct.
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Just turn the knob all the way from one extreme to the other, it should click around the outside temperature number. That usually indicates it is working and accurate.
It's possible some other relay or control will be heard when you turn below the outdoor temperature. It is turning on the system.
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream
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It appears that control had been replaced by L6008 A1242. the $60.00 will not work for you. You will be hard pressed to find a discounted low temperature Remote bulb Aquastat like the one you have.
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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If you have to replace it the correct control is a Honeywell T6031A1029. Supply House.com has them. $170. Temp range is -30—+90
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