Print

[Roger2561]

This has to do with my oil fire burner.  I have baseboard heat in my house; 4 zones using Taco zone valves; a Taco circ on the return line before entering the oil burner; on demand coil in oil burner.  It has a Honeywell 8151 triple aquastat.  The high set-point is at 180, the low set-point is at 160 for DHW.  My problem is after the oil burner has run for a few minutes due to a zone calling for heat or keeping the water temp from falling too far, I notice that the water temp will go above 200 degrees before the oil burner off.  If the water temp is above 200, the oil burner will still fire up even with a temp over 200 degrees.  Thinking the temp guage may be faulty I changed it but it made no difference.  So, now I'm wondering if the well into which the aquastat bulb sits is corroded to the point that the bulb on the aquastat is getting a faulty reading or perhaps the triple aquastat itself is faulty and needs replacing.  Can anyone offer any suggestions (other than calling plumber) or know of some trouble shooting techniques I can use to narrow down the problem?  Thanks.  Roger 

[slimjim]

More than likely the aqua stat bulb is not getting a true reading, they are supposed to have a graphite looking paste type product in the bulb that helps with a true reading but most guys will not use it because it over time will harden and make removing the probe impossible, my suggestion would be to simply turn down the high set point to where it shuts off at the desired temp and give that a try for a while. A service guy will more than likely change out the probe and Aqua stat which will get expensive!

[Roger2561]

That's what I was thinking too.  Is changing out a tube and aquastat something the DIY'er like me can do, who's pretty handy with tools? I would think that the hardest part is not to kink the capillary when inserting the bulb into the tube.  Other than that I would think it would be a pretty straight forward job.  Roger 

[slimjim]

If you can get it out then yes you can change it but most will need to change the aqua stat as well because they can't be disconnected and just change the bulb. Be sure to turn off all the power to the aqua stat and mark your wires. If the well is nasty, it may need to be removed and cleaned as well which will mean bleeding each heat loop, do you know how to do that correctly? zone valves can be tricky!

[Roger2561]

I know how to manually open the Taco zone valves, if that's what you mean that's not a problem.  And, draining the oil burner of water is no problem either.  I know purging air from the system can be time consuming but something I've done in the past and very important.  Roger     

[slimjim]

Ok keep us posted.

[Roger2561]

Slimjim - You asked that I keep you posted on swapping out the triple aquastat and immersion well on my oil furnace; I finally got to it today.  It went very good.  The old immersion well was very corroded and inside the well that the bulb goes had no heat conductive paste in it.  When I started to refill furnace the boiler drain started leaking and I couldn't stop it so I had to swap that out too.  Once it was finally filled with water and the air purged from it, the furnace cycled a few times, it settled down and it now turns off around the 180 high set point.  It took me about 3 hours to get everything done.  I was taking my time to be sure I didn't miss anything.  I find it hard to believe they wanted to charge me more $700.00 to do that job.  Roger   

[slimjim]

Well with parts and labor that is close to what I would expect, most oil guys get at least 100% markup on parts and all their travel time paid. Better off burning the house down for heat than calling them on a Saturday night for a no heat call in the winter months.