After destroying my inverter in a sleepy stupor the other night followed by a 4hr power outage the next night and a modest overtemp my aquastat doesn't seem to function. Is there some type of manual reset or could the sender portion be damaged? I don't know the model # other than it's an open on limit Honeywell. The sender is mounted in a well near the boiler and the aquastat is not near enough to a heat source to be damaged. My problems are small compared to the thousands without power in our region.
Did a power out overheat damage my aquastat???
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I've overheated several boilers with Honeywell aquastats sunk directly into the pressure vessel, and never killed one. One way to test the probe is to stick it into a pot of hot or boiling water and see if you can feel it click when it makes temp and engages. That will tell you whether it's an electrical problem or an issue with the probe. No click on either temp rise or temp drop, and it's toast.
I just went out and opened up the boiler and bled out some air. The aquastat opens and closes when I adjust the dial, but it seems to require the setting to be about 15 degrees higher than the previous setting. I'm going to babysit it and see how it acts for a few cycles. I wonder if the differential is a little screwey also?
Well nearly a week has passed and everything is pretty good but I'm a little nervous. The aquastat is functioning normally but the temp swings are a bit larger than before. My temp/pressure gauge is indoors near the sidearm. I just checked a few minutes ago and noticed pressure was at 50psi and the pressure relief wasn't even wet. The pressure relief valve is an adjustable spring and disc unit which is set pretty low and was working during the power outage. I drained some water and the pressure is normal now, the gauge seems ok. Looks like I better take advantage of the warm weather and tinker with the pressure relief valve tomorrow. What material is in the bulb portion of the aquastat that operates the switch portion? I'm beginning to wonder about the aquastat occasionally sticking allowing a boiling condition.
Well it's about 25-30 below zero wind chill and everything's been working fine, but I just had another high pressure event. I'm really thinking the aquastat is and has been just fine. My pres/temp gauge was about 35-40 psi and about a cup of water had leaked past the pressure relief. The system temp was a little higher than normal 150 deg. F instead of 140 deg. F as measured at the sidearm. I'm thinking maybe my autofill valve could be failing or there is some localized steam flashing in the boiler. This is my fourth winter with this homemade boiler/heat exchanger system and I really thought all the bugs were worked out. What would be required to increase the normal operating pressure of the system from 12psi to 20psi or is that a bad idea?
When my tanks are up to temp I'm running at a pretty consistent 20psi so I don't think that is a "bad idea". I'm at 10-12psi cold (tanks cold).
Why do you continue to struggle with the pressure? Do you have properly sized expansion tanks in your system? Are they just due to power failures??
Why do you continue to struggle with the pressure? Do you have properly sized expansion tanks in your system? Are they just due to power failures??
The pressure spikes are a new intermittent problem. To increase system pressure do I release pressure in system and charge bladder to desired pressure then fill and adjust autofill to desired pressure? The expansion tank is the typical 2-3 gallon unit and the total volume of the system is small maybe 20 gallon total. Would 20 psi cold be a good starting point? My first guess is localized steam flashing. It seems to occur when the wind howls and the boiler might be slightly overfiring. I can't detect any air in the system like I did when the power out overheat occured. What type pressure relief valve do you use and is it adjustable? My pressure relief valve is an old spring and disc device thats woked fine in the past but probably not the best.stee6043 said:
What do you figure you would gain by running at 20psi? Typically to get your system under pressure you start cold and at zero psi. Make sure your tank has the proper pre-charge on it (most are 12psi if I recall correctly). Then you hook up house water supply and charge until you hit your desired start pressure. I started mine at just over 10psi cold. Typically you don't "set" your system pressure with your expansion tank, you set it with the amount of water you force in.
Sometimes having too much of a pre-charge on your expansion tank can lead to too much system pressure while you're running. Have you checked it? A high pre-charge effectively reduces it's acceptance volume. If I were in your shoes I think I would be going in the opposite direction. I think I'd try starting with a lower cold pressure, say 5-8psi. And I'd make sure I have the right pre-charge on the expansion tank.
My pressure releif is a standard unit such as those found on domestic water heaters. It came with the boiler. 30psi releif pressure.
Sometimes having too much of a pre-charge on your expansion tank can lead to too much system pressure while you're running. Have you checked it? A high pre-charge effectively reduces it's acceptance volume. If I were in your shoes I think I would be going in the opposite direction. I think I'd try starting with a lower cold pressure, say 5-8psi. And I'd make sure I have the right pre-charge on the expansion tank.
My pressure releif is a standard unit such as those found on domestic water heaters. It came with the boiler. 30psi releif pressure.
The reason for bumping up the pressure is to increase the boiling point a bit to reduce steam flashing. My "boiler" consists of an old OWB with five 60' loops of 3/4" K copper with a 1" copper manifold at the top connected first in last out. The copper surrounds the firebox, the outer jacket is replaced and filled with pea gravel. This is my fourth winter and I've never had these pressure issues before. My expansion and fill valve are at the original factory settings of 12psi. The reason I asked about the expansion tank charge is because my well bladder tank says to charge with air to 2psi below the cut in pressure. I'm not too certain that cleaning all the ashes out before the cold blast worked against me as the ashes helped reduce hot spots. Oh yeah---the power did go out last night for 4 hours but I had a generator to save me. I'm still waiting on an invert/charger. That 30psi can't be right, is it 130psi? Free heat can't be beat. LOL
Is it possible that your expansion tank is waterlogged (the bladder has ruptured) and it therefore is acting as a much smaller tank than it used to? That would make your pressure rise much higher than it used to. And continue to get worse as it gets more waterlogged, I think.
My DHW always carries 35-50 psi so that valve would blow even if cold. Maybe some navy guys here with nuclear experience might help.stee6043 said:
DaveBP said:
That would by my guess as well. Once I overheated a boiler and "steamed out" the expansion tank. In other words, the heat killed the bladder, meaning that the tank filled with water and eventually, quit working altogether. That would certainly give you high pressure readings when the boiler heats up. You should have your pressure tank checked (they can do it at a heating supply place with a bicycle pump) and make sure that it's sized right for your system.
How do you test for a waterlogged tank? With weather like this I'm not going to be doing any nonessential repairs.DaveBP said:
If your system pressure rises to near or above 30 psi when the boiler heats up, then I'd say you've got a waterlogged expansion tank.
If you can isolate the tank with a valve, then wait until the system cools down a bit and take the tank off. Be careful, as you'll get a face full of water if you don't wrap a towel or something around the connection when unscrewing it. If the tank is heavy, then it's full of water and probably bad. You can check the bladder pressure with a tire pressure gauge once you get it unscrewed. It should be at 12 psi. If it's zero or near zero, then you can try pumping it back up to 12 and see if it holds pressure. If not, then it's time for a new tank. If it holds pressure, then you might be in luck. Reconnect it to the system and see if things are any better.
Another cause of excessive system pressure can be a bad water make-up valve, allowing domestic water pressure to leak into the heating system. Try shutting it off and see if the problem goes away. A tankless water heater or other domestic hot water heat exchanger can also spring a leak and push system pressure up over 30 psi. Again, isolate any heat exchangers containing domestic water if you can, to see if that makes a difference.
I'd do both of the above before fooling with the pressure tank, unless you have reason to believe it's the tank. If your problems started right after a boiler overheat, then I'd say odds are it's the tank.
These are just observations based on my own experience. Any professional advice you can find is obviously better.
If you can isolate the tank with a valve, then wait until the system cools down a bit and take the tank off. Be careful, as you'll get a face full of water if you don't wrap a towel or something around the connection when unscrewing it. If the tank is heavy, then it's full of water and probably bad. You can check the bladder pressure with a tire pressure gauge once you get it unscrewed. It should be at 12 psi. If it's zero or near zero, then you can try pumping it back up to 12 and see if it holds pressure. If not, then it's time for a new tank. If it holds pressure, then you might be in luck. Reconnect it to the system and see if things are any better.
Another cause of excessive system pressure can be a bad water make-up valve, allowing domestic water pressure to leak into the heating system. Try shutting it off and see if the problem goes away. A tankless water heater or other domestic hot water heat exchanger can also spring a leak and push system pressure up over 30 psi. Again, isolate any heat exchangers containing domestic water if you can, to see if that makes a difference.
I'd do both of the above before fooling with the pressure tank, unless you have reason to believe it's the tank. If your problems started right after a boiler overheat, then I'd say odds are it's the tank.
These are just observations based on my own experience. Any professional advice you can find is obviously better.
After several days of head scratching and the boiler just not quite acting right, yet always keeping the house warm, I stumbled across the following. The capillary tube on my aquastat was touching the jacket of the boiler, since temps of the boiler can exceed the water temp., the aquastat was receiving a mixed signal. I guess when I vented air out after the overheat while repositioning the insulation I must have moved the capillary tube. I've been away most of the day but so far things seem to be ok. Even though I've got a fully functioning gas forced air furnace these problems make me extremely nervous, I'd hate to call the gas man. Thanks to all for the helpful advice.
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