Boiler temp not matching Aquastat

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Alex Fessak

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Hi, I have a question for you guys.I have a Buderus Logano G215 boiler just for baseboard heating. It has a new Honeywell L7224u 1002 Aquastat installed last week. I also have 3 Grundfos zone valves with circulation pumps for each zone and each is set to med circulation.. It is an oil fueled boiler.

Now before last week the heat was fantastick, rooms would heat up fast and boiler wouldnt fire for a while. On Friday while I was at work 3 hours away my wife calls and says there is no heat. I have her check the boiler and it blew the fuse. She resets it at the fuse box and boiler powers on. She says she hears the boiler make noise but I think it was the circulator pumps turning on, not the boiler. Water was also leaking for the air vent on top of boiler. Temp in the house showed 47 at the thermostats. After an hour she calls me back and the temp only rose to 48. I called for emergency service and the tech came and changed the air vent and said the Aquaststat needed to be changed. The new one is the L7224U 1002 all i know about the old one is it was Honeywell also.

Now my problem is that the rooms dont get hot like they used to. Temp on the Aquastat says boiler is 183 but the temp on the boiler with the gauge is around 160. The Aquastsat has been set to 180 hl and ll off. Is the Honeywell faulty? Or not programmed correctly? And basically is there anything I can do so not to get charged another service fee?

At night with temps here below 0 I hear the boiler firing about 5 times an hour with the 55 degree setting for overnight. Also some zones dont really get that hot but the pipes are hot.
 
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Dana

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If the thermal bond in the sensor well for the aquastat isn't good enough (there's some goop that's usually applied to make that) there will be a discrepancy between the aquastat and the boiler temperature. But with the thermal bond connection too weak the boiler runs hotter than the aquastat is registering, not the other way around.

This is more than a dumb aquastat. Do you have the outdoor reset control option, and is it enabled? If the outdoor reset got re-programmed or lost it's curve parameters during the swap they may need to be updated.

Have you discussed this with the tech who installed it? (Always the first order of business.)
 

Alex Fessak

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If the thermal bond in the sensor well for the aquastat isn't good enough (there's some goop that's usually applied to make that) there will be a discrepancy between the aquastat and the boiler temperature. But with the thermal bond connection too weak the boiler runs hotter than the aquastat is registering, not the other way around.

This is more than a dumb aquastat. Do you have the outdoor reset control option, and is it enabled? If the outdoor reset got re-programmed or lost it's curve parameters during the swap they may need to be updated.

Have you discussed this with the tech who installed it? (Always the first order of business.)

Sorry but I forgot about the thread as we haven't been at the house all month.
As far as I remember no I don't have an outdoor reset controller. Anything I can try next time i go to the house?
 

Dana

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Try reading the installation manual, to verify that it was done correctly, including verifying that the sensor in the well has the necessary thermal compound.

IMPORTANT Best thermal response is obtained with a well that snugly fits the sensor. Insert the sensor until it rests against the bottom of the well. Use a well of correct length and bend the wiring, if necessary, to hold the bulb against the bottom of the well. If the well is not a snug fit on the sensor, use the heat-conductive compound (furnished with TRADELINE® models) as follows: Fold the plastic bag of compound lengthwise and twist it gently. Then snip off end of bag and work the open end of the bag all the way into the well. Slowly pull out the bag while squeezing it firmly to distribute compound evenly in the well. Bend the wiring, if necessary, to hold the sensor against the bottom of the well and to hold outer end of the sensor in firm contact with the side of the well. See Fig. 3. Wipe excess compound from the outer end of the well.

Water leaking from the vent is an indication that the system pressure may be too high, or becomes too high during a burn. Verify that the system pressure is 12-15psi when cold, and doesn't go over 25psi during a burn (<20 psi would be better.) If it's the right pressure when cold/tepid but spikes high during a burn the expansion tank may be shot or improperly pre-charged. If the pressure is high even when the boiler is on the cool side the system is overfilled, which could be from a seeping auto-fill valve, or a pinhole leak in the heat exchanger of an indirect water heater.

Read and understand the programmable operation settings of the aquastat, and verify that the parameters are all set where you think it needs to be. (I haven't digested the manual myself, but I surely would if it were on my boiler, especially if the boiler wasn't doing what I thought it should be doing.)
 
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