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Heat Switched Off, but Radiators Warm with Calls for Hot Water

ktccapo
ktccapo Member Posts: 35
in Thermostats and Controls
I have an oil-fired steam system run with a Honeywell VisionPro 8000 with Redlink, utilizing a wireless equipment interface module. The system also provides domestic hot water utilizing an external holding tank with circulator, and an Aquastat L4006A controller.

The temperature on the Aquastat is currently set to 130, with a 10 degree differential. The boiler almost always fires whenever hot water is called for, and now that's it's warmer outside, we're noticing that some of the radiators are getting warm during the hot water call.

Should the Aquastat be adjusted differently? Could the way the Aquastat is wired to the equipment interface module have something to do with when the boiler fires for hot water (much more frequent than before the install of the Redlink system)?

Any advice and/or suggestions would be much appreciated. Many thanks and best,

KTC

Comments

  • Paul48
    Paul48 Member Posts: 4,469
    None of those things have anything to do with your problem. You have circulation where there shouldn't be any. Either something is missing from the installation or is not functioning correctly. Without more details and photos, we can't really diagnose your problem. We can help, if you give us more.
  • ktccapo
    ktccapo Member Posts: 35
    Hello, thanks for responding...

    I've attached a few photos of the hot-water side of the system, the Aquastat, and the new EIM (which was installed with the new Honeywell Redlink system).

    The boiler/core system were all installed in 1994; other than two new circulators and annual cleanings, nothing has been done to the core system since (with the exception of the new Redlink system last Nov).

    A couple of others here on the forum have suggested trying a higher differential setting on the Aquastat (setting the temp to 150 and the differential to 30). Would you agree or disagree with this suggestion?

    Or could a bad circulator be causing the problem (it's pictured in the photo attached to the piping near the bottom of the holding tank).

    Your advice and/or suggestions are very much appreciated. Thanks and best,

    KTC




  • Paul48
    Paul48 Member Posts: 4,469
    I'm sorry......I missed that it was a steam system.
  • JeffM
    JeffM Member Posts: 182
    I think there's probably something not right with your aquastat - here's how I get there:
    It's a steam system, so you'll only get hot radiators when the boiler gets fully hot and makes steam (212 F) - that should only happen when called by the room thermostat.
    Your aquastat is meant to keep the boiler water warm/hot (but NOT at 212, something lower like 150-180) so that when the hot water tank temp drops it can turn on the circulator and get heat from the boiler right away. The boiler may fire when you're adding heat to the tank (determined by aquastat), but should not exceed the aquastat temp. That means no steam (unless the room thermostat is also calling).
    Since the radiators are heating, you're making steam. If the room thermostats aren't calling for that, then something is likely wrong with the aquastat.
  • Steamhead
    Steamhead Member Posts: 17,358
    Try turning the aquastat down on the boiler. I can't make out what the current setting is, but drop it at least 5 degrees. If that doesn't solve the problem, drop another 5 and so on.
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Consulting
  • Paul48
    Paul48 Member Posts: 4,469
    @Steamhead

    I believe he said that was set to 130, but that doesn't make a lot of sense.
  • BobC
    BobC Member Posts: 5,501
    Look at it with a magnifier and a flashlight, that 130 might be 180.

    Bob
    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • Steamhead
    Steamhead Member Posts: 17,358
    Paul48 said:

    @Steamhead

    I believe he said that was set to 130, but that doesn't make a lot of sense.

    He might have been talking about the aquastat on the tank, not the one on the boiler...................
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Consulting
  • ktccapo
    ktccapo Member Posts: 35
    Good morning all, many thanks for your responses...

    I was indeed referring to the Aquastat on the boiler; as far as I know, there is not one on the holding tank.

    The current settings on the Aquastat are 130 (not 180) and a differential of 10.

    The oil company that provides a service contract for the boiler had at one time several years ago had it set at 160, but turned it down when we experienced a similar phenomenon in the warmer months (radiators getting warm with hot water production).

    A couple of people on the forum have suggested a temp setting of 150 with a differential of 30 in order to reduce calls on the boiler for hot water. Do any of you concur with that suggestion?

    Other than that, could either the Aquastat itself be bad/wired wrong? Or a perhaps a problem with the circulator, holding tank, or internals of the boiler itself?

    Again, many thanks and best,

    KTC

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