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GB142 - AM10- BC10 and domestic hot water

GB142
GB142 Member Posts: 33
I have a GB142 question that I have been perplexed with for years... along with others whom I have asked.

My GB142 has been running for 17 years. I run in AM10 which is set between 115 and 125°F. When the temps dips way down into the minus teens I may move it to 125F.

My BC10 is set at MAX 125°F for domestic hot water and MAX temp of 155°F for my boiler temp.

When hot water is used in the house it’s natural for the boiler to throttle up to heat and replenish the water. The boiler will typically throttle up to 198° then back down and cycle like this multiple times which I’ve always found perplexing. It has never in the past just stayed at a high temp and heated the hot water.

I’ve also noticed that inadvertently the boiler will begin to heat the domestic hot water at any point in time even when no hot water has been used.

However, this morning while it was -2°F and my AM10 set at 125°F, it had the BC10 programmed to 131°F .

However, my GB142 was calling for and the BC10 was showing192°F for domestic hot water when no one had used any hot water over the night.

When I turned my domestic hot water temperature down to zero then my BC10 and AM10 both are synchronized at 131°F and sure enough, the temp on the BC dropped to 131.

I have always had confusion about why my domestic hot water is calling for heat when no hot water has been used in the house.

It seems very inefficient for the boiler to be operating at a temp so high just to heat my domestic hot water?

Is there a sensor specifically on the GB 142 that communicates the returning hot water from the boiler that could be malfunctioning?

Comments

  • Ironman
    Ironman Member Posts: 7,366
    No, the boiler is heating the indirect tank when it senses a drop in tank temperature. It doesn’t heat the tank based upon a demand at a faucet. It’s not an instantaneous water heater, but a tank loading concept.

    If it operated as an on demand, you’d have insufficient hot if a faucet hadn’t been opened for an extended period and the tank had cooled down.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
    Rich_49
  • GB142
    GB142 Member Posts: 33
    What component is sensing? It seems incredibly inefficient for it to call the heat as frequently as it does.

    It would be helpful to hear from some folks that have installed a bunch of these and have the perspective to tell me that this behavior is normal, or that it may have a bad domestic hot water sensor?
  • Ironman
    Ironman Member Posts: 7,366
    edited January 2022
    It’s sensing the water temperature in the indirect tank. Again, this is the only way that it can be done.

    IDK if something’s not functioning correctly in your system or if you just perceive it to not be the correct way to design something. Let me assure you that neither you nor I are smarter or more knowledgeable than the German engineers who produced that. And that is the way that all manufacturers control an indirect or any tank water heater.
     
    And I’ve installed dozens of those boilers and indirects and still service many of them.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
    kcopp
  • GB142
    GB142 Member Posts: 33
    edited January 2022
    Fair enough. I am not looking to beat a horse to death here, but my GB142 appears to be running for extended periods at 194F, heating both the domestic hot water and home heat. It is not modulating off and on, my BC10 displays 94F.

    However, when I turn the domestic hot water dial to the off position, the BC10 immediately drops the temperature reading to match that on my AM10 based on the outside temperature for heating my home.

    Several months ago, this part #7735502288 was ordered. However, the technician only installed a part which was self contained on the underside of my boilerplate. I have taken a picture of the the parts which were not installed.... would this suggest it he didn't install all the correct parts?

  • Rich_49
    Rich_49 Member Posts: 2,766
    edited January 2022
    Ah hah . There's your problem probably . How old is the boiler mate ? When you touch the tank can you feel heat ? The sensor being at the bottom is a possible issue , good quality indirect heaters have the sensor located about halfway up the reservoir . The bottom is the worst place for that sensor as tanks stratify , even faster while colder in the area they reside .
    You didn't get what you didn't pay for and it will never be what you thought it would .
    Langans Plumbing & Heating LLC
    732-751-1560
    Serving most of New Jersey, Eastern Pa .
    Consultation, Design & Installation anywhere
    Rich McGrath 732-581-3833