Descaling a tankless water heater

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Kebo147

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Why is the unit turned off during a descaling process? If one is using a low head pump and the velocity of the solution is not more than the unit can handle, wouldn't the heat from the unit running help the white vinegar to do it's job?
 

Terry

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You're recircing into a bucket, not running off the main cold supply.

Just a few paragraphs from a manual. There is a lot more to it than this though. A lot.

Make sure the water heater is turned off and the power supply is disconnected before cleaning the water heater. The water heater may remain hot for several minutes after it is turned off. To prevent burns, wait until the water heater has cooled down before cleaning.

To clean the water heater, wipe the outside with a damp cloth. Use a non-acidic, non-abrasive cleaner to remove any surface stains. The front panel is moisture resistant, but it is not waterproof. Keep it as dry as possible.

You need to drain the water heater before performing maintenance tasks, such as cleaning the inlet water filter, or to prevent the water heater from freezing when it will not be used for an extended period.

Before flushing the Heat Exchanger, gather the following items:
● A bucket that is 5 gallons or larger
● Cleaning solution diluted with water
● 3 hoses
● A water circulation pump


 
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Kebo147

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You're recircing into a bucket, not running off the main cold supply.

Just a few paragraphs from a manual. There is a lot more to it than this though. A lot.

Make sure the water heater is turned off and the power supply is disconnected before cleaning the water heater. The water heater may remain hot for several minutes after it is turned off. To prevent burns, wait until the water heater has cooled down before cleaning.

To clean the water heater, wipe the outside with a damp cloth. Use a non-acidic, non-abrasive cleaner to remove any surface stains. The front panel is moisture resistant, but it is not waterproof. Keep it as dry as possible.

You need to drain the water heater before performing maintenance tasks, such as cleaning the inlet water filter, or to prevent the water heater from freezing when it will not be used for an extended period.

Before flushing the Heat Exchanger, gather the following items:
● A bucket that is 5 gallons or larger
● Cleaning solution diluted with water
● 3 hoses
● A water circulation pump
I understand the entire process of descaling a tankless water heater. I have been in the industry for 28 years and am the service manager for a PHC company in Telluride, CO. Let's say the aquastat temp is set at 120 or even less. The overall risk factor of burns is minimal. You are circulating white vinegar via a pump, which will heat to 120. As the temp increases in the bucket, the unit will modulate down until no more additional heat is required.

The question is more, is it really necessary to turn off the unit and/or turn off the gas? Will it harm the unit in anyway to have it fire during the process? Wouldn't a warm vinegar solution be more effective than a cold solution? I have read the process from multiple manufacturers, but none offer a reason for why the unit should be off. I'm wondering if anyone knows the reasoning behind that portion of the procedure.
 
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Dana

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Most tankless units have a minimum pressure (12-15psi above atmospheric) at which they will safely operate. Some will just not fire and spit an error code if the pressure is too low, others will flash-boil and make a lot of noise if fired at low pressure.
 

Kebo147

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Thanks Dana for that input. If one uses a seriously weak pump, flashing may occur. I can see potential damage by that. I was also thinking back to the HeatMaker boilers and how they would blow an exchanger if not fully purged. That said, I fail to see how operating the unit during a purge, with proper flow rate simulated via a pump, and flowing vinegar causes an issue beyond dealing with the vapor from the vinegar.

When we look at both chemistry and physics, there are 3 ways to speed a process. We can crush something and there by increase surface area. We can stir, or we can heat. The science alone says the unit should run during a descale. But that also assumes the tech has created the correct pressure, flow rate, and stability to maintain it. Any failure of the above can cause a meltdown of the exchanger, just like the HeatMaker. TY DANA! Your comment answered what no tech support has.
 

Stuff

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I look at it as all of the safety devices are designed with the thought that it is in a functional configuration. When flushing there are failure conditions that were not factored in. Liability issues as well. The court won't side with them if you get hurt from instructions that don't say to turn off power.
 

Michael Wieland

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I am currently looking into buying a recirc pump for descaling my tankless heater- any recommendations for a good pump that is not made in China? Thanks
 

Ladiesman217

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I am currently looking into buying a recirc pump for descaling my tankless heater- any recommendations for a good pump that is not made in China? Thanks


I bought this unit from Amazon. I think it is made in China, but who cares for low cost disposable items that are rarely used.

Just wondering, do you have a big ticket cost water heater that was manufactured in the US with US manufactured parts?

https://www.amazon.com/gp/product/B000X05G1A/ref=ox_sc_sfl_title_6?ie=UTF8&psc=1&smid=ATVPDKIKX0DER

A bucket, two 5/8" hoses and three gallons of white vinegar and you are good to go.
 
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