Ug needs help ! / Indirect HW Heater Issues

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Uglysquirrel
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Post by Uglysquirrel » Fri. Jan. 19, 2018 7:06 pm

Here is something I need help with .

Have hydronic oil burner heat since house was new as backup to the Pocono with a 10- 12 year old 50-60 gallon indirect water heater. Over the last several months it seems like less and less hot water is being heated with recovery longer. It has never been drained. City water,not hard. An recent inspection of a 1/2" cold water copper pipe ID showed a very clean interior after 30 years.

I'm thinking that at minimum the indirect tank needs to be drained with plans to shut the burner down, shut the hot water outlet valve immediately near the unit,hook up two garden hoses one to the bottom drain of the indirect tank and one to the (left open) over pressure value. Plans are to leave the cold water on so it stirs up the bottom sediment and use the two garden hoses to flush the entire tank really well. Then I'd shut off the cold water and let it drain from the bottom drain while using the over pressure valve as a top of tank bleed. After that plans would be to run the hot water washing machine faucet to the outside to clean any remaining pipe debris after the tank is refilled..

The sludge and whatever is in there will be put in the sewer drain which will be below the tank bottom from an elevation perspective.

My question: After 10-15 years is the crap on the bottom like a sludge such that it will clog the indirect drain valve ? Like...what will be the consistency of the stuffi in the indirect tank bottom? And does the sludge exist at a level that covers some of the boiler water coil?

Also,is this drain process going to solve my issue or is there (likely) so much scale on the OD of the indirect heater's staninless steel coil (that circulates the boiler water inside the indirect's tank) that I need a new indirect tank?

Lots of questions.....but I know there are a lot of boiler guys out there !

Thanks !

Ug


 
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coaledsweat
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Post by coaledsweat » Fri. Jan. 19, 2018 8:21 pm

I'm thinking the coil needs an acid wash. I doubt the sludge in the tank is affecting the ability to heat the water.

 
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Uglysquirrel
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Post by Uglysquirrel » Fri. Jan. 19, 2018 9:10 pm

coaledsweat wrote:
Fri. Jan. 19, 2018 8:21 pm
I'm thinking the coil needs an acid wash. I doubt the sludge in the tank is affecting the ability to heat the water.
Coaledsweat, so an acid wash gets the buildup of scale off the coil OD, correct ? Given that, how does one prepare and execute an acid wash ? :o :o

 
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Post by Pacowy » Fri. Jan. 19, 2018 11:26 pm

If this change has occurred over a period of a few months, I don't understand why the focus is on scale buildup. How does anyone know this is anything other than the byproduct of seasonal reductions in inlet water temps?

Mike

 
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Post by coaledsweat » Sat. Jan. 20, 2018 5:47 am

The third sentence is telling.

The ID of the coil. As scale accumulates, the boiler can't transfer as much heat into the coil and the coil can't transfer as much heat into the heater tank.

An acid wash is not something I recommend for the novice. It is a really nasty compound. If you do it yourself, be very careful.

 
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Post by lsayre » Sat. Jan. 20, 2018 6:11 am

We may be beginning to see a similar problem with our boilers DHW coil. Our well water has a TDS of a whopping 876. The house has a dual resin bed softener, but I'm not sure that the softener is always working at peak efficiency, as it is now 18 years since it was installed to replace the highly dysfunctional softener that was in the house when we moved in. My wife just brought to my attention yesterday her perception that our water pressure is beginning to decline. The change is so subtle over time that it can easily go unnoticed. A year and a half ago we had our well pump replaced, so it isn't likely that the problem lies there.

 
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Post by Rob R. » Sat. Jan. 20, 2018 7:09 am

Before you wash anything, make sure the controls are working correctly, and that the zone valve or circulator serving the indirect is working correctly. If everything appears to in order, see what the difference is between the indirect supply and return temperature on a heat call. If the temperature difference is small, (less than 20 degrees), I think the suggestion that the coil has a layer of scale or sediment on it is probably accurate.

What make and model is your indirect?


 
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Post by McGiever » Sat. Jan. 20, 2018 9:57 am

OP has not revealed what mfg'r of indirect tank, but some models have large oval bolted access covers or some bolted removable HX coil assembly.
This would allow for easy inspection and remedy.

 
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Post by Uglysquirrel » Sat. Jan. 20, 2018 6:31 pm

Rob R. wrote:
Sat. Jan. 20, 2018 7:09 am
Before you wash anything, make sure the controls are working correctly, and that the zone valve or circulator serving the indirect is working correctly. If everything appears to in order, see what the difference is between the indirect supply and return temperature on a heat call. If the temperature difference is small, (less than 20 degrees), I think the suggestion that the coil has a layer of scale or sediment on it is probably accurate.

What make and model is your indirect?


Its a Mega Store, about 5 ft tall, blue, round. Probably 10-12 years old, coil water in the boiler hasn't been changed for that long, no air I can hear. A picture is appropriate in the next day. I'll check the circulator pump for the happy hum.

McGeiver, thanks for the idea of replacing the coil though if you want so spend a w/e in CT doing that for good more than you can handle food and drink, come on down. We'll put you up the the barn, that's how nice we are. Coffee in the morning with cast iron campfire bacon, eggs, peppered home fries. Anchovies a minimum 50 feet away please.

 
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Post by McGiever » Sat. Jan. 20, 2018 7:14 pm

Dang, Sorry to report, but coil is not replaceable...I'll go and unpack my bag now. :lol:
Mega-Stor has a removable cap on top for easy access to coil and tank.
The domestic side has constantly changing water with some constant minerals, were the hydronic closed loop side is sealed...it may just be "scaled minerals" on outside of coils.
Cleaning coil's interior can be done by a flush hook-up by normal tank connections...cleaning coil's exterior is a different story.

If coil was leaking the lifetime warranty would cover that. ;)

 
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Post by Uglysquirrel » Sat. Jan. 20, 2018 7:41 pm

In addition to the lack of recovery, got a hot water pressure reduction while cold is full bore same tub faucet and everywhere especially on 2nd floor. What causes a hot water pressure reduction?

Recent 1/2" coldwater copper pipe 30 years old showed ID of pipe entirely free of scale.

 
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Post by Rob R. » Sat. Jan. 20, 2018 7:43 pm

I have heard of guys draining the tank, and running very hot boiler water through the coil to dry/crack the scale. Refill the tank and the hot coil will boil the first water that touches it, further dislodging the scale. I have never tried this, only heard of it.

Proceed at your own risk.

 
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Post by McGiever » Sat. Jan. 20, 2018 9:08 pm

Uglysquirrel wrote:
Sat. Jan. 20, 2018 7:41 pm
In addition to the lack of recovery, got a hot water pressure reduction while cold is full bore same tub faucet and everywhere especially on 2nd floor. What causes a hot water pressure reduction?

Recent 1/2" coldwater copper pipe 30 years old showed ID of pipe entirely free of scale.
Does the system have a mixing valve?
Hot water flow volume decrease can happen w/ a mixing valve needing attention but has nothing to do w/ indirect tank recovery time taking longer.
Now the pump working well does effect recovery times.
I'm believing that the coil acid flush is not needed...if it were a tankless coil that would be a different story. ;)

 
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Post by coaledsweat » Sun. Jan. 21, 2018 7:43 am

McGiever wrote:
Sat. Jan. 20, 2018 9:08 pm
Does the system have a mixing valve?
Hot water flow volume decrease can happen w/ a mixing valve needing attention but has nothing to do w/ indirect tank recovery time taking longer.
Now the pump working well does effect recovery times.
I'm believing that the coil acid flush is not needed...if it were a tankless coil that would be a different story. ;)
Very good point and the first place to start.

 
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Post by CapeCoaler » Sun. Jan. 21, 2018 10:08 pm

could be the sink or shower valves are crudded up...
check the set temp of the tank and controls...
The indirect at the 'rents house has been going since '91...
No issues...


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