potable hot water expansion tank question

leonz · July 5

Greetings fellow board members,

I am going to order a potable hot water expansion tank so I can use the domestic coil on my coal stoker.

Yes, it should have been done 11 years ago but in January I was making many parts runs to town for what the plumbers needed as they did not have everything they needed let alone a pipe threader and black iron pipe.

I have a mixing valve already plumbed into the system from the original installation and I need to know where I should park the expansion tank.

The propane dealer stuck me with a 40 gallon Bradford White propane fired water heater instead of a 30 gallon unit like I wanted saying that they no longer make a 30 gallon tank and they lied to me about that as I found out later Bradford White still made the 30 gallon propane fired water heaters. I need to know what size expansion tank and where I should have the new expansion tank plumbed in.

Hanging it on the wall close to the domestic coil connections would be ideal.

I want to avoid having the fittings and pipe blow apart like they did 11 years ago when they used propress fittings on the domestic coil connections as the fittings blew apart and ran my well dry in the middle of the night making a mess that took 2+ days to dry out.

Would I be out of my tree using 3/4"stainless braided steel washing machine hoses for the hot water connection from the 1/2" domestic coil in the stoker to the expansion tank hung on the wall that would be reconnected to the hot water heater feed from the domestic coil or should I stick with 1/2" k copper pipe and fittings and new bronze male to male connectors at the 1/2 inch NPT domestic coil fittings. My plan is to use a 5 gallon potable hot water expansion tank just out of caution in any case and hang it on the wall and use 3/4" copper to feed the blended/mixed(cooler) hot water to the propane hot water heater.

I never had a bit of trouble with the 3/4 inch external domestic coil that was installed with the hand fired wood and coal boiler I used for 33 years before this. The hot and cold water copper pipe feeding the home from the old connections is all 3/4" copper and I would use 3/4" copper from the expansion tank to the hot water heater.

Thanks much for the help in this matter.

Larry Weingarten · July 5

Hi, I'd like to see a schematic of the system, so I could offer up good advice. Normally, on the cold supply to the tank heater is good, but I'm not clear on where the coil is, or any check valves might be. 😉

Yours, Larry

EdTheHeaterMan · July 5

One thing to consider is that the water inside a potable-water expansion tank may remain there for a long time. It may never reach a temperature high enough to control microorganisms that can grow in stagnant water at room temperature.

In fact, some manufacturers of potable-water expansion tanks have designed special connection fittings or flow-through designs to reduce stagnation. The idea is that normal water movement past the connection can create some movement in the tank, allowing at least some of the water to be exchanged instead of remaining stagnant.

Using a piece of hose to make the connection, as you suggested, may defeat that feature and create a stagnant dead leg.

Just something to think about.

hot_rod · 2:20AM

In Amtrol speak

ST 5 = 50 gallon

ST 8 =80 gallon

ST 12 =120 gallon

Amtrol also has a Venturi type fitting in the tank to encourage “stirring” of the tank, as water moves in or out

Thermal tanks will work on hot or cold, but on the hot side they can hold a cold slug of water. The tank cools after the heater goes iff and may cool to room temperature

leonz · 2:54PM

Good morning Mr. Weingarten, Ed the heater man and Hot Rod/Bob

The kaa-4-1 and larger coal stokers use a circular copper coil to create the domestic hot water in thier coal stoker boilers.

I had so much trouble with this boiler in the beginning because of the chinese hydrolevel controls that allowed it to overheat and go to steam.

Replacing those 2 sets of defective controls with the mechanical Honeywell L8124L triple aquastat, Bell and Gossett RB-122-E low water cut off switch and the Marsh Instruments Triple Gauge solved that control problem for me with absolutely no help from keystoker.

I can safely run and have run the stoker at 150 Degrees Fahrenheit Low Limit Temperature; 170 Degrees Fahrenheit High Limit Temperature all winter long with no issues.

In my opinion with my past 22 years of using mining machinery manuals for maintenance my opinion of their installation manuals and drawings are extremely poor based on thier schematics.

Each model stoker boiler should have its own manual with its serial number.

According to the keystoker boiler installation manual on pages 24 and 25 they want you to use 1/2 adapter fittings which I find odd to begin with and the female coil tapping's are 3/4".

I believe 3/4" bronze nipples could be used safely to connect the 3/4 k copper pipe and fittings could be used.

This keystoker requirement required the clown car plumbers I hired to run 1/2 copper to the 3/4 inch copper cold and hot water domestic hot water lines already in place. I will need to buy a new 3/4 mixing valve as I would want to run 3/4 copper in any case replacing what keystoker insisted must be installed.

The Keystoker direct vent boiler manual applies to my boiler except that I do not have a direct vent draft inducer on my stoker.

Pages 5 and 6 of the keystoker manual for direct vent boilers applies to my stoker boiler.

My keystoker KAA-4-1 stoker boiler is not equipped with a direct vent draft inducer, it is piped to my 16 foot tile lined block chimney.

Their schematic drawings with regard to the installation of the PH-5 expansion tank leave a great deal to be desired.

I will do whatever is required and suggested by you all.

keystoker-direct-vent-boiler-k2-k4-k6-with-6-inch-stack.pdf

I have decided not to attach the other keystoker boiler manual to my post to avoid further confusion.

I suggested to the owner of Keystone who is Dan Snow that they should provide the buyers of thier stoker boilers with copies of "CLASSIC HYDRONICS", "PUMPING AWAY and "HOW COME" to the buyers of thier stoker boilers, whether his did this or not I do not know.

As far as I know they still provide the hydrolevel 3250 plus triple aquastat in thier ready to install wiring harnesses.

At the time I returned the defective triple aquastats to the local keystoker dealer keystoker had 66 of these units returned as defective. They bench tested these units and they stated they were not defective.

I sleep very well at night knowing the Honeywell L8124L and Bell & Gossett RB-122-E are protecting my coal stoker boiler during the heating season.

Leon

hot_rod · 3:08PM

Ideally the thermal DHW expansion tank would be on the cold feed in this pic. (domestic cold water input) As long as tnere are no check valves between the boiler DHW coil and the expansion tank connection.

No harm in oversizing the thermal expansion tank, the 8 gallon DHW tanks are not so common, so a #5 or #12, 50 or 120 gallon tank size, should be adequate.

Corrugated copper flex lines rarely fail, braided EPDM probably a safe option, although they do have a temperature limit. Another reason to have the tank on the cold inlet, keep it operatig in a cooler temperature water for extended life.

leonz · 3:31PM

Hello Bob,

thank you for your comments, they are most welcome. What bugged me about the whole thing is my external domestic hot water coil that was mounted on top of the Switzer CWW 100 had a huge 3/4" copper coil that served us for 33 years before this with no issues.

My initial plan was to use a 5 gallon domestic expansion tank for this new installation attached to the wall with 3/4" K copper pipe and fittings.

I will mount the new 5 gallon tank on the wall and connect it to the cold side of the domestic hot water coil per your suggestion.

Larry Weingarten · 3:36PM

Hi, Where is the 40 gallon tank in relation to this? Is the boiler preheating/feeding that tank? Are there any check valves? Can you take some photos of the setup as it is now? I just don't want to give ideas that could be damaging. 🙀

Yours, Larry

leonz · 3:44PM

Hello Larry,

The stoker would be preheating the domestic water and mixed with cooler water before it enters the 40 gallon Bradford White propane fire hot water heater.

The new (3 year old) propane fired hot water heater is 12 feet+- away in a direct line from the stoker boilers domestic coil. There are no check valves in the domestic coil but I believe the 40 gallon Bradford White propane fired hot water heater has a check valve in it.

Thanks much,

Leon

I will use my wife's smart phone to take pictures and upload the rats nest of piping I have. I may have already uploaded pictures of this with my previous stoker boiler posts on the forum too.

leonz · 3:58PM

Hello Larry and Bob, I have to correct my error, there are two 3/4" flap check valves on the hot(out) and cold(in) lines that fed the old electric water heater which was removed when the first 30 gallon propane fired water heater was installed in 1987.

Perhaps I should just leave well enough alone now that the stoker is working the way it should with the mechanical controls as I sleep very well at night now?

hot_rod · 6:11PM

You could always install a "lazy hand" indicator gauge like this to see if you get expansion related pressure increases. It's really the only way to know IF and how much pressure increase you are getting.

Spring checks without some good differential are not a "bubble tight" seal, so some expansion could slip by.

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potable hot water expansion tank question

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