Hot water storage tank built-in well?

SweatyInToronto

We have a Rheem ST-120 gallon commercial storage tank with what appears to be a galv metal pipe with a cap on it sticking out about the water inlet and outlet. Tanks about 15 years old. Is it a watertight well, or just a tapping for a well that would need to be installed when the tank is emptied? Also I'm not clear if there's an anode in it as described by the brochure. Didn't see a cap on the top for one.

Will get photos and post if this helps!

EdTheHeaterMan

So if you are talking about the opening with a plug, in location A and B in the diagram, they are probably the Anode rods installed at the factory. If the tank is 15 Years old, they are probably gone by now. Time to replace the rods.

If you are speaking of opening C ,... I would hope there is a temperature control already in there to operate the heat source.

Replace rods with something like this: https://www.supplyhouse.com/Rheem-SP11309C-7-x-44-375-Magnesium-Anode-Rod

SweatyInToronto

Here's a really poor quality image of the nub on the bottom which I believe is for the aquastat. However I'm not clear if it's an installed well waiting for the aquastat or if water would come out if the cap was taken off! I'll get a better shot tomorrow.

The aquastat is in the dedicated boiler currently, so the pump has to run continuously so that it knows the water temperature. However the goal is to put an the aquastat in the tank so that the pump then can run when there is a demand for heat only.

So anodes are used in plain storage tanks? Would they need to be drained to replace or it is enough to turn off the cold water intake and pumps. I'll double check for those plugs in A & B tomorrow thanks!

EdTheHeaterMan

Yea... The picture is of no help. The Rheem ST-120 model number you provided has this specification sheet
http://bostonheatingsupply.com/Rheem Storage Tank/ST80-175 Spec.pdf
The second page is where I got the illustration.
Can you tell me what opening on the illustration you referred to in your Original Post/ Is the illustration I posted the correct representation of your Rheem ST-120?

SweatyInToronto

Believe that I attached the same document  in my original post. The pipe nub, about 3 or 4 inches with a cap on it, is coming out of C on the diagram. Is that likely a dry well?

I'd say so except the cap makes me wonder if there is water behind it. Further photos to follow thanks! 

EdTheHeaterMan

That is a plug or cap with water on the other side. This is the part you need to put in the opening after you remove the plug. https://www.supplyhouse.com/Honeywell-121371B-3-4-Aquastat-Well?gclid=Cj0KCQjw8rT8BRCbARIsALWiOvSkoNWiNySxReK9_oJPLu5flqmp98ysuecZPME-UJEQLeL-oWbE05UaAsn_EALw_wcB
I have made that change on the fly without fully emptying the tank.

1. Remove the pressure from the tank, by shutting off the inlet to the tank then opening up the boiler drain. Once the water stops flowing out of the tank, there will be a slight vacuum at the plug marked C.
2. Now close the boiler drain valve
3. Get the well-adaptor ready for the quick change, pipe sealant or Teflon tape
4. Remove the plug C. As you get near the end of the threads push in the plug to keep the air leaking in (which will also let water out like an upside-down beer bottle as each bubble enters the bottle with a glug glug glug). once the plug is ready to fall out of the way, quickly insert the well-adaptor to block the opening. (try to get it on only one glug)
5. Tighten the adaptor to the proper torc to prevent water leaking.
6. Turn the water pressure back on and check for leaks.

SweatyInToronto

That's quite a procedure. We just had the damn tanks empty too but didn't plan for this.

How much water would you expect would come out of the tank?

In any event it makes sense Edtheheaterman thanks very much! 

mattmia2

Might want to have a rag with a corner twisted up about the size of the hole ready to go if something goes awry with the well as well.

hot_rod

You could probably strap a sensor onto the nipple in the top of the tank, insulate around it and get about the same temperature reading as that short well will provide. Maybe off a few degrees, adjust the control accordingly.
Or fasten a sensor against the tank itself near the top, slide it under the tank insulation.

In the solar business sensors are strapped on the collector piping and against the tank all the time, some, like Rheem weld a bolt onto the tank to fasten a sensor. Electric tank water heaters use sensors pressed against the tank, for control and high limit.

Plenty of strap on sensors and controls available.
If you don't want to get wet

SweatyInToronto

hot_rod said:

Electric tank water heaters use sensors pressed against the tank, for control and high limit.

Plenty of strap on sensors and controls available.
If you don't want to get wet

Well, the closest reading to the water temp I could get was at the pipe inserted in the well cavity. It read 20 degrees lower than the
actual water temp, but may be closer after it's wrapped on and insulated.

Am planning to use this aquastat with the remote bulb.
https://www.supplyhouse.com/Johnson-Controls-A19ABC-12C-SPDT-Remote-Bulb-Temperature-Control-100-240F-w-Adj-Differential-8-Cap - mainly because it seems cost effective.

That said, I'm assuming it's more efficient over the long haul to start and stop the pump based on the demand. It might save 90% of the electricity cost, and reduce chimney effect cooling from the circulation through the cooler exchanger. Perhaps longer pump life. But is there is a downside to it that I'm missing?

These aquastats require no external power is this right? It's just wired direct to the boiler from what I've seen...

mattmia2

You probably want to read the temp near the bottom so you can react before the cold water reaches the outlet.

an aquastat is just a switch operated by energy from the temp changing, requires no external power.

SweatyInToronto

mattmia2 said:

You probably want to read the temp near the bottom so you can react before the cold water reaches the outlet.

Yes, the nub is in the bottom 3rd of the tank, shown in the diagram above referring to the 3/4 inch NPT aquastat opening...

SweatyInToronto

Following up on this, finally, I've decided to first attempt the external sensor to keep it simple. The hot water boiler is a Laars Mighty Therm2 with a copper exchanger that is piped to two 110Gal storage tanks. There's an internal aquastat on the boiler, and the motor runs continuously currently. I'd like to use the external aquastat and have the motor go on when there's a demand for heat, which is supported directly by the boiler using terminals 3/4 on the field interlock.

However, in order to to this the manual is pretty sparse. It just says

6.C External Boiler Operations Use the field interlock terminals located in the control box area. Remove the jumper and attach your "T-T" or "CH" demand here

This is what the control box looks like. I can remove the jumper per above. But it's not clear to me what wires from the aqaustat need to go where.



The Penn A19 aquastat has 3 screws for, blue, yellow and red.
I'd want to use it as a low-limit, so


The wires need to go to the 3/4 but which ones where?

The motor is wired to the boiler already, so I believe the only other thing needed is to switch from constant to auto, once the above is completed.



Once it's working I'll tweak the settings as water temp will probably be higher than the bulb indicates. There's a gauge on the boiler that will provide the actual temp so i can sync the two.

Should I have a pro do this? Probably. However, if one can give me guidance that would be second best. Trial and error would not be something I'd want to rely on.

Thanks so much!

EBEBRATT-Ed

On terminals 3 &4 there is a metal jumper on the right hand side of the terminals. Remove this jumper. Wire from your Penn control to terminal 3 & 4 on the boiler and use Red & Blue on the Penn. It doesn't matter if terminal 3 goes to red or blue. Same thing with #4

I don't know what your doing with the pump

SweatyInToronto

I'll give it a go.  Thanks much!

The circulator I believe is already wired through the appropriate terminal on the boiler. And there's no pump outside of what's between the boiler and tanks. If this doesn't cycle on and off in auto mode that would be a problem!

SweatyInToronto

So I lowered the built in aquastat to 100 removed the jumper and did this connection of blue and red to the field interlock 3 and 4 and turned the pump to auto.  I turned the external aquastat temp up high to be sure it would demand heat no heat. 

What was strange was I turned the built in aquastat up high and that did cause the burners to fire. However I thought the built in was no longer in charge when I took the jumper off.  Are there other connections that need to be removed?

I can try tech support at laars to see what they say as it could be model specific...