Indirect Coil Piping Rusted - Use It As A Storage Tank?

NTL1991

Hey guys.

Got a call from the parents yesterday. Their 41 gallon BoilerMate was leaking all over the basement floor. I isolated the indirect and re-activated the tankless coil in their Utica boiler. (We left the coil and Taco mixing valve piped in. Really glad we left it. Just had to throw some valves and enable the low limit and they had hot water again.)

Drained the indirect and the coil zone and cut it out of the system. The return elbow on the bottom of the tank was rusted through, and snapped off inside the tank.

Would it be possible to use the indirect as a storage tank fed from the tankless coil? Maybe wire up a circulator between the coil outlet and the tank cold inlet triggered by the BoilerMate's aquastat to keep the tank at setpoint? I've got a Taco mixing valve that I can use on the outlet of the tank to temper the hot water supply.

Would this work?

HVACNUT

Using a tank in conjunction with a tankless coil is what's know as a booster.
Not sure about using the indirect but here's typical setup in this manual.

NTL1991

Great, thanks. My indirect has a tapping at the top for the DHW outlet and the T&P valve, as well as the cold inlet at the bottom of the tank, which doubled as a drain. Just two tappings to work with, as opposed to 3 that I see for most Boosters.

There is a 1/2" drain at the bottom of the tank as well. I'm assuming its for the DHW side and not the boiler side. If I can get the drain out, That would give me another tapping to use.

Zman

I knew it was a boiler mate from the title. Next the coil gasket will go.
For a long term solution, consider a new indirect.

NTL1991

I think you're right... A DHW circ alone is going to be about $200, or about a quarter the cost of a new indirect. They don't have NG, and are apprehensive to install LP piping through the basement for a new gas-fired water heater. I think they'll have to live with some variations in DHW temp from their coil, and burning some oil to maintain a low-limit until I can install a new indirect for them. The more I read about the BoilerMates, the less I want to spend time fooling with it.

Thanks guys. A great help as always!

SuperTech

Is this a boilermate with the piping on the bottom? I have one of those that I got for free from a job we did. My coworker decided to cut it out with a sawzall not knowing that I might want it. I replaced all the nipples with 1" copper. That's an easy solution if your only issue is the nipple. I've been using my "pre-owned" indirect for a few years now without any problems.

NTL1991

Yeah, it's that type of BoilerMate.

The issue is that it's not the nipple, but the street elbow. It snapped off inside the coil.

NTL1991

Okay, so the parents want another indirect installed. Any recommendations on brand? Burnham Alliance, Triangle Tube Comfort, Lochinvar Squire. Don't think I'd recommend another Amtrol...

kcopp

How long did the Amtrol last? Looks like an older unit.... I would go w/ the Ch-41 series. All top mounted piping. For the money its a good unit.

SuperTech

The Amtrol is a good indirect tank. I'd wager that the corrosion is a result of not using a dielectric union to prevent electrolysis.
The Burnham Alliance is a good option, I've rarely seen any problems with them.

HVACNUT

I would stay away from the TT if it's still a bladder tank.

NTL1991

Thanks guys.

Good point on the dielectric. The Amtrol was second hand. My brother was upgrading his and installed it for the parents roughly 7 or 8 years ago. Not sure how long he had it, but my guess is 5+ years.

Had to go over today to correct the tankless coil piping. I added a globe valve to the cold inlet to the coil to throttle the supply down a bit (didn't have time to order a Watts P3), and found the cold inlet to the mixing valve almost completely shut, with the handle removed and a tag labeled to not touch. Looks like they were throttling the cold supply to the mixer and not the coil, which wasn't helping things. Also, the mixer was gummed up a bit. Removed the spring and piston assembly, cleaned it up, and reassembled. Works great now.

Tub/shower has WAY too much flow. Parents told me their shower head was from QVC... Ugh. No GPM marking or any marking of any kind on the shower head. Researched a bit and found it is a "Down Under Wonder" rainfall shower head at 2.5GPM... PROVIDED the original restrictor plate is installed... And guess what? It doesn't come factory installed; they throw it in the parts bag. No wonder why they had an indirect installed to begin with. The coil could barely keep up with the shower head alone.

My plan was to throttle the tub/shower supply valve in the basement, but of course, it was frozen. Untouched since 1972. So the plan is to sweat in a new globe valve and throttle it back a bit to get their shower to a reasonable flow rate.

HVACNUT

Why not just get another new shower head?

Are you still doing the indirect, or staying on the coil?
Do the indirect.

What aquastat is on the boiler now? If it's not modern, an easy upgrade can offer domestic priority, Low Water Cutoff, Thermal Targeting, Condensate Protection, Boiler or Outdoor Reset, etc.

It can also be configured as a cold start boiler, rather than maintaining a minimum temperature because of the tankless coil.
Installed properly, it will save on fuel consumption.

NTL1991

New shower head would be the obvious answer. 90 year olds are set in their ways. Also, when filling the tub, the flow is so great that the water is not picking up heat from the coil properly. If I throttle the inlet to the coil, the tub/shower steals all the flow, and the other fixtures have little flow. If I can throttle the shower, that’ll keep some flow for the sinks and dishwasher.

I put in a L7224U with wired outdoor reset and a Taco ZVC405. It’s a huge Utica Starfire SFH4150WT boiler. We had the boiler configured as cold start with the indirect, and I wired the aquastat to override any outdoor reset when the indirect calls.

The plan is to get an indirect but the coil is what’s holding them over until then.