Indirect Hot Water Heater Inconsistent Temps

raquettelaker2

I had a Heat-Flo HF-40 indirect water heater installed in January 2022 to take over from the tankless coil in our boiler (Weil-McLain WTGO-3). It was said that this tank would provide nearly endless hot water for our 3 bed, 1.5 bath house, and it pretty much did, for about 8 months.

Around August I noticed if I was the second person to shower, I'd run out of hot water. Maybe 10-minute showers, with a 2gpm shower head; nothing crazy. I also noticed that the initial burst of hot water is extremely hot: 170+ degrees, then as you shower you have to keep turning up the hot water to keep a steady temperature, until you just run out of hot.

If I run the tub on full hot the tank will completely deplete itself; hot water pipe out of the tank is bone cold, and the aquastat won't kick the circulator on for 30+ minutes. Then it'll just run for the rest of the day almost. Both boiler supply and return pipes are un-touchable hot, but the boiler temps barely drop, as if it's barely transferring any heat into the tank. Yesterday after the circulator had been running for 4+ hours, I removed the aquastat and put a temp probe into the well. I got 120-degrees (aquatstat set to ~125). At the sink 20 feet away, I got 171-degree hot water.

I can't get the original installer to return my calls, and so far a new plumber has replaced the aquastat and then came back to add thermal paste to the well to make sure the probe was contacting the well, with no improvement.

Is it even possible that scale or sediment could have built up in 8-12 months to be causing this level of performance change? We have city water, and it does leave white spots on our glassware, and we get some white build-up on our shower head. Nobody has suggested flushing it yet, considering its age. And Feat-Flo advertises that it has a smooth stainless steel coil which resists scale build-up. I'm at my wits end and just want a consistent hot shower again!

Thanks in advance for any guidance you may be able to provide!

pecmsg

The cold supply should have a dip tube that allows cold water to flow to the bottom of the tank. It might have come loose.

Nice on the installing contractor to not install unions.

What temperature do you run the tank at? ASHRAE recommends 140°F to kill legionnaires bacteria but point of use can't be above 120°F. Where's the mixing valve?

yellowdog

sounds like the coil and the aquastat well are both scaled up and need to be cleaned. have someone pull the aquastat well and inspect it. that will give you a rough idea of what the coil may look like and whether or not it is scaled up.

hot_rod

170F at the top of the tank, yikes Is that a measured temperature?  What temperature is the tank set to?
if you are running the tank that hot you should have plenty of DHW

raquettelaker2

hot_rod said:

170F at the top of the tank, yikes Is that a measured temperature?  What temperature is the tank set to?
if you are running the tank that hot you should have plenty of DHW

170 was measured at the basement sink across the room from the tank. The aquastat is set around 125F.

Thanks to all for the replies! I'm waiting for my plumber to recover from his backlog from last weekend's sub-zero temps for next steps.

HVACNUT

Also notable is they reduced the supply and return from 1" to 3/4". Does the circulator match the requirements of the tank?
It seems a relay was added to the side of the boiler to control the indirect, but is it wired correctly using ZR,ZC so the boiler knows there's a demand rather than just maintaining low limit?

raquettelaker2

Updates:

The manufacturer suggested that they used the wrong anode (magnesium) in assembling the tank, and said to remove it. Plumber is still here flushing the tank to get rid of the residual on the coil and within the tank. This is after ONE YEAR of service! So is this caused by the magnesium or something in our (city) water?

pecmsg

raquettelaker2 said:

Updates:

The manufacturer suggested that they used the wrong anode (magnesium) in assembling the tank, and said to remove it. Plumber is still here flushing the tank to get rid of the residual on the coil and within the tank. This is after ONE YEAR of service! So is this caused by the magnesium or something in our (city) water?

What did they recommend replacing it with?

Send that picture to the water department and ask them WHY?

raquettelaker2

EDIT: Stamp on the anode cap actually indicates it was aluminum. Not magnesium.

Manufacturer said not to replace the anode. Just cut it off? My plumber was confused as to why they would have used an anode at all if the tank and coil are supposedly made of surgical grade stainless steel.

Jamie Hall

Step back a moment and reflect on the purpose of the anode. It is to sacrifice itself, chemically, to prevent or at least reduce electrolytic reaction involving other metals in your system. While it may be attractive to blame the water company for the problem -- "they did it" -- they didn't, though they may decide to pay for the work to replace the anode with the correct one and the cleaning, simply because it's cheaper than a lawyer.

A cleaning and the correct anode will probably help you a lot. However, if some of the debris has made it into the mixing valve, it could and probably is still sticking and needs to be at least cleaned.

raquettelaker2

Thanks all for your comments. They flushed a whole bunch of gunk out of there and tried to shake the coil free of further build-up. Per the manufacturer's recommendation they just removed the anode altogether (I also found this online). They buttoned it back up and it heated the full cold tank to temperature within 20 minutes (hallelujah!). The aquastat well was also covered in build-up. I'm still confused about how this much stuff built up within 8-12 months; is this just going to be a recurring problem? My neighbor had their water tested not too long ago; seeing if she can find the results.

GGross

@raquettelaker2

I would suggest having your own water tested. If you are on a well it is possible that your water is different from your neighbors, the water quality can also change drastically over time. A simple hardness test to start, which you can do quite easily yourself, or possibly your HVAC guy knows someone in wholesale who will do it for you.

unclejohn

In your update post you said “ they used the wrong anode “ if they is the manufacturer I would ask to have a new tank. 

hot_rod

HeatFlo is one of the few stainless tank manufacturers the put anodes in. In your case it looks to be doing more harm than good😗
If you are on city water, by law they are required to provide the test results, usually you can find it on their website. My city sends it out in a newsletter once a year.

You can take a water sample to a lab. Any Ag schools nearby they usually have water test labs. That much deterioration that quickly may be water related. If you take a sample to a lab, tell them your concerns. Most health depts test water for bacteria or other heath related concerns. Not necessarily for corrosion.

Did HeatFlo suggest not using a rod, plugging off that port? Maybe that is what they meant by cutting it off?