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Old 06-15-2021, 05:40 PM   #1
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Not enough heat from & unknown boiler antifreeze for PrecisionTemp TwinTemp Jr.

Hey, folks. I've searched and read many threads and the primary impression I get is to dump this PrecisionTemp unit and upgrade to an Aqua Hot but I'm thinking that, at that price, this won't happen until we upgrade our RV.

So in the meantime, I am trying to resolve a problem where our hot water will not stay hot. It starts out hot--at about 110--but as soon as the water from the holding tank runs out, the temp drops fairly rapidly, down into the 80s. After a couple of calls with the PrecisionTemp Support team and turning up the mixing valve to maximum with no change to hot water delivery, we've narrowed it down (hopefully) to either some sludge in the antifreeze tank (which is preventing adequate heat transfer while running the hot water) or scaling inside the mixing valve (which is not allowing enough hot water to pass through).

I truly hope that one of these will fix the problem but I'm not confident after reading all the posts about all the problems with these units and the fact that this unit is only 2 years old (or less!). Still, I am planning to start with a flush and cleaning of the antifreeze so that I have a fresh start. (We bought this RV back in December so I don't know when it was last changed but this unit was installed in 2019 so it's likely due for an antifreeze flush, anyhow.) '

As for which antifreeze to use, I've asked PT Support in three different calls over the past couple of months to make sure I don't mess it up and here is what I *think* I know so far:
  • Most common brands are Peak, Camco, and Century.
  • Must use an antifreeze "for multiple metals." (Does "safe for aluminum" mean it is safe for multiple metals? Because I haven't seen this "safe-for-multiple-metals spec" on any listing.)
  • Should NOT use a "pre-mix" (diluted, "ready to use," 50/50, or other) solution.
  • Should mix the antifreeze at 60/40 for Peak or 50/50 for the other two (where 60 is antifreeze and 40 is distilled water).
  • "It should say "boiler antifreeze" on the bottle." (I have not seen these words on any bottle I've found online or on the two spare partially full antifreeze bottles that came with the RV.)
  • Should use propylene glycol only (or at least do not mix ethylene glycol with propylene glycol--insta-sludge and voided warranty would result if mixed).
I've searched locally, on Amazon, and on Google and I can't figure out which product to buy that will fulfill all of the above requirements. Most appear to be diluted or pre-mixed and none say "for boilers" or "heat transfer fluid" and many say they are for winterizing (but I don't think that in itself means it can be used as the heating fluid).

So does anyone have a definitive answer regarding at least one option that fits the bill and does not void the warranty?

And if anyone has advice on other things to try regarding the inability to maintain hot water, that would be great, too. Because after I flush this thing, if it's still not staying hot, then I'll need to remove the mixing valve, soak it in CLR, and *hope* that does the trick (and I'm guessing it won't--maybe a bad mixing valve?).

Thanks in advance for any guidance on this one!
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Old 06-15-2021, 07:45 PM   #2
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I have the same unit in our coach. When we picked up our 07 in late 18 I had no idea what the maintenance history for the heating system was. We used it for a full year before suspecting it wasn't running right. The hot water wasn't consistent and the heating system was incapable of keeping the coach warm when it was 50 or below. It would short cycle whenever I used the shower or heating system (burner would cycle on and off every 5-10 seconds). After talking with Gary at Precision Temp he convinced me to flush the total system, including all the lines and heat exchangers. After refilling, the system immediately worked just as advertised. Hot water forever and the heater easily heats the coach in any weather. Since this is our first coach with hydronic heating I don't know if these systems are anymore problematic than other types.
I use Century Transfer Fluid #19910-C6 and I don't dilute it.
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Old 06-15-2021, 10:17 PM   #3
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Quote:
Originally Posted by bhammond1980 View Post
I have the same unit in our coach. When we picked up our 07 in late 18 I had no idea what the maintenance history for the heating system was. We used it for a full year before suspecting it wasn't running right. The hot water wasn't consistent and the heating system was incapable of keeping the coach warm when it was 50 or below. It would short cycle whenever I used the shower or heating system (burner would cycle on and off every 5-10 seconds). After talking with Gary at Precision Temp he convinced me to flush the total system, including all the lines and heat exchangers. After refilling, the system immediately worked just as advertised. Hot water forever and the heater easily heats the coach in any weather. Since this is our first coach with hydronic heating I don't know if these systems are anymore problematic than other types.
I use Century Transfer Fluid #19910-C6 and I don't dilute it.
Thanks for the quick response, bhammond1980! I'm hoping, now, that a full flush will do the trick for us, too. It would be nice to have the hot water working as advertised (and make the wife happy, too! ). So it looks like this is the stuff, right? And I think I read somewhere that this thing will suck up a little over 6 gallons by the time it's full again--does that sound about right? I'd like to order it ASAP so it shows up this weekend or early next week before we leave our current campsite.

By the way--Gary was GREAT! He helped me to diagnose the first problem we had (a bad thermistor) that was preventing the blower from turning on. I hated to lose him but he retired at the beginning of this month. So Ray is the Man, now! =) Between you and him and a little luck, maybe I'll have consistent hot (110+) water by next week.

Thanks again!
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Old 06-16-2021, 11:34 AM   #4
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UPDATE: I received a reply from Ray at PrecisionTemp this morning and he said:
  • He is not familiar with that Century product but "it looks ok; just make sure it is propylene glycol and has inhibitors for multiple metals."
    So I believe we're good there.
  • He also reiterated that they recommend mixing with distilled water (50/50) and, again, at the end of his reply, he doubled down with "I would not recommend not mixing the antifreeze with distilled water."
    Should I be concerned? You say you've been running it full-strength for a year or more, now--is there any chance doing so will result in a sludge/build-up (faster than otherwise) that will start impeding the heat transfer to the water?
  • Also FYI: although my unit is not under warranty (as the second owner of this unit) , in general, using this particular propylene glycol transfer fluid and *not* mixing it with other brands will not void the warranty of the unit.
  • The tank holds 2 gallons of antifreeze (the manual says 2.5) and the heating loop holds approximately another 3 gallons so you need to start with 6 gallons and there will be some left over to refill the overflow/expansion reservoir as needed.
I'm leaning toward using it without the mixture with distilled water but am curious what you and others think about the impact mixing has versus not mixing it.


Thanks again!
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Old 06-16-2021, 05:18 PM   #5
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Century sells both a concentrate and premixed. I bought the premixed so it's already diluted.
Since you are ordering on line will Precision Temp sell you their recommended fluid? I couldn't find their recommended so went with the same fluid approved for Aqua-Hot. If your system is like mine, it has the stainless tank and heat exchanger.
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Old 06-16-2021, 05:29 PM   #6
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Picture of the container.
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Old 06-16-2021, 07:09 PM   #7
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That's perfect, bhammond! Thanks for the photo--that is exactly what I ordered through Amazon (7 gallons to be delivered by Monday). I think I only need a little over 5 so will likely return one; depends how much of the 6th gallon is left over as a reserve--maybe I'll keep them both.

I did not see the note on the front of the picture in Amazon that says "use full strength / do not dilute" -- that seals the deal for me. (I also do/did not see anything that says "pre-mixed," which the PrecisionTemp manuals say to avoid.)

I could not get a specific recommendation from Ray (PT Support) for a preferred product/part number, which is why I was struggling to determine which ones are safe *AND* best for this unit. He did not offer for me to purchase it directly through them so I assumed that they don't sell the stuff... but I'm betting Amazon is cheaper anyway if they did sell it.

So I'm going to give this a go... I hope it solves the problem but I'm still concerned...

Did you also experience symptoms where the GasStop continuously shut off each time the water heater furnace fired up? Or where the water would start out nice and hot and seemingly stay there for 15 minutes while doing dishes but then never got even luke warm the next day (even though the gas is on and the blower is exhausting hot air)? I think there may also be an issue with the mixing valve but it just seems hard to believe that it can be caused by scaling in just under two years of use. Although the previous owners were full-timers and maybe they didn't use a filter all the time?

Will report results next week.
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Old 07-11-2021, 11:54 PM   #8
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As promised, here is the (delayed) update--hopefully the last one on this topic.

I was finally able to make time to drain the tank and the heating/furnace loop (I think) and refill it all. However, all the instructions I found suggested that there should be between 4 & 5 gallons of fluid (maybe a little more even) but I was only able to pull out about 3 gallons and put back in about 3 1/2 gallons. That said, the instructions I found and that Ray sent me seemed to cater to the TwinTemp-2 unit and mine is a TwinTemp Jr.. Still, Jerry thought the Jr. should only carry about a gallon less than the TT-2 so I was hoping to get at least 4 gallons in there.

Initially, I worried that I'm short and I keep going out to check the overflow tank and it's rising and lowering with use but not "disappearing" into the system. So now that I've done all the burping and letting it run that Jerry and Ray (@ PT) instructed (in winter mode), my hope is that maybe there was some fluid still in the loop somewhere that makes up for the missing half-gallon or so. So far, so good!

Thanks, PrecisionTemp Support team! SO appreciative of your time and guidance!
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