Question for Rinnai tankless heater users

[beejay]

We are using a RC98 tankless heater with the commercial controller to allow us to heat to 185. Lately, and randomly, the unit only heats the water to about half of the set point. So we set it at 185 and water comes at about 120. The flow rate is obviously higher than when it normally goes at 185, but can't seem to find what is causing this. We do flush the heater with vinegar once a month to prevent mineral build up which is common at these higher temps.

Anyone have this problem before? Any advice would be great.

[jvandenbrink]

We had Two Rinnai R98s in series to get us to the flow rate we needed for our 15bbl brewhouse. We began to experience exactly what you are talking about and discovered two things

1. We had just done some plumbing and the plumber had made a mistake and the cold water was backflushing into the hot water. But based upon his mistake it only happened when someone was using our mop sink. So make sure your hot and your cold are completely separated.

2. Once we fixed the above we still had the problem but not as severe. So we also had a tech come in to inspect the older of the two systems. He took it apart, showed me the heat exchanger and declared that it was toast. The system had to be replaced. So we took it off and installed a much more robust on demand in its place. We got 2.5 years out of the Rinnai and the tech said he had never seen a Rinnai more worn out than this one. Compared it to being in a house for 20 years.

Good luck, I understand the frustration with having your on demand go in and out on you. Makes brewing difficult.

[Moonlight]

Sometimes mine does that when it is shutting off during flow. This can happen for two reasons that I've seen. Because there is a minimum flow rate for the thing to work, if flow rate drops below that minimum, the burner shuts off. If you are right at that flow rate, it can go on and off frequently, leaving you with the temperature half of being on and half of being off. I have seen this same problem with other error codes, such as Lime condition or wind caused exhaust problems. (mine are outdoor)
My two workhorses have been running and well-used for ten years.

[The BrewShed]

I have 2 in my home. when temperature does not hit target, it usually means mineral (especially calcium) build up and needs to be cleaned. the other possibility is the screen on the inflow is clogged, slowing the flow rate and turning off the burner hope this helps
http://www.eztankless.com/support/se...d-maintenance/

[uabericm]

We had the same thing happen as jvandenbrink before the second unit controller was installed correctly. We were getting cold water mixing from the second unit.

On a side note, I have a question for those using tank-less hot water heaters. If you are using the tank-less heater for mash / sparge water, how are you adjusting the pH of the water?

[YSBrewer]

On a side note, I have a question for those using tank-less hot water heaters. If you are using the tank-less heater for mash / sparge water, how are you adjusting the pH of the water?

Ditto... I was wondering the same.

[Bierkoenig]

Ditto... I was wondering the same.

Acidulated malt.

[YSBrewer]

Interesting! Never heard of it... Till now

General brewing information

Acidulated malt was traditionally used to adjust mash pH in cities with extremely alkaline water. However, the lactic acid used also contributes its own distinctive flavor to the beer when used in significant amounts. Over about 10% of the mash, it becomes more difficult to work with.

Weyermann Malting produces an acidulated malt designed to adjust the pH level in mash or wort. Weyerman and Brewer's Supply Group recommend using the following formula to calculate the dosage of acidulated malt: use 1% of Acidulated malt to reduce the pH by 0.1. (Example: 3% Acidulated malt reduce the pH in mash by 0.3). However, this is an estimate as the exact effect depends on the special conditions in the mash or wort (buffering capacity) and on the composition of the brew water. Weyermann produces their acidulated malt by using lactic acid, which is generated by natural occurring lactic bacteria on the grain. This allows acidulated malt to be used to produce beer styles with a typical “sourish” character like “Berliner Weisse”. Brewer's Supply Group recommends that to reach the Berliner Weisse “sourish” character, 8% of Acidulated malt is a good rate. Brewer's Supply Group and Weyerman also provide a sample malt bill for "Berliner Weisse" as the following: 40% Weyermann Pilsner Malt; 45% Weyermann Wheat Malt Pale; 7 % Weyermann Carahell®; and 8 % Weyermann Acidulated Malt.

[CaptainEBC]

We run our tankless into an insulated tank, then make adjustments with lactic acid and minerals.

[barleyfreak]

Hey Chris -- can you share info on what type of insulated tank? My plans also are sans an HLT and instead I'll use two tankless water heaters. My brewhouse is teeny but I might be able to get a tank in there for water treatment, depending on size. What is the capacity and foot print?

thanks,
Dave

[CaptainEBC]

Here is a pic of our layout.

http://www.enegrenbrewing.com/3bbl-c...ewery-overview

For our 3 bbl brew system we use a 4 bbl tank and have 1 RC98hpi tankless heater that fills it at about 3.5 -4 gpm at 185F.

[Fullcourt]

jvandenbrink, how did the inside of the tankless look in regards to calcium build up? Since you were flushing with vinegar, I am wondering if there was any build up. And also if the vinegar had a hand in the failure of the heat exchanger.

[Moonlight]

As with Captain EBC, ditto on using a tank of water to adjust pH/minerals before pumping through the heaters into the mash tun. This is water collected from the heat exchanger from cooling the previous brew. My system is a 20 bbl and it does work on that scale, too.

Rinnai says not to, but I use acid cleaner instead of vinegar. The vinegar may not touch the kind of deposits you may get from certain water.

[gallon]

I have two Rinnai as well. I have very soft water and never have scale build up but I never thought to clean them. Have do you circulate the vinegar or acid through them?

Also, I usually fill the mash tun first, stir in my salts and then pour in the grain. I'm just pouring pre-milled grain through the manway. Anything wrong with treating the water in the mash tun before mashing in?

Thanks,
Tim