The mini-indirect

SpeyFitter

There seems to be a few mod-con boilers out there with plate or similar heat exchangers, and then there is the standard 30+ gallon indirect. I'm curious if you guys see the mini-indirect market emerging at all in the near future? I'm picturing a 5-20  gallon indirect tank with a high output coil where you have enough buffer capacity to not short cycle the boiler like a heat exchanger for small draws like a quick handwash, but the output of the coil may be enough to sustain a shower and another load - say 2-4 GPM-ish, depending on the boiler's output.  Something like this would also need to be very well insulated, which would reduce standby losses which could overtime alleviate a few short cycles from heat loss (smaller water volume = quicker/more heat loss overtime).

Jack

We have one in

the Rinnai the Q175C unit. 6.1gal indirect w/175kbtu input. 4.3gpm continuous at 70F rise. It is a great unit...if you aren't oversinig the bejeepers out of the boiler to get that dhw flow. That hot water flow is equal to an R75 tankless. Whenever I discuss this unit I always ask the dealer to compare the cost of the 175C with a perhaps, smaller, right sized heating only boiler with a separate tankless or indirect.

Greg Maxwell

MINI INDIRECT

I would prefer a heat only boiler with an indirect sized for the needs of the job. Most combi boilers have flat plates, which at best will only give you 2.5gpm, which wont cut it in most houses. If you do need a combi boiler, I prefer the Prestige Excellence, PE-110, which has its own built in tank.

Now, talking about wall hung boilers, we are starting to quote buffer tanks on any boilers with Giononi heat exchangers, to prevent short cycling. A Boiler Buddy, or a Superstor SSU20B. We prefer to have the boiler run longer, but less often, hitting the steady state, and making the homeowner happier with his fuel bills.

What is everyone else doing?

JGR

Rinnai Q175C

I would agree that the Rinnai Q175C is ideally suited to what you are looking for.  The PE110 does not have the continous output of the Q175C, nor does it have the fully modulating pump in the Q175C and it can't modulate its three way valve to handle both heating and DHW loads at the same time.  I feel the Q175C is the clear winner.  Also consider you are now hanging an additional 62 pounds of wieght on the wall.

Simply Rad

Reverse Indirect

Scott



I have used these tanks with great success> great output with little storage. You must provide enough Btus with the heat source to recover the tank and coil(DHW).  They are unique because they are opposite an traditional indirect tank.  The heating water is the tank and the DHW is a single pass coil with lots of surface area.  I have a HUGE custom home(18,000 ft/2) with 7 baths and no consideration to "low flow" fixtures.  I used the 80 gallon vessel and the owners have never run out of hot water.  I do have 2-215,000 btus boilers to provide the heat.  The other end of the spectrum... I installed the 30 gallon tank for the contractor of that huge house.  I replace his 80 gallon in-direct tank with the 30 gallon tank and they have plenty of hot water.  The tank only uses an 80,000 btu boiler.



http://www.thermo2000.com/content/en-US/s2_produits/optimizer.aspx



They work great!



Good luck Jeffrey

superdave

Baxi boilers

I am a certified Baxi installing contractor. I install both the HT380 with on-demand and HT1.33 with a 21 gal. stainless steel tank that is very well insulated. The HT380 I hang on a 2x4 wall with 3/4" plywood painted black. The HT1.33 seats on the 21 gal. Modulo tank. The one thing I have notice is that most indirect tanks are over sized to the boilers. I have done allot of service work on no heat calls and most of them are to SSU119 tied into a boiler that only has an out put of 112,000 BTU. When they are on priority DHW call they need to re-heat the tank and if the home owners are looking heat it take allot longer to reach temp.

So when sizing up the heating also look at the DHW out put that is need to help make a proper size. That is why I love the 21 gal. tank it comes up to temp very quick and also delivers 140 gal. every 30min. Also you can install re-circulation line into with no problem. The HT380 Will also give you 3.9gpm at 80 delta that will never run out.