Indirect as a buffer tank

[Deleted User]

So the Voyger has a crack in the tank and it needs to be replaced. I was going to install a new munchkin and a super store tank. The problem is of course the munchkin needs a buffer tank to handle the light heating loads. I know there is someone out there who could draw a little diagram on how to plumb in the indirect tank as a buffer tank, raise the temp a little and install a mix on the DHW. I have my ideas on how this should be plumbed but I would love to hear your side of the story. Thanks , Mike

Paul Rohrs_2

Check out.....

the RPA's "Radiant Precision" by Mr.Siegenthaler. A tremendous book. Page 136, figure 5-9. Also, Siggy has written several articles in PM magazine. I have the link to his June 2002 article. Great stuff.

http://www.pmmag.com/CDA/ArticleInformation/features/BNP__Features__Item/0,2379,78589,00.html

The resistance I have been running into lately is that the manufacturers I deal with, love the concept,but have no data to back up what temp and flow rate we can sustain with the setup. I have contacted the RPA for data, hoping they have something on file.

Regards,

PR

If you love what you do....it's not work.

[Deleted User]

Thanks Paul

I have looked at the site you sent me to and and I like the drawing but I have a problem,there is a 8 gpm shower head in the house and the owner likes to use it. Not knowing the flow capacity of that design I could see where there could be a problem. I was thinking to just plumb the floor supply and return into the same pipes that would supply the DHW heat exanger from the Munchkin. I would think with the use of spring checks I could T into the boiler supply pipe to the tank exanger and return from the radiant into the boiler return.With spring check valves to cause resistance the floor water would be forced through the tank exanger and drop the temp in the tank. The tank aquastat would sence the low temp in the tank and fire the boiler.??? Am I Lost??? A mix valve would be installed to keep a constant temp of like 120 to the floor and a mix on the DHW to keep 115 going to the house.

PJO_5

How about...

an Ergomax tank? It's designed for this very purpose...although I use mine as a heat exchanger for my non-barrier tubing as well as a buffer.

The smallest one holds 23 gallons of boiler water, and if the Munchie is running at 120F or so it would be perfect...higher temps require the mixing valve to do it's job.

It takes up some space, though...maybe you can pipe it so the Munchie sits on top?

Just some thoughts. Take Care, PJO

Waylon Lowery

Hold on I missed something...

the munchkin is a modulating boiler...why do you need a buffer tank?

Paul Rohrs_2

Short Cycle

Even though it can modulate down to low fire, it can still short cycle with micro-load zones. If a Munchkin M80 low fires at 27,000 BTU's and it is trying to satisfy 1 zone at 5,000 btu's, it could still short-cycle. The buffer tank will act as a thermal shock absorber and will lenghten run times based on it's differential.

Regards,

PR

Waylon Lowery

True....

> Even though it can modulate down to low fire, it

> can still short cycle with micro-load zones. If

> a Munchkin M80 low fires at 27,000 BTU's and it

> is trying to satisfy 1 zone at 5,000 btu's, it

> could still short-cycle. The buffer tank will

> act as a thermal shock absorber and will lenghten

> run times based on it's

> differential.

>

> Regards,

>

> PR

Waylon Lowery

I understand the concept and need for

buffer tanks...but a buffer tank with any modulating boiler sounds like over-engineering and an over-expense to me.

It is more likely that more than one zone will be requiring heat at one time. Heck in Europe they rarely even use t-stats.

Robert O'Connor_3

That 8GPM shower worries me.

If you allow the micro load to cool the DHW tank down to 115, will the T50 be able to catch up if the shower comes on? With the reverse indirect like the ErgoMax, you're pulling heat out of the 20 gal of boiler water buffer, not the DHW.

[Deleted User]

Voyger replacment

I know many people have replaced the voyger with a munchkin/superstore combo but have failed to deal with the low load ( micro zone )situation. I guess I could just get a tank with 2 exangers, one for the boiler supply and one for the radiant. da