Munchkin P/S piping

T.J.

Having a new Munchkin (80M) boiler installed in my house this week and I see something that does'nt seem right, I hope some experts here can help.

The boiler is piped as a primary/secondary with 2 closely spaced tee's into the secondary header.The primary boiler circulator (Taco 007) is correctly pumping into the boiler however, the hot water supply out from the boiler is connected to the secondary header upstream of the return water tee connection. To me this does'nt seem correct.

In my mind i see the hot boiler water mixing with the return water and giving the boiler a false return water temperature.

Every piping schematic I've seen from Munchkin or even Dan's book always shows the supply water from the boiler downstream of the return water connection. I hope I've explained myself clearly.

Wayco Wayne

If I understand you correctly

the water coming back to the primary loop is mixed temp water instead of straight return water. It's not a large difference, maybe 10 degrees. This is sometimes done with cast iron boilers to bring back warmer water to the boiler so you won't condense. With a Munchkin you want it to condense so it should be piped to bring back return water as cool as possible.

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T.J.

Wayne,

Said another way: The return water from the zones enters the header. Next: The first of the closely spaced tees is the hot water leaving the bolier. Mixing takes place in the short distance before the next closely spaced tee which is the boiler return water.

As you mentioned the return water back to the boiler will be slightly warmer than the true system return temps. Since this is a condensing boiler I want cold return temps, not what I see piped now.

Do you think I'm out of line asking for the proper piping arrangement?

Thanks for your input.

Floyd_5

No... your the one....

who gots ta live with that sucker after the knucklehead that installed it grabs his money and runs.

Make him install it right, you'll never regret it.

Check this out .... pages 28-33

Do it once, pipe it right....the frist time

http://www.htproducts.com/literature/lp-61.pdf

Steve Eayrs

Its called reverse return piping and I agree its not for the Munchkin type boiler. You also menioned you have a 007 for the primary loop. I believe that could be too small for a Munchkin primary, but some of the Munchkin-ites on this site may know better.

If teh pump is smaller than the specs call for I would ask for it to be changed too.

Its always good to see informed, educated HO's. You seem to understand the system better than most owners, (and sadly some installers). Congradulations....its really only consumers like you that will be able to hold a high standard in this trade.

Of course this could just be an honest oversight from an overworked, tired, underpaid tech. Was he the cheapest bid?

Steve

Mark Wolff

Primary/Secondary Piping

You are correct that it is piped wrong. Secondary manifolds need the two tee's as close together not only on the secondary side, but ALSO on the primary side. It cannot be run as a typical supply on supply side, return on return side. The primary manifold requires the secondary supply branch off tee to be the first tee on the supply pipe, then as close as possible (within 4" center to center) the return from the secondary manifold is installed. Then leave room after that tee-typically 16"-24" is practical. All other standard primary manifold zones can be put in, supply to supply, return to return side. The supply and return manifold on the primary piping must be connected by a crossover at the top, don't run it full manifold size, choke it down to 3/4" and depending on the number of zones, you might need to put in a balancing valve on it, to allow for flow through any of the primary loop zones. The 007 should be plenty big for most residential systems unless you have a very large house (4000 plus sq ft AND a lot of zones on the primary manifold.

The secondary manifold also needs straight pipe on both sides of the supply/relief (ITS NOT RETURN) tees. You will need a variable speed injection pump installed on the relief pipe, and the secondary manifold system circ pump. The variable speed inj. pump runs off temp about 6"-12" past the secondary supply tee. The secondary circ pump runs off a call for heat from zones in the secondary system.

Hope this helps, email me if you or your installer have questions.

Wayco Wayne

The Taco007

is the right circ for the 80,000 boiler. I would ask for the contractor to set it straight. He might even appreciate the lesson found in the repair (if he has a good additude) WW

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Cliff Brady

The new Munchkin/Pinnacle piping docs

specify minimum flow rates (4 GPM for the 80) but give an example based on 20 degrees delta-t. The example given for the 80 uses net output at 80% as

GPM=(80 * .80)/(20 * 500)= 6.4 GPM

Using the 007 flow curve, I would esitmate you would get 8.5 GPM for a 15.5 degree delta-t. You could go for a smaller pump for a larger deltat-t if that is what the design calls for. A 007 with integral flow check might give slightly lower GPM.



Standard HO disclaimer applies.

T.J.

Thanks

Thanks for your reply. I think my project is only their second Munchkin installation so I have to believe that they may not be totally up to speed on this product. Thats what makes this site GREAT. Knowing I can bounce a question off hundreds of experts and get responces within hours and sometimes minutes...makes me think about quiting my job and becoming a wetheat like the rest of you.

Sincere thanks to everyone.

T.J.

Primary to me is the piping in/out of the boiler. Secondary is the header piping out to the zones. I think your description of these two terms is the opposite of mine. Am I correct in this assumption?

Mark Hunt

Piping

The Munchkin 80m is not required to be piped primary/secondary. A taco 007 or grundfos 15-42 is the factory recommended pump for the system. These pumps can supply the necessary flow through the boiler. The 925 control board with the step modulation also reduces the instances requiring a buffer tank for a low flow zone. Hope this helps.

Dave_13

Maybe.....

Maybe it's not required, but you better make sure you use some method to maintain minimum flow through the boiler. I just saw a 007 with zone valves- with 1 or 2 zones calling, that Munchkin was short cycling like crazy!!!!!!

Mark Wolff

Primary/Secondary

No, you are right. Primary piping is the supply coming out of the boiler and the return going into the boiler; secondary piping is a seperate flow, manifold piping system that derives its heat from a supply/relief piping arrangement and is most often used for lower temp needs such as staple up infloor, slab infloor, snow melt, etc.

Mark Wolff

Delta T

Depending upon load demand, the primary loop may only lose 5 degrees temp when circulating, especially if there 20' or less of tubing it is running through. The delta t will increase only if there are additional demands made upon the primary loop, ie. baseboard zones, indirect water heater zone, variable speed injection pump for secondary loop kicks on, etc. At times the 007 may be more than the MINIMUM required, but it is not oversized by any means.

Jim Eastman

Check to make sure that the supply piping (the hottest water) is coming out of the front tapping on the boiler. I received a Munchkin from the factory with the lables for "boiler input" and "boiler output" reversed. I wasn't paying attention and piped the closely spaced primary tees in the mannor you have described. We had all sorts of problems with the circuit board being confused about the temperatures that the themistors were reading! Once we corrected the primary connections to the secondary loop, all of our lock out problems ceased!!! Boy, did I feel silly!

In other words, IT DOES MAKE A DIFFERENCE and please have your contractor correct the connections. If he has adequate isolation valves in the system, it shouldn't be a big deal to change the piping.

Jim Eastman
Precision Plumbing
Boulder, CO

Unknown

TJ, no

The primary loop is the one that carries all of the heated water in a circle.

Secondary loops are the boiler loop, a baseboard zone, an injection zone, a mixing valve zone, an indirect water heater zone, etc.

The boiler is a secondary loop, and it is because not all systems have only one boiler.

You could have a 1,200,000 BTU primary loop with four 300,000 boilers feeding it, as secondary loops. Primary loop is always running with a demand, secondary loops aren't always running.

Noel

Mark J Strawcutter

how many circulators?

How many circulators do you have (including any that may be internal to the boiler - but I don't think the Munchkin does)? If only one, then you aren't piped primary/secondary. Each loop in P/S will have it's own circ.

Mark

PS - how about a drawing?

T.J.

Changed the piping this A.M.

Your situation is exactly what I was concerned with,false return water readings. Glad to hear you were able to figure out the mislabeling by the factory.

My good news: Contractor changed the piping first thing this morning after I spoke with him! No problem. I'm not sure I would have had the confidence in myself without everyones help here. Thanks everyone!!

Mark Wolff

Disagree

I disagree with you completely. In my experience dealing with contractors, suppliers and manufacturers, all drawings, specs and accepted practices refer to the primary piping as that related to high temp supply and return. That includes the boiler or boilers, the high temp manifolds and any zones tied into the high temp manifold, and any other heat load tied into the high temperature side of things.

Secondary piping in a hydronic system always refers to a low temp system drawing heat from the high temp system by injection. It would be used in applications ranging from radiant heat to snow melting.

Mark J Strawcutter

two loops

If you have two loops (circ on each one), one with the boiler and one with the radiators, which would you call primary and which secondary?

Mark

T.J.

I have two pumps

One pump(taco 007) for the primary boiler loop pumping into the boiler( water in and out of the boiler) and a second pump pumping away from the expansion tank feeding the zones (using 5 zone valves). This is one of a few piping schematics that HTP recommends for their Munchkin.

Mark Wolff

2 Loops

If I have 2 loops w/seperate circ, the one connected to the boiler is primary. I don't see a need for a 2nd loop until you have a lower temperature requirement. Your radiators should be running at your boiler temp. (either full 180* or lower by outdoor reset) and don't need to be on a 2nd circulation loop, the zones feeding your radiators or baseboard can be run right off the boiler pump (upsize if needed)when they are tied into the boiler supply and return manifold, and would be considered a part of the primary system.

hr

True enough, Noel

here is a demo of a primary loop, in a circle configuration even! Think of the primary loop as a "transmission". In this case it recieves input from a wood fired boiler and storage via a VS pump.

I try to run the wood boiler (secondary) at 180 for most efficient use of the fuel.

Other branches are takeoff points for the radiant floor. The "circle primary loop" temperature varies with the reset info running the VS pump injecting into it. In this case 130 is maximum that this loop can recieve based on the info programed into the tekmar control injecting into it.

If I had high temperature emitters to connect to that loop I would run, possibly 180- 190 f temperatures.

When I connect my MZ into the loop I may run 100- 120 degrees, as that is the max I require for the current load.

Of course a boiler could be piped into that circle in series. Then it could be said the boiler is the primary loop.

This loop was shown in Siggy's November PM column, also.

hot rod

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Mark J Strawcutter

exactly

With only one circ and rads running off "boiler loop" then you don't have primary/secondary and calling anything primary doesn't make sense.

Likewise, you can have two circ loops - one with the boiler and one with the rads. Either one could be considered primary. I tend to think of the primary loop as the one with the expansion tank.

You don't have to have injection pumping to have P/S

Mark

Mark J Strawcutter

OK

That wasn't real clear (at least to me :-) from your post. Glad to see your installer corrected things.

Mark

tim smith_2

what they are called

The mechanical engineers I deal with always call the boiler loop the primary and the system loop secondary.

T.J.

picture before & after

Thanks again to everyone for all your input and help.