Munchkin Plumbing

munchkin-man

80M = 8gpm minimum, 140M = 14gph minimum, 199M = 19 gph minimum. If you can achive the minimum required flo through the boiler then you will may not need p/s piping. The issue is to avoid flashing. This is the worse case sinario. If you do not have sufficiant flo the boiler will flash to steam before the ECO / high limit knows you have exceeded that limit of 225*(remember you are under pressure) it will bang/pop and then eventually the ECO or supply thermister will sence this high temp, and shut the burner down. It will fall to the set differential and start all over. We have seen this in applications with several zones no p/s when the circ with the most friction loss comes on with no other zones calling the flashing starts and when a few of the other zones come in it stops. We have several Munchkins out there with no p/s but consideration was taken before the circs were sized.

The other problem is when you do not provide quite enough flow the Munchkin it can short cycle. Hits limit falls to set diff. and comes on again and repeats this over and over.

One could install a pressure by pass valve or simply install a ball valve between the end of the supply and return. Run the zone with the most friction and addjust the by pass to that zone. Many times one has just put the bypass into full open position. This in most cases prevents the boiler from flashing and or short cycling. This of course will depend on the boiler model and pump size.

The by pass can be one diameter size smaller than the manafold and will be more than sufficiant. When at all possible the primary secndary method is the best way to go.

See www.htproducts.com click on the 3d Munchkin and bring up the Manual it has some suggested piping drawings. Buta bing buta bang.

[Deleted User]

Munchkin Plumbing

I have this job coming up and i am having a hard time understanding why I have to do P/S loops when it is a radiant heat only job with 4 manifolds and each manifold will have a zone pump. When any one of the manifold pumps turn on it is plenty of flow for the munchkin to perform properly. So why the dedicated Primary loop in this situation? I look forward to getting your responces, thanks.

Wayco Wayne

It all depends

What size Minchkin to begin with. They want to insure that there is enough flow through the heat exchanger. I did several 140 size munchkins and needed a fairly large circulator. (Grundfos 26-64, or Taco 0010 or equiv. look on page 18 of installation instructions) If you can assure yourself that there isn't enough friction through the radiant floor loops to slow down the flow I suppose go ahead. I personally would rather go P/S and take be able to be certain I have adequate flow. WW

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Wayco Wayne

It all depends

What size Minchkin to begin with. They want to insure that there is enough flow through the heat exchanger. I did several 140 size munchkins and needed a fairly large circulator. (Grundfos 26-64, or Taco 0010 or equiv. look on page 18 of installation instructions) If you can assure yourself that there isn't enough friction through the radiant floor loops to slow down the flow I suppose go ahead. I personally would rather go P/S and take be able to be certain I have adequate flow. WW

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[Deleted User]

Thanks Wayne for a responce so fast. I have read someplace the min. flow for a munchkin is one gal per min. I have also seen this boiler installed as if it were a cast iron boiler with no primary loop and there has been no problems.

Mark Hunt

If


you are using the new 925 control, you will probably not have to worry about flow.

If flow is an issue, I would install a buffer tank.

Mark H

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Cliff Brady

One gallon per minute per 10,000 btus per hour

as I read it in the manual. That would be 14 gallons per minute for a 140 from a Taco 11.

Pete Dwyer

my $0.02

Where this boiler has a modulating temperature control, you are better off with more flow to give a true representative sample of system temp.

-Pete

ken_6

925

mark specificly why do feel flow is less critical with the 925?


thanks

ken

Mark Hunt

The 925


will start the burner in low fire and ramp up as needed. This does not happen with the current board.

You may still need a buffer tank if you have many "micro" zones that do not require the minimum firing rate of the particular Munchkin.

Mark H

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Cliff Brady

Thread from the grave but here is new info

I looked at the Peerless web site today and see the have a new "Piping Supplement" pdf. It has more reasonable numbers for pressure drop and GPM recommendations but no particular circulator recommendations. It appears that some Munchkin employee originally based and documented the GPM recomendations on the Boiler Input BTUs rather than the Net I-B-R as is explained in the piping supplement.

It also has some pretty low minimum flow recommendations as well. You can't push 14 GPM at 11 feet of head with a 0010 as they said in the old manual. But you can do 11.2 GPM at 8 feet of head as you now say is recommended for the 140M.

http://www.peerlessboilers.com/home/_images/user/products/IOM_pinnacle_piping_suppl.pdf

Darin Cook_2

Just obey the factory recommended piping configurations and pump specifications and you will not have a problem. If you go with a P/S set-up having the new 925 board you will not have to use a buffer tank.

Cliff Brady

My point is that the Munchkin/Peerless documentation has been

erroneous until very recently. It has been questioned here by numerous posters and with no acknowledgement from HTP. Every time this has been pointed out it, it is either ignored or followed up with an unnecessary lecture on circulator sizing. HTP has been publishing inflated recommended flow rates based on one GPM per 10,000 btu input not one GPM per 10,000 I-B-R btu output. The new manuals correct this by using the one GPM per 10,000 I-B-R btu output at 20 degree delta-T rule.

The new manuals no longer recommend specific circulators but
the new recommend flow rates and corresponding head losses call into question the formerly recommended Taco circulators for the 80M and the 140M. The 0010 as formerly recommend for the 140M now makes a good fit though.

For the new flow recomendations for the 80M, 6.4 GPM with 5 feet of drop makes the 007 as formerly recommend quite oversized when even a 005 is still quite oversized and a 006 just undersized.

For the new flow recomendations for the 199M, 15.9 GPM with 13.2 feet of drop makes the 0011 as formerly recommend a bit oversized although a 0014 looks just right.

I am not trying to bash HTP, they have great products and support, but I wanted to set the record straight on their documentation error and recent corrections/revisions since it has been difficult getting straight answers on this for myself and others in the past.

In the interest of being helpful to HTP, I would like to point out that Table 3.3 on page 5 of the Peerless Pinnacle I&M manual dated 10/2003 has wrong values filled in. The Flow Rate column is filled in with BTU input values and the pressure drop column is filled in with I-B-R output values.

Mark Eatherton1

Wow...

You've been reading WAY too many manuals lately...:-)

Thank you for bringing that to our attention. I knew there was some cornfusion there,somewhere, and you've hit the nail on the head.

Leave it to the manufacturer to over size things. They do it because they know that no one in the field is reaming their pipes, consequently there is more resisitance than WE anticipate. Now I know that most everyone who frequents the wall reams their pipes, because it's the code, and if you don't and you work for me, you won't be working for me long (MANDATORY) because it's the right thing to do. And as we all know, there is no right way to do things wrong!

Thank you for pointing out those discrepencies. Duly noted.

ME