PUMPING AWAY from a Munchkin?

Nick_11

of the Munchkin systems in their install manual, show the primary pump on the return side. Pumping Away theory says its better to have pump on the supply side.

Is there some reason that Munchkin has to have it on the supply side? - Doesn't it matter, or just old habits?

Thanks

Nick

Nick_11

Correction...

I meant to ask, "Is there any reason Munchkin has to show their primary pump on the RETURN side of the boiler?"

Mark J Strawcutter

primary vs secondary

Think of the primary loop as the one with the expansion tank. The boiler loop becomes a secondary with the common piping between the loops as the PoNPC. At least on the diagrams on the HTP web site, they show the boiler loop pumping away from the common piping (PoNPC).

If the system fill pressure is really high you could have trouble poping the boiler's relief once the circ's differential was added to it.

Mark

Uni R

Yes...

They want to keep water pumped into that heat exchanger.

Mark Eatherton1

It's intentional...

and critical. Theres a pressure switch on the Munchie that needs to see positive pressure. If you pump away from it, and your expansion tank is on the return, there will be JUST enough of a pressure drop to cause nuisance drop outs.

There is technically nothing wrong with pumping into a boiler, so long as you pump AWAY from the expansion tank.

Dans reason for saying to pump away from the boiler and the expansion tank is because most older cast iron boiler had the system expansion tank connected to the boiler, hence it was proper to pump away from the boiler. The key is to pump away from the EXPANSION tank.

Follow the HTP diagram and you will not go wrong. Yes, it is different, but so is the appliance...

ME

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harvey

pumping away

pumping away means away from the expansion tank and towards the area of most head loss, in this case the munchie

GEO_3

early munkins

The early munchkin diagrams showed pumping away. My thought was with a low mass boiler it's best to pump into the boiler. Aparently HTP thinks so too. But they will tell you it works both ways. If your knocking the boiler presure switch off you've got other problems.

Mark Eatherton1

The droop...

I posted a picture once that I dug up from an early B&G drawing. It showed that the more pressure drop you had between the exp tank and the pump, i,e, the pressure drop of a Mucnhkin or other high pressure drop boiler, the residual pressure actually dipped down below the static fill pressure of the system. This consequential "droop" in pressure occuring within the heat source could very well cause a flashing to steam. Hence, the need to expose the heat source to positive pressure, where the boiling point is RAISED, not lowered.

This pretty much applies to any high PD appliance.

ME

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munchkin-man

Mark is correct pump away from the expansion tank

I was trying to see this pressure drop on systems so I could fully undertsand it and could never see it happen. I was at wet head 5 and saw a set up that let one do it both ways and when pumping in to the expansion tank the pressure droped. See the wet head pix of the B&G pump and expansion tanks. I liked it so much I am gong to build one for training.

We are pumping away from the Munchkin out the supply. The return is the nipple closest to the rear of the unit. Look at the drawings again