Loops???

Dave_13

Most radiant systems I see look like the one attached. A supply and return manifold. Is there still a Primary Pump in a system like this. If there is not, wouldn't the boiler short cycle because of the low flows running in the zones(And then through the boiler)? I must be missing something.... Thanks.

Mark Hunt

As the contractor


that installed that job, thanks for visiting our web site, what you do not show in that picture is the Munchkin modulating boiler that is driving that system.

If this had been a fixed firing rate boiler we would have incorporated P/S piping for the very reasons you mention.

We do not normally use TMV's, but in this instance the customer could not swing the added cost of variable speed injection.

Mark H



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Dave_13

So, I'm guessing the Munchkin modulates it's firing rate for the low Delta T Temp. difference across it's supply and return? If the zone is radiant floor with an extremely slow flow rate, is the munchkin able to handle it without short cycling? Thanks.

Mark Hunt

It depends

on the Munchkin size.

Most often we use a buffer tank.

The new 925 board step modulates starting in low fire so short cycling will not be as big an issue. That is not to say that it completely removes short cycling from EVERY application.

With VS injection, a buffer tank or P/S piping will be needed.

Hope that helped!

Mark H

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Dave_13

Thanks Mark. I am planning on a six zone system - all radiant,1 HWBB and 1 IHWH. I am looking heavily into using the munchkin. Staple up, carpeted in spots. Still debating on Prim/Sec or not. Would like to use outdoor reset also. Any suggestions would be apprec.- thanks again and nice looking work you've done.