Head + Head = ?

Terry Larsell

I used HDS program to come up with 10 gpm and 8'head for downstairs and 3.24 gpm and 10'head for upstairs. If I put them together for one circ I know the gpm adds together but what about the head? I'm thinking it would remain the higher of the two but I'm not so sure.

Terry

Weezbo

Head +head= EARTH MUFFINS.

Terry Larsell

Thanks Weezbo now I get it... Hey I thought there was no such thing as a stupid question.

It just started dumping snow here in the Columbia River Gorge. It's been dry and cold so far this year, California's been getting all our precip

Terry

jackchips_2

Come on Weez

everyone knows Head + Head = 2 Head. :-)

By the way, what the heck are earth muffins?

Ron Schroeder_3

Hi Terry,

It depends on the pump that you use. Since the heads don't match, the ratio of flows will change a little. The loop with the higher head will flow proportionatly a little less than the one with the lower head. Fortunatly the head of the two loops is close. If your pump flows both loops at an 8' head, the flow in the upstairs loop will be about 2.9 gpm. If your pump flows both loops at a 10' head, the flow in the downstairs loop will be about 11.2 gpm.

Ron

Weezbo

Earth muffins?

the daughters of two heads. Every body know That! VWsubX-2 E 1+1n = nations.

Mark Eatherton1

Head and Meadow Muffins...

An elk and a moose walks into a bar in Alasaka... Never mind..

Head is not additive unles the circuits are in series with each other, in which case you MUST add the head.

GPM is cumulative.

If using a single pump, the head would be the worse case scenario (series or parallel circuits) and the TOTAL GPM required by the system.

In your case, you'd need 13.24 GPM @10 feet of head, using a single pump. Or as Ron said, you could go primary/secondary and size each pump to its' own load. Your assumption would be correct.

If using a single pump, in this case it would be wise to incorporate a pressure activated bypasss so the pump doesn't over flow the small circuit when its calling. You'd be able to hear the water moving through the pipes at a higher velocity than it was designed for. Hydronics is SUPPOSED to be virtually silent.

Using Siggys HDS, you can plug and play a PAB into the scenario and see what happens. I LOVE that software. It takes the guess work out of contracting.

Worth every penny.

ME

Terry Larsell

Thanks, that makes sense, kind of like dumping two liter bottles out at the same time. Twice as much liquid but the same time to get out.

My last job I put a PAB in and it works well but it does make noise when it is working. At first I thought it was pump noise but it was coming from the valve. I dumped the bypass to the return and one thing I noticed was how it raised the temp and shut the burner down quicker. Next time I might try dumping the bypass back to the inlet of the pump for a little minny loop, seems like this will keep the return temp lower for longer. I have seen this minny loop detail on some of siggys more recent pipe diagrams.

Terry

Weezbo

as long as we are planning on series pumping....

in this post Firedragon ,is a fairly clear idea or two on series pumping ,pump curve,some associated problems,by passes,and some of the advantages and limitations...one thing that i didnt recall saying though was the thing about cavitation is relatively severe,. pumping away is definitely a good stradgey.

Andrew Hagen (ALH)

Pipe Networks

With parallel pipes the head loss is equal in each, and the flow is additive.

With series pipes the flow is equal in each, and the head loss is additive.

You're just above the 15-58 curve, but well within the 26-64 curve. Flow rates are heavily dependent on delta-t. With the 15-58 you have approx 26.5 delta-t at 10gpm(approx 10' head with 15-58) This assumes you were using 20 deg delta-t originally.

The 15-58 is definitely not as noisy as the 26-64. If you're ok with a slightly wider delta-t I'd use the 15-58.

The piping of the differential pressure regulator could vary as to what's ideal depending on what boiler and piping arrangement you have. Be aware of the flow ranges acceptable for each DPR as specified by the manufacturer.

-Andrew