Circulator Layout

[kurt]

This is a sort of strange arrangement for the radiant system. It's not a primary-secondary loop system; it's got the return and supply both on the same loop....sort of.

Is this right?

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[Jim Katen]

Is this fed by an on-demand water heater?

What's to stop a short circuit between the supply and the return?

[kurt]

Yes, and exactly. I don't understand what prevents a short circuit.

The floor warmed up just fine, came to temp, nothing seemed strange, but I'm still confused how it's working.

[Jim Katen]

As far as I can see, there's only two ways that it can work. Some of the freshly heated water goes right back into the water heater or some of the cool return water goes right back under the floors.

My bet is that installing one more valve would correct the issue and boost the efficiency and the effectiveness of the system. Of course, you'd probably have to rebalance the whole thing afterward.

[Jim Katen]

Maybe you should post it over on The Wall to see if there's some magic method at work here.

[kurt]

Good idea....

http://forum.heatinghelp.com/discussion ... k/p1?new=1

[mjr6550]

I think it works because the pumps push the water in the right direction so it does not have a reason to short circuit. Does this explanation make any sense?

[Bill Kibbel]

I think it works because the pumps push the water in the right direction so it does not have a reason to short circuit. Does this explanation make any sense?

Kinda. It only works when there are two closely spaced tees, no more than 4 pipe diameters apart.

[kurt]

What Kibbel said. It's about the closely spaced tees. The term we need to learn is "hydraulic separation". Google it, it explains everything.

I'd not heard of this before. Hydraulic separation is the new terminology and standard of care for these systems.

http://www.caleffi.com/sites/default/fi ... n-tr07.pdf

My (minimal) understanding at this time sez the tees should have been much more closely spaced, and there should have been at least 12" of pipe before connecting to the system loop.....or something like that. But, overall, not wrong.

[kurt]

Go to youtube and check out the caleffi stuff.

[Bill Kibbel]

This explanation is more on my level of comprehension:

http://www.radiantcompany.com/heatsourc ... -plumbing/

[kurt]

Yes, not bad. The whole primary secondary looping methods were problematic, I know that, not the least of which was the expense. The hydraulic separation method makes for a simpler less expensive installation.

[Marc]

I get the concept of accomodating supply and distribution loops where the sum of distribution GPMs doesn't always match the supply GPMs but I'd like to hear some theory about why the two tee's have to oriented in such way and no more than 4Ds apart.

Marc

[kurt]

There's some things humans are not meant to know, Marc.

[SNations]

I get the concept of accomodating supply and distribution loops where the sum of distribution GPMs doesn't always match the supply GPMs but I'd like to hear some theory about why the two tee's have to oriented in such way and no more than 4Ds apart.

Marc

My bible for this stuff is "Modern Hydronic Heating" by Siegenthaler.

When you have two closely spaced tees on the primary loop there is very little pressure difference between them. And that's what you want. If the tees are far apart then there's a pressure difference, and that pressure difference will induce flow between the points through the secondary loop.

To minimize turbulence in the flow you want at least 8 pipe diameters of straight pipe in the primary loop before the first tee, and at least 4 pipe diameters of straight pipe after the second tee.

In Kurt's picture it looks like the primary circulator is bigger than the secondary, so you won't get the short circuiting. But Siegenthaler says that if the closely spaced tees principle is done right the primary circulator doesn't need to be any bigger than the others -- just sized right.

[Marc]

I get the concept of accomodating supply and distribution loops where the sum of distribution GPMs doesn't always match the supply GPMs but I'd like to hear some theory about why the two tee's have to oriented in such way and no more than 4Ds apart.

Marc

My bible for this stuff is "Modern Hydronic Heating" by Siegenthaler.

When you have two closely spaced tees on the primary loop there is very little pressure difference between them. And that's what you want. If the tees are far apart then there's a pressure difference, and that pressure difference will induce flow between the points through the secondary loop.

To minimize turbulence in the flow you want at least 8 pipe diameters of straight pipe in the primary loop before the first tee, and at least 4 pipe diameters of straight pipe after the second tee.

In Kurt's picture it looks like the primary circulator is bigger than the secondary, so you won't get the short circuiting. But Siegenthaler says that if the closely spaced tees principle is done right the primary circulator doesn't need to be any bigger than the others -- just sized right.

Ahhh. The intention seems to be minimizing the influence of primary pump force on the secondry loops so that secondary flow rate follows as much as possible only the secondary pump force. These are obviously very low pressure loops.

Thanks.

Marc

[SNations]

Ahhh. The intention seems to be minimizing the influence of primary pump force on the secondary loops so that secondary flow rate follows as much as possible only the secondary pump force.

That's one way to put it, I suppose. But the intention is to not have any induced flow in the secondary loop when that loop is supposed to be off. The intention isn't to not mess up the flow rate when that loop is active.

These are obviously very low pressure loops.

No, I don't think that's right. The secondary loop might be quite large and need a big circulator. You'd simply size the secondary loop circulator for whatever flow and head loss requirement you have -- big or small.

[mlparham]

I get the concept of accomodating supply and distribution loops where the sum of distribution GPMs doesn't always match the supply GPMs but I'd like to hear some theory about why the two tee's have to oriented in such way and no more than 4Ds apart.

Marc

My bible for this stuff is "Modern Hydronic Heating" by Siegenthaler.

When you have two closely spaced tees on the primary loop there is very little pressure difference between them. And that's what you want. If the tees are far apart then there's a pressure difference, and that pressure difference will induce flow between the points through the secondary loop.

To minimize turbulence in the flow you want at least 8 pipe diameters of straight pipe in the primary loop before the first tee, and at least 4 pipe diameters of straight pipe after the second tee.

In Kurt's picture it looks like the primary circulator is bigger than the secondary, so you won't get the short circuiting. But Siegenthaler says that if the closely spaced tees principle is done right the primary circulator doesn't need to be any bigger than the others -- just sized right.

Ahhh. The intention seems to be minimizing the influence of primary pump force on the secondry loops so that secondary flow rate follows as much as possible only the secondary pump force. These are obviously very low pressure loops.

Thanks.

Marc

I expect this post to be deleted but what is the the difference between primary and secondary thrust modes? Maybe a nap?

[kurt]

I expect this post to be deleted but what is the the difference between primary and secondary thrust modes? Maybe a nap?

Of course a nap...after a cigarette.....

[hausdok]

Bleaaahhh,

Never understood that cigarette thing. When I see it happen in a movie it grosses me out.

There aren't many things less attractive than a woman with a cigarette between her lips.

[kurt]

Calm down.....it's called a joke.