Circulators with internal check valves

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Old 01-24-14, 07:38 AM
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Question Circulators with internal check valves

When using circulator pumps with internal check valves (ala Grunfos 15-58FC) do the pros here still use a seperate check valve someplce in the loop? If so, what kind? Swing gate, spring type?

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Old 01-24-14, 08:22 AM
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You don't need redundant check valves... the one in the pump is sufficient... unless there's some other reason that you need another for something or other.
 
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Old 01-24-14, 08:36 AM
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Thats what I figured, thanks for the quick answer!
 
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Old 01-24-14, 04:15 PM
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An integral flow check valve inside a pump will prevent reverse flow through the pump - which might occur in multi-zone systems, with each zone served by its own individual pump. No need for a redundant check valve for that issue.

Another issue is gravity flow, where water circulates by gravity when there is no call for heat and no pump running - room temps can then become too hot, particularly with warm-start boilers. A check valve in the pump won't prevent that. For that, a flo-control valve (a.k.a. lift-check valve) may be needed. It prevents both gravity flow and reverse flow.

A flo-control valve or redundant check valve can be helpful when preforming certain system maintenance without draining the entire system. I have shut-off valves on the boiler return and flo-control valves on the system supply - which allows the pump to be pulled without draining the system.
 
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Old 01-24-14, 04:39 PM
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Another issue is gravity flow ... A check valve in the pump won't prevent that.
Why would it not Gil? Curious to hear your logic.

In some rare cases it IS possible that gravity flow could still exist with a check valve on one end of the circuit only... because large enough pipes can support gravity (thermosiphon) flow in BOTH directions, but in general with the smaller piping used these days not so much possible... at least not with enough volume to be a problem.
 
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Old 01-24-14, 05:13 PM
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I'm thinking about it.............................................

OK, I'm back. A pump's IFC will block reverse flow, but not forward flow, right?. Gravity flow, when it occurs, is typically in the forward direction - the hot leg rises and the cooler return leg descends.
 
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Old 01-25-14, 06:38 AM
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But if there is only one zone running, wont the pressure from the single zone push back against the check and keep it closed against the minimal pressure of the gravity rise? I understand when all pumps are off, but the heat left in the boiler will be minimal and dissapate within a short time, long before enough water gravity flows to heat another zone??
 
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Old 01-25-14, 07:43 AM
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I think you are correct - if one or more zone pumps are running, that would prevent gravity flow in the idle zones, if there is an IFC in each of the pumps.

The amount of heat bottled up in the boiler when there are no calls for heat, depends upon several factors. First, if you have an older, warm-start boiler, like I do, the boiler never cools off during heat calls. And, it also depends upon the water volume of the boiler. Under some circumstances, gravity flow can be a major headache. I have flo-control valves in each of my major loops - when one of them started leaking past the seat, some rooms became intolerably hot until I replaced the flo-control valves.

But, if you haven't had problems with gravity flow, then you can forget about it.
 
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Old 01-25-14, 07:52 AM
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A pump's IFC will block reverse flow, but not forward flow, right?. Gravity flow, when it occurs, is typically in the forward direction - the hot leg rises and the cooler return leg descends.
Right. But being a spring loaded check valve, gravity flow won't make enough pressure to open the valve and allow gravity flow.
 
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Old 01-25-14, 09:51 AM
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My original pump was a B&G 3-piece - no IFC, of course, so flo-control valves were originally installed. If I had known about the spring-loaded checks, I could have installed a 007-IFC, and just replaced my old flo-control valves with straight nipples.

The flo-control valves can be manually jacked open in the event of a power failure - but I'd still need to rig up my electric backup to get the gas valve open - so, then I could then run the pump from the emergency source as well. The flo-control valves are handy during boiler maintenance to avoid draining the whole system. I have ball valves on either side of the pump, but they don't help if I'm working on the boiler itself.
 
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Old 03-29-14, 07:02 PM
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Has it been decided that an inline check valve (like the Taco Flochek) is not need if the circulator has one?

I'm replacing an old circ. with one with an IFC and also bumping the piping to 1". I'd like to not spend the $50 on the 1" Flochek if I don't have to.
 
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Old 03-29-14, 07:42 PM
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You don't need two flow checks...
 
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Old 03-29-14, 08:08 PM
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Forgot to mention this boiler has a tankless coil and is always warm. Not sure if this matters.
 
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Old 03-29-14, 08:12 PM
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I repiped a friends boiler after a freeze/break issue a couple months ago. I followed Troopers advice and just relied on the single IFC. Using grundfos pumps with internal FC's I had no issues with gravity feed. System has a warm start boiler that maintains a minimum temp of 140* and has 3 zones (basement, first and second floors). With all zones off and a hot boiler, two feet above the pumps the pipes stay cool unless the zone calls for heat.
 
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