Recirculating Loop Problem ??

[maarass]

We have a recirculating loop in our new construction home. Gas fired HWH. All faucets and showers are on it but two faucet downstairs over the HWH. A short run so I guess not needed. This is a pump loop with the pump on the return side right before the HWH. Electrician has yet to wire up the pump, but I figured it would still work as a gravity feed system, right ?? - Wrong. This is weird, the two faucets not on get piping hot. All others just get warm. At first I figured it cause all the others are so far away. But wouldn't that it just take longer to get hot water ? I'm just guessing, but it seems that the cold water in the loop pipe is somehow flowing backwards and mixing with the Hot water to make warm water. Is this cause the pump is not hooked up yet, and if so then when ever the pump is off (on aquastat) I get this backflow ?
What's going on here ?????

[bkrahmer]

I had a similar problem with my radiant system when I first plumbed it. I had a check valve in the wrong place. You should have a check valve in place so that a demand on a unit won't cause a backflow and pull cooler water from your recirculation path.

[maarass]

Thanks for the reply. Where would the check valve be placed ? The plumbers said once the pump is hooked up it might take care of the problem. But that would just make the pump stay on all the time. I'll inquire about the check valve.

[Sparks]

Sounds like there is siphoning taking place here. When the hw is running to the upstairs it's siphoning some cold water with it, right? I really don't see how wiring the pump will remedy this. The pump will only run when the hw supply temp. falls below a pre-set temp, obviously then, it won't solve the issue when it's off. I guess I would wait and see on this one but I'll agree that a one way check valve may be needed between the hw supply and the cold loop return. HW supply > cold loop return to tank. Arrow on valve as shown. Although some pumps are designed with check valves built in, maybe yours isn't.

[maarass]

Thanks I will pass this info along. Hopefull that's all the problem is.

[rabadger]

Question ...

By any chance are the fixtures that deliver warm water shower/bath fixtures?

[maarass]

Yes, there are two showers, four sinks, and kitchen sink that are affected. The powder room and laudry room which are not on the loop are uneffected, but I don't think the anti-scald valves are the problem. In my shower I have two shower head on opposite walls. When one is on with valve turned to hot all the way, warm water comes out, BUT when I tun on the other at the same time with the valse about the middle position, the first shower head get way hotter. ????? And when I turn the second valve to cold the first one gets colder too. Both shower heads are feed separetly form a main 3/4 " feed. Loop returns to cold side of HWH like this :

LOOP--->aquastat--->pump--->T into cold--->HWH
So is this siphoning ?

[rabadger]

Is this the small Taco or Grundfoss pump that has a timer?

I agree with the others. Sounds like a ckeck valve is needed. If the pump is on a timer you will run into the problem every time you draw water during the off cycle.

[maarass]

OK new plumber came and said loops was on the wrong side ! It was exiting in the cold water inlet before the tank. He said it should be exiting in the hot side out. The pump draws the loop water and also sucks out the HWH water to keep the loops hot. How's that sound ?

[rabadger]

cut and paste for grundfos pump hot water circulation.

http://www.grundfos.com/Web/HomeUs.nsf/Webopslag/D6600B14F5C7C73386256AE9005326AE

[maarass]

Thanks for the link Richard. I checked it out and downloaded the pics. Found another site with pics. Seems ther are two way of doing this. One is like on the Grundfos site with the loop returning to the bottom faucet thing with check valve between the pump and HWH the other returning through the cold inlet with check valve as well. So plumber redid it WRONG again. He returned the loop to the HWH hot side ! So return water does NOT pass through the HWH. He said ... well.. uh... when pump is running it will draw up hot water up from the HWH. ?????? So what's the purpose of the loop if cold return water doesn't pass through the HWH ? I'll just be putting cold/warm water back into the loop. Man I'm confused . I think he did it wrong. I appriciate all your time and input. Thanks much

Here's what he did: (see attachment)

[rabadger]

That does not look right. I take it this plumber has never done it before.

[maarass]

Exactly, he said he's been doing plumbing work for 25 years. Hmm, whatever. I know squat about plumbing but still knew it was incorrect. I think he suspected it was wrong. On his way out he said if it doesn't work call and he just wanted to get me hooked up tonight. Which way is better : Returning into the cold water line at top of HWH or returning to drain valve at bottom of HWH as in this daigram:
http://www.autocirc.com/IM-16.pdf

[rabadger]

I like lang way better. That way you can still use the water heater drain cock.

[bkrahmer]

Yeah, tee into the cold before the HWH

[maarass]

Great thanks. Plumber is comming tomarrow to redo it all.