# Advice for filling radiant floor



## Greenfield Dave (Nov 15, 2009)

HELP!  I finally got my plumbing all done on my garage floor heat.  I have a 40 gallon electric water heater for backup and storage, but the primary heat source will be my OWB.  So, I am using a sidearm exchanger, going to 5-300' loops of 1/2 pex.  I have the taco 3 speed pump and mixing valve.  I put the water in at the top, using my fill valve on the supply side, and the vent on the return side.  I have most of the water out, I think... I can't get the flow meters to show any flow on 3 of the loops!  I know there's some flow, the PEX is warm.  What the heck??  2 of them show flow, so what, do I have air trapped in the other loops??  Do I have to do anything to the manifold to get them to work?  I don't think it's a quantity of flow thing, because I can shut off the working 2, and the others do nothing..

Of course the manifold came with no instructions....thanks EBAY...ya get what ya pay for, I guess....

Thanks!
Dave


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## trumpeterb (Nov 16, 2009)

Dave,
I just installed radiant loops in my house as well.  The first time I filled the system, I had no flow to my loops either...and I had a secodary pump to help out.  My pex was air locked.  To fix the problem, I first shut off all ball valves leading to the pex, and filled the main loop which runs from the boiler to the hot water tank side arm and back to the boiler.  Once this was filled and free of most air, I opened the ball valves to the loops one at a time, starting with the one closest to the boiler (although I am not sure that it really makes a difference which one you open first).  While that loop was filling, I opened the valve on the return manifold for that loop, and allowed all of the air in the line to purge as the line filled with water.  Make sure if you do this that you have a large bucket handy, or you may get an unwanted shower.  I repeated this process for every loop.  I also had several loops that were not tied into manifolds, but rather just came right off of the secondary heating line.  For these, I took the "screw" out of the bottom of each zone valve on the return line and allowed the air to purge there.  This seemed to work just as well.  Once I purged all of the air from the lines, the system worked great....keeps the house nice and warm all of the time and heats the domestic water.  I am no expert for sure, but it seems that the secret is to purge each loop individually and one at a time, making sure to do so directly where the pex returns to the manifold or line.

Andy


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## Greenfield Dave (Nov 16, 2009)

Thanks Andy, I will try that method tomorrow!  

It's too late to warn me about the unwanted shower though, I have already had two

Dave


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## sgschwend (Nov 16, 2009)

I just filled my floor loops too, and it was challenging to get the air out.  I tried to drive it out with a pressure line at the storage tank, I tried opening the return line to drain; neither worked.

What did work is to have a drain valve at my return manifold, then open each loop one at a time and drive the water from the storage tank through the loop and then to the open drain at the manifold.  I also have two air separators at the storage tank to pick up any small air bubbles.  The air separators are: 1) at the top of the storage tank, 2) on the plumbing high point in the return which is connected to the expansion tank.

Works fine now.


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## rowerwet (Nov 16, 2009)

I just put in a baseboard in my bathroom and ran pex from it to my boiler loop from my opb, one side of the baseboard is connected to each leg of the boiler loop. I opened the valves and heard water rush into the new run, went up stairs to the baseboard in the second floor and it was cold and didn't warm up. I went back down and shut off the boiler loop at the HX for the oil boiler. That still didn't do the trick. I ended up having to open the return line (I love sharkbites!) from the baseboard and suck hard on it to get the water being driven by a 007 taco to flow up to the second floor and back down to the open end, after letting it run until there was a solid stream of water I jammed the return pex back into the sharkbite shutoff. Now it does work, but the taco 007 didn't do the trick all by itself. Using my fill valve from the house water (60 psi or so) and the shutoffs in the boiler loop I could have also done it, but would have required a lot of running back and forth.


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## heaterman (Nov 17, 2009)

Does your manifold have an isolation valve for each loop?


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## sgschwend (Nov 17, 2009)

From:  Sgschwend:
Yes, there is an isolation valve for each loop.  

I also have a input hose bib at the storage tank output so I can charge the system and use it to drive water through the loops.


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## in hot water (Nov 17, 2009)

Take the system pressure up to a few pounds below the relief valve setting.  Close all the manifold isolation valves but one.  Usually there is a purge cock on the end of the manifold with a hose thread, if not maybe one can be added.  Also an isolation valve on the connection to the manifold helps, so water flows to the manifold through the open loop, hits the isolation valve and burps from the purge cock.  close that loop when it runs clean and move to the next.

Remember to lower the pressure at the fill valve to 12 psi or designed fill pressure after you purge all the loops.  

This can be done at the boiler also if you installed a few ball valves with purge cocks or boiler drains.

The key is one loop at a time, and higher pressure to move the fluid at 2 fps or more to carry the air with it.

 hr


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## heaterman (Nov 17, 2009)

in hot water said:
			
		

> Take the system pressure up to a few pounds below the relief valve setting.  Close all the manifold isolation valves but one.  Usually there is a purge cock on the end of the manifold with a hose thread, if not maybe one can be added.  Also an isolation valve on the connection to the manifold helps, so water flows to the manifold through the open loop, hits the isolation valve and burps from the purge cock.  close that loop when it runs clean and move to the next.
> 
> Remember to lower the pressure at the fill valve to 12 psi or designed fill pressure after you purge all the loops.
> 
> ...




Exactly.


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## Greenfield Dave (Nov 22, 2009)

Well, thanks to all the advice I received, I got it filled  I realized I had created a 'figure 8" loop, that when filled, caused a dead head in the direction of the floor loops.  The storage tank was full, but the floor was not.  I closed all but the first isolation valve, removed the return line of the first loop to a bucket, then turned on the pump, and nothing!  I thought I had a crimped loop, or something in the pipe.  So, I isolated and removed the supply line of loop 1. Then used my air compressor to blow through the loop into a bucket.  It was full of air pockets, that caused the air lock!  I hooked the supply line back up, and used a submersible garden hose size pump to purge the line of air.  Then did the same  to the other lines, and mysteriously, it works

What I don't understand is the only way fluid will flow through the manifold is if I unscrew the flow meters about 5 turns from the manifold.  Is this normal??

I get about .5 GPM per 300' loop, with the Taco 00R-IFC pump..no matter what speed i choose.  I may need a bigger pump..

Thanks for the advice guys


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## in hot water (Nov 22, 2009)

what size tubing are those 300" loops?  .5- .6 gpm is plenty for 1/2" pex and should give you about 20 BTU/ square foot of output at 12" OC spacing.  What does your heatload require for btu/ ft.?

 hr


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## Greenfield Dave (Nov 23, 2009)

OK, so the flow is OK at .5-.6 GPM, but why does it stay the same, no matter what the speed of the pump?  Do I still have air trapped somewhere??


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## in hot water (Nov 23, 2009)

if the flow meters rise up when the circ is on, you probably have circulation.  Turn all but one completely off, does the flow rate on only one loop go above .5 gpm?

Check the spec on the manifold, it may not move more than that if it has a restrictive port opening?

 hr


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## Greenfield Dave (Nov 24, 2009)

in hot water said:
			
		

> if the flow meters rise up when the circ is on, you probably have circulation.  Turn all but one completely off, does the flow rate on only one loop go above .5 gpm?
> 
> Check the spec on the manifold, it may not move more than that if it has a restrictive port opening?
> 
> hr


The flow rate stays the same, no matter what the speed of the motor is, or the number of loops opened.  

So... I guess I must live with it...

So...my heat load is irrelevant...grrrr.

As a wise old man tells me occasionally, "It costs money to go to school."

Thanks to everybody for their input

Dave


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## heaterman (Nov 24, 2009)

I think the factor that is probably more critical than the flow rate would be the temp drop from supply to return. Check that if you can and report back. That will tell the story as to whether you are going to have problem.


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