Why won't my new radiant circuits work?

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HeatFarmer

HeatFarmer

Member
Sep 22, 2011
144
Montville, Maine
I just added a new set of radiant slab loops to my boiler. The closely spaced tees and everything had been there since install. The manifold consists of two cement slab loops--currently turned off due to other issues--and two fresh loops going to a tile floor on plywood and one under a laminate floor. Due to the laminate and slabs I have a mixing valve turned down to 80 degrees.

I filled the loops through the manifold, opened the valves to everything and then added more water/pressure to flush out any remaining air...... The first thing I noted was that the temp climbed way over 80. This loop draws off of the boiler return line so that it can always have access to water at least 100. At the moment the boiler is running and the return temps are maximum. The water to the manifold is hitting 120. But I see no climb on the return line. Neither do I feel any difference. I checked the line going to the cold side of the mixing valve and it seems fine.

The pump running this circuit is a Taco 007. The pump seems to be running very hot, even though the incoming side is cold and the discharge side is hottish. I have this loop set up to pull the water through the radiant loops.

Attached is a photo of this part of my system--it's on it's side..... I just can't figure out what's going on....the rest of the system is working fine--except, perhaps a slight leak in my storage tank which just developed (but we won't mention that just yet...). My much more complicated radiator system and all of it's loops came out of summer moth-balls just fine. This radiant thing has me stumped.

Could it be the pump placement?
radiant loop.JPG
 
More likely an airlock somewhere, than pump placement, IMO. Venting hydronic systems is a black art. Do you have vents on all return lines flowing down (i.e., with gravity)?
 
Vented the manifold, the pump, the mixing valve at the cold side.....not sure what else I can do....perhaps I'll go crack the supply lines individually at the manifold...something's got to give and get the water flowing......
 
Eric Johnson said:
More likely an airlock somewhere, than pump placement, IMO. Venting hydronic systems is a black art. Do you have vents on all return lines flowing down (i.e., with gravity)?
Click to expand...

I'm with eric. You got a lot of length there. My staple up was a pain, just once though. I'd bleed, pump up pressure to 25lbs. Took a while. Than another time, bled out quick and easy. Good Luck.
 
I helped a fella some years ago with a similar problem. He had such long in-slab lines and a small-ish pump that we ended up disconnecting the plugs at the end of the manifolds and setting up a jet-pump to push water from a bucket through the tubing and back to another bucket. Crazy fun. IIRC, there was only one loop so this wasn't a big effort. What I do remember is all the air and crap that came out of the pipes - obviously the contractor did not do a sufficient flush. I would also ensure that the mixing valve has the normally-open and common port correctly placed. The intention is to provide an open recirculation path for the pump from tubing supply to tubing return when the temperature is good. When the thermostat in the valve opens the valve, the pump should draw off heat from the hot loop close 'T' and then return cold water from the slab to the close-spaced 'T'. Sorry if this is all old news to you. Also, have you ensured that all the balance valves, if present on the manifold, are wide open?

Further, you should ensure the armored electrical cable is not touching the pipes as the armor is aluminum and it is galvanic to the copper.

Good luck.

SNIP ...

HeatFarmer said:
I just added a new set of radiant slab loops to my boiler. The closely spaced tees and everything had been there since install. The manifold consists of two cement slab loops--currently turned off due to other issues--and two fresh loops going to a tile floor on plywood and one under a laminate floor. Due to the laminate and slabs I have a mixing valve turned down to 80 degrees.

View attachment 76234
Click to expand...
elp
 
You reduced the pipe size from your return at that tee to your mixing valve, which could be restricting flow A LOT

Can you flush each zone individually @ city water pressure? I like to do that, then heat up the system @ 2-3 PSI, (Lower pressure with high heat purges air easier), then top off the system.

Is primary loop pump running?

Can you turn the mixing valve all the way down / force it to pump via the return only? This will cool off the lines very fast, and you will know you have flow.

I've never installed a pump on the return for a radiant. Putting it on the supply puts the point of highest pressure where you want it.


3 way valve diagram.jpg


GOOD LUCK!
 

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Put me down for a BIG flush too.

When my home was built the plumber used a jet pump to bleed it all out... not the small circulator.

Can't hurt.

JP
 
Thanks everybody for the input so far! As to the reduction before the cold side of the mixing valve--not ideal, but it was what I had at the time....It doesn't seem to cut back the flow in any significant way....I may just fix it now anyway because I have everything torn apart..... As for the flushing....the first thing I did was hook the system to a hose with 30psi and put the water to 'er..... I was hovering just below blow off pressure on the entire system. This has always worked well in the past, but today it wasn't doing much.

Meanwhile, I may have discovered one reason things weren't working well....the taco pump is toast. It barely runs and when it does it's sluggish. It may have burnt up last year during slight freeze we had in the boiler room during launch. Not sure, but a new Alpha pump has been ordered to replace it. I thought the taco was running a bit too hot!

Fortunately, replacing the pump should be a breeze when it gets here. Then I'll have a go at flushing the whole system again with high pressure before running anything. I think part of today's problem was having the system up at full steam....can't tell you how many times I dodged scalding water as I tried to bleed lines...... With a fully functioning, smart, pump I should make better sense of things.

BTW....would having the two loops in the middle of the manifold shut off have caused any problems? I know for a fact that one of the slab loops has a leak, which should be easy to repair, but will take some time to get to it. Should I relocate the two dead-ended loops to the last two slots on the manifold for the time being? At least until I can trace the leak and fix it......?

Let this serve as a warning to new installers.....NEVER try to fill and launch your system on the coldest day of the year, however desperate you are to get heat! AND if you do, make sure you don't fill your slabs up until you actually have some hot water circulating!!
 
Glad you are figuring it out!

Up here we glycol a lot of systems (-40 2-3 monthes... one day down can be a disaster), so I put valves / drains on everything, even the circulator pump connection. Good side - No freezing / peace of mind Bad side - Gotta maintain it, and you want valves/drains everywhere. I run 60/40 in my system.

I would think the lines would run fine, it would not hurt to locate the other lines though, especially if its easy / you really don't know when you are gonna fix the other loops.
 
We always install the pump on the outlet of the mix valve. The other thing that is nearly mandatory in my book is a ball valve in the "leg" that goes back to the cold (return) side of the mix valve. If you don't have a way to isolate there purging can be much more difficult.
 
heaterman said:
We always install the pump on the outlet of the mix valve. The other thing that is nearly mandatory in my book is a ball valve in the "leg" that goes back to the cold (return) side of the mix valve. If you don't have a way to isolate there purging can be much more difficult.
Click to expand...

Second that.
 
Move the circulator to the supply of the radiant. TheMightyMoe said this as well. Try that first and up the size of the return as the majority of flow just goes through the radiant around and around with little comming in through the supply.

TS
 
I agree with moving the pump to the supply. I have never had good luck trying to pull water through.
 
Perhaps a bad comparison but when I did my addition - including 3 floors and the old portion of the house - the taco 007 was not enough. I went with a Grundfos - the nice thing here was I went with the one with the 3 position flow adjustment lever. The taco 007 is no slouch - but switching the grundfos immediately made it up to the 3rd floor. With the adjustability of the grundfos you can tweak it to get the right temp drop at the return.
My pump position remained at the return.
 
jjs777_fzr said:
Perhaps a bad comparison but when I did my addition - including 3 floors and the old portion of the house - the taco 007 was not enough. I went with a Grundfos - the nice thing here was I went with the one with the 3 position flow adjustment lever. The taco 007 is no slouch - but switching the grundfos immediately made it up to the 3rd floor. With the adjustability of the grundfos you can tweak it to get the right temp drop at the return.
My pump position remained at the return.
Click to expand...


I'd move the pump to the mix outlet of the 3 way. Piped on the return can cause some issues, see the article below from the P &M magazine archive April 2003.

Your manifolds are all set up to power purge. With the pump switched off, close the red and blue valves at the manifols S&R. Connect a garden hose to the supply side, top purge valve, close all but one of the manifold outlets with the white plastic caps.

Put a short hose on the hose connection on the return purge valve, put the end in a white plastic bucket or pail. A wash machine hose is ideal for a purge hose, and to attach a garden hose to the fill valve as it has two female connections.

Open both valves on the top of the manifolds (purge and fill valves) Flow water until it runs air free in the bucket. Turn off that branch on the manifold (white cap) go on to the next.

Purge the loops one at a time until they run clear. Then re-open the S&R valves to the boiler, adjusty the fill pressure and fire up the pump.

I wouldn't install the Alpha until you move it to the correct location.

hr
 

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TheMightyMoe said:
You reduced the pipe size from your return at that tee to your mixing valve, which could be restricting flow A LOT

Can you flush each zone individually @ city water pressure? I like to do that, then heat up the system @ 2-3 PSI, (Lower pressure with high heat purges air easier), then top off the system.

Is primary loop pump running?

Can you turn the mixing valve all the way down / force it to pump via the return only? This will cool off the lines very fast, and you will know you have flow.

I've never installed a pump on the return for a radiant. Putting it on the supply puts the point of highest pressure where you want it.


View attachment 76248


GOOD LUCK!
Click to expand...

Nice Diagram!
 
Bob Rohr said:
I'd move the pump to the mix outlet of the 3 way. Piped on the return can cause some issues, see the article below from the P &M magazine archive April 2003.

Your manifolds are all set up to power purge. With the pump switched off, close the red and blue valves at the manifols S&R. Connect a garden hose to the supply side, top purge valve, close all but one of the manifold outlets with the white plastic caps.

Put a short hose on the hose connection on the return purge valve, put the end in a white plastic bucket or pail. A wash machine hose is ideal for a purge hose, and to attach a garden hose to the fill valve as it has two female connections.

Open both valves on the top of the manifolds (purge and fill valves) Flow water until it runs air free in the bucket. Turn off that branch on the manifold (white cap) go on to the next.

Purge the loops one at a time until they run clear. Then re-open the S&R valves to the boiler, adjusty the fill pressure and fire up the pump.

I wouldn't install the Alpha until you move it to the correct location.

hr
Click to expand...

Good flushing advice, but 'Figure 2' isn't the same as the OP's circuit. His pump is on the opposite side of the tee going back to the mixing valve. Pump should work fine where it is.
 
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