Radiant Heat Loop Not Working #2

Ralphxyz

Thanks again everyone for your help with Radiant Heat Loop Not Working

I "thought" it was working BUT now it does not appear to work, well occasionally it heats up but never
hot.
I am wondering if I need to replace the tempering valve?



Now I "thought" the Red port was Supply (red), the blue Return (blue) and the Mix (pink).

This is a RTI (Radiant Technology) mixing valve which is >10 years old so I do not have any
documentation.



I get warmer water when I turn the knob to the left contrary to the arrow.

Here is current piping:



Somebody has to be familiar with this mixing valve. RTI was a large distributor of radiant heat materials
10 years ago.

Should the Return go to the Red port and Supply to the Blue port?

It is strange the first time when everything was cold when the thermostat called for heat
and the circulator kicked on with the mixing valve turned all the way to the right the pipes
did not get hot on the supply side but when I turned the knob all the way to the left the supply
got hot and the Mix got hot.

Now with the circulator running I barely feel the Mix side heat up and that appears to be coming from
the return as that is warmer than the supply.

The warmth in the return is residue from running all morning, it had gotten warm (not hot).
But at 10:00 a.m. I could not get any new heat from the supply it remained cooler than the return.

No matter where I turned the mixing valve knob I never get the supply to heat up.

Thanks for the much needed help.

It's down in the 20s in the early morning so I sure need to get this working.

Ralph

hot_rod

It takes some time to bring the temperature up, don't expect to see instant temperature change. The cold water coming back blends the MIX temperature. With the knob all the way to hot, the cold port should be almost closed off and the valve seeing mainly the boiler temperature. That low Cv valve with your circulator probably moves around 5 GPM.

The spool inside do tend to stick after time, it may need to be cleaned or rebuilt.

It looks like an ESBE brand, RTI probably re-labeled it. Supplyhouse.com sells that brand as well as many wholesalers.

If you replace it, find another with the ports in the same configuration or you will need to repipe.

Most, not all 3 way are H on one side, C directly across, and the mix on the bottom of the tee.

Ralphxyz

Thanks for the reply hot_rod, as I said the first time the supply and mix got instantly hot when I moved the knob to the left.

So I have instantaneous response.
I will look at Supplyhouse.com.

The mixing valve is >10 years old and I used to leave the circulator running 24 hours a day for at least 6 months of the year so it has thousands of hours of use.

Ralph

DZoro

I assume you found a way to turn the boiler on when the radiant floor calls for heat?

Ralphxyz

Hi Dzoro, I do not turn the burner on with the radiant loop.
The boiler is always hot and the burner comes on when the temp of the boiler cools, the boiler has a tankless water heater which cools the boiler turning on the burner often, so the boiler is always hot.

I have ordered a new tempering valve, the radiant loop is > 10 years old so there are >40,000 hours on the components.

Luckily when I repiped the loop I used Unions so it will be a 10 minute operation to replace the old mixing valve.

I see at Supplyhouse.com that there are replacement cartridges and repair kits for mixing valve so I believe it is not unusual to repair or replace one, which hot_rod had suggested.

Ralphxyz

Besides the tankless water heater cooling the boiler and calling for heat my aquastat is set 180° off 160° on, why would I worry about turning on the burner? The supply water is never<160°.

My RTI control box has the capabilities to turn the burner on but I never saw why I should do that.

Possible the new high efficiency boilers run cold except when heating so then I could see a need to turn on the burner, also then there would be a lag time between the thermostat calling for heat and the time the loop actually got hot as hot_rod said.

Thanks again for the help.
Ralph

Ralphxyz

Still does not work!!

I replaced the mixing valve but the only time the radiant loop gets hot is when the house circulator is working!
The loop circulator apparently has no effect!

Boiler Supply:


Tee supply for radiant loop.


Mixing valve:


Boiler Return:


Radiant Loop Header:

hot_rod

Put your hand, or point an infrared thermometer on the "red" hot supply to the mix valve. It should be seeing boiler temperature water when that radiant circulator is running. If not the valve will not be able to supply a consistent mixed temperature.

Ideally that hot supply wants to bat least 20° warmer than the mixed outlet.

So if for example you want 120° mix, you need at least 140° to the hot port of the mixer, constantly. Without that temperature delta (difference) the valve will not regulate accurately and will hunt around providing inconsistent mixed outlet temperature.

Could it be the boiler supply temperature is falling behind with a cold start or high load on the radiant?

Tom_133

I guess I also want to know if you have any air caught up in the radiant or the circulator to the radiant loop is DEFINITELY working and moving water?

Side note: Ralphxyz you are tenacious, typically the work you've done would have basically stopped most people and they would have hired someone. Im sure you are also learning alot as you go. Nice Job

hot_rod

In a nut shell, you need flow and temperature to transfer heat energy. Somehow, somewhere you are lacking one or both.

HomerJSmith

Is it possible the circuit is air bound? I would like to see a picture of the whole sys.

Ralphxyz

Thanks for the replies!!
The loop heats when the house circulator is operating, so it is not air bound.

When the house circulator is not operating the supply pipe feeding the mixing valve is cold, the loop circulator is operating!

The house supply is at least warm, residue from the last run.

My wife and I installed this radiant loop >10 years ago.
It never did work, except when the house circulator was on.
We only kept plants in the room which did well.

Now the room is being used as a bedroom so I would like to be able to control the heat.

65 years ago my father had a Plumbing and Heating company.
So I grew up working plumbing and heating jobs. I had my Master Plumbing license when I was 21. I worked a few years
doing commercial plumbing and heating but did most of my work building waste water treatment plants, but that was 30 years ago. Since then I have been doing computers.

There has to be something obvious that I am missing.
I have been known to have DUH moments.

I am "thinking" (watchout) that possible a circulator on the supply side might work?

Thanks for the help and the encouragement!

Ralph

Ralphxyz

HomerJSmith, essentially you are seeing the whole sys.
The radiant loop starts at the Header which is 20' from the circulator, there really is nothing more to see.

Zman

@HomerJSmith, I asked for a drawing of the entire system over 3 weeks ago, good luck with that one
@Ralphxyz , We are unable to help you because you have not provided a drawing. It is super common to get tunnel vision after spending so much time troubleshooting. It happens to everyone. Posting a drawing so everyone can see the big picture is the answer.

icy78

Can you remove the loop circulator and prove that it actually creates a pressure differencial?

Ralphxyz

Ok here is a drawing, the pictures show it much better but ...


the mixing valve Circulator detail:

It really is just a simple loop.

Canucker

If I'm reading your drawing correctly, you have no hot supply to your radiant unless you have the house zone going. That will need to be repiped if you want them to operate independently.

hot_rod

This article shows and explains how the 3 way needs to be piped, and 3 options.

It needs a constant supply of HW from the boiler to work. doesn't look like your piping allows that?


https://www.pmmag.com/articles/84495-a-little-floor-warming-please-john-siegenthaler

Ralphxyz

It has a constant supply of hot water!!

Ralphxyz

Canucker, that is correct "you have no hot supply to your radiant unless you have the house zone going". How would they need to be repiped to operate independently




Essentially the supply is a manifold where else would the supply come from but the supply header.

Do you want the supply to come off before the expansion tank?
I am open to all of your help.

Ralphxyz

Wow hot_rod that is the first time I have seen the return being piped into the supply.

I wish I could see figure 2 they are too small.

GroundUp

As I told you 3 weeks ago, there is no hot water supply to the mixer unless the main system circ is running. The water will simply short cycle the path of least resistance through the mixer and not pull anything from the boiler itself. You can either run a new supply line all the way back to the boiler and build a 2 zone header similar to the return side, or cut in a bypass with a 3 way zone valve to bring on the primary circ during a heat call from the radiant but bypass the baseboard unless it is also calling for heat. See how easy that was, providing a drawing after it's been asked for 100 times and getting answers almost immediately? Could've saved yourself a lot of headaches

hot_rod

yeah, if it works fine with the boiler pump running, then it is not an air or circulator problem. Really all that is left is a mis-piped tie in.

It's a common mistake with two temperature systems, you just need to trace in your minds eye how the flow moves under the various conditions.

Ralphxyz

Thanks for the replies.
re: You can either run a new supply line all the way back to the boiler and build a 2 zone header similar to the return side

What would that look like?

re: The water will simply short cycle the path of least resistance through the mixer and not pull anything from the boiler itself.

Yes that is what it is doing but I do not see how/why.

Curious what is seen in the drawing that you could not see in the pictures? The only additional thing is the loop which I thought could be pictured. One radiant loop pretty much looks like another function wise.

Now for some more questions.

This is the input to the circulator when I moved over next to the house circulator like a new baseboard loop on the return:


This is the input to the circulator on the mixed side of the mixing valve:


Now this is strange Boiler pressure:


I did not take the pictures at the same time so possible there would be similar readings.

I wonder why the inlet to the circulator after the mixing valve is so high?
I thought I might have installed the circulator wrong:



Return at the Boiler:


Would putting a globe valve on the return line to the mixer help?

hot_rod

Maybe this pic clears it up better.

In all 3 of these examples two circulators must run to supply the radiant. One moves the heat from the boiler, the second, after the mix valve moves the heat thru the radiant.

I think the issue with your system is the boiler circ is moving heat thru a zone when it is not needed or wanted? And also you only get radiant flow when the main (boiler) circ is operating?

Follow these drawings and see how flow is moving the two different piping circuits.

IF you want the radiant to run by itself, on a separate thermostat and independent of the high temperature loop, you need to consider one of these.

Basically the hot port of the mixer always needs a supply of "hotter" water from the boiler.

Primary secondary is another piping option with closely spaced tees, that would be a major repipe for you, however.

Ralphxyz

Actually the house circulator is all that is needed. The radiant loop circulator adds nothing.

I have a 1 1/4" header that the radiant loop tees off of.

I "could" add a zone valve to the 1 1/4" header isolating the house:


I'd need help with the control wiring.
Turning on the house circulator when either the radiant loop or the house called for heat.

Supplyhouse.com has a Honeywell Zone Valve
Not sure about the Maximum Ambient Temp 125F if it being used in a hydronic heating system.

Ralph

hot_rod

Just to be clear, you want to run the house only, the radiant only, or both together?

If so you need two thermostats one in the house and one in the radiant area.

The middle drawing maybe?

Two pumps, two zone valves?

A zone control relay box would simplify wiring, not sure how well versed you are in wiring relays and controls?

GroundUp

No you can't, because you need the circ to pull through the mixing valve in order for it to work. Why must you insist on arguing with everyone trying to help you? You need two circs for this to work with your mixing valve- there is no way around that. Again, you can run the hot side of the mixing valve all the way back to the boiler supply header and have it pull full temp water directly from the boiler. The supply header would look just like your return header, and each zone would be able to operate independently from each other. A Taco SR502 switching relay and two thermostats would get you fixed right up

Ralphxyz

Sorry, if I seem argumentative, that certainly is not my plan.

Ok, again sorry if I assumed you would just know things.

I have two thermostats one for the house and one for the radiant loop.

I have two circulators one for the house and one for the radiant loop.

The radiant loop works when the house circulator is running.
The radiant loop circulator does nothing it does not circulate any hot water.

The house circulator is certainly not pulling through the mixing valve. It "appears" to be pushing through the mixing valve.
i.e. it is raising the the supply side head.

As GroundUp said: As I told you 3 weeks ago, there is no hot water supply to the mixer unless the main system circ is running. The water will simply short cycle the path of least resistance through the mixer and not pull anything from the boiler itself.

The house circulator makes a hot water supply (pushed from the boiler) the radiant loop circulator is just bypassing through the mixing valve.

Since the radiant loop works with the house circulator I "thought" I could use the house circulator as the radiant loop circulator and house circulator by isolating the house with a zone valve and the radiant loop with a zone valve, I would control both zone valves from their individual thermostats.

I would also have to turn the house circulator on and off or just let it run continuously.

What is not understood about my current piping, which does not work, I have a supply header which is essentially the same as my return header.



I believe the house and the radiant loop need to be isolated.

Since the radiant loop circulator does not work but the house circulator does then why not use the house circulator.

Clearer than mud, Thanks everyone WE will will work this out.

Ralph

hot_rod

I thought you mentioned when both circulators run, only then the radiant works? Not with only the one boiler circ running?
Is this correct, if so you need to change some piping. or live with what you have.

Think of your system as two independent heating systems that happen to have one boiler source. Either or both need to be able to provide adequate flow and temperature under any heat call condition.

All the various piping arrangements we all have suggested and shown work, without question. You need two circulators, period.

Pick one schematic that would be easiest for you to repipe and we can all have a warm comfortable winter season.

If you use the middle piping drawing I showed above.

Here is a wiring schematic that will work with a Caleffi ZVC panel. And Caleffi Z-One zone valves with end switches. Disclaimer: I work for Caleffi.
I tested it out on my own shop relay box to confirm the logic. I have a Gen 1 board, I'll check Monday with tech support to confirm our Gen 2 versions have the same logic, we did add features. We have 3 relay outputs and can change the status configuration between those outputs, not sure other brands can do that.
Ignore the red boxes, they are showing unique features of the ZVR.

I modified the drawings a bit to better represent your system, or the system I propose. 2 wire thermostats will work fine if that is what you have. Both pumps P1 and P2 wire to the relay box.

A ZVR 103, 3 relay box is what you need, use two, have 1 spare. This schematic happens to be a 6 zone ZVR 106.

jstratz

Looks to me like the only issue is the when the house circulator isn’t running the infloor zone is pulling flow backwards through the main loop instead of the through the boiler due to a failed or absent check valve. Once the main circulator comes on it reverses that flow to the correct direction and you finally get hot water to your mixing valve from the boiler. If you had a check valve on the main supply after the tee where the two split off this should solve your issue. Should be able to test this if you have a valve somewhere that you could shut off to prevent flow through the main loop.

However once the in floor zone gets to full temp it will start bypassing quite a bit and not pulling enough water through the boiler to meet its minimum flow causing short cycling. I would try a check valve and if that doesn’t work then you may need to add a primary/secondary setup.

The infloor pump can pump from the boiler independently without any additional pumps as long as the flow can be isolated to just the boiler with a check valve. When the mixing valve is functioning properly it will shut off its cold water inlet when it’s outgoing water is below its set temp. This forces full flow from the hot side through the mixed side directly. And since water leaving the in floor loop can’t go through the cold side of the mixer with it closed it has to go back to the boiler. This will force flow through the boiler.

GroundUp

You do NOT have a supply header, that tee is like 8 feet from the boiler (after figuring in the friction loss from the elbows) and it should be a few inches. Your pump is located on the mixed side of the mixing valve, pumping away from it, so it is very much pulling through the mixing valve. Cap the existing tee and run a new 3/4" line back to the boiler like the return side is, and you will be done. The installation was butchered from the start, but I think you could cut in a new tee immediately after the air scoop for the radiant supply and have it draw through the boiler independently from the radiation, so only the radiant circ would need to run for heat in that zone. If it were mine, I'd start over but the aforementioned tee will be a band-aid. Any thermostatic 3 way mixing valve will require 2 circs to run this system- there is no way around that.

Ralphxyz

jstratz re: The infloor pump can pump from the boiler independently without any additional pumps as long as the flow can be isolated to just the boiler with a check valve.

Sorry I cannot picture the location of the check valve.

hot_rod, I love that control and thanks for the wiring screen shots. If I went to zone valves I'd be a customer.
I watched your installation video, thanks.

Here is a revised image of the piping:
How is the house circulator affecting the radiant loop?

GroundUp re: Cap the existing tee and run a new 3/4" line back to the boiler like the return side is, and you will be done.

What? Cap the tee on the supply? At the 1 1/4" supply?
and then run a new 3/4" line back to the boiler where?

Ralphxyz

Darn my revised piping image didn't make it.

jstratz

The house loop piping: furthest pipe at the top left in the drawing. If there is no check valve then the radiant is possibly inducing flow backwards through the house loop instead of the boiler. Try shutting off a valve on the main house loop somewhere to isolate the radiant to just the boiler. If it starts working with the main loop valves off then my theory is right.

You shouldn’t need to add a line back closer to the boiler. Your common pipe is the same thing as long as it is large enough to carry the full water capacity for both zones. Repiping closer doesn’t accomplish anything except maybe being slightly less likely to go backwards through the main house loop. I’m almost positive it just needs a check on the house loop since it works fine with the main house circulator pump running

hot_rod

jstratz said:

The house loop piping: furthest pipe at the top left in the drawing. If there is no check valve then the radiant is possibly inducing flow backwards through the house loop instead of the boiler. Try shutting off a valve on the main house loop somewhere to isolate the radiant to just the boiler. If it starts working with the main loop valves off then my theory is right.



You shouldn’t need to add a line back closer to the boiler. Your common pipe is the same thing as long as it is large enough to carry the full water capacity for both zones. Repiping closer doesn’t accomplish anything except maybe being slightly less likely to go backwards through the main house loop. I’m almost positive it just needs a check on the house loop since it works fine with the main house circulator pump running

You need a path for flow back to the boiler when radiant alone is running, IF the main circ is also running. Otherwise he will get heat in the main zone when the main circ is running and doesn't call or need heat.

I think his issue is no heat in the radiant unless the boiler circ is running, not overheating the main zone with the radiant. How will a check fix that? He already has a flow check at the boiler, probably stopping flow to the radiant mixer being on the suction side of the mixer.

Screw open the flow check just for grins and see what happens, disconnect power to the main circ, when the radiant alone calls, what happens? Then a check downstream of the mix valve connection on the main line. Pumps need to be wired separately also. What tells both to run on a radiant only call now?

As piped and wired, I think both circs need to run to supply radiant, so the main zone will always get flow.

The 3 drawings I show hydraulically split the two independent zones, providing 100% either or operation. Properly piped they assure the exact flow required under any condition, no pumping conflicts.

Seems like you have done enough trial and error piping, why not pipe a proven solution?

jstratz

I agree. Would be much better with it all piped primary/secondary and done right.

Currently tho It won’t overheat the main loop with it backfeeding because it’s just short cycling cold water around. Can’t get the hot water from the boiler with it backfeeding through the main loop. The check won’t help at the boiler because that’s not where it is flowing backwards. Just needs one on the main loop after the tee where they split off. All assuming that the diagram drawn is 100% accurate of course. Proof in the pudding is to just shut a valve on the main loop somewhere so it definitely cannot flow through it. And then run the radiant zone pump and see if it can finally force water through the boiler.

Should be able to since the cold inlet on the mixing valve will close when the loop temp is cold. This will pull water through the hot side of the valve from the boiler which allows the water on the return of the radiant zone to only be able to go back to the boiler since the cold inlet on the mixing valve is closed. This will create a loop to the boiler without a second pump.

Still should be repiped in its entirety but this would at least prove the concept

Ralphxyz

There is no valve on the house supply!

The backflow is going through the mixing valve.
Circulator OFF boiler:


Circulator OFF boiler return:


Circulator OFF radiant loop:


Circulator ON boiler:


Circulator ON boiler return:


Circulator ON radiant loop:


I need to induce a 7# pressure drop on the return feed to the mixing valve!

Thanks for all of the help I really appreciate it!!

Ralph

GroundUp

The 1-1/4" x 3/4" tee you have currently running to feed the hot side of the mixing valve. Cut the 3/4" pipe off, and cap it the stub sticking out of the tee (or remove the tee altogether). Then run that 3/4" line all the way back to the boiler and cut in a new tee immediately after the air scoop, as I said in my last post. This will allow hot water to be drawn directly from the boiler, using the radiant circ. I do not know how I can possibly be any more clear.

HomerJSmith

I'm not very smart so I do like to see a panoramic view of your system.

So, let me get this straight. You don't have any flow on the radiant loop. hmmm, and it never worked from the start. hmmm, and the radiant loop is heating only when the boiler circulator is turning. hmmm, well, I can see this is a conundrum, inside a mystery, inside an enigma.

Not wanting to appear foolish and give away my low IQ...
You do have power to the radiant pump and it is turning?
What controls the radiant pump and what supplies the power to the radiant pump?
You want the radiant pump to operate independent of the boiler pump?

I would want to verify that the pump has power and is turning. I would take the pump apart and rotate by hand the rotor and check the volute and impeller for any debris that might impede its rotation.

Ever think that the radiant pump is just too big a pump for your application?

Ralphxyz

GroundUp, thank you, I could easily do as you suggest, but I lost my two 24" pipe wrenches. A friend even dropped off a Rigid adjustable thread so I could cut and add the tee and cut new threads but not with a 18" pipe wrench.

HomerJSmith, the radiant loop heats up only when the radiant loop AND the house circulator are running.

Yes I want the radiant pump to operate independent of the boiler pump?

I do not want to heat the whole house just to heat the radiant loop.

re: "Ever think that the radiant pump is just too big a pump for your application?"

Now that is a interesting thought. The circulator is the one RTI furnished when I bought the materials.

Grundfos 15-42 F:


Curve:


How would one determine the correct size, besides comparing curves and guessing?

It is appearing that if I just add zone valves and isolate the loops would be the simplest thing to do plus move the tee if I can find my pipe wrenches.

Ralph