Zone that doesn't heat properly

Intplm.

@ntonkin . When you did the blow down, and all the sludge came out, did it help to improve anything or is it too early to tell ?

ntonkin

I have a contact thermometer on the secondary supply pipe about 3" from the separator that reads ~ 20 degrees higher than the system temp boiler screen indicates with no zone calling for heat. The system sensor is clamped on ~ 12" further down the pipe. With a zone calling for heat the thermometer reads ~ 5 degrees lower than system temp on the boiler screen. The slowest flow I can get is 2 gal/min by putting the pump on fixed speed |. hot_rod said earlier that all the flow this zone 3 needs is .85 gal/min. Should I leave it on fixed speed |?

Where should I measure the temp for each zone to see if they are consistent? I'll get some more contact thermometers so I can put one on each zone.

SuperJ

It makes sense that the temperatures don't match when zones aren't calling because there won't be any flow on the secondary side (and hot water rises in a stagnant situation). Once you have flow a 5degF spread is reasonable if you're just measuring surface temperatures. I'd expect sensors in proper wells, with thermal paste to read closer together.

You can leave the pump on fixed speed one. The pump readout is not always accurate, especially with check valves such in the mix. Don't get too hung up on what the pump says.
I would focus on whether the zone heats properly, and then look at the temp delta. You want to the return to come back cooler than the supply. The amount of delta depends on the type of zone (radiator, inslab, etc). But generally you want the delta to be higher (cooler return temps), in order to maximize boiler efficiency.

If the zone is heating fine, and the delta is low then you can throttle a ball valve, to reduce flow and raise the temp delta. If it's a tough to heat zone then your delta might be as small as 5-10degF, or if it's easy to heat maybe 20degF or larger. If it's infloor then 10-15degF is usually the max or you'll end up with unheated portions of the floor.

You can go through this process on all your zones to balance them out.

The supply water temperatures should be the same to all the zones, assuming you have functional check valves on each zone. I'd confirm that. Once you've proven that, it's really the return temps that are going to vary depending on the flow and heating load of each zone. If a return temp is exceptionally low, that may be an indicator of insufficient flow, if it slowly increases than it might just be a lot of thermal mass (think cast iron, or concrete (days to warmup sometimes)).


Also not if your outdoor reset has reduced the temperature you delta will probably be smaller too since the water is closer to ambient temperatures. The delta that really tells the true story is what occurs at max load and max temps (Coldest days of the winter).

If you are throttling valves, for balancing, you could also use one of the constant pressure modes, that way the pump will back off a bit as you throttle using a bit less power.

Gordy

Measure the temperature at the beginning, and end of the baseboard for the whole zone..

So if there is one, or three in a zone. Measure at the beginning of the first one, and the end of the third one.

You want to know what’s going on at the emitter.

ntonkin

How should I look at delta T? If I subtract the return temp from the system supply temp, I get 15 degrees... but the boiler screen indicates delta T of 2 degrees (I am assuming this is the primary delta T). Which of these should I be concerned with trying to keep high? I would assume it's the secondary delta T I want to keep high. This is a bit confusing as the point of maximizing delta T is that the boiler will be more efficient, right? and yet it's the secondary we are maximizing, not the primary (the loop the boiler is in)???

I don't have a check valve in Zone 3, I have a BFP in the return. Should I put the check valve in so I have two?

Does the flow restriction caused by a check valve (which is uncontrollable) have some benefit over a BFP?

Does it matter where you "throttle" a zone with a valve? I have 3 valves on each zone, one on each side of the pump and one on the return, before it joins the other zones' returns.

Just so I'm clear on this "balancing".... the object is to maximize delta T for the zone while maintaining radiator heat output, right? Another thing, do I need to have all zones calling or can I do the balancing when only the one zone is calling?

ntonkin

Gordy said:

Measure the temperature at the beginning, and end of the baseboard for the whole zone..



So if there is one, or three in a zone. Measure at the beginning of the first one, and the end of the third one.



You want to know what’s going on at the emitter.

How close to the radiating fins do these readings need to be?

SuperJ

15degF is in the ballpark of what's ok for many systems.

The as the return water drops from around 130 to 90f it will become more efficient. If you pump too much hot water thru a zone loop it won't be able to give up it's heat fast enough, and will come back hot, making your boiler less efficient.

You can measure in your basement on the supply and return manifolds. You can probably just use the system supply temp for all your supplies, and individually measure the returns.

If your boiler delta is only 2 deg F, it sounds like your primary pump is running too fast. What is the boiler fire rate at 2deg F delta (primary) and what is the pump speed, and possible pressure drop across the boiler if you have the gauges? What are the actual in and out temperatures of the boiler?

If you have junk in your loop, it can cause other problems that are hard to diagnose until you have good water quality and clean pipes.

As for where to throttle a valve, it's better to throttle on the discharge side of a pump rather than the suction. So throttle the valve on the return from the zone (so the pump has to push thru the restriction, rather than pull).

ntonkin

The primary pump has been set at low speed for some time now. When the boiler is firing at around 50%, the delta T goes up to around 10 degrees. When it was at 2 degrees, I think the boiler wasn't firing.
The boiler outlet was 190 and the inlet was 185 but delta t had dropped to 5 and the boiler shortly was at setpoint. Again it's a moving target.

hot_rod

The purpose of balancing is to assure each zone or loop gets adequate flow, but not excessive to the point of causing noise, wear, etc.

"A properly balanced system is one that consistently delivers the proper rate of heat transfer to each space served by the system"

Just to be clear, the faster fluid runs thru any heat emitter, the higher the output. This is because the AWT thru the heat emitter is higher. It's not about the ability of BTUs being able to jump on or off.

That being said, a low ∆ thru a boiler can cause inefficient short cycles. The challenge is between the heat emitters and the boiler. We would like to see a tight ∆ on some types of heat emitters, radiant floors, for best comfort would like a tight , 15 maybe even 10°, this help assure a consistent floor temperature

Panel rads, cast iron radiators, if sized large enough could run 30 40 or more ∆, as long as the last on the loop has sufficient output at the lower SWT it will see. Generally no more than 3 panel rads on a loop running a wide ∆, for example.

To prevent the low ∆ and short cycling in the boiler, either modulate the fire down to match the load closely, or add a buffer.

What you will find is it is much much easier to regulate heat output via temperature modulation compared to flow modulation due to the fact that flow modulation is very non linear and at very low flows heat transfer really declines quickly.

ODR excels at matching load to input a curve set at 1 for example would increase SWT 1° for every 1°the outdoor temperature drops, a very liner relationship, easy to accomodate.

The ∆T throughout a system will always be moving around to some degree. We chose a number to design and size to at one particular operating condition, typically design day. Any condition other that that the ∆ may, will be different.

In hydronic heating systems there is no reason to try and impose or limit that movement as the system is finding it's thermal equilibrium, it's sweet spot so to speak. Loads may change second by second, allow the ∆ the ability to change or move with the transient condition a heating system imposes.

Lastly the heat emitters dictate the boiler operation, not vice versa.

These attachments better explain the math and show, in color, the difference in output between a low ∆, low flow and a high ∆ high flow circuit, same SWT in this radiant loop drawing. Same applies to any heat emitter or exchanger.

ntonkin

The zone 3 pump set at speed | is now stabilized at an indicated 1 gal/min flow drawing 6 watts and the delta T is 32 degrees. If I change the pump to low level constant pressure, the wattage draw almost triples.

SuperJ

ntonkin said:

The zone 3 pump set at speed | is now stabilized at an indicated 1 gal/min flow drawing 6 watts and the delta T is 32 degrees. If I change the pump to low level constant pressure, the wattage draw almost triples.

Ultimately you need to give the zone just enough flow to satisfy the heating load. As hot rod said, high delta are nice, and low wattage is nice too, but you don't want to impose them artificially. A reasonable delta, and low pump wattage are the result of a good design, but if you impose a high delta and low pump wattage on an incompatible system you are going to have comfort or performance issues.

It's worrying that your boiler is so hot, 190degF is really hot.
What was the system setpoint and temperature when this was occuring? Seems like your boiler is bouncing off a high limit which isn't good.

Gordy

I agree with Bob, but I also feel getting a handle on what the emitter is doing as far as the delta is concerned sheds a little light on the possible flow rate, and how well the emitter is doing with its output.

This has sort of turned into doing everything in the boiler room, and not checking back with the emitter to see how changes effect the emitter.

A zone, or Room not meeting set point is a generalization. With many possibilities as to why not. Those of which are not always a heating system issue.


With out going back to the beginning there is multiple sections of baseboard in this troublesome loop zone three correct?

So what is the temp at the beginning of the first emitter, and the temp at the end of the last emitter of that zone three? During a heating cycle of course. If it were me I’d check at the beginning of the call, and readings near the end of the call once the emitter has reached equilibrium.

Gordy

While i do agree emitter deltas, and system deltas are a floating target until equilibrium is reached. I also believe with a well designed system it can be a constant repeatable number from start to finish of a heating cycle. I’ve witnessed it myself.

hot_rod

Gordy said:

While o do agree emitter deltas, and system deltas are a floating target until equilibrium is reached. I also believe with a well designed system it can be a constant repeatable number from start to finish of a heating cycle. I’ve witnessed it myself.

Or was the needle on your gauge stuck

Jamie Hall

Department of minor thoughts -- if that "back flow preventer" is as you describe -- a simple flap -- that is not a backflow preventer. That's a check valve. Very different critter.

Gordy

hot_rod said:

Gordy said:

While o do agree emitter deltas, and system deltas are a floating target until equilibrium is reached. I also believe with a well designed system it can be a constant repeatable number from start to finish of a heating cycle. I’ve witnessed it myself.

Or was the needle on your gauge stuck

No sir!

ntonkin

Gordy said: With out going back to the beginning there is multiple sections of baseboard in this troublesome loop zone three correct?

So what is the temp at the beginning of the first emitter, and the temp at the end of the last emitter of that zone three? During a heating cycle of course. If it were me I’d check at the beginning of the call, and readings near the end of the call once the emitter has reached equilibrium.

Yes there are three (3) baseboard - an 8', a 6' and a 4'
On Jan 30th I put the strap on thermometers right at the beginning of the first radiator and the other at the end of the last radiator and the delta T for the zone was +15 degrees (ie; supply side is 15 degrees hotter than return side. Things have changed since then.
I just drove 50 miles to Rhinelander to get the strap on thermometers and they don't carry them any more so I ordered them online. Should have them next week.

I just went down and looked at the boiler and it seemed pretty stable with the screen showing 30% firing level, System temp 165, outlet temp 177, outdoor temp 10, inlet temp 171, outlet temp 178, delta T 6, and Flue temp 184.
The thermometers on the secondary read 153 supply and 136 return. This was with 2 zones calling for heat and one of them was zone 3.

Presently, another zone started calling and the boiler fired up to 100% system temp 157, outlet temp 171, outdoor still 10, inlet temp 146, outlet temp 169, delta T 23, Flue Temp 184.
Secondary Thermometers read 152 supply and 132 return.

The zone 3 pump indicates 6 watts and 1 gal/min and the zone 6 (largest zone) pump indicates 14 watts and 2 gal/min.

When the 4 new strap-on thermometers arrive I will put them on the radiators in zone 3 and another zone and report the emitter deltas.

Would it be useful to hang a simple bulb thermometer above the emitter to get some measure of how much heat it is giving off?

Tom_133

Has anyone looked back at his piping on the first page? It looks like he tied the outlets of the separator together and has random returns dumping in the supply header? Am I seeing that wrong?

Gordy

Yes the supply side of the separator is clean as far as supply, and returns direct to the separator.

I do wonder about the loop to loop pipe in image 921 with the valve off on the left. What is that tying together?

Gordy

EBEBRATT-Ed

Are you running lower water temperatures now than you used to? Have the control settings been changed?

ntonkin

Gordy said:

Yes the supply side of the separator is clean as far as supply, and returns direct to the separator.

I do wonder about the loop to loop pipe in image 921 with the valve off on the left. What is that tying together?

That is a cross-over apparatus whereby I can change the below slab heating pipes to be heated by a wood stove with a water heating unit. When operating with only the wood stove, a separate pump is used for the floor only. The room also has baseboard radiators which are only connected to the boiler's zone 1. The past few years I haven't been burning wood so I've been heating both the slab and radiators with the boiler. It actually works very well.

SuperJ

I think there is problem beyond just balancing still...

It seems to me there is some obstruction in the hydro separator preventing the expected flow and mixing from occurring. (seems to be a bit of a barrier between primary and secondary). The primary shouldn't be running that much hotter than the secondary side without seeing a lower inlet temp. Perhaps everything ok and the temp readings just aren't that accurate too?

Could you raise the primary pump speed from min to max for one heating cycle? and record your boiler (in/out), secondary (supply(system)/return). The higher pump speed may promote mixing.

ntonkin

EBEBRATT-Ed said:

Are you running lower water temperatures now than you used to? Have the control settings been changed?

Yes, as I remember the old HE- 4 ran above 180 degrees. The Lochinvar was initially set up by a technician who sold Lochinvars and he put the setpoint at 165 degrees. I haven't changed them since.

Gordy

This manifold set feeds?

ntonkin

Gordy said:

This manifold set feeds?

This is the mixing system for the pex in-floor garage heating zone.

ntonkin

SuperJ said:

I think there is problem beyond just balancing still...

It seems to me there is some obstruction in the hydro separator preventing the expected flow and mixing from occurring. (seems to be a bit of a barrier between primary and secondary). The primary shouldn't be running that much hotter than the secondary side without seeing a lower inlet temp. Perhaps everything ok and the temp readings just aren't that accurate too?

Could you raise the primary pump speed from min to max for one heating cycle? and record your boiler (in/out), secondary (supply(system)/return). The higher pump speed may promote mixing.

Boiler firing at 66% primary pump on "high"
inlet temp 170
outlet temp 182
Secondary supply 153
return 113

The garage zone has been calling for a while.

Tom_133

Can I get another pic of the piping from a little further back and a couple different angles. It seems a little wonky but it could be me

ntonkin

Tom_133 said:

Can I get another pic of the piping from a little further back and a couple different angles. It seems a little wonky but it could be me

Gordy

SuperJ said:

I think there is problem beyond just balancing still...

It seems to me there is some obstruction in the hydro separator preventing the expected flow and mixing from occurring. (seems to be a bit of a barrier between primary and secondary). The primary shouldn't be running that much hotter than the secondary side without seeing a lower inlet temp. Perhaps everything ok and the temp readings just aren't that accurate too?

Could you raise the primary pump speed from min to max for one heating cycle? and record your boiler (in/out), secondary (supply(system)/return). The higher pump speed may promote mixing.

In order to gain lower boiler return temps at the sep system side flow must be greater than boiler side.

With the temps he’s seeing on the boiler side the system side is flowing less than boiler side.

Most baseboard charts start at 2 gpm. I doubt he’s seeing that much.

With a 2699 circ and a 20 delta that boiler should be seeing 9.8 gpm.

Gordy

I doubt unless with everything calling the system is seeing that kind of flow.

ntonkin

Gordy:
The two zones with the alpha 2 pumps that indicates flow, I have throttled back to 1 gal/min on zone 3 (smallest) and zone 6 (the largest) is 2 gal/min on AutoAdapt with no throttling back

zone 3 is drawing 6 watts and Zone 6 is drawing 14 watts

I just reduced the "throttle" on zone 3 to allow a flow of 2 gal/min and the wattage draw went up to 7

Gordy

Hence my point......

Gordy

So what’s going on is the boiler pump is screaming flow, and system side is a trickle in comparison by a factor of 3.

Gordy

There is only one possibility where system side temps equal boiler side, and that’s with exact same flows. Everything else has near infinite mix possibilities. Depending in your case which zones, and emitters are calling at a given time all, one, two, etc.
baseboard, radiant etc.

Was the hydro sep always a part of the system with old boiler?

ntonkin

Gordy said:

So what’s going on is the boiler pump is screaming flow, and system side is a trickle in comparison by a factor of 3.

Should I turn the boiler pump speed back to "low"?

Gordy

What’s it on now?

ntonkin

Gordy:
No, the hydro separator was installed along with the Lochinvar.

Gordy

So same system side that worked for 22 years with the old boiler. You replaced with new boiler, and added the hydro sep.

Gordy

So your old system with old boiler was piped direct with no primary secondary piping, and only the zone pumps to circulate the water?