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Zone that doesn't heat properly
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Outlet temp is 168 degrees
outdoor temp is hooked up
I really don't know about heating curve programing - that's what I pay the heating tech to do. How do I check this?0 -
Chris M put this Excel together to help calculate those blended temperature
It is rare that the boiler and distribution are exactly the same, so blending is happening.
That is important with condensing boilers. Under some flow conditions you may be raising the return to the boiler above condensing temperatures.
This would apply to a 4 port buffer also.
Let me know if this attaches smoothly.Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream
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If your outlet temp at the sep is 168, and the inlet to the base board is 145. You are losing 23 degrees before it even gets to the baseboard.ntonkin said:Outlet temp is 168 degrees
outdoor temp is hooked up
I really don't know about heating curve programing - that's what I pay the heating tech to do. How do I check this?
Right now your average water temp through the baseboard in question is only 130 degrees. 145-115=30/2=15+115=130. Not much output at those temps.mwhat type of baseboard. The manufacturers post outputs at different awt.
What’s the return temp at the sep?
What’s the boiler side temps?
@hot rod_7 posted some material that shows how mixing occurs inside the separator. Very important.
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Ideally a modcon should have a system supply sensor on the secondary outlet side of the hydraulic separator so it can compensate for when the secondary flow exceeds the primary flow. If the sensor exists it should be confirmed the boiler is actually setup to control off that sensor (many boiler will control off boiler leaving temperature unless told otherwise).
A good modcon can compensate (keep secondary supply at ODR setpoint) for unbalanced flow until it reaches it's max temp delta (often around 40degF), or max discharge water temp (maybe around 180F depending on the venting material).
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^ yes if one is installed which I do not see in the pic with the hydro sep.
Here is a link to the manual also if you don’t have it. Well worth getting fluent with.
https://s3.amazonaws.com/s3.supplyhouse.com/product_files/KBN106-install.pdf0 -
I second this... far too many really high quality boilers are stuck with mediocre performance because they are missing a relatively cheap and easy to install sensor.Gordy said:
^ yes if one is installed which I do not see in the pic with the hydro sep.
Here is a link to the manual also if you don’t have it. Well worth getting fluent with.
https://s3.amazonaws.com/s3.supplyhouse.com/product_files/KBN106-install.pdf2 -
- A thought to consider? The Back-flow preventer that you installed, is it a reduced pressure zone device (RPZ) ?
- If it is a RPZ it can drop pressure significantly. As much as 7+psi.
- And is the back-flow preventer rated for high temperatures? If not, and is rated for cold temps. it might have deteriorated internally and is causing a pressure drop greater than the other checks combined ***with*** the back-flow preventer.
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there is a sensor on the Califi but it's centered between the supply connections on the separator. You can see it in the pictures I've posted above. It is connected to the boiler per directions specified.0
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I can't find or remember where I bought the backflow preventer but it is just a simple brass fitting with a flap inside that is suspended from the top and it only swings one way - - the other way and the flap closes off the pipe. It has an access cap on top with a gasket (the only non-brass part).0
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That location is no good. It needs to be on the system supply pipe, and we’ll insulated.ntonkin said:there is a sensor on the Califi but it's centered between the supply connections on the separator. You can see it in the pictures I've posted above. It is connected to the boiler per directions specified.
Where it is now it’s just picking up a random mixed temperature with in the hydro sep.
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As I remember, the boiler came with the sensor which fit right into the plugged threaded hole in the Califfi hydro separator. It was the only place on the separator to install the sensor. It's centered between the inlet (from the boiler) and the outlet side to the secondary. These are the two top connections. I have both the installation & operation manual you referenced and the service manual as well. I installed the system myself and then hired the plumbing/heating dealer (from whom I bought the boiler) to inspect the installation and do the start-up & set-up. The guy is no longer in business so it's possible he had some competence issues. Maybe that's part of my problem here. Guess I'll have to study this procedure and get "fluent" with it.... so I know what I'm doing. There really aren't any Lachinvar Knight dealers in this area and the plumbing/heating business I've been dealing with of late is starting to work with Lochinvar products but I don't think his guys are Lochinvar certified as yet.0
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Yeah that port isn’t for a supply sensor. The supply sensor needs a good reading on the system supply pipe. Either a well, or strapped to the pipe with conductive paste, and pipe insulation.0
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The return temp at Sep is 123
outlet at Sep is 140
boiler inlet 153
boiler out 173
System 165
The first two temps I measured with spring contact thermometers the last three I read off the boiler screen
the boiler inlet and outlet goes up to 165 and 180 when firing0 -
Looking at the numbers shows that the boiler side flow is more than the system side flow.ntonkin said:The return temp at Sep is 123
outlet at Sep is 140
boiler inlet 153
boiler out 173
System 165
The first two temps I measured with spring contact thermometers the last three I read off the boiler screen
the boiler inlet and outlet goes up to 165 and 180 when firing
Especially considering where the supply sensor is located.
The system temp which I assume to be the one in the hydro sep is more than the system supply out
Your AWT In the system is still only 130 ish. Verified by your temp readings from the baseboard in the problem room.
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How can all the other zones in the system be operating normally?0
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Well if you go around to all your zones and check the temps going in and out of the baseboards they must be close to the same as the supply, and return temp of the one in question.
Which could mean the zones that are fine may have more baseboard than needed for the heat loss in the room, and the one that’s a problem doesn’t.
Maybe before with the old boiler you were running higher temps so it was never noticed as being smaller than the others, and it satisfied the zone with the higher output due to higher water temps.
Now you have a mod/con with outdoor reset, and was the hydraulic separator always there, or was it installed with the KB installation?
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This is your shortest zone. Can it be the path of least resistance as to why this one is the only one noticeably affected?0
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Is that baseboard that’s a problem the only one in that zone or is there other baseboards for other rooms, and this one is at the end of the run getting cooler water temps.
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Intplm,
The bfp has NL on the outlet end and 200 WOG in the middle of the valve and a symbol of a house on the other side. It has a large screw cap on the top and a small plug in the side with the house symbol.0 -
In the end the reading ps don’t lie anymore than the instrument used to take the measurements.
You are sending 145 out to the zones, and getting 115 back. Yet the boiler side is sending 180 to the hydro sep, and getting 165 back.
This says that the boiler side pump is moving water faster than your system side pumps. If the flows were equal you would be sending 180 out through the system, and getting much higher back.
If the boiler side was flowing less than the system side you would be getting warmer than 145 out to the system, but not 180, and colder return temps back to the boiler than 165.
As it is there is some mixing out to the system in the hydro sep, but most of the hotter water is going back to the boiler for another lap.1 -
Just so you understand, a hydraulic separator works. It allows the system flow to be different than the boiler flow with out interference of each other. So as the flows change some mixing occurs in the separator when flows are different between the system side, and the boiler side.0
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@ntonkin
I had this happen to me on a short zone on a commercial system that was steam. Not hot water as yours is.
After many ,many call backs I found A obstruction feeding a short single zoned radiator.
I think you just might have the same problem.
The million dollar question is where is it obstructed on that zone?
Or, what is sending the cooler water temp to that zone so that it doesn't heat?
Is it the hydraulic separator passing return water to the supply?
Is the check valve(s) you have installed inter-fearing?
The bfp is really just a glorified check valve. Is more than one check installed on that zone causing A obstruction?
And in one of your pictures, the upper left corner shows a bypass installed. What is that bypass used for?
Lastly, Do you have a bad ball valve. rarely the case for a bad ball valve but I have had them fail. (Thank heaven not as much as gate valves that can pass water when you believe they are closed.)
Some of what I am thinking is far fetched to some. But when a problem like this shows up I feel that they should be considered.
I would hate to see you rip it all out just to have the problem still be there after all that work.
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Here is the square feet of heated space per linear foot of radiator.
Zone sq. ft. Total Radiator length # radiators sq. ft./ ft. of radiators
1 465 16’ + floor 2 29.1
2 475 22’ 2 21.6
3 366 17’ 3 21.5
4 417 15’ 3 27.8
5 840 in floor N/A garage
6 668 38’ 8 17.6
As you can see, zone 3 has about average amount of space per linear foot of radiator for the house. When I took the temperatures for zone 3, I put one thermometer just before the pipe entered the first radiator in the zone and the second thermometer just after the last radiator in the zone.
I've just ordered a couple of the grundfos alpha2 pumps and when they get here I'm going to slap one into zone 3 and see what the flow is.... I understand you can view the flow rate in the LED display on the pump.
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While those numbers are good to see. What I don’t know is if zone three has the same heat loss as the zones that are working with the similar amount of square feet to linear feet of baseboard ratio.
For all I know zone three is all glass with twice the heatloss of any of the other zones.
What I can tell you is that 16’ of baseboard with 130 awt is putting out a little over 5200 btus. Is the room in questions heat loss at the outdoor temperature less than that? From my end I have no idea.
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A couple of good primers on how hydraulic separators work.
https://www.youtube.com/watch?v=qTm2Y6h-aH8
https://www.caleffi.com/sites/default/files/file/hydraulicseparation-tr07.pdf0 -
Gordy,
If you are referring to zone 3's position on the manifold, it is third from the right in the picture. Just to the left of the zone with no pump. Zone 3 has 3 radiators along the outside wall of the kitchen/dining room.0 -
Somethings not right with either the numbers or the separator.
If the boiler entering temp is greater than the return temp then the boiler flow is greater the secondary flow. If the boiler/primary flow is greater, then, the secondary supply temp will equal the boiler supply temp.
In this case boiler rwt is > than system return (implying higher primary flow). But secondary supply is < boiler supply implying great secondary flow.
I wonder if the mesh inside the separator is clogged with something which is allowing both the primary and secondary to recirc up/down their respective sides instead of flowing across horizontally like they should.
Here are the three options (what appears to be happening should not be possible which is a mix of 2 and 3 below):
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Zone 3 (366 sq. ft.) has a 6' sliding patio door and a 32" x 40" garden window and the two rooms are 29' x 14' the one outside wall is R-16 and facing south. The ceiling is R-40 under two roofs.
Zone 2 (475 sq. ft.) has a 6' sliding patio door, a 7' bay window and two 32" x 38" crank-out windows. Zone 2 has three outside walls insulated to R-26, the floor insulated to R-20 and the ceiling is R-50 also under two roofs.
Both of these zones have heated space below them.0 -
Actually mixing in the sep occurs when system side is greater than, and less than boiler flow rates depending on flow which we don't know for sure either. Around 9 gpm by the delta on the boiler side WAG.0
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Intplm,
I installed the bfp last fall as I thought I had heat moving the wrong way as the zone 3 return was hotter than the supply. Now I'm thinking this might have been heat transference as I was measuring a couple feet from where it joined the other return lines. I've had the problem for 5 years and have been working on various things to cure which I think have helped slightly. The "bypass" you see is my under-slab floor heat in zone 1 whereby I can heat the floor with either my woodstove or with the boiler. Right now I have it set up to go under the slab first and then through the radiators.
I guess a bad ball valve is possible. I am aware that one should exercise ball valves periodically and I've made an effort to do that at least annually. I have ordered a couple of the grundfos alpha2 pumps which should be here next week. I'm going to put one in zone 3 and see how much flow is going on.0 -
Do you think it would help to put the boiler pump on "low" speed?0
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I've only got two of those contact thermometers so it will take a while to measure all the zones. The separator was installed with the new boiler in 2013.Gordy said:Well if you go around to all your zones and check the temps going in and out of the baseboards they must be close to the same as the supply, and return temp of the one in question.
Which could mean the zones that are fine may have more baseboard than needed for the heat loss in the room, and the one that’s a problem doesn’t.
Maybe before with the old boiler you were running higher temps so it was never noticed as being smaller than the others, and it satisfied the zone with the higher output due to higher water temps.
Now you have a mod/con with outdoor reset, and was the hydraulic separator always there, or was it installed with the KB installation?
The reason it took so long to figure this zone wasn't heating properly is that we used to heat primarily with wood and zone 3 has a wood stove at one end as well as one right below in the basement. I'm over 70 now and the wood heating has tapered off.0 -
Does it go on the primary supply side or the secondary supply side?Gordy said:Yeah that port isn’t for a supply sensor. The supply sensor needs a good reading on the system supply pipe. Either a well, or strapped to the pipe with conductive paste, and pipe insulation.
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From the manual:
It goes on the secondary supply.
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Once you move your sensor you may notice the boiler supply is above setpoint, but the system/secondary supply should stay pretty close to setpoint. Make sure you get as good of connection as possible to the pipe and that you wrap it with some insulation. A bit of thermal paste can help with conductivity between the copper pipe and temp sensor.0
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