Lochinvar Noble new install questions: system supply sensor, circulator pump, and general feedback
Comments
-
As feared and expected, I met with one of the company's master plumbers. He doesn't think the lack of service/isolation valves is a problem and also doesn't think the distance between the Ts matters, so they're refusing to do anything about it. I don't really see what else I can do other than try to find a plumber who knows better. I certainly won't be using this company for annual maintenance.
Thanks all for the info!
Edit: the best part was when I started asking about increasing the length of cycles, maximizing efficiency, etc. his response was something to the effect of "well then you get into all these complicated questions about heat loss and boiler sizing. We don't do that". Finally - an honest answer!
1 -
It depends on the boiler. My Lochinvar Knight maintains a ∆ with it's variable speed circ. The boiler controls that circulator. I'm not sure if that is adjustable however.
With a Nobel combi you would size the pump to the flow needed to give you the 30∆. It may require a balance valve to dial it in exactly. The Lochinvar 110 Combi would want 6.7 gpm flow to get the 35∆.
Lochinvar shows up to a 45∆?
Then on the "B" side of the separator that circulator is sized and or balanced to get the desired 10 or 15∆ through the distribution loop.
That is the main intent of hydraulic separators, maintaining different flow requirements. Intended to assure coil type mod cons get the required minimum flow, regardless of the distribution side needs.
The ∆ on the system side will vary with a fixed speed circ, based on the load at any given time. You pick a number to design to, but it may never run at exactly that ∆. Remember always, the load will dictate the operating condition of the boiler, separator, etc. Unless you put a control in place to limit the operating conditions to a safe condition. Limit switches, return mixing valves, etc.
Some suggest a fixed delta T circ on the distribution. If the loops are flowing .5 gpm, you can only slow to flow so much. At some point your flow goes transitional, then laminar and heat transfer plunges, unable to keep up with a small load. The graph shows the rapid drop of in heat transfer below .5 gpm in a 1/2" pex loop.
I believe there is a bottom end on ∆T circs so you may not maintain a fixed ∆ anyways?
The flow calculator at PPI is a good tool for looking at flow rates.
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream0 -
What I said is the couple of extra elbows and length in the OP's PS loop is not an issue. I would not call what he has an install error.
They did a pretty decent job with the DHW pipes in the way.
1 -
If there were a textbook example it might look like this. Outside of this, it may not work exactly as designed.
It depends!
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream0 -
@hot_rod surely you're not suggesting that somebody install a balancing valve in the boiler loop of a combi in order to raise the delta through the HX? They're built to maintain a constant flow rate and that delta listed in the manual is merely what's expected at a given BTU output. Cutting the flow to maintain a large delta isn't going to sit well with any manufacturer- that's why they come with an onboard fixed speed circulator.
0 -
I know what you said, and it's false. Hydraulic separation is extremely important (hence why the manufacturer requires it), and the way it's piped is absolutely not hydraulically separated. If there were ever a warranty claim on the boiler, it'd be denied because it's piped wrong. Also, the DHW pipes are only in the way because they put them in the way. This is very easily done correctly.
0 -
thanks for Brad’s info. I’ll put it to use.
0 -
cutting the flow to maintain a desired delta is exactly what the variable speed circulators that come with the Knights do! The control watches the delta and adjust the flow rate via the speed.
Or you could state it as at a 6.7 gpm flow, the pressure drop will be 17’ and the delta will be 30 degrees.
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream0 -
We're not talking about a variable speed circ in a Knight. We're talking about the fixed speed circ in this Noble. I asked how you would propose to raise the delta through the boiler to 30* in this scenario with a 5-10* load delta (since you suggested it was an option) and you said you'd add a balancing valve. Is that correct?
0 -
Quick RTFM and looks like the noble just turns the pump on/off. For any sane person, best is to leave it as is. It also means that is not much to be gained by adjust the secondary flow rate.
For me, I would set the max fire rate to about match the max heat load of the place, turn on all zones and adjust primary loop flow rate (flow setter on primary loop) to get the delt T I would want on the boiler. From there adjust the secondary loop to about match it, can be done even with a fixed speed circ by throttling it.
1 -
I am going to leave as is. But I’m just curious…
@Kaos what did you mean when you wrote “flow setter on primary loop”? How would you adjust primary loop flow rate if the primary pump rate is fixed?0 -
I believe I suggested with a hydraulic separator you can run two different flow rates and two different deltas. The is what hydraulic separation is.I I would flow 6.7 gpm across the boiler to obtain the 30 delta. As the manufacture gives you that data.
On the B side, the load side I size that pump to obtain the delta I desire.
Is you want a set or specific flow rate through any device, boiler or water heater, heat emitters, radiant manifolds, buy the exact pump , a one in a thousand chance of that, or add a balance valve if you want exact flow regulation control.
With multiple speed circs you can get close and some boiler specs tell you the pump model and speed setting to get the flow they suggest.
With the avail of variable speed, delta circs, you can keep the distribution side flow rate accurate as zones open and close. A delta P or T circ can do that for you. A variable speed circ is kinda a balance valve and a pump in one package.
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream1 -
So for the third time, how do you propose to establish a 30* delta through a Lochinvar Noble combi boiler (or any combi, for that matter) with a fixed speed onboard circ while the load has a 5-10* delta?
0 -
for the last time, the manufacturer is giving you the answer to the boiler side sizing.
You the designer calculate the distribution sizing. Lochinvar has no idea what you are connecting the boiler to.As you yourself have mentioned various times, the separation as the installation manuals show you various options, some manufacturers actually supply the separators already attached to the boiler. the key to a successful installation.
Idronics 15 explained more about hydraulic separation concepts
If your boiler wants to know the blended temperature to the system to accurate adjust it, the system sensor should be used downstream of the sep.
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream0 -
As @hot_rod said, with PS piping you can have different flow rate thus different delta in each loop.
So lets take a stab at some numbers for the OP. I would guess the building load is about 20k, so 10% max fire. Lets start with 10F delta, so you need about 4GPM through the pump. Above the min flow rate, good there and the fixed speed can be throttled down to that.
Emitters would need to deliver similar heat with 180F supply but say we want 5F delta. So secondary loop would run at 8GPM.
So to make the 180F water at 8GPM, the boiler would have to supply 185F at 4GPM, this mixes with 175F secondary return water at 4GPM. The boiler would see a return of 175F water at 4GPM. All flows and BTU/h are balanced and the system is happily running with different deltas.
@kidfresh63 A flow setter is simply a fancy valve. You essentially restrict the pump output.
0 -
@GroundUp so what are the consequences of insufficient hydraulic separation due to my distantly spaced tees? It seems based on videos and reading I've done that it might unnecessarily lower the GPM flow rate on the secondary loop, is that right? And an install out-of-spec could void my warranty, right? What else am I missing?
I seem to be able to find plenty of resources I've shared with my contractor about how they should have done it, but as you can imagine…so far they shrug their shoulders and say "we always do it like this, don’t you worry your pretty little head you homeowner. Our master plumber says it’s a-ok!”.
0 -
That has nothing to do with what I asked. You said that you can get a 30* delta through this Noble combi while the system only has a 5-10* delta. I am asking you how you would propose accomplishing that feat.
0 -
The consequence is insufficient flow through the heat exchanger when the smallest zone(s) is/are calling alone. There is really no set-in-stone designation, so I don't know what you're referring to as the secondary loop. Either way, Lochinvar will absolutely deny any warranty claim on the heat exchanger due to improper piping. They're pretty lax about most things, but flow is one thing that is not negotiable.
1 -
@psb75 thanks for sharing Brad’s info. I got him involved and that seems to have lit a fire. They are now coming back to redo the closely spaced tees.
0 -
I noticed that you live in a city with a Lochinvar rep. Many others are not so lucky.
1
Categories
- All Categories
- 86.7K THE MAIN WALL
- 3.1K A-C, Heat Pumps & Refrigeration
- 56 Biomass
- 423 Carbon Monoxide Awareness
- 104 Chimneys & Flues
- 2K Domestic Hot Water
- 5.6K Gas Heating
- 103 Geothermal
- 158 Indoor-Air Quality
- 3.5K Oil Heating
- 68 Pipe Deterioration
- 938 Plumbing
- 6.2K Radiant Heating
- 385 Solar
- 15.3K Strictly Steam
- 3.4K Thermostats and Controls
- 54 Water Quality
- 43 Industry Classes
- 47 Job Opportunities
- 18 Recall Announcements