To determine the correct differential pressure set point for your hydronic system, the answer is "It depends". There is usually a lot of confusion regarding the correct value to use.
Here are a few of the factors that determine the set point and sensor location:
For simplicity sake, let's...
I typically recommend using TEFC motors whenever the equipment is in a new construction area simply because ODP motors can suck up a lot of dirt. A lot of times the equipment is run several months before final completion. During those times the mechanical room is typically very dirty. An ODP...
BronYrAur,
I'm sorry that I am just getting back to you regarding your chilled water system. It sounds like you are seeing the same thing that we see a lot. The building side is operating at a low Delta T. Until that gets addressed, the plant will always run at a low Delta T. The poor...
Hi BronYrAur,
I run into this a lot but a few questions first:
1.) What is the original design Chilled water temperature for you chilled water plant? 45F? Is your system for comfort cooling primarily or is it an industrial process (as suggested above)?
2.) I'm guessing that you have a...
You cannot solve Low Delta T in the chiller plant. You can add VFD's on your secondary (distribution) pumps but if not properly controlled you will still have Low Delta T. I have seen a lot of systems that add VFD's to all the chilled water pumps and still have Low Delta T issues.
All Low Delta...
Hi stevenKm,
(1)From your picture it appears that you may have a 1/3-2/3 control valve arrangement so that the small valve is modulating open until it cannot satisfy the load and then the larger valve starts to open. When the larger valve starts to open, the smaller valve may modulate shut (or...
capaula,
To me, running additional chiller(s) to accommodate the additional 4100 GPM being bypassed qualifies as wasteful and inefficient. You not only have to to run the additional chiller(s), but you have to run the additional chiller pump(s), additional condenser water pump(s), and probably...
capaula,
If you can believe your flow meters and temperature sensors, you are bypassing almost 4100 GPM of nice cold chilled water you just made and are dumping it into the return line, warming it up.
In order to maintain the setpoint you need, you need to chill that mixed chilled water...
Capaula,
Don't fly those guys in just yet. Your piping diagram indicates a typical primary secondary chilled water system. Is this process cooling? Why are you running such low chilled water supply temps (39F)? Are your coils designed for 39F or do you have to run so low to maintain discharge...
Capaula,
It is not unusual for multiple chillers piped in primary secondary configuration to be unable to fully load. The reason is that the primary loop flow rate and secondary loop flow rate are very seldom if ever the same. This is because the primary pumps are typically constant speed and...
If the valve is old (I'm guessing it is because very few new installations use 3 way control valves on large chilled water coils) you may consider replacing it with a 2 way pressure independent modulating control valve. These valves are rated for bubble tight shutoff at large pressure...
MarauderX,
In almost 30 years of dealing with primary-secondary I have never experienced a case where the primary pumps force flow into the secondary. However,I can see that happening if the bridge piping is undersized. I hope this helps.
rskrumha
FYI
We have just recently worked on a chilled water system that is approximately half the size of the one you are working on and the addition of pressure independent control valves saves approximately $140,000/year (we used $.07/KwH for electricity). This equals about a 2 year...
rskrumha,
Accurate system flow control will be the key to your success. A little more information is required:
1.) Are the chillers variable speed?
2.) What is the total tonnage of the chiller plant?
3.) What will be the total number of chillers installed?
4.) What will be the total number of...
