CDU capacity at site conditions
A CDU rated at a 5 K approach, installed on a site running 24 K, is not the CDU you bought.
What runs out
Heat rejected from the technology cooling loop to facility water, at the approach temperature the site actually offers.
The relation that governs it
Usable duty falls as the approach between facility water and the platform's maximum inlet temperature widens. A unit quoted at a 5 K approach delivers materially less at the 20–25 K approach a legacy 6 °C loop presents.
Worked example
What approach does a 6 °C loop offer a platform accepting 45 °C?
45 °C − 6 °C
39 K approach
A unit selected at a 5 K approach is being asked to work at four to five times that.
Reproducible by hand. A page that asks you to trust a number has taught you nothing.
How to tell whether it binds in your hall
Take your facility water supply temperature and your platform's maximum technology-loop inlet temperature. The difference is your available approach. Ask for the selection output at THAT approach — not the datasheet figure.
What relieves it
Additional CDU capacity, or raising the facility water temperature so the approach widens in your favour.
What that relief costs beyond money
A linear derate against approach is a screening approximation. Confirm against the manufacturer's performance curve before committing capital. Technology-loop water chemistry is a warranty question before it is a capacity question.
Indicative relief lead time
16–40 weeks
European retrofits. The schedule, not the capex, usually decides.
How we currently price this relief
E0
A placeholder with a −50%/+100% band, not a price. It is replaced by a quotation the first time we tender this relief on a real project.
The mistake we actually see
The single most common way a liquid retrofit under-delivers: rated duty taken from a datasheet at a reference condition the site does not have.
Basis
- — OCP Water-Based Transfer Fluids Guidelines; manufacturer performance data at stated approach.
These usually travel together
Does this one bind in your hall?
Seven numbers you already know, all thirteen constraints evaluated, and the one that stops you first named with its basis in engineering units. Free.