Q: I have a Kromschröder pressure switch, model DG 6U-3, which I do not find on your website. Can you quote this model? Do you have any stock available?
A: Certain product families, like the VAS, DG, and IFS, are segregated into two branches: T-Product and European Standard. T-Product models are manufactured with the North American Market in mind, and in many cases carry approvals which are not required worldwide, but which are desirable for insurance purposes and NFPA® 86 code compliance in the USA and Canada. Other considerations apply as well, including piping connections in NPT and ANSI (instead of RP and ISO), and flame safety times greater than one second.
Because the T-Product versions are those most often specified for new installations in the USA, and because these are the versions most-requested by our customers, these are the versions we typically stock. That’s why you see DG 6T listed on our website, but not DG 6U-3, which is the European Standard equivalent. We can certainly order European Standard models from the manufacturer in Germany, though the lead times can be prohibitive. In many cases, the European Standard version can be replaced with a T-Product version almost seamlessly.
Listed here are the two models, along with their descriptions:
DG 6T DG pressure switch for gas and air, for positive, negative, and differential pressure, adjusting range 0.2 – 2.4 “w.c. (0.5 – 6 mbar), electrical connection via screw terminals, with 110 V control lamp, FM and UL approved
DG 6U-3 DG pressure switch for gas and air, for positive, negative, and differential pressure, adjusting range 0.5 – 6 mbar, electrical connection via screw terminals, EC type tested and certified
From these descriptions, the only notable differences are the approvals and the addition of a 110 V control lamp on the T-Product version. The control lamp voltage is important to note, because DG pressure switches may be powered with 100-230 VAC; a special model is required for low voltages (gold plated contacts are needed), but otherwise the only voltage restriction resides in the lamp. If you are replacing a DG 6U-3 with a DG 6T, and you use 230VAC to power the switch, the 110V lamp will fail in a short amount of time. This shouldn’t be much of an issue though, as the DG 6U-3 doesn’t ship with a lamp included, so you wouldn’t have been using one previously.
The other difference is in the threading of the connection(s). The European Standard pressure switches have DN 6 RP thread connections, approximately ¼”. The T-Product versions have ¼” NPT connections. Due to the differences between these thread types, it is typically not recommended that they be mixed – a DN 25 (approx. 1” RP) pipe nipple does not create a reliable seal when threaded into a 1” NPT connection. However, the difference between ¼” NPT and DN 6 is slight enough that an RP pipe nipple threaded into the ¼” NPT connection on a DG 6T should tighten against leaks. Our experience is that customers who purchase a T-Product switch as a replacement for a European Standard model have not had a problem.
Please keep in mind that Kromschröder pressure switches are often better-than-suitable replacements for existing switches in combustible gas and air installations. Our customer service team can assist you in crossing over to Kromschröder – all they need is the complete manufacturer’s part number and description from your current pressure switch, and the set point you are using.
There are dozens of manufacturers providing the industry with components for combustion systems, and everybody does things differently. Please don’t hesitate to email questions that arise as a result of, or due to confusion regarding a pending, Kromschröder purchase to email@example.com.