The 3-wire configuration is not typical of a home heating system, but may be appropriate in your case. PLEASE CONFIRM YOUR APPLICATION BEFORE BUYING. RETURNS WILL NOT BE ACCEPTED IF THIS PART DOESN'T FIT YOUR SYSTEM. The part is as-described. Please understand what you are buying!
Each powerhead includes a matching M 3.0x1.5 adapter ring appropriate for the ProRadiant 1-1/4" stainless heating manifolds. Other manifolds may require different adapters.
It is the buyer's responsibility to determine that this part is compatible with their system.
For those interested in DIY or building management information I can provide spec sheets from Viega for this product. Please message me or search on the internet for Viega part #15068.