Before we could have the heat pump commissioned the other week we had to make sure the heat pump could control the pumps for the underfloor heating manifolds. As there is one manifold for each floor of the house, each with it’s own pump to drive the warm water through the floors covered by each manifold, you cannot connect lots of pumps to the heat pumps “P1″ terminal, you have to use a relay with sufficient “ways” on it to deal with the number of manifolds and pumps that you have. It is a normal 230V relay, which sits on a base and has a cover to protect it.