Bosch Greenstar Combi 151p Boiler not heating and no pressure

guidoism

Our hot water heater / boiler stopped working recently. I'm not actually sure when it stopped working since we are not living there due to a renovation. The water heater is new, it's a Bosch Greenstar Combi 151p Boiler set up to provide hot water and to also provide supplemental heat to the heat pump's air handler.

I've read all of the documentation I can find and have narrowed the (or at least the first) problem down to there being zero pressure in the dial as pictured below.



I cannot for the life of me figure out how to re-pressurize the system. The documentation mentions this but doesn't describe the process. This is what the bottom of the unit looks like, looking up:



The five pipes from left to right are: 1. Supply, 2. DHW, 3. Gas, 4. Cold water, 5. Heating return.

I would like to learn how the system works to be able to troubleshoot and fix this myself. I understand that supply is the cold water coming in. DHW is the hot water going out to the fixtures. Gas is the fuel. I don't know what cold water is for and I would think that heating return is the hot water that was used for heating comes back to be re-heated.

So, any thoughts?

How do I re-pressurize this system?

And while I'm here, what are the two pipes on the right for (cold and heating return)?

kcopp

A picture from further back would help us ID the fill valve. Its not on the boiler itself.

Ironman

Being renovated?

Did someone shut a valve or line that supplies water to the boiler?

psb75

DId you want some help from this forum? It works best if you respond. It could be something very simple. But it requires a modicum of exchange.