Pressure

The furnace guy came out this morning, and it’s “all better” again. Here’s the scoop:

Our furnace is an old-old-old school “tankless” system with a low pressure “zone” for the hot water. The water is heated by going through a pipe which is in a fire, and is then routed directly to the house heating radiators and the showers and stuff. As I now understand, there are three components to the system that matter to the problem I was having:

Water comes in from the house system. It comes through the pressure reducer, which looks like this:

This piece is adjustable based on how much pressure you want in the system that it’s protecting. Fundamentally, this piece controls the pressure in the rest of the system. In our case, that piece needs to be set to allow about 15psi in the low pressure zone. Immediately after that, there is the blow-off valve. It looks something like this, except that there’s an additional pass through on the left side:

The blow-off valve drains if the pressure hits some level. So, you set the pressure reducer to, say, 15psi, and the blow off to, say, 30psi, and all is well with the world.

The third component is a “bladder tank”, which is a little tank that contains a rubber bladder which expands and contracts … acting as a capacitor for pressure in the system. It smooths out the rough edges, and allows for thermal expansion in the system (i.e: You load up the pipes with cold water and then heat it).

Problem 1: Our pressure regulator had crapped out. It was letting too much pressure through the system. The blow-off drain was doing its job. I perceived that as a leak, and called the plumbers. They replaced the blow-off and the pressure reducer, stopping the leak, and called it a day.

Problem 2: We turned the furnace back on, and as it came up to temperature, the bladder tank gave up the ghost. So now we’ve got water expanding in the pipes with nowhere for it to go. So, a pipe elsewhere in the house decided to pop a leak (it had been rubbing against the foundation for many years.

The furnace guy replaced the tank and adjusted the pressure regulator valve to make the “zone” a little bit lower pressure. He didn’t charge me a goddamn dime, since we’ve got the “ultra-premium-deluxe” service package with them.

Wow, I really didn’t want to learn that shit today, but it’s substantially cheaper than a new furnace.