More pressure

I learned more about my furnace today.

I’ve been keeping an eye on the boiler, since it started exhibiting these odd and plumber-requiring behaviors. The furnace tech told me that the pressure gauge on the front should stay between 10 and 20 psi. This morning, it was topping out above 30, so I called the furnace place again.

My understanding in the previous post was not strictly accurate. There are two subsystems: One for heating, and one for hot water.

The low pressure “zone” that I talked about yesterday serves the baseboard radiators. The low pressure water sits primarily in a “boiler” above the fire. That boiler is controlled by a thermostat in the furnace. The *house* thermostat actually controls a pump that circulates water from the boiler through the radiators. Between the two of them, hot water circulates through the house, or not.

There is a totally distinct system for the “house” hot water. This is the “tankless coil.” Water from the street comes to an input on the side of the furnace. This input leads to a series of S-curved pipes, which are *inside* the boiler. The boiler is heated by the flames … and the hot water pipe is heated because it’s submerged in the boiler.

Today’s furnace tech was an experimentalist with clear explanations. I liked him. He installed a shutoff valve on either side of the tankless heater, as well as a spigot to which he could attach a pressure gauge, between the cutoffs. He then sealed off the input to the low pressure system and drained it down to about 10psi.

He opened the supply from the street, and closed off the output to the rest of the house. The pressure gauge shot up to about 60 psi. He then closed off the supply and waited. If the system was intact, then the tankless coil, sealed on both ends, should hold pressure. Instead, it slowly and steadily dropped. There was a corresponding small but noticeable rise in pressure in the boiler. He explained that there was most likely a pinhole leak in the tankless coil. Water was moving from one system to the other, inside the boiler.

Now I get it. I love it when we can use an experiment to understand the world.

Here’s the really fun part: My hot water system went from being automatic to being manual transmission today. The leak is slow, so we can run things for a few hours at a time without risk … provided that we know what we’re doing. So, when we decide to take showers and run laundry we go down and open up the supply to the tankless system. We do what we do, and then we close it off again, kill the supply to the low pressure system, and drain off the excess pressure that has developed.

Wheeeeee.

The possible solutions all suck:

* Buy a new tankless insert for the boiler. Perhaps $700 for the parts, plus installation. This leaves us with a patched, ancient hot water system still fed by oil.

* Buy an electric water heater (tanked or tankless) ~= $700 plus installation (which may be free … depending). Electricity is the most expensive way to heat water, and this would send our power bills through the roof. However, electricity is also the power source most likely to become locally available if wind or solar power catch on. I.e: It’s the most likely of the three options to become “free”.

* Buy a gas water heater. Installation most likely included in the $200 price tag. However, we would also need to get the gas company to hook us up to the gas that’s already in the street. Previously, they quoted around $500 for this … but there’s digging and poking through the foundation involved in this solution. I think that installing gas to the house would add value – not a bad idea since we’re still going to sell in the near future.

A solar pre-heating tank would be a nice addition to any of these solutions … but I’m already reeling from the unexpected multi-thousand dollar plumbing fiasco which is my home this week.

Did I mention that we’re moving at the end of the summer? *sigh*