I am seeking an answer on a issue I am having with my boiler furnace. The heating unit is about 12 years old and has worked fine until I had a Plumbing and Heating service tech work on it a few years back. It has a cast iron tank, and is natural gas fired.
About 2 to 3 years ago I had a service tech just do a check up on the boiler, well he told me that the system needed drained and fresh water put back in, so me not being to bright about what would happen told him to go ahead and do it. At about mid winter out furnace started to sound like a coffe maker, we have all low profile baseboard heat and 1 inch copper lines. Then we started to get air in the system soon after the the noise started on the boiler. We road it out for the remainder of the heating season and made plans to have the service tech take a look in the spring. His advice was to flush the system again and bleed the air out or put a new boiler in, which he suggested would cure it, he said our boiler is old. So I did the water change again on his instructions. Well the next winter brought more noise from the boiler and air in the lines, bled off air out of the baseboards and boiler, it seemed like all winter that year, the noise was just terrible.
I ended up contacting another service tech about the problem and he took a look at the boiler and explained that it was limed up do to to much fresh water being added. He inspected for leaks and did notice the high preasure releif valve was dripping which could have lead to the lime build up in the tank. He gave me instructions on how to delime the boiler, but was not real clear on some of the instruction. He said use muratic acid 50/50 mix, close the input and out put of the feed lines and drain boiler and fill with mixture of acid. I did do this and what a stinky mess it made. I did rinse the boiler tank several times and then drained the whole system again and refilled with 50/50 of water and automotive grade antifreeze, which I just found out is a " big no no'' for the weil McLain boilers from the manufacture. We got through most of the winter with no noise problems or air in the system, but it started up again at the end of the heating season. I called both tech, and they are eager to just install a new boiler. I would rather delime the unit again, and we are having a water softener installed this week, so we have soft water in the boiler, our water is very nasty anyway, I know this will help the boiler from liming up again. And from what I have learned, the 2 service tech pretty much did everything they could to help it lime up. Below are a list of question I really need answered and help with, going to try this myself again.
1. Should I use muratic acid to clean it, and what ratio should I use?
2. How long should I let the acid sit in the boiler before I dump it?
3. How many times should I rinse the boiler after delime work is done?
4. Should I run just straight water in the system or put in a additive?
5. Will the soft water prevent the lime build up?
The sytem is a sealed closed loop system which when operating right gets no air unless you have a leak in a line I have inspected for leakes several times this year and found none. But if tank is limed up, the deposits will produce bubbles when boiler gets up to temp, just like a pan on the stove boiling, hot spots in other words. My boiler temp is set on 170 degree's.
From other things I have learned that antifreeze in the system mixed with water will walk when it is heated so to speak and cause's foaming at the pump, which in turn will lead to air bubbles later. The auto bleeder is working fine on the boiler. It spips water every now and then with air bubbles in it. I really need some advice from someone.