I would agree, Tech#1 caused the problem by not bleeding the air out after he filled with water.
It doesn't sound like the boiler itself has any problems and they usually do last a long time.
The in line valves open and close according to demand from the thermostat and that sounds like the only thing that was replaced; it is possible they didn't need replacing.
There is a little motor that mechanically opens and closes them and sometimes the spring/mechanism gets full of grime and dust. A blast of compressed air and some lube usually does the trick.
In the end you will have difficulty "proving" Tech #1 messed up but for sure he should have bled after topping up the water.

Thanks so much.

I'm a little confused about your message. Are you saying that the thermostat is the only thing that was NOT replaced? (True.) And that little motors open and close the VALVES?

When Tech #1 failed to bleed the system, what do you suppose happened to cause the 'no heat'? What SHOULD Tech #2 have done instead of replacing valves? (We do have heat now, even before the mixing valve has been replaced. It has a tiny bit of moisture on its exterior. No 'puddle', just if you feel it your finger comes away with a bit of moisture.)

The valve Tech #2 already replaced was the pressure reducing valve. He ordered the mixing valve, and its cost is in the $700. I am going to have to pay the labor charge for them to come back and actually install the mixing valve.

I feel like telling them 1) Tech #1 messed up, 2) I want a refund of $285 for the mixing valve, 3) cancel the instalation of mixing valve, 4) they've lost a customer. I'm afraid that's the best I can hope for.

I think you would be best served to contact the manufacturer of the boiler and get their take on it. Im surprised you dont have a service manual for the unit. The techs on your unit might not be familiar with it, though that is no excuse. If unfamiliar they could get that way right quick these days of the internet. You can do the same.

I spoke with the company owner yesterday -- twice. All I got were apologies: That they didn't call back; that there was dust; that the techs over the years have claimed the furnace filters didn't need relacing. (I bought eight or ten on sale at Home Depot when we moved in seven years ago and there's still one left in the basement!)

It's their claim that Tech #1 did *nothing* wrong, and that the system just failed for some unknown reason after he'd checked it. Once the valves leak, they have to be replaced. It happens. It's happened to one-year-old systems. Blah. Blah. Blah.

Monday they're coming to replace the expensive mixing valve. And, far as I can see, I'm paying them to do the work.

I'd write more, but I'm all sticky from the syrup poured over my head. Time to find a new HVAC company.

Hope it all works out and sorry you're going through this. Hopefully the new hvac outfit will be familiar or at least be "pro" enough to take care of it without playing games. Customer service, competent work is lacking big time these days in all trades. Trades that dont back up their work is a sign of self doubt, imo and shouldn't be in business, but because of the ego factors, they wont admit to being inept at certain projects and are only interested in self monetary gain at the expense of the customer....sad!

I'm a little confused about your message. Are you saying that the thermostat is the only thing that was NOT replaced? (True.) And that little motors open and close the VALVES?

Yes, sorry if it read unclearly. I am saying that from what you initially wrote it sounded like they only replaced some valves.
The valves I am referring to are an inline solenoid valve that gets a demand signal from the thermostat to open or close via "the little motor". Tech#2 didn't replace those, he replaced the feed valve (pressure reducing) which sets the operating pressure for the lines. If there was a leak in the feed valve it could lead to air in the lines which could potentially cause the no heat situation.

When there is significant air in the system the hot water can't flow through the lines and you would get rooms downstream from the point of the "air clog" with no heat.

If the feed valve was leaking then I don't think you can fully fault Tech#1 but why didn't he notice this? I still contend that he should have bled the system if he did add water/antifreeze to it.

Thanks demerara. I certainly agree with you. Tech #1 did what he did and left, saying the boiler is fine. When we need it later...it's not working.

Bottom line is that I'm getting no satisfaction from the company. Just syrup.

I'll let them put in the mixing valve and we'll see who else we can employ. If nothing more goes wrong with the boiler system, it'll be A/C check-up time before we have to find a new company.

I'll ask about the 'feed' valve Monday when they come to install the mixer.