Best Of

kinda hard to do this from connecticut, without being there and touching,

my bet is on the middle(upper) red circ, which I believe is your primary circ getting heat to your zoning, either electrical or mechanical(seized/stuck), can't tell, or it could be air bound, as was mentioned earlier,

was the system noisy when it worked last? could you hear the water flowing last winter?

and what Homer says, these boilers like to be massaged every year or 2, but it's heating the domestic so hold off there, I do see your pressure up around 30, that's too high, 12-15 is a target, so once you re establish flow, follow up on the expansion tank and pressure,

not correct pump. Still may not be problem.

Weil McLain CGa is the simplest offering the Weil McLain offers today. It is basically the same 76% efficient CG boiler they introduced in the 1960s with a few tweaks to make it more efficient. To get to the minimum 80% AFUE they added electronic ignition to eliminate the standing pilot, and added a vent damper to close off the vent connector to the chimney to keep the heat in the house during the off cycle.

That said, your Hydrotherm was probably installed when plumbers thought "Bigger is Better" and is probably oversized. In my opinion, you have 2 choices. Keep the boiler you have as long as there is no signs of leaking boiler sections. the parts in that boiler can be replaced as needed for a lot less than a new boiler install. The moving parts like a circulator pump, gas valve, limit controls and other interesting things can be replaced with new upgraded stuff.

The other option is to get a new boiler that will not offer you any real savings over the Hydrotherm. The efficiency will go from 77% to 83%, which will save you about 8 cents on the dollar of gas usage. But getting the proper size, like perhaps the CGa 6 at 166,000 BTU input, if it is large enough may add a few more thermal efficiency points to reduce short cycling. Then you may get your total savings over 10%. That choices is not going to break the bank in fuel savings. but the load calculation will let you know that you do not need to use the CGa 7 at 200,000BTU input (because they don't make a 180,000 BTU input boiler.

If you go the new boiler route, the CGa 5 may even be enough for you, Have your contractor do the load Calculation for you. You may be surprised.

When was the last time the boiler"s heat exchanger and sensor cleaning? Service Due is probably a reminder to do a service after a programmed length of time in the boiler's program. The time is set in the programing. Much like a maintenance reminder lite on your car's dash.

I changed out that same boiler for someone, only it was 100,000 Btuh input.

It is notable that that boiler is rated for 100 PSI.

I did that change out because the old boiler was stuck in a closet with water heater on a carpeted floor.

The carpet was burned and after pulling the old unit out there was a hole burned in the floor……hopefully not your situation. The pump was not accessible being in the back corner, the exp tank was the same. The age was with the 1960's house.

I did a simple heat loss on the house, (1960's double wide with hydronic baseboard heat….how about that?) Old school, one page, heat loss called for 63,000 required. It came down to the fact that he had only 100' of 3/4" BB connected in a single loop.

100' of 3/4" BB at 550 BTUH per foot meant the BB could only deliver 55,000 BTUH at 170 average water temp.

So a Buderus/Boch GC 124/19 85% AFUE rated at 74,000 input was installed. Approved for combustible floor installation, has riser legs and also 2" concrete block platform was installed under it.

The homeowner did call the first winter that it was not quite warm enough in the house (usually runs temp at 74 or so). So he turned up the water temp for that time.

If you have been in the house for a while you probably have some experience with what percentage of the time the boiler is firing during the coldest weather. If it’s firing 75% of the time or more during the coldest nights, don’t reduce the size. If it’s firing continuously and the room temperature remains below setpoint increase the size.

If you’re new to the house, I suggest having someone clean it and adjust the burners. Some of the cast iron boiler designs have a very long lifespan, some fail very predictably at 7 years or 14 years, etc. The boiler has been there for quite some time, it may be one of the designs that lasts indefinitely. Since you would replace it with a non-condensing boiler, there isn’t a significant efficiency gain or impressive technology update. Don’t express an urge to replace the system to your heating professional at this point. Many heating professionals will interpret that to mean that you’re hoping they can find something that helps you justify the expense of a new system to yourself even if they might otherwise say it’s aging well and will last at least another 5 years. If there’s any sign of a boiler leak or burner defects or other significant problem they’ll tell you.
Every boiler manufacturer periodically loses control of the quality of their grey iron casting line and the boiler sections have excessive internal stresses and/or material consistency issues. The result tends to be boilers that leak and fail in much less than 20 years. Sometimes just 2 to 5 years. Since your objective is reliability my suggestion is to keep an eye on the casting you have and when it needs to be replaced look for one from a manufacturer that hasn’t had any models with problems in the last 10 or 15 years. Don’t consider a sheet steel boiler instead of cast iron, there are a different set of problems that limit their working life. There have been good welded steel plate boilers made or imported from Europe in the past. I’m not aware of any being widely marketed for gas burners right now, but I don’t follow it that closely.