Best Of
Re: What’s the issue?
First look in the manual and find out how much water the boiler holds in gallons. Then add 1 lb of TSP for every 50 gallons of boiler water.
so if the boiler holds say 10 gallons of water use 1/10 of a lb of tsp. Mix the tsp in hot water add it to the boiler and skim as usual.
When done let the boiler cool, drain the boiler fill with fresh water drain refill and start. You need tsp to get the oil out. I would not use any other chemicals
Re: Am I being dense?
looks like you have 2 zones pumping into the boilers. The two green hose bibs are the drains. The pipe coming out of the top is boiler out.
I see the domestic supply coming down from top with pressure reducer at top right. I assume the shutoff valve for supply is off screen.
What type of emitters do you have? Baseboard?

Re: Am I being dense?
Yes the shut off valves and the drains are reversed. The shut off valve should be below the drain. You can't purge the way it is
Re: How to set valve on expansion-tank loop
That at best is a attempt at something ,i've seen similar to in renovation ,add a level and flippers .You would be best advised to have that mess corrected for better operation .The top of the spirovent looks as though its been leaking for some time being the calcium build up . As improper as it looks if i was left to get working i would adjust the valve open enough to have some flow through it while maintaining flow through the zone valve i see, being i would image there's a circulator pump for the radiant zone and the other zone is using the circ on the boiler ? common things in lower grade work or just lack of knowledge . IF there is a seperate circulator for the radiant i would shut that zone off and turn the zone using the zone valve and then adjust the valve i think i would also check and see if heat is bypass through the mixing valve if so throttle back , Simply amazing i firmly believe the reason it works is due to the fact that i did not do it because if i did it would not work at all . It just goes to show how forgiving some system can be w improper piping . The catch is how well is it really working not only in comfort but in fuel usage .Also a lot of things just squeeze by until ya hit the single digits thats when the goin get tough.
peace and good luck clammy

Re: Suddenly getting water hammer and cold radiators
are you sure of the 2 psi? which is just a bit high, and is the pigtail clear all the way back to the boiler?
post a pic of the Ptrol, gage, and pigtail,
water dirty in the glass? another picture?

Re: IBC SFC125 combi 2023 install, poor DHW production;
I have A lot of those out there including a similar version in my own home.
Hot water has been decent.
Have you called tech support?
Where is this install?
You prob need to go into the installer parameters and make dure the settings are proper. Its possible they got switched at some point.

Re: IBC SFC125 combi 2023 install, poor DHW production;
Make sure there is not a crossover somewhere else in the domestic water that's inadvertently mixing down the temp for DHW.
Does the DHW temp drop to 106 as it comes out of combi boiler? or is it just at the faucet? ie, is the temp coming out of the combi 120(or whatever its set to) and then it gets mixed down by the time it hits the faucet?
Re: IBC SFC125 combi 2023 install, poor DHW production;
the unit needs a minimum amount of flow to fire and keep running. A small lav faucet may not be adequate, especially if the aerator is partially plugged. Do it do this with a tub filler running?

Re: B@J Big Mouth Serviceability
I got it off using some manly measures, found what appears to be dried antiseize inside the body and evidence of steam leak.
Installed new high temp orings, cleaned all threads/antiseize and retightened hand tight plus half turn with a couple wrenches.

Re: B@J Big Mouth Serviceability
I have rebuilt mine, the oring that I have found to work best is this one from McMaster Carr
9396K428
Since it is based on a trap, you unscrew the cover and simply replace the oring.
