Best Of
Re: Replacing a nat gas combi boiler with electric alternative
Before you go too far down the electric rabbit hole, check & see how much power an equivalent electric heater will require. You might be a few hundred amps low for a direct replacement.

Re: Homeowner with Burnham Boiler that needs service - what parts to purchase - Pics.
Firebox kits for this boiler are no problem to get. Cleaning everything out, installing the new kit and tuning everything up is likely to take most of a day, though.
And lousy service is way too common, unfortunately:
Re: 1970 Boiler 5000 gallon a month leak
How often are you adding water. 2nd off, I would highly doubt it is the underfloor piping causing 5000 gals a month loss unless it had an auto fill that was ice cold and constantly running or unless he is constantly filling daily. Shut the main water line valve off in the house and go out to water meter and see if it is still spinning. I would be more likely to believe a bad water main coming to house from meter. Again without little more information hard to say. Of course having to add water regularly to heating system still indicates a leak that will need to be addressed, just maybe not the big cause of loss.
Re: radiant initial setup & numbers
At such low temps it won't matter much, but it is still a bit better efficiency to get higher delta T on the boiler. Turn down the boiler circ to get the two delta Ts to about match.
You might also want to limit the fire rate of the boiler, to need for it to fire a much higher than what your space heat actually uses.

Re: radiant initial setup & numbers
boiler is fine. For floor heating, you typically want a smaller delta T. So get those flow rates up!
After that, lower supply temp is better.
Re: Water boiler with tankless coil not enough for DHW
I am not sure if this will work, but I should.
- Set the high limit to 160 or above (If you don't get enough heat on the coldest winter days then set higher)
- Set Low limit to lowest temperature or OFF
- Add a switch to connect L1 with ZR on the Hydrostat 3250 control
- Set the Indirect / zone switch to I
- When the switch is turned ON the burner will operate to maintain 160° and the circulator will be turned off for up to 45 minutes. after 45 minutes the DHW priority will time out and the circulator will operate for space heating. This is a feature you want to have in the event you forget to turn off the hot water manual switch.
This is the simplest, most energy saving way to operate your system using the water heater on manual demand. When the switch is off, your boiler will operate like a cold start boiler. That is the most efficient way to operate a boiler that does not have a tankless coil. In the winter when your boiler is operating on and off as the thermostat calls for heat, you will get warm water from your tankless coil for hand washing and other short uses.
Let me know how this works out. I'm no longer able to go into basements and test this out for myself.
Re: Where can a get an old style compression tank
Several factors go into this: boiler size, type of radiation, etc. I have one of these books that contains the method, but not in front of me- besides, you'll want your own copy. You may need to copy and paste the link:
https://www.ebay.com/sch/i.html?_nkw=bell+%26+gossett+handbook&_sacat=0&_from=R40&_trksid=p4432023.m570.l1313
Re: Why does Gorton not make adjustable rad vents?
It would still be increased cost because 1) they would still want to make the fixed orifice model for reasons aforementioned and 2) although non-orificed units could be inventoried unpackaged easily enough it would require costly labor to match them to the correct orifice and install it before shipment (cheap enough in China but certainly not here in the US).