Oil Boiler build up… Cold start (and run?) problem

My house (2200 sq ft) was built in 1925 and I bought it a

few years ago. It looks like the original heating system was a gravity fed coal

fired system. A new Burnham V8 oil boiler was installed in 2000. The large cast

iron radiators and 2+ inch pipes are still being used. Domestic hot water is

supplied by an electric hot water heater. When I open my boiler up for cleaning

once a year it is always filled with red, green, and yellow gooey material that

is difficult to remove. The passages in the boiler are nearly blocked with this

stuff.





I think the problem is caused by low exhaust (flue?)

temperatures. The system has one zone. When the thermostat calls for heat the

circulator and boiler turn on. The boiler only shuts off when the thermostat is

done calling for heat. The aquastat is a Honeywell L8148A1017 and only has a

high limit control. The high limit is never reached.





I’m guessing that since the house has 14 radiators and the

big steel pipe, the 100+ gallons of water never gets hot enough to reach the

high limit. If that is the case, the flue temperatures never get hot enough and

that is why I’m experiencing the build up in the boiler.





The oil servicing company isn’t much help. He just says to

make sure it gets cleaned every year.













A few questions for the experts:

1. Am I correct about the build up in the boiler?





2. If I don’t do something about this am I shortening the

life of the boiler?





3. If this is a problem I’m thinking that some kind of

mixing valve would work to constantly circulate hot water through the boiler

and “leak” hot water to the rest of the system. Do they make a valve that does

this?







Thanks