Heating capacity of 520

I am new to this site but would appreciate your help. I live in an older cinder block and stone house with over 4000 square feet. I presently heating house with a EFM VT oil burner. I believe it is a VT 1000. Oil usage has averaged 2500 gallons a year over last 4 years. I need to change to coal heat. Local dealer was here today. He is not sure 520 would be big enough, may need a EFM 900. He also has a used Losch coal boiler in his shop that he said would work. He said it is about 30 years old but in good shape. My heat is hot water with radiators.
I was thinking of using the 520 but not sure now, does anyone have any suggestions? Thanks.

Even if you were firing at the highest nozzle used in a VT1000, your gross BTUH/net BTUH would be 191K/166K. The 520 stoker has a gross/net of 220K/188K. It should work. Best bet is to do a professional heat loss on the house.

If one 520 won't do the job , two will Scott

I am having new EFM 520 installed at the end of august. Had a heat loss done and the 520 should do the job. Needed a new chimney built, also new system will have 3 zones. Losch Plumbing, an EFM dealer is doing the work. Should pay for itself within 3 years plus should have a warmer house. Thanks for your advice, Stoker-man.

My pleasure.