steam boiler making pressure

hrcheat

We recently removed a 25 year old 2000series 5sec. Smith-Mills steam boiler in a large colonial up in NH. Edr load was calculated out at about 590 and no dhw off the boiler. We chose a Peerless EC05 for the replacement(rememember we were taking out a boiler with a capacity of over 1000 sq ft of steam and the Peerless has a capacity of between 660&990)
The two mains are 3" and 2.5" and are fully insulated. The new boiler was piped with 2-2" supplies, per manuf. specs., with a 1.25" equalizer line off the end of the header, and it has a hartford loop on the 2" main return. The boiler was fired, Squick was added and two days later the boiler was skimmed. Some of the radiators are heating fine, some only partially, and a couple not at all. The strange thing is that the house is heating OK, but the boiler is short cycling, and going off on pressure. The pressur-trol is set a 1psi, and when steaming the boiler only runs 1 min., and goes off on pressure. If you raise the pressur-trol to 3psi, the boiler will run longer but use up its water and have feed itself to satisfy the feed switch in the lwco. We have down fired the boiler from 1.75 to 1.50GPH @140psi, which is at the low end of the boiler capacity. Any ideas?

Unknown

It sounds like a venting problem on the mains

What type of steam system is it?

Noel

hrcheat

Noel
Thanks for the response-the answer is one pipe steam