I recently had a new boiler installed for my two-zone slant-fin baseboard heating system. The old boiler was 30 years old, and the new one is pretty much the exact same model, but with electronic controls. However, I am running into a tricky problem that I can't seem to pinpoint. When running any one of the two zones, boiler works fine. Heats up to 180F and restarts at 160F as long as the heating call is in effect. When running both of the zones simultaneously, things don't go as smoothly. Below is a detailed explanation; -Boiler heats up to ~155F and the boiler starts pulsating until the PRV opens (obviously water boiling in the boiler) -Boiler temp skyrockets to 230-240F, until it comes back down to about 210F when the pressure drops enough to allow replenished water to re-enter the system and cool the boiler back down. -Boiler restarts at 160F and repeats the process. I have checked a few things; -Fill valve is filling the system to 12psi as it should. It is not overpressurizing the system -Expansion tank is set to 12-15 psi (checked with the boiler water drained when it was cool). -Both zone pumps appear to work effectively, as the return piping heats up shortly after the zones are activated. -System pressure does not exceed 20psi, until the popping noises start, then it pulsates higher. Items to note; -We never had this issue with the old boiler. Nothing new was installed except the boiler, nothing else. All piping and accessories were rerouted to the new boiler (Same locations since new one is similar to the old one). Only exception is new draft damper and drain valves. -I currently have the max boiler temp set to 150F with a restart temp of 130F. This heats up the place fine, but I'm not happy that something is not right. Please help! I've spent hours trying to troubleshoot this but haven't made much progress.

Hi there. New to the forums so hopefully I'm posting this correctly. A little back story. Last year I decided I wanted to design and build a house all myself. I've very handy and a quick learner. The house is a 3 bedroom, 2 bath, 2440 sqft slab on grade built in a small town North of Winnipeg Manitoba Canada. The system: (I designed myself with plumber help) Zone#1 = 4 Loops - 1 for each bedroom and 1 for the bathrooms Zone#2 = 3 loops - Kitchen/Dining, Den, Living Room Zone#3 = 3 loops in Garage Steibel Eltron Electric Boilers = Floor-19KW, DHW-29KW Wood Boiler - Walltherm with 1000L Tank with DHW coil (Not installed yet) So the problem is the pumps just aren't giving me the flow required. Now this might be an air issue but the plumber and I have eliminated almost all the air (so we think). I think its an issue with the design the plumber did on the wall (see pics) but he assures me that's not the issue. Any help would be greatly appreciated. [url]http://imgur.com/a/hPZ1W#0[/url]