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DHW PUMP advice

VancouverG Member Posts: 33
I have an IBC DC 33-160 combi boiler.  But unfortunately didn’t do my homework and trusted the plumber that it would be enough for my hot water needs.  It wasn’t. So I added a 50 gallon storage tank and now I truly never run out of water. 

Basically when there is a call for DHW the water comes out of the storage tank (water stored at 140F and goes thru a Taco 5000 mixing valve to reduce down to avoid scalding. Once the thermostat in the tank drops it triggers the Taco 0013 which pumps into the boiler and that flow triggers the boiler to turn on and supply 149F water to the tank.  The issue is the plumber incorrectly originally had a 3 speed Grundfos 15-35 which unfortunately couldn’t over come the head and was allowing only 1GPM flow from the boiler.  We switched to the Taco 0013 and on low speed it gets to 1.6 on medium 1.9 and high 2.0.  The question is does anyone know what pump would would be able to get the flow to 3 or 3.2 which is max for DHW from that boiler. Unfortunately I don’t know the head and IBC couldn’t help me either.  I always like to have a backup for all my plumbing and will purchase a pump anyways and thought I would see what you guys think