Circulating pumps

mcoeks

I have a high efficiency boiler the primary loop due is 1'' due the pipes coming off the boiler. The secondary loop is 1-1/4 inch that branches off to 3 zones that go down to 3/4 inch. When one zone is one the boiler will fire till the water makes it way back then shuts off never ramps down. If I have 2 zones running it will ramp up but settle down to 1% and run like that. Would a variable pump help at all with just 1 zone so the boiler ramps down? Would I need two variable pumps on the primary and secondary? Thanks for the help.

hot_rod

Are the heat emitters getting warm? If not you may have an air lock

If yes, maybe the boiler is oversized for the emitters connected to it.

EBEBRATT-Ed

As @hot_rod mentioned

when you run only the small zone

that zone It could be air bound
It could be too small for the boiler output
or it may not have enough flow

mcoeks

Yes the emitters are getting warm and the zones are large. Could the flow on the primary be to much and the secondary not enough?

Thanks

hot_rod

One of these two conditions is usually going on. If you had some data or even a temperature gauge you can predict that mixed temperature.

The best control is the boiler sensor a foot os so downstream foam the closely spaced tee.

mcoeks

I have a temperature gun at work I can bring home tomorrow and get some readouts. The boiler sensors are built-in to the boiler so I can't move them. I figured the primary loop is running at 8 gpm and secondary loop is running at 4 if a single zone is on, another zone kicks on and runs at 8 gpm which pulls the additional heat from primary loop.

Ironman

How about posting some pics of the boiler and its near piping and the size of the boiler and house?

The sensor that hotrod is referring to is an additional one that's added when you have p/s and multiple zones.