A little primary secondary piping

[heaterman]

This small P/S piping setup illustrates the concept pretty well. It's small, only two heating loads and two inputs , which are the OWB and the gas boiler. The heating loads are 1 low temp radiant slab and one high temp for the DHW.
We set it up so the gas boiler is controlled by an aquastat which looks at the incoming water temp from the OWB. When it drops below 125-130 the gas boiler will be called on and it will run on it's own aquastat until the OWB loop is satisfied or the heating demand from either of the two loads ends.This allows the homeowner to leave for a weekend or a few days without having to worry about the outdoor part of the system freezing up. It also provides a little storage capacity in the OWB. Not super efficient but it's not used as such for long periods of time.

The single zone Honeywell controls the primary loop pump via signal from the connection in the Taco zone control box. All calls for heat go through the Taco so the the primary loop circ runs whenever anything happens.

 

[BoilerMan]

You've got Wilo, Grundfos, and a Taco pump in there....... Any B&G?? Do you like the plastic pex fittings used with crimp rings?

TS

 

[heaterman]

Some of the items were owner supplied, hence the mix and match. The stuff you see made by Wilo is what we supplied.

Young couple just starting out and I give him credit for tackling what he could by himself. I also give him credit for knowing when he was in over his head and calling in some help. They have a nice little slab on grade 1,600 sq ft house put up and finished for under $65,000 last I heard.
The plumbing pex and plastic fittings were done by the owner and a retired plumber that helped him out on the job. There's a little bit of everything in the plumbing package.

Both the gas boiler and the Hardy were used. In fact that is the second time I've installed that particular Hardy. I put it in for another customer in 1995 and I think it has seen 2 other places in between.