Piping design recommendations.

Jim_4

As an alumnus of one of your past heating seminars, some years ago, I hope this allows me the opportunity to request
your comments (corrections) on a piping layout on a job we are doing. I faxed a copy the other day, but realized from your columns ( which I enjoy very much) that you publish the e-mail address, and that may be your communication vehicle of choice. Hopefully, I have correctly sent the
piping layout attachment. Thank you in advance if you have the time to look at this design. By the way I did not want to put a circulator on the radiators in the garage, to keep the cost down, and a consistent temperature in the garage
is not of concern, only whatever heat is produced by his
old radiators for the garage. Thanks, Jim Chittester

heretic

Design

Not sure how much this matters, but it would seem that common practice places the (High Temp) DHW loop first.

According to Mr. Siegenthaler:

"Secondary circuits that require high water temperature should be connected near the beginning of the primary loop. Circuits using a mixing device to lower supply water temperature should be connected near the end of the primary circuit. Depending on the number and temperature requirements of the loads, this approach may allow the primary circuit to operate at temperature drops of 30 degrees, even 40 degrees F. The larger the temperature drop around the primary circuit, the lower the primary circuit flow rate. This, in turn, often reduces the size of both the primary piping and circulator. First cost is lowered, as is the system's life cycle operating cost."

Also, without a checkvalve on the primary, you would likely get gravity flow through the garage loop when the primary circ is off. In general, the garage loop will likely be wild and unpredictable, since it gets supplied anytime the primary fires, and the supply temp may vary dramatically depending upon which zone (or zones) are calling upstream, and the temperature drop they impose.