Did the space heating system have the "panel per 1000 sq ft" industry
rule of thumb, plus a "panel per adult in the household" as well?
Installers do face hurdles. Sticker shock from the client that reduces
ideal setups, space constraints at the tankage location, alot of things
can get us straying from the ideal path.
But this system needed, worst case, a 300$ NIB unplugged electic hot
water tank to act as a preheater for the DHW, and, as you said,
everything would have been alot better.
A few weeks ago, I got brought in on an emergency call to fix a SDHW
system (not a TD this time), that a licenced plumber, who had been
"installing them for years" pooched really stupidly. Co-incidentally,
it also had a second tank with a heat exchanger, rigged, this instance,
to an outside wood furnace. But THREE tanks total in this case. The
wood furnace on one, feeding DHW to a preheat with two panels, then the
powered tank. A nice system in that the wood stove made DHW in the
winter, the panels did it in the summer. Everything manifolded. Very
nicely plumbed. The errors came in the installation of the boiler
unit, stupid piping errors.
As you say, this isn't simple plumbing. You have to "get it" to do it
well. And there are, it seems, an awful lot of professionals out there
that just don't get it.
So, is this client installation getting fixed?