A header without a hydraulic separator

scrantch

As with my last post, a lack of room may have caused some mistakes to be made. A Rinnai condensing 155000 btu tankless heater was used to heat 3 different loads. A 3 season type room, all glass walls, cathedral but well insulated roof. 16x28 room with a 7x14 5 foot deep concrete pool/spa sitting in the floor. This did not leave much room around the pool for pex in the slab. 400 ft. 5/8 in the floor on one pump, a 10000btu European style radiator on one the few spots on the wall used as a towel warmer/ radiator, and a large HX to heat the pool fast. The header does not provide hot enough water when everything is calling for heat. And adding up all loads together comes nowhere near 150000 btus. The pumps are fighting each other with none having priority over the other.
Has anyone had good luck with Caleffis 559 series combination separator/ manifolds? They have in and out for the boiler and can be ordered with many configurations of zones all in one unit. This way I can use a larger pump to push water through the rather low volume of flow heater. And have separate zones for each load all able to fit in the tight space that was left for this equipment.

Ironman

Why are you using a tankless water heater in place of a boiler? It's the wrong tool for the job. A tankless is neither designed, controlled or approved for this. The HX has far too much head for it to allow proper flow.

You need to install a properly sized mod/con and work outward from there.

scrantch

I agree totally however the hx works fine alone, raising 2300 gallons from 80 to 100 in an hour. $2300 difference for
boiler. Just wondering if anyone ever used the Caleffi 559 hydrolink separator/manifold with success.

Ironman

To raise 2300 gal. 20* in one hour would require 383k btus at 100% efficiency. Please explain how a 155k btu water heater accomplished that?

scrantch

Are the flow rates for boilers and heaters calculated the same? And does it mean the same thing? For instance my ru80i heater says 8gpm at 5ft with filter installed. Their comparable boiler is rated less at less head. The heater goes to 185 degrees and they warranty it in a heating application as long as there is at least one fixture. So an outdoor shower that never gets used in winter works. The rep who came with the plumber to size everything to redo the header had no issues with using the heater. He just wanted to replace the Polaris in the other side of the house.

scrantch

Page 43 of the manual, combination

Ironman said:

To raise 2300 gal. 20* in one hour would require 383k btus at 100% efficiency. Please explain how a 155k btu water heater accomplished that?

I can't, but I leave the pool control at 80, turn it up an hour before I want to use it and it reads 100. I don't doubt your calculations, I surely ain't no plumber, but it does work. Even with a less efficient nickel hx

Gordy

I think you meant to say 480 gallons. 8 gpm x 60 min.=480 gallons. 480 gallons x 8.34 lbs. = 4003 lbs.

4003 lbs x 20 TD= 80,006 BTUH. At 100% efficiency.

The pool holds 3298 gallons at a depth of 4.5 feet

Which would be 27511 lbs of water, which would require 550519 btus to raise 20 degrees........

A 150000 btu pool heater will raise 15000 gallons of water 1/2 a degree per hour.

To answer your quest just pipe primary secondary with the loops off the secondary.

Gordy

You will have different temperature requirements for each emitter, and HX. The towel warmer, the slab, and the pool HX all require different temps. I suppose the pool HX, and the towel warmer could use same temp, but the slab should not see above 110-120..

scrantch

Thank you gordy, I was planning on getting one those Caleffi headers to save room and only put mixers on the floor heat and the shower. The Caleffi mixers that fit their 559 hydrolink are super expensive when the pump is also on the one unit but they look so nice and save the most time and space. But I will tackle this after the the other problem with the Polaris circulator. Thanks again and Merry Christmas