Instantaneous domestic hot water from boiler

MikeJ

Seen in a Viessmann training webinar they mention a plate style instant water generator using a boiler.
Would like to fine more information about them (any brand) , and if any one has use one and if they work.
They said it had a built in pump and valves.
https://www.screencast.com/t/vStbUYoJFi
Thanks
Mike

hot_rod

i have never seen a flat plate HX with 6 connections, if that is what is shown. Typically it just pipes to the boiler as another load, either with a separate pump or three way zone valve.

What size boiler, you ant 120,000 or more to get 2.5- 3 gpm.

A common, off the shelf plate HXZ 5X12- 30 plate is usually plenty. Most of the combi boilers with HX built in have 5X8 20 plate.

You can size an exact HX at GEA website, you need flow rates and temperature require.

There are a handful of piping schematics here as well as a sizing example.

https://www.caleffi.com/sites/default/files/file/idronics_11_na-r1.pdf

MikeJ

Its for a friend of mine that has a 220,000 BTU condensing boiler. His tank is starting to leak water, and we are kicking the idea around of trying instant domestic hot water. ( I love trying things on friends houses)
I will stick with a tank, I installed 3rd line to my faucets when I remolded the house, Like having hot water at the faucets as soon as i open them. Turn off the cir pump several years ago can not till the difference at the faucets, still have hot water present right now. turn the shower on step in at the same time.
Don't think you could get that with instant?
Flow switch my be the way to go for turning on the boiler, open hot water tap, get flow and turn boiler on.
Thanks
Hot Rod

hot_rod

There is definitely a delay on the external plate method. First the boiler needs to fore and rev, then it needs to circulate thru the HX for a minute, then the distance to the faucet needs to flush, so not nearly as quick as a recirc equipped tank.

And you need to source a low flow type flow switch.

Paul Pollets

Why not a SS indirect tank? No moving parts except a pump for tank recovery. No HX to clean or maintain.

MikeJ

Paul, there is a tank already installed its starting to leak. Problem is it sits under the stairs. The tank was installed then all the piping was done in front of the tank. Installed like the tank was never ever going to go bad. So we were just kicking the idea around of going with something different. Have not yet found what Viessmann is showing in that drawing I posted.
More then likely going back in with a tank again will be the best option.