Wiring Lochinvar Knight + single Grundfos Alpha

Gordy

Minimum flow rates

Those are the minimum flow rates at maximum fire. You have to be at least those gpm at differing deltas at maximum output. You can't design around the minimum output of the boiler. Maximum output is when the HX will see the most stress so you have to keep the HX happy at maximum conditions if you do that then everything else falls into place down through modulation.

djohn

minimum vs maximum

Sorry Gordy but that makes no sense to me. WHN110 needs minimum 10gpm at 20F delta-T? Meaning it can do more than 10gpm at 20F?



And minimum 6gpm at 35 delta-T? Meaning it can do more than 6gpm at 35 delta-T?



Normally mod-con boilers and mod-con tankless water heaters list maximum gpm at given delta-T (or temp rise with WH) For example, my Richmond/Rheem tankless fires at between 11k and 199k BTU and can do 45F rise at 8.4gpm up to 77F rise at 4.9gpm, with 0.26gpm min and 9.5gpm max flow.



I still think it's other way around and WHN110 can sustain 20F delta-T at up to 10gpm, by using modulation. Up to, not minimum. At over 10gpm, the delta-T will go down, not up.

Gordy

I think

You want to,do what ever makes your heart content. Not the boiler.

Steve Whitbeck

Gordo

good answer.

djohn

You keep thinking this is a cast iron boiler.

For some strange reason you think that your boiler will know that only one zone is running and the boiler will be at the proper BTU firing rate per the zones GPM flow.

The boiler WILL fire up and go to full firing rate faster than the controller can modulate it down.

Have you installed the Knight boilers before???

What You could do is use a Honeywell three zone panel, wire the TT terminals from each zone to one thermostat input on the zoning panel.

Set the zoning panel to stage the boiler according to the number of zones calling.

Wire the zoning panel to the three separate space heat inputs on the Knight boiler.

set input one to a max output of 33%, input 2 to 66% and input 3 to 100%.

That way the boiler would modulate but never exceed the capacity that the zone can dissipate

But that control will cost more that the cost of P/S..

djohn

flow

Ultimately, boiler always holds the same amount of water and will lock out before overheating. Overheating is the only condition that can make that boiler fail.



Overheating will happen only when flow is so little, that even at minimum fire rate, water temp will go above 200F and turn back on when the water temp is 190F. Even then, boiler would simply stop firing and let the pump circulate until thermostat is satisfied. Do you think boiler will not shut off in time, when outlet temp reaches design temp of 125F and will ramp through the safety at 200F? That would be crazy.



And yes, boiler knows the incoming water temp and outgoing water temp. These sensors are built into WHN110. They kick out when delta-T goes past 55F delta-T and modulate the fire to the lowest and finally shut it down at 60F delta-T. That would mean crazy uncontrolled water temp of 180F after some crazy boiler control failure.



As for boiler knowing about zones - kind of yes, it does. With 3 zones, come 3 set points and 3 reset curves.



I am not worried about destroying this boiler and I am looking forward to tweaking the temps and Alpha to make it run as efficiently as possible.



BTW, I will be using HZ432 for central air so I will be able to try it out with boiler system, if I have to.

Steve Whitbeck

I underestand now

It is now VERY obvious.

You have never installed a Knight before.

GOOD LUCK

What you think you know YOU DON"T.

I am done here.

He doesn't want to listen.

He doesn't like the answers.

djohn

thanks

Sorry but you haven't proven anything I said to be wrong or inaccurate.



Thanks for your help, Steve.

Gordy

Design

Why would anyone want to design a system around the premise that boiler protection sensors will protect the boiler. Should you not be designing your system so the boiler won't lock out. Or do you enjoy resetting the boiler, and repiping reconfiguring controls so it will work right with out your undivided attention.



I think if you reread most posts above they sway to P/S once the full picture of what you are trying to do comes to light.

djohn

premise

I am not designing anything along this premise. I think it will work and I won't need protection features unless there is some control failure.



I simply mentioned boiler protection features to prove that yours and Steve's catastrophic predictions will not happen. Even if you are right and I am wrong, boiler will simply lock out.

djohn

P/S

If you ever read my original topic on this design, you would learn that I used to be an old school P/S guy that had to have a primary pump and zoned using nothing but pumps.



It was SWEI and Zman that opened my eyes and shown that with modern, non-restrictive fire tube boilers, one could design a simple system that would run on single pump. Simple meaning single temp (or similar temps).



It took me a while to give up my original idea and look into the numbers that say that it just should work. I used the Knight's diagram for this design. Knight does not require P/S piping.



I will be more than happy to post install pics and describe how the system works (temps, settings) once it's complete.

Eastman

to djohn

What you want to do is not considered best practice. I read through your prior threads and current posts. I believe you have misinterpreted information from other heatinghelp posters and Siggenthalar's book. In the past, single pump systems have been promoted by me and others on this forum, but I can not think of single instance where an electromechanically zoned modcon system has been recommended without some form of P/S. I wholeheartedly encourage you to try it, but clearly such a setup, as you have noted, is entirely reliant on various boiler self protection sensors.

djohn

pioneer

I absolutely understand that this is not a normal practice and I will be doing somewhat pioneer work here. I am not deaf or blind and if it doesn't work, well... then I will consider other options including P/S piping.



Right now almost entire system is made of brass so it will be easy to reconfigure.

Gordy

Loop,deltas

And boiler delta will be your battle.