sizing

Dave Palmer

Going to do a heat losse for a job tommorrow,they want to remove 2 boilers and replace it with one and a hot water maker.My questions are the second floor is baseboard and the first floor is LARGE hot water radiators. Do I size the radiators as I would a steam job for btus? My second question is I would like to offer a reset control but can I with the different heating elements (300 pound cast & copper fin).Would like to run it 3 zones ,the 2 floors and hot water maker.But what controller that will not be a nightmare to wire? Thanks Dave

Pete Dwyer

> Going to do a heat losse for a job tommorrow,they

> want to remove 2 boilers and replace it with one

> and a hot water maker.My questions are the second

> floor is baseboard and the first floor is LARGE

> hot water radiators. Do I size the radiators as I

> would a steam job for btus? My second question is

> I would like to offer a reset control but can I

> with the different heating elements (300 pound

> cast & copper fin).Would like to run it 3 zones

> ,the 2 floors and hot water maker.But what

> controller that will not be a nightmare to wire?

> Thanks Dave



Part 1:

Do a heatloss on the house and size the boiler accoringly. Do not size by installed radiation. The only reason you do it with steam is with steam you need a boiler that will produce enough STEAM for all that condensing happening out in the system. Not required with hot water.

You also want to make sure you have a boiler that has anti-shock protection built-in (Like a Buderus), or use a condensing boiler (Like a Munchkin) since you have all that cold water coming back. If you don't use one of my shameless promotion boilers, you should at least install a boiler bypass to temper the water returning to the boiler.

Part 2:

Outdoor reset will work fine so long as the baseboard and radiators are on separate zones. The heating curves are different for the two systems but if there is a thermostat controlling them independently all should be fine.

Good Luck

-Pete Dwyer

Boilerpro_3

Sizing and control

As above size to heatloss. For control,I'd use a tekmar 370 house control. All of the functions are controlled by one box and you get auto boiler differential, outdoor reset, indoor temp feedback, Dhw production, and variable speed pumping for boiler protection, if needed. You can also provide two reset curves off this control just by providing a second fixed mixing point off the higher temperature supply (probably the baseboard zone) to feed the lower temp zone (probably the rads). The issue of low temps and thermal shock, even with a condensing boilers, is something I have not seen addressed very well. I doubt that all condensing boilers are thermal shock resistant.

Boilerpro

Dave Palmer

so would I have to do constant circulation? How would I keep 2 separate temps in the 2 zones with out going over board piping it? thanks Dave

kf_2

My suggestion....

use an outdoor reset control that operates a 4-way motorized valve and also resets the boiler. The higher heating curve needed, in most cases, for the baseboard can be run off of the reset for the boiler. This curve would be set so that at its lowest temp it would still be above the boilers dewpoint.

The 4-way valve would also be able to be reset based on outdoor temp to a lower heating curve to satisfy the much larger (probably oversized) radiators. The 4-way valve will also protect the boiler from lower water temps returning to the boiler.


kf

Boilerpro_3

Nope, but that may be nice...

And the piping is pretty easy, but hard to describe (need to get my new digital camera going). There are several ways of doing this. The basic concept is that you provide higher temperature reset system water to your high temp zone. Then off this reset loop you provide a fixed amount of this higher temperature water to mix with the cooler water coming off the cooler zone and send it out to the cool zone. A mixing valve that can be set for a fixed amount of mixed flow (NOT A FIXED TEMPERTURE) can do this with a seperate pump supplying the cooler zone. I pipe the mixing device P/S to a bypass line around the high temp zone valve and use balancing valves to keep flows right. Got to go out and take some pictures..... They're worth a thougsand words.

Boilerpro

Dave Palmer

any

suggestions for valves?

Dave Palmer

photos

would be great,my minds eye is a little slow these days.Ballpark idea what piping in a 4 way and control would add too the cost? $1000-1500? 11/4" feeds and returns,thanks Dave

kf_2

Diagram

There are many choices Viessmann, Tekmar, Danfoss, etc...

Take a look at the attached diagram. Be careful not to oversize the 4-way or it will constantly hunt to find the right temp. Most manufacturers will have easy charts to size them.

kf

Boilerpro_3

1st try with digital pictures..two temps from one reset control

Let's see if this works, Dave.


Boilerpro

Boilerpro_3

Let's try that with a little smaller file..NM

Boilerpro_3

Whoops, too small, lets try somewhere in between

kevin

Let me ask a dumb Question...

Is it possible to use injectioncontrols/circ. instead of a 4 way valve for this type of application? kpc

tombig

Nic Pics Dave

tombig

Nic Pics Dave

I'm still shopping for the digital camera thing. Is that a manual balance valve between the tees on the low temp loop? Pex feeds on the injection temp? Lookin good.


Tom

Dave Palmer

great

ideas,keep them coming.Injection piping may be the way to go,would keep the cost down I think.Well off to work to do a change out.Lucky(I think) its right across the street so I shouldn't hit much traffic.Thanks Dave

Boilerpro_3

Not sure of the question, but.....

that is a variable sppeed pump set up on the attached panel. The pump up to and to the right is the boiler loop pump. The pump below the blue tekmar box is the var. speed pump. The pump just left of it is the main system pump for the three higher temp zones and the bypass supply piping for the low temp zones. The circuit setter for this bypass is just left of the three Erie zone valves. The 1/2 inch injection piping for the low temp zones is next with a throttling valve on the low temp side to divert water though the injection piping. This farthest left pump provides flow through the low temp zones and is controled by the end switches of the Erie zone valves. The low temp zones and the higher temp zones are all controlled through the Tekmar 371 control using indoor RTU's so indoor feedback is available to all zones. Yep, that is 5/8 Pex return piping for the higher temp zones. Higher temp zones are about 150F supply at design (joist space heating and plates), low temp zones about 85F supply at design (slabs). Both have full reset water temps available. Joist heating/ plate zones worked all winter with no insulation behind them and maintained temp. Yes, joist space heating does work!

Boilerpro