Question on Boiler layout

jtm311

Quick question I'm going to do the same installation as show in the drawing, however I'm using a standard cast iron boiler don't like the fancy new stuff:) My question is do I still need a circulatory pump show from the boiler or will the zone pumps handle the flow needed? If I need another pump is this considered and zone or is it wired when heat is called? Thanks

jad3675

If you're piping primary/secondary, then yes the system pump is required.

jtm311

Thank you Jad, so my zone 1 will be for second floor baseboard zone 2 would be first floor. Zone 3 is future use and 4 is for the indirect water storage. My thought was to make zone four primary if my research is correct. So with that primary do I need a 5 zone relay controller over a 4? thanks

Dave H_2

If you are going to use that particular wired and piped panel, it is already configured for primary/secondary piping arrangement. So regardless of the boiler, you would need that boiler pump. The SR504 switching relay on that panel is an -EXP controller and it has a terminal for a boiler circulator labeled "Primary." So you do not need to get a 5 zone controller, a 504 is perfect

Dave H.

jtm311

Great I was reading the document from the 504 not the EXP version now I see the primary which doesn't take a zone. Perfect. BTW I'm not buying the pre-made HTP solution going to build my own but same layout.

jtm311

If I may ask another question I'm going with the Aqua-Plus 45 Pewter Indirect Water Heater. Can you tell me how much up-sizing of the boiler do you add when installing an indirect or is their a calculation I can use? Thanks

HVACNUT

You might be confusing primary with priority. 

Dave H_2

With that tank, the literature calls for a 150,000 BTUh boiler in order to get the demands of the tank at 180 degree boiler water and get 307 gallons per hour at 115F. Not knowing the size of your heatloss, most systems are now sized to match the hot water demand rather than the heat loss.

Also with the SR panels, they all have Priority, which is used for the DHW circulator. That can be turned On or Off (default is off). With the EXP controllers, there is an extra terminal for a Primary circulator.

A primary circ will turn on when there is a call for any zone circulator.

A priority circ will turn on when there is a call for that circ and then turn OFF all other zones prioritizing all the heat from the boiler to go to that zone.

Dave H.

jtm311

Dave thanks for the extra explanation and I got. Seems like the payback to add that large of a boiler may be overkill maybe I will go with the gas water heater

mattmia2

You can use a larger indirect tank to get more hot water to cover your peak demand. Your usage pattern and the incoming water temp have a lot to do with how much hot water you need to store or how quickly you need to be able to replace it.

Dave H_2

You don't have to upsize the boiler for the tanks purposes, as long as you understand what you are going to get. Do you need the 307 gph?
What made you choose that particular tank and what is the boiler size you have or what is the heatloss of the project?

Lots of variables that come into play when selecting the right equipment needed.

Dave H

GroundUp

Why do you want to pipe a CI boiler primary/secondary? The odds are very slim that it's necessary, and if it's not necessary, it's silly. In order to pipe P/S, yes you need that pump. If you pipe it the way a CI boiler is normally piped, then you do not need that primary/boiler circ because there is no primary/boiler loop.

As far as the indirect goes, the 150k rating is merely that- a rating. It will make 307 GPH if you have a 150k input. If you have a 100k boiler, you will get roughly 200 GPH from the same tank. A typical 50 gallon gas WH will only make around 100 GPH. Never upsize the boiler for an indirect tank- always size the boiler to the space heating load, and go with a bigger tank if you need that much hot water.

My advice, find a new diagram made to be used with a CI boiler and/or hire someone who understands how these systems work.

jtm311

So the house is 2000' two level 30 year old home and I've calculated total of 120' of baseboard. The Boiler calculation came to 90,000 btu but I was going to use a WM 117,000 btu. As one day the basement will be finished and need to add that zone.

EBEBRATT-Ed

@jtm311

Your calculations are off. 120 feet of baseboard will only output 70,000 btu, That's what size boiler you should pick (72000 ) boiler output......if your heat loss is right Anything else is two large. Re Check your heat loss.

You don'r need to add anything to the boiler size for the indirect....that's what priority is for.

Pipe it primary/secondary like your drawing with the added boiler pump

You will have less problems and will always have the correct flow through the boiler

jtm311

Thanks guys.. boy I thought I knew enough until you ask experts So the 120' I based on the finished part of the house and was only upsizing the boiler for when it comes time to add the additional for the finishing of the basement next year. I didn't do for the heat loss. With all the comments I now understand the priority will kick in for DHW which is why you don't upsize the boiler.

jtm311

Back with a question as I'm getting ready to wire the taco sr504 I have two questions.
I'm using priority zone for the indirect water heater.
on the attached they show the end switch to turn on the boiler, is this 120v? why would I not use zc/zr?
second question do I need to provide 24v to the connection on the board or is this used for "C" on a thermostat?

Thanks