Why So Complicated?

JackW

I'm have a 45x30 foot Morton building and am redoing my 2 zone radiant heat system. The water heater that I used died the other day so I am putting in a wall hung boiler and new manifolds and lines. I've spent some time looking on the internet for some new layout ideas but they all seem so complicated. The simplest one I found is the picture below but even it has several bends and routing that don't make sense to me. Looking at the hot water line out why is the cold water return connected to it at that tee? Then why make the 90 degree drop, to the left of the air separator, only to come back up to the pumps then turn around and go down again? Why not just run straight across to the pumps? And the same for the cold water return lines, why not just go straight across to the boiler instead to going up over the pressure tank then down again? Also what is the pump for on the cold water return? I apologize for all the questions but it just seem so complicated?




Thanks,
Jack

Zman

That is piped primary/secondary. They did it that way because they needed to have one flow rate to allow for adequate flow through the boiler. The flow to the zones will vary depending on which zones are calling.
Most boiler manufactures recommend that design in their I&O manual

JackW

Thank you for your reply. So is that a shared line for both output (hot) and return (cold)? And what does the pump do on the return (cold) line?
Jack

ratio

The pump on the cold line circulates water through the boiler. The other pumps circulate water through the system. Through the miracle of modern physics, the system pumps & the boiler pump can run independently without significantly effecting each other. Get yourself a copy of Pumping Away, it explains it in a very accessible way.
There's also various issues of idronics to read, which will help you understand—although they are quite a bit more technical in nature.
In short, the picture you showed is about as simple as things can get using modern practices & equipment. After you read Pumping Away it will all make sense, after tou read through some of the idronics issues you'll be able to tell if another piping arrangement might suite you better,

DZoro

There is some ups and downs that are not needed. More thought could have been used with the layout design. The connections are all correct but how they got there can be changed/simplified.
Boiler owners manuals usually have a basic design layouts that you can follow.
D

Zman

Sure they could have straightened it out a bit. Maybe they didn't realize you can rotate the circulator motor or they thought a heat trap would be advantageous. Overall the picture in your example is how a system like that should be piped.

Zman

JackW said:

Thank you for your reply. So is that a shared line for both output (hot) and return (cold)? And what does the pump do on the return (cold) line?
Jack

Don't think of it as hot and cold, think of it as 2 loops with different flow rates.

JackW

What are the two fixtures on the top line on either side of the air separator? The other fixture looks like a pressure release valve. Looks like there is one on the return side also.

DZoro

Looks like that is where they are filling/purging the system. There is a ball valve there so they close it off during the filling process, hook a hose to one of the boiler drains to fill and a hose to the other boiler drain to let out the air through out the purging process.
Yes the other item is a pressure relief, I personally would like that closer to the boiler on the outlet side.
D

pecmsg

You might want to consider hiring a knowledgeable contractor to design and build your system, there's a lot of ways of screwing it up real bad!

JackW

Ratio thanks for the book recommendation, ordered it this morning from Amazon.

JackW

Is there a one way valve before the cold water circulation pump? If not what prevents cold water from being pulled into the hot water stream from hot water pump instead of going to the boiler?

JackW

DeZoro it looks like they have a pressure valve right at the hot water outlet so isn't it odd that they would put another one that far away from the boiler?

DZoro

What is even more odd is that there is no drop tube installed to the floor. There are a couple other questionable things in this picture also.
D

JackW

I agree. I posted this earlier but didn't get any answers, do you know if there a one way valve before the cold water circulation pump? If not what prevents cold water from being pulled into the hot water stream from instead of going to the boiler to be reheated?

DZoro

I'm assuming the pumps have internal check valves inside them.
The pump to the boiler will always be on with any call for heat from either one of the 2 zones.
D

JackW

DeZoro is there any reason I couldn't use an inline check valves?

DZoro

nope, but many of the pumps come with flowchecks. They give us the choice to use or not use them. Saves money, time and space when designing the system also.
D

JackW

DZoro I looked into them and will be getting three new pumps, thanks.