need advice on my 1st draft of boiler setup - DIY Chatroom

rschwanke · 10-25-2009, 04:03 AM

Ok, try not to laugh - but I sketched out a draft of my boiler setup (don't worry I'm getting help, I just need to understand it better first). I have one radiant heat zone for my concrete pad (first floor), and eventually will run tubes for one other zone on the 2nd floor. It seems all the pics I can find and friends' systems I look at have individual zone pumps, but I am using a single circ pump and 2 zone valves instead.

I keep seeing tips on placement of certain things like the circ pump should be on the end of the return line, and the zone valves should be on the return lines - to keep the temp down for pump/valve longevity. These tips make sense, but they are contrary to all the installation manual diagrams - where both are on the supply lines.

I also know there needs to be a bypass to keep the temp down going into the tubes (and up going into the boiler), but maybe just one initial bypass is enough? I saw a system with individual bypasses on each zone (just before the mixing valve), so I penciled them in - not sure if they will help... maybe just make extra work?

It all seems like it will work considering the mixing valves help water flow a certain direction, and I penciled in a few check valves for good measure.

Couple specific questions - is my Pressure Pal (glycol storage tank) in the right place, coming in above the expansion tank? Do I need a pressure reducer after this tank? Also, on the main system bypass, can this just be a line or does there need to be a bypass valve in there? Not really sure what a bypass valve would do.

I would be interested in any comments or advice.

Thanks
Beck

beenthere · 10-25-2009, 04:45 AM

There are a few more hydronic devices you can add to your pic. But not

many.

Keep it simple.

Start over.
A check valve is not the same thing as a flow check. Don't confuse them.

rschwanke · 10-25-2009, 08:19 PM

I said it was a first draft... okay so a few too many gadgets? I read I don't actually need flow checks with a zone valve system (only with a multiple pump system), so maybe they can go. I guess I'll have to look deeper into what exactly a check valve is, they seem to be interchangeable with flow check valve in a lot of discussions. Anyways I was referring to a backflow prevention valve.

Are you saying one single bypass is plenty?

beenthere · 10-25-2009, 08:25 PM

Yep. When piped right. One is enough.
Back flow preventer. Is only needed on the fresh water supply line.

A check valve is not a flow check. A check valve won't stop gravity feed(unless its a spring load check valve).

rschwanke · 10-25-2009, 10:19 PM

Okay, here's my second take - much simpler. I don't have water to this garage yet, so there's no water supply, just a Pressure Pal glycol-mix storage tank. Do I need a flow check on this line?

Is it best to put the pump on the return, lower temps? I moved the zone valves back to the supply lines because the water temp should be low on this system - looks more conventional anyhow.

beenthere · 10-26-2009, 04:43 PM

My drawing doesn't show air eliminators/vents.
But, its just to show a simplified piping method.
You really don't need a glycol tank.

rschwanke · 10-27-2009, 03:24 AM

Thanks - I appreciate the diagram. I thought about using just one mixing valve, but I'm only doing the first zone for now, and I was thinking it would be easier to use 2 valves - for ease of putting the 2nd zone in later. I might redraw to use just one. The makeup tank is spendy, $740, but it provides a piece of mind knowing the system won't run low, and it makes filling/draining really slick... still thinking on that one. So many choices, not enough time! It's snowing out.

rschwanke · 10-27-2009, 03:27 AM

I was told by one person to use dielectric ss fittings between steel and copper, but then another person said don't bother (unless using an electric hot water heater). Not important here?

beenthere · 10-27-2009, 06:58 AM

SS dielectric is not required. Too expensive. Dielectric fittings are always a good idea.

The glycol tank. Is a false sense of security. Since it won't add any unless your system has a leak.
All systems with glycol, should be checked yearly for strength.

You can use 1 mixing valve. Leave a tee with a shut off valve in the mixed line for the second zone.

Viper16 · 10-27-2009, 11:44 AM

Quote:

Originally Posted by rschwanke

I was told by one person to use dielectric ss fittings between steel and copper, but then another person said don't bother (unless using an electric hot water heater). Not important here?

It does not matter how the water is heated in a boiler. The electrolysis is created between two dissimilar metals, creating a corrosive environment. you don't need a SS dielectric, just a standard dielectric union will do. Make sure you get the appropriate one for your specs. Also it doesn't hurt to get one for your gas supply as well...depending if you are going from an iron pipe to a copper supply.

Viper16 · 10-27-2009, 11:50 AM

You would only need glycol in your system if you think you are going to see any freezing conditions on your system. From what was explained to me once, a long time ago, is that if lowers the freezing point of your liquid. Much like antifreeze.

yuri · 10-27-2009, 06:20 PM

If you are using glycol in the system you need a bigger boiler or more BTU's as glycol reduces the capacity. By how much I don't know. Depends on the strength of the mixture.

rschwanke · 11-14-2009, 01:30 AM

Thanks all for your good comments. I'm on to phase 2. Got the boiler setup and running, but I have a problem. My control box on my boiler doesn't allow me to reduce the upper shutoff temp, 180 is as low as it goes. When the boiler temp gets up above 159 degrees though, the system stops circulating and hot water backs up the return. If I could set my upper shutoff temp at 155, I wouldn't have this problem, but I can't. I want to understand what's happening.

I have a Caleffi 521 series mixing valve. It seems to let hot water through to the cold side when the supply temp gets up to 159+. On initial startup it was fine, the boiler temp stayed down, I had the mixing valve on MAX (which is max temp = none of the return coming back in), and the supply temp wasn't getting above 140, so all was fine. Now the concrete pad is warm, and the boiler temp wants to rise to 180. I tried to change the mixing valve some, i.e. let some return water back in, but then the flow seems to stop through the tubes and the system backs up. I have premixed 60/40 glycol, so it shouldn't be too thick. The tube runs are all <150'. The cold/hot or hot/cold pressure differential isn't supposed to be more than 1:2 for the mixing valve, so maybe this could be a problem? The Grundfos pump is the one the plumbing supply sold me (no specs in front of me). Could it be insufficient? I don't understand what's happening. Any ideas?

rschwanke · 11-14-2009, 02:01 AM

The only solution I can come up with for now is to add a backflow preventing check valve above the bypass to keep hot water from going back up the return. This would keep backflow hot water off the cold side of the mixing valve, which could be messing things up. The max outlet temp of the mixing valve says 152, so maybe this is causing the problem when the hot inlet temp is 159+ and the cold inlet temp isn't cool enough or flowing fast enough to bring the mixed temp down below 152. But still, why does the system seem to stop circulating above that temp, bringing hot water back up the return... both issues seem to hit at the same time

beenthere · 11-14-2009, 06:17 AM

You installed the mixing valve wrong.

The circ MUST be on the mixed water line.