OK guys, I've been reading past threads on bypass piping and have questions. First some background info, boiler is oil fired, cast iron, oversized , 1.10 gal nozzle, 4 spaceheating zones, 40 gallon indirect for DHW, all controlled with zone valves, convectors are 3/4 inch fin tube. I've installed a Tekmar 260 on this system during the summer. I think I should have boiler protection as I would like to run the 260 in full reset mode. Currently the low limit on the 260 is 130 degrees. The 260 has the indoor temp sensor also. I would like to use a Danfoss thermic valve, 113degree for oil. I did a manual J and will loose about 60,000 BTUs in an hour at zero degrees. Here are some pictures for your viewing pleasure

http://i244.photobucket.com/albums/g...Firstfloor.jpg
http://i244.photobucket.com/albums/g.../MainLevel.jpg
http://i244.photobucket.com/albums/g...2/TopLevel.jpg
http://i244.photobucket.com/albums/g...2/IMG_1154.jpg
http://i244.photobucket.com/albums/g...2/IMG_1153.jpg
http://i244.photobucket.com/albums/g...2/IMG_1155.jpg
http://i244.photobucket.com/albums/g...2/IMG_1156.jpg



Hey Trooper, I have a Beckett HM that I removed from the boiler so I could use the 260. I told you in an earlier thread that you could have the HM. If you want it PM me an addy and I'll ship it to you. I'll pay shipping.

 

Many bypass questions may be answered here.
http://www.comfort-calc.net/Bypass_P...laination.html

 

Joe, is it intentional that you have the exposed wall factor for the 1st floor at 0.27 ? No insulation on the first floor ?

Those stupid 9Ds always seem to leak. I'm not sure from the pic, whether that's the side with the nylon washer or not... but at least one side does... not too hard to fix really ...

Go to big box store, see if they have one on the shelf. Open box, take apart, see how to fix ... buy 25C washer... I've got a red rubber washer in mine. Couldn't get them nylon ones to stop leaking. Rubber ones been in there a good long time now.

 

NJ, The .27 is intentional. The exposed walls are 8" hollow cinder block with furring strips and drywall on the inside. Classic 60's building techniques if you will.

What is this 9D you speak of ? Is it the circ ?

What do you think of the pictures ? I'm going to re-pipe 2 zones so all the zones line up in a manifold type setup. That will also clean up the maze of pipes on the boiler supply side and provide a stub for the bypass loop.

 

sorry... the 9D is the backflow preventer on your water feed line. There's a bunch of green crud on it... there's even a close-up pic of it...

I did the same thing with mine... I kinda thought that might be the case... in ours the 2nd floor is 10 years old, the 1st is over 55 ... it's been insulated and new windows and all, but the 1st is still way leakier than the 2nd ...

I've gotta spend a little more time looking at the pics ...

Did you know that you can 'export' the heat loss files ? Screen shots are good and all, but I keep going to click on the buttons !

 

Come on guys can you share some knowledge with me ? Please.
I'm looking at sketches and diagrams from previous threads and also on the Danfoss site but I'm not sure how to pipe the boiler bypass, specificially in the area of the circulator. Mine is on the boiler return side, do I put the "T" in between the circ and boiler or before the circ ? My thinking is if I place the Danfoss before the circ the water will not flow fast enough through the bypass as the water is not directly going through the circ first. Does that make sense or am I overthinking this ? Also, regarding the other side of the bypass, the hot water output from the boiler, do I need a monflow T or a standard T ?

 

Here's two ways to do a bypass.





I don't believe either of these will provide enough protection to allow full ODR on a conventionally piped system.

(note: some components not shown for clarity)

 

So your saying that this type of boiler bypass would not fully protect the boiler from condensing ? Even with the Danfoss valve on the bypass ?

 

I think it's important to understand that the Thermic Bypass Valve STARTS to open at 113... and it's 'all in' by around 135 or so.

Answers depend on the thermal mass of the piping (black iron (slower to heat), or copper), which effects the response time of the boiler sensor, and the same of the response time of the Thermic Valve.

You WILL have a region of operation of the TBV between 113 and 135 that some mixing of boiler water and system return water will occur. You MAY be able to depend on operating in that region...

Remeber that the water coming back from the system may be 20-30* cooler than the entering temp. ( DT , Delta T )

 

So Troop do you think the 113 TV is a bad choice ? Should I go with the 140 ? I have 3 of these thermometers that will be piped into the lines. http://www.grainger.com/Grainger/items/2A611 The majority of my piping is copper with the exception being were the circ is and the boiler output side have black iron. The boil water sensor for the 260 is on black iron. What does the dotted line represent that goes from the boiler to the circ, is it electric ? Do I need check valves or similar in this design ? This topic is somewhat confusing to me, can you tell.

 

Oil fired ? I forget ... too lazy to read back.

Oil, use the 113

Gas, use the 140

I only put those thermometers in there for illustration... you don't need to install thermometer in all those locations. No, that would be overkill.

In fact, the only one I would install one is on the return line going into the boiler.

You can read the temp of the supply loop on the 260 display.

The boiler should already have a thermometer, and you can use that one for the supply temp. It may not be exact, but it should be close enough.

Yes, the dotted line is electric, but again, this is just an illustration, it's not intended to show how your system should be... it is a quiz... I was hoping someone would answer. In your particular case, that circulator will probably be run by the 260.

I do have an answer from someone on that exact diagram that I would like to use if it's all right with him ... Xiphias ? you reading this thread ?

My whole point is that if you are going to try to do FULL ODR with a setup essentially similar to that illustration, you will be faced with unpredictable results. Your boiler may cycle in odd patterns... etc ... or, it just might work OK ... but personally, I wouldn't do it... I would either stick with PARTIAL ODR, or repipe for PRIMARY / SECONDARY with a variable speed (or a 4-way valve) injection loop... and that's a lotta work, and a lot to get done before the heating season. It means two more circulators, and a more complex $$$ control.

Is there a cheap and easy way to do FULL ODR with a conventional system ? probably not ...

 

Yep oil fired boiler. Stay with 113, got it. I just happen to have 3 thermometers, I did not think they would all be needed but if they were I had them on hand already My circ is controled by the 260, not the 8124C aquastat on the boiler.

About the FULL ODR, you're thinking it might not be a good idea on this boiler ? I would prefer to not rot it out so what other choices to I have. Could I set the boil min setting to say 115 and protect the boiler ? Also, would I need a check valve to help the water move along in the bypass ?

 

If you want full ODR and have room for a buffer tank, that's what I would do. The boiler charges the tank, the tank heats the house. Long run times and full ODR, but you have to warehouse some BTUs to get any real run time for the boiler. Do continuous or near continuous circ on the heating side, and leave the other circ for charging the tank on demand.

 

Who, how would you control that buffer tank with a 260 ?

Joe, yes, setting the BOIL MIN to something a bit above the opening temp of the Thermic Valve would be OK... but now you are only doing PARTIAL ODR, and not FULL as you desired.

 

Yeah, I'm reading. Go ahead and mine my comments, for what they're worth.

I like Who's idea of the buffer tank. If you could control it with a zone valve to keep it in use during space heating calls, and take it out of the loop during DHW calls, that might do it. An extra relay somewhere? (As you know, that would be beyond me, electrically.)

Sizing the buffer to allow full ODR and force the boiler to always work beyond condensing temps when it recharges would be important. How do do that?

 

Problem is I don't have space for a tank. The whole setup is in the garage wich is rather tight now. So my wish for full ODR is not going to be possible. I could do well with partial ODR, right ?

 

Joe, have you already purchased the 260 ?

How much re-piping have you got in mind ?

Partial ODR would save a bunch... not as much as you could save if you were able to go full though...

 

Moot point now, but I'd put the supply sensor where the piping leaves the buffer tank for the heat distribution side. Put a thermic valve on the boiler side of the buffer tank. The circ on the heating side could be totally continuous.

 

Trooper, The 260 is installed at running. Right now I,ve got the boil min set to 130. I'm zoning with zone valves and only have one circ on the system. I don't mind repiping, just not sure of the correct way to do it. I'm very confused on how the Danfoss valve works, I can't even begin to tell you how many times I've read the supporting documents from thier website. Even tried reading first thing in the morning cause my mind was fresh. Port 2 is the thermostaticaly controled port but what gets connected to it ? Is that the pipe that leads into the boiler return ?

 

OK, yeah, I thought you said you already had the 260 ...

On the thermic valve...

One port comes from the system, let's call that A

One port comes from the boiler supply, call it B

One port goes to the boiler return, call it C

Refer to the thermic diagram above.

Below 113*F, almost all the flow will be from B to C, with perhaps a little from A to C.

Between 113*F and appx 135*F the flow will be split. A and B will come together and return MIXED to the boiler.

Above 135*F most of the flow will go to and from the boiler, with perhaps a trickle through the bypass.

In other words, as the port from B to C begins to close at 113, the port from A to C opens ...

The valve will 'modulate' a bit between 113 and 135, so you can do some passive mixing of supply water and return water in that region. I believe that it's in this region that the 260 and the TV will play nice together.

When the valve starts to open the water that starts flowing from the system may be cooler than 113... this will slow the opening of the valve a bit... ensuring that the boiler return never sees a temp below 113 ...

Have you ever measured the temp difference between the supply to the system and the return water from the system ? (otherwise known as Delta T or DT, or if I could do that triangle symbol, that too... )

That delta would be good to know in your case, because you want your BOIL MIN set to that difference, PLUS 113* ...

I would install one of them thermometers on the boiler return.
How do they mount ? It said SIX INCHES ? how you put that on a pipe ?

 

Thanks Trooper for the TV valve explanation. I will read your last post again later to make sure I have the valves' operation correct in my head. No, I have never measured the delta T of the supply and return water from my system,(BTW no triangle button on my computer either ). As far as the thermometers in the link they have NPT threads behind the face so the stem will actually be submerged in the boiler water via a copper T fitting and a female NPT adaptor. The end of the stem will be reading the water temp.

 

What about check valves guys ? I see in this diagram there are 2 swing check valves, will I be needing these also ?

s


I'm not exactly sure how the water will know where to go when it leaves the bypass and rejoins the boiler output water. Hope that makes sense.

 

Let's back up a little bit ...

There's sorta two discussions going on here that are related, but I think clouding the issues...

BOILER PROTECTION : FULL ODR

How do I explain this ...

If you put the ESBE thermic valve on the boiler as shown earlier, your boiler will be protected, no matter what.

The problem comes when you try to do FULL ODR with that setup. The times that the 260 targets a temperature that is BELOW the temp of the ESBE, will cause unpredictable results.

The boiler may cycle in wierd patterns, depending on a number of factors ...

It's not that you will lose the boiler protection if you do FULL ODR, it's that the control won't know how to handle the fact that it has to wait for hot water, and then when it does get hot water, it's already TOO HOT (above the targeted BOIL MIN) ... then it will freak out, shut down the burner ... then it will cool again and the burner will re-fire ... or some other behaviour entirely ... but the 260 won't be happy about it.

What I'm saying is not that it won't work, but that it will be unpredictable as to what it actually does do ...

In order for you to be able to control the boiler PREDICTABLY and do FULL ODR, you need TWO separate loops ... one around the boiler, and one around the heating loop, with a bridge in between ... AND a more expensive control.

Keep that in mind when thinking about re-doing the system, because you probably won't be able to use your existing 260 for that... probably be a 360 series...

There's a Tekmar essay that you should read ... I think it's E021 ... lemmee get a link here ... ok, two links...

First four pages in particular of this one (click here) E002

This one has some good info (click here) E021

 

The 260 is basically a BOILER RESET controller. It's designed to control the boiler... resetting the water temp in the boiler based on outdoor (and optionally indoor) temps. It's drawback is that for a NON-CONDENSING boiler, you can only do PARTIAL RESET. (BOIL MIN must be set to prevent condensation).

MIXING RESET is when the water going to the SYSTEM is controlled in response to outdoor (and optional indoor) temps.

The 260 isn't designed for MIXING RESET.

In order to do mixing reset, you need a control that will operate either a variable speed pump, or a motorized mixing valve. To also have boiler protection, you need more sensors than the 260 has.

 

Thanks Trooper for your continued support on this topic. I printed the Tekmar essays that you linked to for future reference.

To get everyone on the same page, I am looking for partial ODR with a non condensing boiler, oil fired. The 260 is installed and functioning properly.

About those swing valves, your saying they're not needed for partial ODR ?

Another thing I don't understand is the ESBE valve placement . I know mine will go on the return side of the boiler. The only circ on my system is also on the return side of the boiler as shown in the pics in the first post. What confuses me is this, does the ESBE go in between the circ and the boiler or before the circ ? All the diagrams that you provided and those on the Danfoss site show the valve before the circ, but how can the circ move the water through the bypass if the bypass starts before the circ ? I hope I explained this correctly.

 

Joe, the swing checks in that diagram are there to prevent the DHW pump from circulating water in the other loop, and vice versa ... they don't really have anything to do with whether or not ODR is being used.

With the ESBE, the valve can go either on the return or the supply ... BUT ... there are different temperature models to be used on the supply side... for boiler protection, it's best on the return I think ...

The circ goes in between the boiler and the ESBE... I think another pic might be easier ... later...

 

Progress update,

After waiting 5 weeks for the Danfoss valve to come from Patriot supply, I have it plumbed in and working. A big Thank You goes out to everyone that helped me, especially Trooper. Later I will post pics of the piping for all to see.