With all the talk about piping and controls on this forum I asked the contractor who quoted a new Crown CT-3 oil boiler to replace my old 35 year old boiler exactly how he intended to pipe the system. I took notes and then created a schematic of what he described. I think I got it right:
http://i202.photobucket.com/albums/a...s/Boiler01.jpg

Hot water is supplied by a new stand alone electric water heater so that's not needed.

My questions:
Is this an adequate way to pipe the boiler?

Is this the optimal way to pipe the boiler?

Should anything be added/removed/changed?

Is it better to use separate circulator pumps for the four zones or would a single circulator with four zone valves be better?

Will this piping support cold start/finish?

He intends to use typical Honeywell RA89A1074 switching relays with programmable thermostats. Should I spec better more up to date controls?

Any comments/suggestions would be greatly appreciated.

 

Might be okay although it violates the prime rule of "pumping away" from the expansion tank.

Definitely not.

Yes, the circulator pumps should be piped prior to the Taco Flo Checks on each zone. It might be easier to use circulators with internal flow checks. Also, remove the automatic air vents from the return lines. Air vents belong on the outlet of the individual baseboard convectors and at any high point in the system.

This question is more of what someone desires. Multiple circulators allow heat in at least some parts of the house if a circulator fails. Zone valves seem to have a higher failure rate than do circulators. Having multiple circulators allow for sizing the pump for the single zone versus sizing for the combination of all zones.

Nothing wrong with that approach although using a multi-zone circulator control panel makes the wiring a bit neater.

 

The piping diagram seems to come right out of the installation manual. Wonder why they haven't changed to show "pumping away"? Here's a link to the manual: http://www.crownboiler.com/manuals/c...20Freeport.pdf

RA89A switching relays will not work. One has to use R845A, RA832A relays (or equivalent) or a zone relay panel made for circulators. The relay panel would be VERY slightly more energy efficient.

I am not at all an avocate of zone valves, quite the contrary, but again there is a slight energy efficiency advantage.

 

I'll guess:

1) poor editing; and/or
2) cost to a) redo the figure and b) reproduce a manual that was laid out with different page layout software than they're using now.

If you look at the Crown Bimini manual (their newish gas modcon boiler), you'll see a very nice set of piping diagrams that get into primary/secondary, closely-spaced tees, indirect takeoffs, etc. etc. It's not only pumping-away, but also way better in general.

But Grady, beware. If you're still on dial-up, that manual is 31+ mb!

And to answer the original poster, I agree with furd and Grady. Piping and control strategy could be much, much better.

It would also help to ask your potential installer about an outdoor reset control. And if the installer says they're not worth it or too much trouble, show him the door and find someone else.

 

Xiphias,
Thanks for the heads up on the file size. I finally got broadband a couple of months ago. Maybe in the next 20 years, I'll be able to get FIOS. BTW, how's the fishing up your way. It's been the dead sea around here.

 

I've actually been well south of you for about a month. Back now. Returned to find a whole lot of very warm (75-77F), fish-poor water. Heading out to some 80-100 ft holes this weekend, looking for doormats.

 

OK, I've tried to take the advice given here and came up with a new piping diagram:

http://i202.photobucket.com/albums/a...s/Boiler02.jpg

Did I get it right? Is this the optimal way to pipe the boiler?

Should anything be added/removed/changed?

Is there any need for primary/secondary piping with a CT-3 boiler used with cold start/finish?

Thanks again.

 

Not quite. The flow direction is backwards. You want the circs on the supply.

Suggest you pipe the autofill/backflow/prv as shown here:

http://spirotherm.com/docs/installation/JrIOM-A.pdf

The air eliminator has a tapping below for this connection (all of them do, not just the spirovent brand). Add a ball valve between the expansion tank and where the autofill/backflow/prv enter the system. That will make it simple to isolate the expansion tank when it someday fails.

Don't use the "spirotop" vent. (They're marketing....)

I would use integrated flow check (IFC) circulators and ditch the Taco flow-checks. Either Taco or Grundfos come in this form.

Suggest putting the ball valves and drains on the zone returns and making the return enter a horizontal header like you have for the supply. Use isolation flanges for the circulators (e.g., Taco Freedom Flange), which serve two purposes: 1) makes swapping out a failed circulator a 5-minute job, and 2) the ball valve on the circ outlet flange serves to isolate each zone on the supply side.

Only if you are going to use an outdoor reset control to run the system with water temperatures below the flue gas condensation point (for gas, about 135-140F).

IMHO, if you are doing a repipe already, then for a bit more time and equipment, it makes sense from a long-term fuel savings perspective. There are some simple p/s diagrams around here, furnished by rbeck. Check out this thread:

http://forum.doityourself.com/showthread.php?t=328683

The p/s diagram in rbeck's post at #27 in that thread is a really clean, no muss, no fuss p/s system that would allow full outdoor reset. You would also need a control such as the tekmar 256 (if no indirect) or tekmar 260 (if using an indirect), although I would probably get the 260 anyway as it has an option for indoor temperature feedback and has DHW support availble should you ever go that route.

Again, more effort up front, but if you're going to be in the house a while, probably worth it in terms of long-term savings.

it's even about a Crown boiler.

 

Xiphias,
Thanks for the great feedback. You've really helped. I will spec all of your suggestions. I may have another question or two after I go through all the details.

 

Ok, taking into account all the suggestions I've received here as well as the referenced diagrams, I've revamped my piping diagram. I think I'm getting closer, please have a look and let me know what you think?

http://i202.photobucket.com/albums/a...s/bolier08.jpg

My questions are:
1). Is the piping diagram correct? Anything else need to be added/removed/changed?

2). I assume the secondary circulator must be turned on whenever any of the zones call for heat. If this circulator fails does it bring down the whole system?

3). I don't yet fully understand the concept of primary/secondary piping. To protect the boiler from condensation I assume the secondary circulator is turned on whenever the return water temp is too low. Is this correct?

4). The system will be controlled by a Tekmar 260. Does this controller control the operation of the secondary circulator both in normal mode and bypass mode? If not what does?

5). The system is going to be used for cold start, cold finish, and outdoor reset with an indoor sensor. Will this piping along with the Tekmar 260 support all of that or do I require additional piping/controls?

6). Do I need the purge valves as shown in the referenced diagram? If so how many and where do they go?

Thank you for all the help.

 

1. looks ok to me. add some unions on either side of the boiler.
2. Probably.
3. p/s still confuses me, too (which is one of the millions of reasons you shouldn't trust someone on the other end of the internet...). The circulator will need to run whenever the boiler fires. Control can be on/off or variable speed. See rbeck's post here: http://forum.doityourself.com/showpo...4&postcount=39 on control and wiring.
4. There is no "normal" or "bypass" mode. If you control as on/off, then what rbeck says above applies to a control like the 260. If you do this using variable speed injection, then you'd need (in tekmar's world) a 356 or 361.
5. Seems ok the way it is. See above about whether 260 is right or not, depending on what strategy you employ.
6. Good purge-ability is a wonderful thing. Put 'em where the diagram shows.

One last thought is that if you have a reasonably-piped distribution system, then I would strongly consider using zone valves instead of 4 circulators. Pipe the zone valve manifold with a differential pressure bypass, or invest some $$ in a smart differential-sensing circulator (Wilo makes them now; other manufacturers have them in the works) that automagically adjusts the pump speed to match the number of zones calling and thus keep the flow rate nominal. Four circulators is a pretty brute-force approach in a simply-piped system (e.g., 4 zones of 3/4" copper + fin-tube baseboard connected in series loops). The long-term cost of electricity to run a bank of circs will catch up with these approaches.

 

Xiphias,Thank you for the input. The solution is getting closer. I will consider the zone valves.

The only remaining problem is how to specifically control this piping scheme with an existing controller. I've been studying the Tekmar literature and I really don't see the solution. Here is my take, please correct me if I'm wrong anywhere:

(Note: DHW is not included in this scenario)

In a nutshell the Tekmar 260 monitors the boiler supply temperature, the outdoor temperature, and optionally the indoor temperature. It then modulates the boiler to maintain a set boiler target supply temperature by firing the boiler on/off based upon characterized heating curves which take into account the data received from it's sensors. This is how it supplies ODR.

It receives a boiler demand signal from either thermostats (via a 003 relay) or directly from Zone Valve Motor End Switches which are turned on/off by thermostats. In the case of multiple zone valves it supplies power to a single circulator pump and hot water is then circulated into any zone where the thermostat has opened the zone valve. See diagram. In the case of multiple circulators it supplies power to each pump via the 003 Relays and hot water is circulated into any zone where the thermostat has activated the 003 Relay. See diagram. After boiler demand is satisfied it continues to operate the boiler pump(s) for an additional 20 seconds to provide cold finish.

Ok that's how the 260 provides cold start, cold finish, ODR, and optionally indoor temp sensing. But how does it provide boiler protection against flue gas condensation?? The only way I can see is via the Boiler Min setting which is the lowest water temperature the control is allowed to use. I don't see any direct means to control a primary/secondary loop.

Enter the Tekmar 360 and 361. These units appear to be a Tekmar 260 with the addition of boiler protection control via a primary/secondary loop. The 360 provides protection via a floating action mixing valve while the 361 provides protection via a variable speed injection pump. They both use an additional sensor (called the mix sensor) in the secondary loop. Both controllers require rather complicated piping requiring specific calculations that in my opinion are too complex for installers who did not graduate from MIT. These controllers may be able to control this piping but it's not yet obvious to me how to do it.

So what to do? I can't be the first person to face this problem. For those using the 260, how do you provide boiler protection? For those using the 360 or 361, were you able to pipe the diagram Tekmar provided? Or did you find a way to use the controller in another way? Can you see a way to use any of these controllers for this piping?

 

The great thing about hydronics is there's so many options. The frustrating thing about hydronics is there's so many options.

Basically, you've got everything straight. Nice work. The good news is that it doesn't have to be as complicated as all that.

The short answer about the 260 is that you can either wire the "central heating secondary circulator" to run as on/off whenever the boiler fires (IF there is some other form of boiler protection, e.g., see below), or you can use a boiler with built-in variable speed injection. In either case, the 260 is none the wiser and it just goes about its business. (FWIW, my system uses the latter....)

The 356 and 361 can control the variable speed injection pump directly. While the full calculation of all that stuff in the tech essay looks daunting, it generally boils down to some very simple paramaters for sizing the pipes and the circulator.

But wait, there's more. You have yet another option. If you go back to this thread

http://forum.doityourself.com/showthread.php?t=328683

and go to post #47 on page 2, you will find a "doctored" version of the diagram that includes a simple ESBE thermic bypass that will provide boiler protection.

Then you could go with the 260, and wire the central heating secondary circ to operate with the boiler per the rbeck post in that thread, and you are all set.

What's an ESBE thermic bypass? This:

http://na.heating.danfoss.com/PCMPDF/ESBE%20TV.pdf

you'd want the 113F model for oil, the 140F model for gas.

Note also that the tekmar 003 relays are just their brand of relays. You can use something like a Taco SR switching relay. Probably cheaper and easier to wire.

 

Ok, if I understand you correctly adding the ESBE Thermic Valve on the return as shown here will give full bypass until the return temperature reaches 113 degrees (oil) or 140 degrees (gas). As the water temperature rises the TV valve will open allowing water to flow through the system while always maintaining a 113 degree or 140 degree minimum return temperature. That's awesome.

So adapting this diagram to mine would now look like this. Is that correct?

This brings up a question though. If the ESBE Thermic Valve is used, then what's the purpose of connecting the supply and return via closely spaced tee's? Shouldn't it now be piped like this (or using rbeck's diagram like this)? Or is the purpose of connecting the supply and return lines together to supply an alternate path for water to flow if the zone circulators are on and the ESBE is in bypass mode?

If Tekmar 260 controls the boiler modulation as programmed by monitoring the supply temperature and turning the boiler on/off to regulate the supply temperature, then the secondary circulator couldn't be turned on and off along with the boiler because if the secondary circulator stops then there's little or no flow to the zone circulators (or valves). Thus, unless I'm missing something, no modulation. I would think the secondary circulator has to be on any time any zone is calling for heat.

Also if the Tekmar 260, while trying to employ ODR using its characterized heating curves, tries to lower the boiler supply temperature to anything lower than the ESBE bypass valve's minimum return temperature, it may get confused if the user does not carefully set the Boiler Min setting into the controller.

I can envision a scenario where if the 260 tried to use a supply temperature of 120 with a ESBE valve rated for 140 the water would go round and round in the bypass loop "forever" while the thermostats keep telling the 260 heat is required. I wonder if the 260 would be smart enough to raise the supply temperature after a while?

I don't know with all these possible problems would the the piping Tekmar calls for here be the better way to go?

Sorry for all the questions but I need to figure this out soon.

 

Looks ok to me.

The purpose is to hydraulically separate the boiler loop from the system loop, so that the system loop can run at the supply target and differential that the 260 decides.

Your modified diagrams do not provide the hydraulic separation that you want to achieve full outdoor reset and boiler protection. The idea is that the 260 supply sensor will go on the system loop (right before the circulators). The 260 will fire the boiler (and the boiler loop circulator) when it wants warmer water. It won't know and won't care about what the ESBE or the boiler loop circulator are doing. It just fires the boiler and watches what the temperature at the supply sensor does.

The ESBE just does its job protecting the boiler and will give water to the system as the boiler loop comes up to temperature. If the supply target is below the ESBE temperature, it doesn't matter. The ESBE will only give water to the system loop when the boiler is protected. Because it opens gradually, the ESBE will basically slowly mix warmer water into the system loop until it gets to the supply target.

IMHO, no. The rbeck diagram with the ESBE is simple, clean and effective.

No problem. Questions are good. It would be helpful to get a couple more opinions, but I think this approach is a good one.

 

Less, the diagram you are looking at is I think an earlier version. Later I hacked the drawing a bit more and moved one of the purge valves to better facilitate the purge process...



Note that in the drawing you are looking at there are two valves on the system side of the ESBE. In this version, there is one on the system side, and one on the boiler side.

There was a spirited discussion a while back concerning what happens when the 260 targets a temperature that is BELOW the temp of the ESBE. I really don't wanna hash that out again, but think it through fully before committing to something like this. If you use the 113° ESBE, you migh want to set it up so the 260 won't target less than that. Is that the 'BOIL MIN' setting ?

 

I've taken the suggestions offered here and have made the changes. I'm ready to order all the parts and begin work.

The rbeck modified diagram now looks like this:


and the schematic diagram looks like this:


Does anyone see any problems? It will be controlled by a Tekmar 260 as xiphias describes above.

Instead of using Tekmar 003 relays I'll spec the Taco SR504-2 4-Zone Switching Relay as suggested.

For air elimination is it better to use a Spirovent or an Air Scoop? The Spirovents cost $175 each. Seems a bit high.

The only place I could find the ESBE valve was Patriot Supply for $207 and it's not in stock. Is there any other place to get one?

In the rbeck modified diagram above I'm trying to understand the A, B, and C dimensions. I think A and C are supposed to be a minimum of 6 pipe diameters or 9" for 1-1/2" pipe. I don't know about C. Perhaps dependant on the air seperator?

 

Looks good to me ...

Just a couple comments:

PHYSICALLY, the components don't have to be exactly where they are shown. The circulator could be much closer to the boiler, as could the ESBE and other associated valving ...

The spacing on the tees is MAX, and the closer the better.

Yes, D is the diameter of the pipe being used.

The distance ahead of the air removal device will be dictated by the manufacturer. If you use a conventional scoop, I believe it's 18" . The Spirovent needs no 'clearance' ahead.

I would strive to not have any elbows 12" ahead of and after the circs...

You may have a hard time getting that ESBE, seems that they've caught on with the wood stove folks... and stoves are selling gangbuster right now... the ESBEs seem to be flying off the shelves.

You might want to go ahead and pipe up the system without it, but leave 'stubs' or plugs in tees, or unions ... so that you can install it later. If you have fin-tube radiation ( I forget if you do...), you may just find that you don't even need to worry about boiler protection.

Consider adding a temperature gauge on the return to the boiler. Check www.houseneeds.com , they have some small analog ones that work for me. There's also a 'cute' little digital one that displays 2 temps, and the delta between them.