I found this drawing in my 'work' folder... there are probably some things wrong with it, i.e. with the buffer tank, the spirovent may not be needed, stuff like that... but the reason I'm posting is as a rough guide for you.



Note the check valve in the boiler return... note that when piping an indirect to the MPO, the indirect return goes to the bottom tapping... note the boiler bypass (which may not be needed)...

[edit note: Looking at the latest MPO I&O, I don't see where they are spec'ing the indirect return into the bottom tapping anymore? ??? rbeck, has this recommendation been changed recently?]

The reason I added the check valve is to 'divorce' the bypass from the circuit during indirect calls, and also to insure that all the indirect flow goes through the proper ports. Without that check valve it would be possible (maybe not probable...) that some of the flow for the indirect would be OUT of the return on the boiler. If it is determined or desired that you do NOT use the bypass, you would not need that check valve.

Also, I'm not sure you will need the webstone purge tee with this arrangement. Closing the throttling globe valve in the injection loop would allow you to purge the heating zones...

This drawing is showing pumped zones. If you go with ZVs, you would want to place a Diff Bypass out at the end of the manifolds.

Anyway... just something to chew on... rbeck (or anyone!), your thoughts?

 

That is right Trooper. With some minor changes we now say it is OK to pipe the IWH in like any other zone. Just add it to the return manifold.

 

OK then, if it's piped into the 'normal' return, and the bypass was used, you would probably still need the check valve. You wouldn't want the bypass in the circuit on an indirect call... right?

But, I'm thinking that you don't really need the bypass at all. When will the return from the buffer tank be cool enough for concern? For a little while the first time the system fires up in the fall?

 

You are correct I would not use a bypass on this application.

 

I keep looking at this, main reason being is that it's what I might do with my own system if/when I get around to actually doing it. I know... I've been saying that for years... but you know how 'other' priorities keep popping up. Anyway...

Looking at the Boiler Buddy installation, and their recommendation to pipe the make-up water into the top port, along with the air vent... I'm troubled by something.

When you go to initially fill the system, you've got massive amounts of water coming in, and massive amounts of air going out. If these two are trying to share the same pipe, it's gonna be problematic.

Can we choose an alternate location for the make-up water?

About the Spirovent and expansion tank on the 'system' loop. Theoretically, the Spiro isn't needed there. Boiler Buddy says that the vent on the tank is sufficient. I'm not so sure... that's why I've put that 'extra' air removal out on the system. You will have relatively small exchange of water between the boiler and the system loops. Full flow in the boiler loop, the vent on the 'buddy' will handle that air. Full flow in the system loop, how much of that air is really going to find it's way back to the buddy? I think the spiro out there is cheap insurance.

The tank location will also establish the PONPC in the system loop, and ensure that the air will be actually moved through the system loops and find it's way back to the spiro.

With this in mind, why not place the make-up water at the spiro/tank location?

I don't see any drawback to this, EXCEPT when purging/filling the system. In this case, you WOULD want to use the Webstone purge tee in order to direct the water where it needs to go. Either that, or possibly a check valve in a proper location to allow purging... but check valves can make noise.

 

OK, next generation of MY system... your mileage may vary!



Note the Webstone Purge Tee.

The 'schtuff' under the SpiroVent could be replaced with the RBFF, or that other one (I forget what it's called)...

Added purge valve on indirect piping to allow filling that loop.

 

Hey All,
Sorry about my horrible diagram but I was thinking about the system again and was getting annoyed that even if I spend big bucks on a tekmar 361 and 260, it doesn't do everything I really want it to Then I got thinking about doing my own controls using the boiler aquastat and an aquastat on the buffer tank to control its temperature. Then I realized why do I need two tanks can't I combine them IDW & Buffer....searching on the internat yielded ERGOMAX, not exactly what I wanted but close.....
Ergomax Heat Exchangers

Sorry about this drawing but I'm running crazy here, just wanted to get you opinions about this..

 

Keep in mind that the Ergomax is really nothing more than a BIG 'thankless coil'. The same limitations that you have with the coil in the boiler will apply to this as well, to a lesser degree perhaps, but never the less...

And, I believe you will have to run the boiler as a 'warm start', because you will need to keep the water in the 'buffer' tank hot all the time, 24/7... $$$ ... $$$ ... $$$

Someone correct me if I'm wrong, but that's what it looks like to me.

Here's a quote from the EM website:

I guess that their idea is that since the tank is so well insulated, it will store enough BTUs in the water in the tank in order to provide 'on demand' hot water use and still run cold start.

I am still a bit skeptical that this type of indirect would be as efficient as one which actually stores a quantity of hot water.

 

Troop,
How is that different than the normal indirect? The Boiler temp has to be ~20F above the target hot water temp right? To me it seems like you cut your stand by losses in half, at least in the cold weather...... The benifits are simpler plumbing, one less pump, boiler reset down to 140F in the summer, DHW temp is ~120F probably ok, don't like hot showers in the summer anyway!

 

I definitely agree about the simplification, and that may be a compelling enough reason to make the choice. In todays homes space is often at a premium, and having to place yet another tank can be a problem.

What's different is that in a so-called 'normal' indirect, there is a volume of domestic hot water stored, 30-40-50 gallons, whatever size it is, and the boiler water goes through the coils and heats that volume of water when the a'stat on the tank calls for it.

The Ergomax is 180° out of phase with that approach. The tank is full of hot boiler water, and the domestic runs through the coils, so there is no 'storage' capacity of domestic hot water.

It may be one of those 6 of one, half dozen of the other things... but having never seen one, tried one, tested one etc.., I just have to say that I'm a wee bit skeptical that it could be just as efficient as the 'normal' indirect. I really do like the idea of not having to run a bacteria breeding farm, and not worry about anode rods... so that's another plus!

 

Finally got a minute to touch up my last drawing, just wanted to get anyone's opinion about this design. I'm going to use the Tekmar 361 to do the mixing control and the Buffer-indirect is going to be wired like an IHW heater initially with a manually set aquastat. I'm little nervous about using the Ergomax combo but I really like the idea so what the heck...

 

Does the 23-gal indirect give you enough buffer to get a sufficient runtime? You want around 7-8 minutes firing.

You can size the buffer like this

Vbt = t(Qh -qload) / (500 *dT)

Vbt size of buffer (gal)
t desired on-cycle (min)
Qh energy source output (BTU/hr)
qload rate of heat extraction from buffer (BTU/hr)
dT temp rise of tank between on/off cycles (F)

and rearrange the terms to solve for runtime

t = (vbt*500*dt) / (qh - qload)

You don't need or want the ESBE if you have the buffer. It's one or the other. Not both.

Use a Wilo ECO or Grundfos Alpha instead of differential bypass on the distribution system.

Put the fill and expansion tank on the distribution system side, not the boiler side.

Make sure you do a proper heat trap and VS injection sizing, per
http://www.tekmarcontrols.com/litera...robat/e021.pdf

 

Hey Xiphias,
The tank is 26 gal. which should give an 8.5 min run time.

(26 x 500 x 30) / (80k - 34k) = 8.5min

The reason I put the ESBE valve in there is so I can run the buffer tank below 140F say (150 hi - 120 low aquastat settings) during the shoulder seasons, I'm hoping the hot water doesn't suffer too much from this but I guess I will find out. From what I understand from the literature, the 361 isn't doing much boiler protection when a buffer tank is installed, it only varies the injection pump speed to protect the boiler return temp, that's not going to do much with a 26 gal. tank. At this point the 361 is a waste, I'm only using a fraction of its capabilities but I don't know of any other controller that will do mixing with indoor reset....

About the heat traps, 12" drop minimum on both supply and return on the injection system. Can I just use a flow check on both sides if space is tight?

I was going to use 007 for all the pumps, I did look at the literature and unless I made a mistake they should work everywhere. I'm going to use the TACO freedom flanges on all the pumps so swapping them out in the future is easy if I want to upgrade to an ECM pump when the price comes down.

I thought the DeltaP valve is a much cheaper solution than a wilco or alpha, the Delta-p is just a pressure relief valve right?

I will put the expansion tank on the distribution side, I was thinking it should be at the point of highest temperature in the system. Trooper kept moving it but I'm kinda dense....

 

ESBE, non-ESBE, whatever you like. Not sure there's an upside, really, as the low tank temps will result in less heat transfer to the DHW coil.

The expansion and air removal should be on the distribution side because that's where the largest pressure drop will be, and where you will want the air elimination. There will be very little pressure drop on the boiler/buffer side due to the volume of the boiler, tank and piping. If you are concerned about air removal over there, stick a vent on the buffer tank or tee off the relief valve tapping of the boiler.

The dP pumps have come down quite a bit, and are competitive with the added cost and time to do the dP valve. They will also save a ton of electricity. Consider around 8-12 watts instead of 80 with a 007.

I'd do the real heat trap. Lots of resistance in check valves.

 

Speakin' of check valves...

I'm not sure I see the reason for that one that's shown in the return from the tank to the boiler ?

Also, on the VS injection pump, my gut tells me that you don't want an IFC pump there... when that pump wants to run slowly, there might be a struggle to open the IFC.

Another vote for no on the ESBE...

Some thought needs to go into the controls... with this setup, the boiler sensor will have to go on the supply out of the boiler... since there will be an a'stat on the tank keeping that hot... lots more thought... the whole scenario needs to be played out, DHW call, vs heating call, etc, ... might not be a bad idea to talk to the engineers at EM and get their input too.

 

I'm sure the brain is involved there somewhere.... Correct. No IFC on injection pump.

IIRC, you can run the 361 with no return/boiler sensor and it will just fire/stop off the boiler aquastat.

 

Thanks for the suggestions, here's the latest.. No more IFC on the pumps, and the thermal traps on the injection ckt

 

don't think you need the check on the boiler pump.

put drain on injection loop at the bottom, not top.

otherwise, quick glance suggests looks good.

 

I guess you don't need the IFC's anywhere... but I was specifically targetting the injection pump with my comment...

That valve at the top of the injection loop is a purge valve... but I guess it wouldn't hurt to have a drain at the bottom of the heat trap too. An extra valve here and there has no consequence, but not having them where you need them is a pain...

I'm thinking that the check on the boiler loop might not be a bad thing... it will prevent gravity circulation through the boiler in the summer time when it's only used for DHW, reducing standby losses in the Ergo... no? If so, I would opt for the IFC pump there, rather than a separate check.

Since the diff bypass is gone, I presume you've chosen to use the DP pump then?

 

FWIW, I'm cool with all that....

 

I should have listened to Trooper earlier about his misgivings about the reverse indirect. After thinking more about the operation of the system, I realized that during the summer I would have to run the boiler at 200F to get the Hot water output that I would need to cover two showers at the same time, very possible in my house...... This ruins it for me, the whole point was to make a more efficient system by lowering the boiler temp. For this reason I'm going back to Troopers original design, I should be able to run at 160F with a 50gal IHW tank.


The house radiation is designed to meet the heat requirements with 150F water, and the boiler temp would be 170F. The BB-80 is to get a long run time with a 20F differential (170-150).
Run time = 80 gal x 8.34 BTU/F.gal x 20F x 60 = 10.8 min

During the summer months when only the IHW is calling for heat, Do I have to worry that none of the water is running throught the Spirovent or the Buffer tank, should I have some sort of air removal on the boiler side of the system?

 

The latter applies here.
..........

 

Added Air scoop to boiler side
Also added the water fill to the Buffer tank, with the purge valve at the tank filling should not be a problem

 

Whole air scoop on boiler side is overkill IMHO. Suggest you do one of the following:

a) stick a Hy-Vent on top of the buffer tank as you are showing now, or

b) stick a Hy-Vent off a tee on the boiler pressure relief valve piping.

That's all that's needed.

There are diminishing returns and even negatives to having too many air removal points.

 

Sorry, but I can't imagine why you would but the fill point at the buffer tank.
You may actually cause yourself some problems putting it there, as your injection pump pumps into a point of no pressure change.

 

xiphias,
What is the negative of too much air removal?

TOH,
I should never try and improve on troopers designs, he is the master!!! Fixing problems that don't exist, I will put it back at the expansion tank... thanks

 

Air removal devices are future leak points. They all leak eventually. Some sooner than others. Leaks require make-up water (and repair...). Make-up water adds oxygen. Oxygen corrodes the ferrous components.

Improperly-placed, they can also allow air IN due to negative pressure at certain points in the system.

 

I just read a lot, and talk too much... and draw pictures... honest! There are many here who are WAY more masterful than I am!

A couple points about the last generation drawing:

You are showing separate pumps and check valves for P1 and P4. They can be IFC type pumps. Not sure if I got misunderstooded when I said not to use IFC somewhere... but they are fine, as long as they are appropriate.

I'm not sure if you answered this or not? I had asked when I noticed that the DP bypass valve was gone from the system side if you had decided on the DP pump out there?

I'm goin' with Xiphias on the air scoop on the boiler... not really necessary. It can't hurt... and I personally like overkill... the cast iron ones are way cheap, so it's not like it will break the bank, but you don't really 'need' it. If you decide to do away with it, still place a vent out there... but place it according to the PHYSICAL layout that you end up with. Put it at a high spot in the piping. Without a scoop under it, an air vent can only trap the air that floats up to it when the pump is not running. Maybe a good idea would be to replace the purge valve on top of the boiler with the air vent?

Or, perhaps even better yet, a high point in the piping on the discharge side of the DWH pump. Since the reason for adding the vent to the boiler side of the tank was for summer operation, it would kinda make sense for it to be on that loop.

I don't think you will need the purge valve on the outlet of the buffer tank if you move the water feed (below).

The guys are talking about "PONPC" (Point of No Pressure Change)... and moving the water feed back to the expansion tank... reason for this is that the pressure in the system will remain almost constant at that point, and fluctuations won't 'mess with' the pressure reducing valve. If you do decide to go to the top of the tank, you want to add another valve between the reducing valve and the tank for service. You want to be able to isolate it from the system. If you go to the tank location, the valve is already there.

You probably won't 'need' the drain valve on the heat trap either... unless you envision times when you might need to drain every last drop of water from the piping. If there's a reason to drain for service, who cares if there's a cup or two of water in that pipe?

 

You don't want the extra air venting on the inlet side of the boiler pump. There will be some negative pressure there. Same with the 'replace the purge at the top' idea.

Really, if you are bound and determined to have some kind of air elimination on the boiler side, put a tee off the pressure relief valve piping at the top of the boiler. Come off the side port of the tee with an elbow, then a short nipple up to a hy-vent. Do a short nipple off the straight of the tee, install the pressure relief, and pipe as normal.

 

I think that's where X said the vent should go, my gut says to put it where the purge valve is now but I haven't been right yet.... moved the water inlet and put a valve in.

The pumps are all 007's except for P3 thats the Wilo ECO.

The reason I went with separate flow checks is in the future if I want to upgrade the 007's to some low power ECM type pumps I won't be restricted to pumps with an IFC.....

 

You won't need the second valve below where the water feed is tee'd into the tank connection... just the one above. If you need to service the feed valve, shut off the upstream one, close the one above, drain pressure from the tank with a hose on the drain... and that's it... this is the same process for checking/charging the tank air charge.

A good option on the water feed chain would be a WYE strainer, between the upstream shutoff and the backflow preventer.

I don't usually disagree with Xiph... but this time I do... because:

He said: "You don't want the extra air venting on the inlet side of the boiler pump. There will be some negative pressure there. Same with the 'replace the purge at the top' idea."

And his proposed location seems to violate those rules. I'm somewhat skeptical that the air vents would actually 'gulp' air on a pump start-up anyway, but an ounce of prevention, as they say...

When the system is actually circulating water, there will be ZERO flow past the proposed location. In order for a vent to vent, air has to appear below the vent. IMHO, that location will do nothing to vent any air. When the water is flowing, the air bubbles will go right by. When the water stops, the air bubbles will float to a high spot, and sit there until the next pump cycle. They will never reach the vent opening.

The whole idea of the vent on the boiler side is for summer operation, right? During the winter, any air elimination will take place in the buffer tank, and at the Spiro out on the system side. The concern here is the DHW loop.

So, if we follow the 'rulez' that the air elimination should preferably be on the discharge side of the pump, and that the vent should be at a 'high point' in the piping, and that this vent only need be 'active' during a DHW call, then it would seem the only place for it would be on the DHW loop, at a high point in the piping, on the discharge side of the DHW pump.

 

Just happened to see this thread while idling away some time. #3 is an EK and it's able to do all it does without ODR, a bunch of additional piping or any of the other bells and whistles that get tacked on to more conventional systems. There's nothing to program, no OEM burners, uses conventional single speed circs and zone valves. I installed close to 70 of them and had no complaints other than one or two who, for some reason, weren't happy that they couldn't hear it run.

Even though the technology used today hasn't changed much since the system was introduced 30 years ago, it's still at the top of the list for efficiency and reliability.

 

I have been away for awhile and not following this link but the latest drawing and last few posts give me a concern. I am not even sure I understand which vent you are talking about but I will assume it is the vent on the boiler due to what "X" said.
I will have to disagree with "X" as the vent should be straight up off the top of the tee so air would get to it. Air does not go around corners where there is no flow. The vent if installed would be straight up off the top of the tee and the relief valve off the branch of the tee with a nipple so the relief valve is vertical as required by code.
Secondly "Trooper's post I disagree that the vent normally would be in the low pressure point of near boiler piping which would be on the inlet side of the pump. When the pump adds pressure from the discharge side of the pump it tries to drive the oxygen back into solution. With that said it could possibly suck in air if on the inlet side of the pump if not near the ponpc.
The drawing shows the vent on a short line out of the flow of the water which means it does nothing. The air will go right past the pipe that leads to the vent.
The fact of the matter is there is no reason to put a vent on that boiler loop at all in this drawing. The pump will move the air with the water to the tank. The tank being a larger vessel than the pipe will cause the water to slow down and the air being buoyant will go to the top of the tank. The relief valve goes on the return manifold on the MPO.

 

rbeck said "The fact of the matter is there is no reason to put a vent on that boiler loop at all in this drawing. The pump will move the air with the water to the tank. The tank being a larger vessel than the pipe will cause the water to slow down and the air being buoyant will go to the top of the tank."

Is this true during the summer when the system is in WWSD and little or no water is flowing into the buffer tank? The thought was that there should be some sort of air removal when only the IHW pump is running.....

 

Then we agree. I haven't been around here lately either.

1) it's drawn incorrectly (incorrectly interpreted from my written description which was probably not very clear)

2) it's not needed (see my "bound and determined" comment in earlier post)

3) agree (again) that one does not need air elim on the boiler loop. Stick it on top of the buffer tank

No, it doesn't matter that there's no air elim in the boiler loop during summer. It's a small loop and the system once purged should be fine.

 

Yup... and even if there is the random bubble of air flowing around, who cares? Being such a small loop, it's highly unlikely that there will be enough air to 'block' the flow... and if it makes a little gurgle now and then, so what? Not like it's a baseboard running through living areas...

I thought I said the opposite of that?