Reset Buffer Protection et all

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Old 12-23-11, 03:19 PM
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Reset Buffer Protection et all

Posted by NJT in a different thread:
If I were going to do it... and I swear I am some day,
)... I would go with a Burnham MPO feeding a Boiler Buddy buffer tank, come off the buffer tank with variable speed injection into distribution system with constant circ. I would use INDOOR feedback to regulate the circulating water temp, and OUTDOOR feedback to regulate the water temp in the buffer tank.
Hmmm
And i swear i want to do this with the old boiler, this spring.
I thought i had it figured out but. there's always a but..

INDOOR reset and outdoor reset.
Veryyyyyyy interesting NJT.
I was thinking of using Tekmar thermostats for indoor feedback but only to tweak the buffer temp.
This idea of variable injection wth constant circulation, controlled by indoor reset, has got my attention.

NJT
Please, pray tell, what control would you use for the Indoor Reset?

And what happens if the outdoor reset temo for the buffer is not hot enough?


Peter
 
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Old 12-23-11, 03:24 PM
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Please, pray tell, what control would you use for the Indoor Reset?
Not sure yet... but I'll spend some time with my pipe dreaming this weekend over a nice tumbler of spirits and try to figure something out.

And what happens if the outdoor reset temo for the buffer is not hot enough?
Darnit! There's another fly in the ointment! Peter, is that one of yours?
 
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Old 12-23-11, 03:30 PM
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I'll drink to that!


Merry Christmas
 
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Old 12-23-11, 04:56 PM
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Don't worry about it. The MPO-IQ only needs 100f return temp and get above that before it shuts off. The only time I worry about flue gas condensation with the MPO is large gravity hot water systems or systems with all radiant floor heat. I don't even worry about it with cast iron radiator systems as long as there are multiple zones.
 
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Old 12-23-11, 05:55 PM
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Hello RBeck,
Sorry to say, i'lll not be replacing my Ultimate pin boiler with an MPO, at this time.
So i do need to worry about it.


Peter
 
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Old 12-23-11, 06:27 PM
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And the reality is that when I finally get around to replacing the boiler (probably next summer if I can talk rbeck into a road trip! ) I'll probably just pipe it up as a standard system... but I like messing with complicated designs, so I'm gonna do that anyway.

I would like to give constant circ a try though... so may end up with something a bit more complex...

Maybe use the MPO-IQ controls and take the boiler demand signal from an aquastat on the buffer tank, use that as a 'battery' and only recharge it when needed... so many ideas, so little money!
 
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Old 12-30-11, 08:17 PM
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I'm working on same design, different boiler, large buffer tank.

I want ODR to control boiler output and buffer tank temperature.

I want the system to draw down the buffer temperature, say 20*

Trying to figure out method to control boiler T-T

If I jumper T-T and set a constant call for heat, won't the boiler fire frequently & short cycle?

thanks BBP
 
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Old 12-30-11, 09:15 PM
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If I jumper T-T and set a constant call for heat, won't the boiler fire frequently & short cycle?
If you are using a large enough buffer, and a wide enough diff, you shouldn't have problems with frequent short cycles. But you don't want to jumper T T on the boiler, the ODR's job is to run the boiler. You would set the ODR for a constant heat call.

You could look at using something like the Tekmar 256. Wire the boiler output on the 256 to the T T terminals of the boiler. Wire the demand signal on the 256 for a constant call for heat. Let the circ pump between the boiler and the tank run off the boiler control. Put the 256 boiler sensor in the well on the buffer tank. Experiment with the diff setting on the Tekmar to get where you want it.

For this to be of any benefit, the tank would have to be quite large... what were you thinking of using? AND you would want it well insulated... standby losses from a large uninsulated tank could be huge.
 
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Old 12-31-11, 07:25 AM
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If you really don't want the buffer to maintain temp this is simple with multiple zone relay. Of course that is presuming that you have a multiple zone relay. I have a large job site in Anchorage Alaska where they were maintaining tank temp. They had the aquastat on the tank wired to T-T. The boiler was cycling on and off in the shoulder seasons and I thought this was a waste of money. We ran the wire between T-T and aquastat in series with the end switch on the multi zone relay. If the tank was hot enough the aquastat would not allow the boiler to run and if there was no call from the multi zone relay the aquastat would not call. This same idea could be applied to the ODR in series with the aquastat and boiler t-t.
BTW NJT just say when and I will be there! You, me and Sam we can figure out anyproblem. Whether it works the next day who knows.
 
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Old 12-31-11, 08:16 PM
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More info

Hello, thanks for input.

Boiler is a Buderus GB142-45-NG It has built in AM10 ODR

142MBH AFUE at sea level, here at 6,000' elevation, around 130MBH?

Buffer will consist of 3x50gal. (150gal.) Electric HWH plumbed in Parallel. (had these on hand & itemporary to keep house from freezing, $450 / month bills)

Large house 4350 ft2 5x zones of heat transfer plates under subfloor. + 2800 ft2 basement pex in slab 2x zones

I used the DOE rescheck online program & get a design load of 80MBH (seems low)

DHW will be 80gal Rheem commercial tank heated via external GEA flat plate heat exchanger

I think that the AM10 ODR controls the boilers variable temperature system ouput ONLY & thus the buffer tanks variable temperature.

This will be high enough to supply the medium temperature heat transfer plates, and will temper down for slab.

I won't be able to use a fixed temperature aquastat on the buffer tanks.

At this time, I don't know if control panel parameters will let me set the system delta temperature, but I think this is not possible as its computer controls this automatically (sorry for bad sentence structure as i'm already having champaign)

Thats it for now, Happy New Year 2012
 

Last edited by NJT; 01-04-12 at 05:00 PM.
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Old 01-02-12, 08:48 AM
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Sorry about being tipsy, I used AFUE of 142MBH, S/B DOE of 142
 
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Old 01-02-12, 09:19 AM
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If the heat loss is 80k, why are you using such a large boiler?
 
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Old 01-04-12, 12:00 PM
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I'm unsure of heat loss, guessing at insulation values. Insulation under basement slab is a guess. Large shower multiple heads, Jacussi tub.

Got an estimate from some company for 300MBH boiler install.
 

Last edited by NJT; 01-04-12 at 05:01 PM.
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Old 01-04-12, 05:04 PM
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rbeck, that's a great idea! I like!

So even if the ODR is wired for constant demand, the endswitch on the zone panel will prevent the boiler from firing in the absence of a heat call and prevent stranding heat in the tank... nice!
 
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Old 01-04-12, 05:56 PM
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I have 2 zone Relay boxes, one medium temperature manifold for the heat transfer plates & a second low temperature manifold for the basement slab zones.

Good idea using relay box end switch, I will try that on the medium temperature one to boiler T-T

It S/B Illegal for "Heating Pros" to sell oversize boilers by a factor of 3X
 

Last edited by NJT; 01-04-12 at 05:58 PM. Reason: no problema!
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Old 01-04-12, 06:01 PM
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When you say 'medium temperature' ... wondering why you can't run both at the same temperature?

By 'heat transfer plates', you are talking about tubing under a floor, correct?

And 'low temperature' ? How low?
 
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Old 01-04-12, 06:15 PM
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Yes, cheap thin aluminum heat transfer plates under the subfloor. Floor coverings & thus R-values TBD

As basement under slab insulation in unknown, water temps are unknown, but will use as low as possible.

If main levels of house require 150* or so, it would be too hot to run throug slab.
 
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Old 01-04-12, 06:20 PM
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Got an estimate from some company for 300MBH boiler install.
That's absurd. You should work with your 80k estimate.

Chances are that there is no insulation under your basement slab.
 
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Old 01-04-12, 06:38 PM
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Original builder was smart enough to put 2 zones of 8 loops each of O2 barrier pex into slab, so hopefully 2" of blueboard under it.

Builder was forclosed by bank & took a big loss. A boiler wasn't installed.
 
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Old 01-04-12, 07:56 PM
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Well then I take back what was said about the insulation under the slab. If it was built with in floor radiant in mind, then I would expect it to be there.
 
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Old 01-04-12, 08:55 PM
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If main levels of house require 150* or so
That's too hot for underfloor radiant as well.
 
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Old 01-05-12, 11:02 AM
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We shall see what temp is required. ODR will allow adjustment.

With large windows in great room, code minimum insulation in walls & cathedral ceiling, wood or carpet & pad floor coverings, I know this zones water temp will be much higher than what is needed for basement slab zones.
 
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Old 01-05-12, 04:03 PM
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Choose floor coverings carefully! Some manufacturers specify a max temp... some of that engineered flooring material can't withstand prolonged temps as high as 150... many solid flooring materials will discolor...
 
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Old 01-06-12, 12:58 PM
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Time Delay T-T control idea

ODR will control the boilers upper output limit on fire & thus the buffers upper temperature.

The "medium temperature" zone switching relays end switch will pass through a 24vac Delay-On-Make Time Delay Relay in series to boiler T-T (say set to 10-17 minute delay, testing required) This should prevent any short cycling.

This will allow small medium temperature zones to draw heat out of the buffer, possibly without firing boiler, if thermostat is satisfied before time delay expires.

This will also allow larger medium temperature zones to draw heat out of the buffer before firing boiler.

A basement slab low temperature zone will draw heat out of buffer without setting a call for heat. Buffer is large enough where it should never drop to 75* before a medium temperature zone calls for heat.

Feedback?
 
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Old 01-06-12, 02:26 PM
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3x50, 150 gallons of water to heat up.
I can't imagine, even with a boiler that big, especially throttled down by ODR, that you would have any need for a time delay.
Besides as far as i understand it, short cycling, refers more to short on cycles, not necessarily a short time between reasonably long on cycles.
At full 130k output, 150 h to 130 low:
Without any load at all, it would take about 12 minutes to heat up the 150g's of water.
With a 20k btu load it will take about an hour and 13 minutes to drop 20*
A 40K load, will take, 37 minutes to cool off 20*.
But then with a 40k load it will take 37 minutes to heat the tanks up again.
Not exactly short cycling, imo.
Additionally.
Presumably, the ODR wouod also widen the differental as needed, in warmer weather, thus extending the cycle times.

Peter
 
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Old 01-06-12, 05:59 PM
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goals

Thanks Peter for doing that math.

I'm unsure of the AM10 ODR controllers algorithms.

Time delay relay cost only $22

When it comes to boiler cycles "longer IS better"

My goals:

1. Heat this LARGE house, with its pex & manifolds already installed, with this boiler as efficiently as reasonably possible, while minimizing expense, using parts on hand.

2. Determine how to manage a large buffer tank, using ODR as high temperature limit and how to call for heat from boiler using its T-T input.

3. Prevent boiler short cycles, when small low mass zones call for heat, which is exaserbated in shoulder weather conditions. Draw buffer temperature down without firing boiler when possible.
 
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Old 01-07-12, 03:23 PM
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2. Determine how to manage a large buffer tank, using ODR as high temperature limit and how to call for heat from boiler using its T-T input.
Perhaps something like this?



With large capacity buffer tanks, boiler bypass will probably be needed.

Zone valves or pumped zones, use appropriate Taco panel.

Pipe buffer tanks as 'reverse return' on both sides to ensure equal flow through all three tanks.
 
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Old 01-07-12, 04:21 PM
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Thanks NJ Trooper,

Yes, same overall function as Tekmar 256, but using the built in AM10 ODR
 
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Old 01-07-12, 04:25 PM
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NJT's diagram would be perfect for an on off boiler, with one exception, imo. I think an active control, based on return temps, is needed for protection, not a fixed bypass.
A further problem might be, that BBill is using water heaters and it might not be easy to pipe them up in the style of a hydraulic separator.
Anyway:

However, i've come to find out, BBill has a MOD CON.
Thus no need for a by pass, at least.
Using a mod con with a buffer, can be a real donnybrook.
We want the mod-con to stay in condensing mode, but the mod-con is going to kick butt trying to get that buffer tank heated up.
It's going to take a goodly amount of trial and error with the ontrols to get that to all work out as desired.
Not easy.

One thing to consider, with the mod con and a buffer..
I've read good arguments for putting the buffer on the return.
This collects and holds the coldest water to aid the boiler for condening mode.
Thus the supply from the boiler to the loads would have the ODR sensor, and the cold return water would load up the buffer on the way back.

Something to think about.


Peter
 
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Old 01-07-12, 04:33 PM
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One thing to consider, with the mod con and a buffer..
I've read good arguments for putting the buffer on the return.
This collects and holds the coldest water to aid the boiler for condening mode.
Thus the supply from the boiler to the loads would have the ODR sensor, and the cold return water would load up the buffer on the way back.
Interesting... I would think that one would want to pipe the system into the TOP of the tank, and the pipe to the boiler from the BOTTOM... yes?
 
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Old 01-07-12, 04:35 PM
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However, i've come to find out, BBill has a MOD CON.
Thus no need for a by pass, at least.
Using a mod con with a buffer, can be a real donnybrook.
I guess I wasn't paying attention...

And now I'm questioning if it even makes sense to use the buffer tanks. What would be the point? Let the thing run and condense to beat the band! Let the built-in controls do their thing!
 
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Old 01-07-12, 04:41 PM
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using water heaters and it might not be easy to pipe them up in the style of a hydraulic separator.
That I actually did think about...

I thought that it might be possible to use the domestic connections to feed and return from the system side, and to use the drain and the relief valve port (relief valve not needed now) to pipe to the boiler side.

I think the 'dip tube' in the water heater would survive the temperatures to be expected... or would it?

But again, what's the real point of the buffers with a mod/con in the first place?

Maybe the best solution has been offered by Peter... put them on the return line to the boiler, and pipe them in SERIES... return from system in the TOP, out the BOTTOM to the TOP of the next, etc, etc...
 
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Old 01-07-12, 05:06 PM
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I've read good arguments for putting the buffer on the return
I started talking about this over two years ago and some people thought it was a crazy idea but now are doing it. They are the ones talking about the benefits now. Of course this would be for mod/cons only.
 
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Old 01-07-12, 05:46 PM
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Interesting... I would think that one would want to pipe the system into the TOP of the tank, and the pipe to the boiler from the BOTTOM... yes?
Yes .
 
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Old 01-07-12, 06:41 PM
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I thought that it might be possible to use the domestic connections to feed and return from the system side, and to use the drain and the relief valve port (relief valve not needed now) to pipe to the boiler side
I believe, that somewhere on this forum i've read that the, top and bottom, electic elements in a typical water come out and there is a threaded opening, (either 3/4 or 1" can't remember,) that can be piped to.
I have no way of knowing the versaity of this. If true, it could make life much easier for BBill.


Peter
 
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Old 01-07-12, 07:21 PM
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They aren't a standard NPT thread. It's a straight cut thread, I believe 1". I have heard of people using them myself, claiming that an NPT adapter fitting will thread in and seal as long as you goop it up real good, but I wouldn't trust that myself. It's definitely 'ghetto' in my opinion.
 
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Old 01-07-12, 10:05 PM
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I would post a picture of design if I could figure out how?
Went to FAQ & searched on pictures, it said go to user panel & click on a link to add an album, didn't see that link????
I need step by step as I'm old. Thanks
 
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Old 01-07-12, 10:58 PM
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Go to Image hosting, free photo sharing & video sharing at Photobucket and set up a FREE account.

Upload your pictures to a PUBLIC album.

Come back here and drop a LINK to the album so that we can go and view.
 
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Old 01-08-12, 10:13 AM
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Hello BBill,
I think the illustrious Xiphias would say the first thing we want to know, is there a heat loss done for the house?
If so what are the results?
If not, then one needs to be done.
Sort of getting the horse in front of the cart, or sumthin'.

Just a quick look. Question.
Does there really need to be a separate boiler loop?



Peter
 
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