Understanding ES-2 IQ ODR module

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Old 12-20-14, 01:47 PM
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Understanding ES-2 IQ ODR module

While working through issues described in posts to my http://www.doityourself.com/forum/bo...s2-boiler.html and http://www.doityourself.com/forum/bo...more-heat.html
threads I have learned a few things about the ES-2 IQ boiler control and the ODR module that others may find useful.

Rather than repeat the details given in the other threads I will just use generic designations (Zone 1, Zone 2, DWH) and give parameter settings without explaining completely again the reasons for them. Also, I will be using the control setting abbreviations from the ES-2 manual (e.g. HL = high limit).
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I will only address those boiler controls that are relevant to operating with the ODR module.

Zone 1 is large mass (cast iron radiators), Zone 2 is low mass (copper fin-tube radiation) with separate thermostats and pumps controlled by a Taco relay panel connected to the TT terminals on the boiler. (I actually have 3 zones but zones 1 & 3 operate in similar fashion. For clarity I will ignore zone 3 in this discussion.) DWH is not connected.

First, here are the initial control settings used to run the boiler (last year) with no ODR module installed:

HL = 150
dF = 30 (This is set at its highest amount to extend the burn time as long as possible.)
St = 140
Pt = oFF
dh = dh.

The problem is that the water temperature is too low for the copper fin-tube to provide adequate heat in zone 2 when outside is close to design temperature (for this example 0 degrees). Setting the HL higher will use more gas and cost more. Reducing the dF will cause the burner to short cycle. (The boiler is rated almost 3 times larger than the BTUH loss for the house.) A suggested solution was to put a zone on the DWH control input on the boiler control panel, but without an ODR control it would just operate on the same high limit setting as the TT input.

So after much mental debate (mostly about cost--it was expensive but there was a utility company rebate), I bought the IQ ODR module. Here is the list of setting options:
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Now I can connect zone 2 (to the TT terminals on the boiler control) and run it on the ODR curve to provide hotter water when the outside temperature is low, and connect zone 1 to the DWH terminals ON THE ODR MODULE to run up to the fixed Domestic Hot Water Setpoint (dS). (There is a discussion in a related thread about the differences between the DWH terminals on the boiler control and those on the ODR module.)

Initially I programmed in the following settings:

dS = 150 (The minimum allowed. I would have liked to go to 140 since Zone 1 works fine at that temperature and it uses less gas.)
Pt = 0
Pr = off
tb = 0
SS = 10 (default)
Hb = 170
Lb = 120
Ho = 65
Lo = 0
Lt = 120.
(Hb2, Lb2, Ho2, Lo2 are used with an IQ relay panel that I do not have. They are on the current versions of the IQ ODR module but do not appear in the on line manual. They are not relevant to this example, however if I did have an IQ relay panel this option for high and low ODR curves is the perfect solution to the problem I am trying to solve.

In addition I changed the boiler HL setting to 180. (The previous setting of 150 would have shut the boiler off before the variable setpoint of the ODR if that was calling for a higher temperature.)

With these settings, here’s what happens:

In Standby mode the boiler control screen shows the operating setpoint (SP) determined by the ODR. (Before the ODR module was installed SP was the same as HL.)

When Zone 1 calls for heat (on the DHW input of the ODR module), the SP changes to 150 and the boiler runs up to that temperature. The “DHW” wire in the boiler junction box is energized but is not being used because the Zone 1 pump is still controlled by the Taco panel. (The Taco panel remains because it controls Zones 1 & 3. If Zone 3 did not exist then Zone 1 pump could be wired to the “DHW” output and the Taco panel eliminated.)

When Zone 2 calls for heat (on the TT input of the boiler control), SP shows the setpoint determined by the ODR and the boiler runs up to that temperature. The “System” wire in the boiler junction box is energized and because I rewired the Zone 2 pump to it the pump runs. (Zone 2 is no longer under the control of the Taco relay panel.)

If both zones are calling for heat at the same time, SP shows the higher of the two settings, the boiler runs to that setting and both pumps run. If the zone calling for the higher temperature is satisfied and its call for heat ends, SP changes to the lower setting and if the boiler temperature (bt) is higher than that, the boiler shuts off. If one zone is calling for heat and the other zone starts a call for heat with a higher setpoint the SP will change and the boiler will continue to run up to it.

The operation described above can be modified by using the Priority, Pre-purge, Post-purge, and Boost functions but those parameters have not been used in this example.

So far, the example is straightforward and can be determined without much difficulty from the manuals and instructions.

Here are some things to watch for and consider:

Keeping boiler temperature (bt) above 100 degrees to prevent condensing
Regardless of any settings for Start Temperature (st), Zone Low Boiler Temperature (Lb), and Minimum Boiler Temperature (Lt) the boiler temperature (bt) can drop into condensing range. In a non-condensing boiler such as the ES-2 this must be avoided as much as possible. The key to doing this is to know and remember HIGH LIMIT DIFFERENTIAL (HdF) TRUMPS ALL!

Here is a scenario that will cause the boiler to operate in condensing range:

With HL = 140 and dF = 30 the boiler will burn up to 140, shut off and cool down to 110 before re-firing. If the boiler is near 110 and large mass Zone 1 calls for heat the return water from it can be as low as 65 degrees (room temperature during setback period), the result can be a bt of 90 degrees or lower. This condition can continue for several minutes until the large mass of water begins to heat up and the bt rises. The boiler will condense during that period and if it occurs long enough or often it can begin to cause corrosion damage.

There are several possible solutions:

Decrease HdF: Reducing the HdF say from 30 degrees to 20 degrees will raise the low temperature of the cycle from 110 to 120 degrees which will bring the bt closer to 100 for the scenario described above. But it will also reduce the burn time and cause more short cycling.

Increase the HL: Increasing the HL say to 150 would raise the low temperature of the cycle to 120 degrees with the same result as above, but is likely to burn more gas and cost more to operate.

Change the Start Temperature (ST): Even though the manual makes this sound like a parameter that can affect the low boiler temperature it will only do that in certain circumstances. The ST determines if there is residual heat in the boiler water and will keep the boiler from firing if the temperature is above ST --ONLY ON AN INITIAL HEAT CALL! It has no effect during a burn cycle responding to a continuous heat call. With HL = 140, HdF = 30 and return water temp of 100+ I have observed the bt drop to 110 before refiring. HdF trumps ST. Increasing ST (say to 150) will have the same effect as increasing HL but not always.

Change the Zone Low Boiler Temperature (Lb): The way the instructions are written it would seem that Lb would cause the boiler to fire if bt went below it. Again this is not the case. Lb only sets the lower limit of the ODR curve, i.e. the lowest SETPOINT for the highest outdoor temperature. If bt is higher than that setpoint when the heat call starts then the boiler not fire. If bt is lower than that setpoint the boiler will run up to that setpoint (say it’s 120) and then shut off. If the heat call continues the bt will drop the amount set by HdF (say 30 degrees) before the burner refires. So in this case 120-30=90 degrees—back in the condensing zone. HdF trumps Lb. Increasing Lb to 130+ should keep the boiler above condensing range except for the worst case when the high mass zone is recovering from temperature setback. (Because of this I have minimized my setback amounts and have seen no significant increase in gas use.)

Change the Minimum Boiler Temperature (Lt): Now this is the one that really got me confused. From the title and the way it is described this sounds like the absolutely positive way to avoid dropping down into a condensing range. Here is what the manual says:

Minimum Boiler Temperature
The Minimum Boiler Temperature parameter sets a low limit for the Reset setpoint. Set this parameter to the lowest supply water temperature that will prevent chimney or boiler flue gas condensation. Always consider the type of radiation when adjusting this parameter. Factory Default is 130 F.

Read the definition carefully—“sets a low limit for the Reset setpoint” (my emphasis). All this parameter does is keep you from operating with Lb too low. Say you set Lb to its minimum of 110 (meaning that you want a bt setpoint of 110 for a high outdoor temperature) but you need a higher temperature water (say 130) to prevent condensing, then Lt will make the setpoint 130. So Lt OVERRIDES Lb but guess what? HdF trumps Lt.

For example, it’s a nice warm day, the system is off all day. In the evening the outside temperature drops to 65 degrees. Say at that temperature the ODR setpoint is 110 and Lt is set for 130 so the boiler setpoint is 130. There is a call for heat, water in the boiler (sitting idle all day) and return water is say 70 degrees. The burner fires, the boiler water (bt) heats up to the 130 setpoint and the burner shuts off. The return water is coming back at 90 and the heat call is still on (there is still a lot of water in the zone to heat up and the room is not yet warm.) The boiler water cools down and you watch the bt drop 130>125>120>115>110>100, the burner fires.

Hey, wait a minute—what happened to the Minimum Boiler Temperature (set at 110 remember?)?! Yep… HdF trumps Lt.

Since the heat call did not end, bt drops 30 degrees (HdF) below the setpoint (130) before the burner refires. The good news in this scenario is that the boiler will overcome the effect of the return water temperature quickly and will probably operate in condensing mode for less than a minute if at all.

So here are my current settings:
Boiler
HL = 180
dF = 30
St = 140
Pt = oFF
dh = tt2.

ODR Module
dS = 150
Pt = 0
Pr = off
tb = 0
SS = 10 (Not using)
Hb = 170
Lb = 130
Ho = 65
Lo = 0
Lt = 130.

Using the DHW/TT2 option
Did you notice that the dh setting above was changed from “dh” to “tt2”? There is a related thread to discuss that issue.

I hope you have found this informative. Consider it my Christmas gift to you. I thank you all for the help given in this forum and look forward to a Happy, Warm, Economical New Year.
 
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Old 12-21-14, 08:45 AM
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Oops! HdF means dF

I think it is obvious, but I started to refer to dF as HdF. Whenever I said HdF I meant dF. Since there is no HdF in any of the listings, I hope there is no confusion.
 
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Old 12-21-14, 08:51 AM
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Using the DHW/TT2 option
Did you notice that the dh setting above was changed from “dh” to “tt2”? There is a related thread to discuss that issue.
And here is the link to that thread.

http://www.doityourself.com/forum/bo...dr-es-2-a.html
 
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Old 12-21-14, 02:05 PM
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Hi 2john –

Well take anything I say with a large grain of salt. I am certainly a rank newbie! A lot of good information there. I’m trying to figure out how all this ODR stuff works and I think I am very slowly making progress. lol But your stuff is very interesting and I would think would be helpful to everyone.

I was thinking that maybe it does in fact make sense that the dF should in fact take priority over Lt if Lt happens to fall in the [HL-minus-dF] range. At least that’s the way it seems to me, otherwise you could get a chatter if the Lt is close up to the HL. It seems to me in that case you could get a rapid oscillation in a small [HL-minus-Lt] range. And it seems to me the same would hold true for Lb – the dF would have to take priority or you also could get an oscillation in a very small range. At least that’s the way it seems to me, but I have a long way to go, lol.


I’m still chewing this over here, and may be still out in left field. Fascinating stuff!
 
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Old 12-21-14, 06:29 PM
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For more info on ODR see comfort-calc.net. Also see the boiler protection info. Condensation in CI boiler is not always related to temperature. Sometimes lower water temp can return if you watch the flow, thus boiler bypass.
 
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Old 12-21-14, 07:43 PM
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Cant read into your novel that much... but..

HL = 150
OK that was without ODR... And how low can you go... Not much right?



The problem is that the water temperature is too low for the copper fin-tube to provide adequate heat in zone 2 when outside is close to design temperature
Add more BB or HO stuff.


Setting the HL higher will use more gas and cost more.
Not really on design degree days....

(The boiler is rated almost 3 times larger than the BTUH loss for the house.)
So after much mental debate (mostly about cost--it was expensive but there was a utility company rebate), I bought the IQ ODR module.
Wrong thing IMO....

Keep low temps but add BB for zones you cant heat... You said boiler is 3 times the size so should be easy IMO...
 
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Old 12-22-14, 08:33 AM
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For more info on ODR see comfort-calc.net
Jackpot!!! That is a great link rbeck. We are all grateful. thanks.
 
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Old 01-09-15, 12:34 PM
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Just a quick note to answer Lawrosa's questions and close this discussion.

OK that was without ODR... And how low can you go... Not much right?
Zone 2 (greenhouse fin tube) calls for heat on TT with ODR settings of Hb=180, Lb=135, Ho=65, Lo=-10. These settings increase the water temperature for the greenhouse above the 150 setting of the other zone when the outside temps drop below 40 degrees. In recent days we had temps near zero and the greenhouse held its minimum space temp of 52 overnight with 174 degree water (at zero* outside) set by the ODR.

Lb=130 with a 30 degree differential keeps the boiler just above condensing temp. Even so, with DWH=150 for Zone 1 the boiler temp rarely goes below 120.

Add more BB or HO stuff.
I understand this but that is not possible due to the current construction but I have added fans to blow more air across the existing fin tubes and the dT has increased.

Not really on design degree days....
Correct. And, since Zone 2 does operate at lower temps on warmer days the gas usage and cost have not increased. More details on that here:

http://www.doityourself.com/forum/bo...s2-boiler.html

So after much mental debate (mostly about cost--it was expensive but there was a utility company rebate), I bought the IQ ODR module.

Wrong thing IMO....
Bottom line: I agree that under "normal" conditions ODR is not needed with the ES2 boiler.

If I did not have the greenhouse I could run the system at 150. The system worked satisfactorily when I tried that at the end of last year and it has worked well this year even with the low temps we experienced last week.

I am using the ODR not to limit the boiler temperature but to allow it to be higher than the "normal" setting (150) when needed.

The ODR allows hotter water to the existing emitters in the greenhouse as the outside temperature drops and they perform better. The Ho and Lo settings being used start that increase when outside temp is 40 (set point 150) and increase the set point as the outside temp drops. The set point will be 174 at zero and will even go to 180 at -10 if needed. Those higher set points only occur when the greenhouse is calling for heat which is less than the amount of time that the other zones call. During simultaneous calls from multiple zones the other zones will be satisfied sooner if the water temperature is higher, but whenever possible the set point for those zones will be limited to the 150 set point.

I hope this helps explain why I am using the ODR with the ES2. Thanks for adding to the discussion.
 

Last edited by 2john02458; 01-09-15 at 02:12 PM.
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Old 01-09-15, 04:41 PM
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Just a quick note to answer Lawrosa's questions and close this discussion.
hope this helps explain why I am using the ODR with the ES2. Thanks for adding to the discussion.
OK discussion closed...........................
 
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