Help needed with Tekmar 260 control


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Old 04-21-14, 05:06 PM
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Help needed with Tekmar 260 control

Hi there,

I need help w/ a Tekmar 260 control on a relatively old cast iron boiler Weil-Mclain Gold Oil (GO-3).

It currently uses a Honeywell Acquastat w/ Low-High and Differential manual settings.

I've read that it's important that the Tekmar control doesn't allow the boiler temperature to drop below 140F. How do I exactly accomplish this? I read that another sensor should be installed on the return line but it seems that the Tekmar unit can only accommodate 1 boiler sensor on terminals 14 and 15 (which I understand you connect to the supply header)?

Please help.

Moses
 
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Old 04-22-14, 06:12 AM
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You say that you have a 'triple' aquastat, probably Honeywell L8124A ?

This would imply that you are producing domestic hot water via a tankless coil inside the boiler, is that correct?

The BOIL MIN is the setting on the Tekmar that controls the low side temperature that the 260 will target. That BOIL MIN needs to be high enough that the RETURN water does not consistently run below say 125-130 for oil fired boiler. Taking into account the 'delta T' (difference between the hot supply and cooler return) which is usually around 20F, it would mean that BOIL MIN should not be lower than 145-150 or so.

This is going to be right around the same temperature, and perhaps lower, than what you have the LOW set on the aquastat.

I don't know that you will see much benefit from the ODR on your boiler. As long as you are using the boiler as a 'warm start' and producing domestic hot water with it, in my opinion there really isn't a lot of sense installing ODR.
 
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Old 04-22-14, 04:40 PM
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I don't know that you will see much benefit from the ODR on your boiler. As long as you are using the boiler as a 'warm start' and producing domestic hot water with it, in my opinion there really isn't a lot of sense installing ODR.
You make a good point, Troop. Some of ODR's best attributes cannot be taken advantage of in those situations.

Although I think in some cases, like my own, ODR can be useful for keeping the return temps high enough to prevent condensation when the outside temps are near zero and the boiler is being asked to provide almost constant heat to 20 separate zones (that's a lot of btus being given off).

By kicking up the boiler temp settings in response to the lower ambient temps, ODR helps keep the boiler (and return piping) nice and hot during those high-duty periods. This can be beneficial, particularly when you factor in the further "btu draw" of the DHW coil on the boiler output.
 
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Old 04-22-14, 09:24 PM
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Hello and thank you for your answer NJ Trooper. That's correct, besides producing hot water for baseboard heating of the house, the boiler also produces domestic hot water via a tankless coil inside the boiler. From your answer, I just need too adjust the BOIL MIN setting on the Tekmar so that the return is above 130F.

However, I'm not sure why there is little benefit using the Tekmar (with its outdoor sensor). Maybe I didn't understand the explanation. Wouldn't I be saving energy during those warm days (32 F) vs. the really cold days (-40 F)? Isn't that the main benefit of the Tekmar?

Thanks much in advance for your answer !

Moses
 
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Old 04-23-14, 05:55 AM
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Wouldn't I be saving energy during those warm days (32 F) vs. the really cold days (-40 F)? Isn't that the main benefit of the Tekmar?
First off, what are the settings on your a'stat, the HI , LO , and DIFF ?

Let's say that your LOW setting is at 150F, with a DIFF of say 20F. This would mean that your boiler is going to cycle ON at 140F and OFF at 160F all by itself, with or without the 260 installed.

So, no matter what the 260 does, the boiler is going to be warm/hot ALL THE TIME.

No matter what you set the BOIL MIN to, the AQUASTAT will OVER-RIDE the 260 control.

The only adjustment range that the 260 will have then is between 160 and 180, and that ain't much.

If the 260 saves you anything at all, I think a generous estimate of the savings would be in the order of say 2%, in YOUR SITUATION.

If you wanted to save fuel, get a real water heater and convert the boiler to cold start... putting ODR on a boiler with a tankless is throwing good money after bad, in my opinion.

Keep in mind though, that with the severity of the cold weather where you live, it may be advisable to keep the boiler as a warm start ANYWAY.
 
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Old 05-06-14, 07:53 PM
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Sorry for the late reply. After NJ Trooper's and Rockledge replies I did more research and can see what both of you say.

The Borough where I live in has a program where as part of a local energy savings program, residents are provided some funds to help them insulate their homes and make other modifications to save fuel. One of those requirements is the installation of those controls. So even a 1% savings is encouraged.

With that in mind, I'm not sure what would be the best way to wire the Tekmar 260 to make it work with the existing aquastat Honeywell L8151A. See attached pictures of the Aquastat.

Right now the aquastat is wired in such a way that the boiler comes on when the TT contacts are closed by any of the zone or water heater thermostats.

Thanks much for your help.

Moses
 
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Old 05-07-14, 07:28 AM
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Are you saying that in order to qualify for the grants one of the requirements is to use part of the grant money to install ODR on the boiler?

That's just silly................................

By FAR the biggest bang for anyone's buck is going to be insulation and air infiltration sealing.

The settings on your 8151... is that the way it has always been? You didn't change anything? And the home has always heated fine?

I ask this because the settings you have are whack.

You've got the HIGH set to 160... that's the hottest that boiler will ever get during a heat call in any case.

Here's the thing though; the HIGH setting should not be closer than 20F to the LOW setting, and it appears that your LOW setting is at 150F, so you are only 10F apart on the HIGH/LOW.

TYPICALLY, and especially in cold climates, unless you have much more radiator or baseboard than the home requires, the HIGH setting should be 180F

Is it correct that I see a DIFF setting of 20F ? If so, that's fine.

One more thing... since you do NOT have an 'indirect water heater', you can use the less expensive Tekmar 256 on your system.

Honestly, I would not install ODR on that boiler and would spend the money on extra insulation, or beer.
 
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Old 05-07-14, 09:55 AM
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THanks for all that wisdom.
Yes I have not changed the settings at all. It's been working fine w/ a High, Low and Diff set at 160, 150 and 20 respectively. I can change the High to 180 if recommended.
The Tekmar 260 is already purchased and non-returnable and need to install it to get the credits. Is there a way to install it in such a way that it doesn't interfere w/ normal boiler operations? Is it possible to install it without disturbing the call to the boiler from the DWH heater?

thanks again !
 
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Old 05-07-14, 10:32 AM
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I can change the High to 180 if recommended
If the home heats fine with 160 water, there's really no reason to raise it other than to maintain the 20F difference that Honeywell recommends for that aquastat. (in fact, I believe if you look carefully at the front of the white part with the dials, you will see that instruction printed there... at least it's there on the newer ones... but I bet it's there on yours also)

So maybe just move it up to 170F to 'clear' the Low setting by 20.
 
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Old 05-07-14, 10:47 AM
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Is there a way to install it in such a way that it doesn't interfere w/ normal boiler operations?
Well... no, not really... because by design, the INTENT of the device is to 'interfere' with the normal operation of the aquastat by cutting off the burner before the aquastat does.

Is it possible to install it without disturbing the call to the boiler from the DWH heater?
Yes, you need to wire it such that the LOW limit (and DIFF) functions still operate normally, there is a way.

I need to spend some time with the manual and see if I can come up with something for you...
 
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Old 05-08-14, 11:56 AM
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Hi there.
I've been thinking hard and reading more about this, and decided not to pursue the installation of the Tekmar 260 any further. I agree that it really makes no sense. Instead to get the credits, I'll propose to install a Beckett 7600 AquaSmart Boiler Control in place of the Honeywell 8151.

thoughts?

Moses
 
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Old 05-08-14, 02:54 PM
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If it were me I would install Tekmar, John Siegenthaler P.E. suggest using a boiler piped with closely spaced tees and system pump and a 3 way mixing valve controller that measures boiler inlet temperature. The operating logic within this controller gives priority to maintaining the boiler inlet temperature above a user selected minimum value . He states, the key to the successful strategy is a mixing valve that senses and reacts to boiler inlet temperature. He also points out that the system must not allow the distribution system to extract heat from the water flowing through it faster than the rate at which the boiler produces heat . In my opinion this can be done using a Tekmar 260 or 256 wired to the TT of boiler triple aqua stat, with a cube relay that prevents water flowing through the boiler when burner is firing and boiler water temperature is below 140f. Once boiler water is above 140f than both can operate as normal . The difference between my solution and the mixing valve is the relay stops water flow to heat emitters until burner is off and the mixing valve will only slow the flow through emitters until the boiler catches up .There is also no need in my opinion to pipe boiler with closely spaced tee and only one pump is needed when using zone valves , a simpler system. The pump must have a check valve to prevent flow through boiler when pump is off.
 
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Old 05-08-14, 03:41 PM
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Yeah... the mega buck repipe the whole system solution wins every time doesn't it!

Sometimes what sounds good on paper really isn't. Not every system will benefit from something you read in an article on the internet.

Sometimes common sense must prevail.

Saves, you seem to be missing the point that this particular boiler will never be below 140F because of the triple/tankless.

When there is a call for heat, if it goes below 140 at all, it will only do so for a short time.

There's no need for all that other stuff.
 
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Old 05-09-14, 12:45 PM
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Do you think upgrading to a Beckett 7600 AquaSmart Boiler Control to replace the Honeywell 8151 is a good idea?
 
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Old 05-09-14, 01:21 PM
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Moses, take a look at the " HydroStat 3250 " and see what you think about that one...
 
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Old 05-09-14, 05:33 PM
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NJ,

thanks for the link.

1. However isn't the 3250 also outdor reset based?

2. For the installation of the 3250, can I just connect each lead currently connected to the Honewell 8151 to the 3250 or additional wiring is necessary?

thanks !

Moses
 
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Old 05-12-14, 05:18 PM
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Well,

I learned more about the proposed control. It has a boiler reset, not an "outdoor" reset. It monitors the frequency for calls for heat and calculates a target boiler temperature. So in a sense, it's kind of a modulating control.

Regarding wiring for DWH, when the ZC and ZR terminals are closed through an end switch, the controller will fire the boiler to the high limit setting. Is this correct?


Moses
 
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Old 05-13-14, 05:28 AM
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Regarding wiring for DWH, when the ZC and ZR terminals are closed through an end switch, the controller will fire the boiler to the high limit setting. Is this correct?
I would need to look at the manual again to verify the specifics, but from what you've told us so far, you won't need to be concerned with this at all... this would only apply if you had a SEPARATE indirect water heater.

You stated that you are using the tankless coil inside the boiler and all you need to do for this is to set up the unit for 'warm start' by setting a LOW and LOW DIFF parameter in the control menu...

... as I recall ... from memory ... look in manual to confirm how to set up for low limit and warm start.
 
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Old 05-19-14, 02:39 PM
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Tekmar 260 issue

Thanks much for everybody's comments and help on this issue. I purchased and installed the hydrostat control, and I think it's working well. I've also learned much on this subject.

It's amazing how much it helped to understand the basics of the aquastat controllers. For example, I didn't understand much about the ZC and ZC terminals, or how the HI and LO and differential settings worked. The pictures on this website helped me a lot:
http://comfort-calc.net/Service/Domestic_Coils.html

In regards to ZR and ZC I didn't really understand how these worked until I found the diagram on Pg 25 under http://www.crownboiler.com/documents...ion_manual.pdf

where I saw that ZR is energized from L1 through an in-line thermostat. When this happens, ZC becomes hot and in turn energizes ZC than can be connected to a circulator for DWH.

thanks again.

Moses
 
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Old 05-19-14, 04:09 PM
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To understand the ZR - ZC a bit better, let's look at the 'historical' use of them first.

You won't see them on anything but a TRIPLE aquastat.

Think of ZR as " Zone Request " and ZC as " Zone Control "

On a SINGLE zone system, neither of these really have any use. The burner and circulator are both controlled normally by the connected room thermostat on T T and by the LOW LIMIT part of the control.

When the aquastat is operating under the LOW LIMIT control, the C1/C2 circulator is DISABLED so as to give PRIORITY to the LOW LIMIT call in order to provide domestic hot water (typically).

When the LOW LIMIT calls for heat, ZC , which is normally 120VAC HOT is DROPPED. ZC is the terminal that sends operating power to the ZONE RELAYS. By dropping the 120VAC during a LOW LIMIT call, the zone relays can NOT operate until the LOW LIMIT call is satisfied, again for PRIORITY to the LOW LIMIT to provide domestic hot water via the tankless coil.

On a MULTI zoned system, when one of the external ZONE RELAYS calls for heat, 120 VAC would be applied by that relay to the ZR terminal, indicating to the aquastat that it was to fire the burner, but NOT the circulator attached to C1/C2 terminals, because that circulator is for zone 1, whose thermostat is connected to the T T terminals.

In the past, ZR is an INPUT; and ZC is an OUTPUT.

There are a few more 'conditions' to this logic, but basically that's it for the older electro-mechanical 'triple' aquastats such as the L8124 series.

The newer electronic aquastats have used these terminals for 'creative' purposes which are varied. They can signal the aquastat that a DHW call is coming in from an indirect water heater and cause it to over-ride and ODR reset curve. Some models allow them to be used for a 2nd zone, eliminating the need for an external zone relay for 2 zone systems, and others which escape me at the moment.
 
 

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