Not understanding relationship between WM ECO and Tekmar 262

Harold

I keep re-reading documentation and keep coming up with little gems that matter; but I did not see/understand that last couple of times I read the manual.

I have spent a lot of time trying to figure out how to get an additional outside thermistor to the ECO input for outside conditions. I just found a WM ECO manual sentence that says the otherwise required external thermistor can be dismissed, if a controller (e.g., 262) controls the boiler. I believe that the 262 gathers outside temperatures being fed to itself and the three additional 369 controllers.

Then the output of the 262 turns on/off the boiler control input for the ECO. I have seen nothing that implies this is an analog or digital data stream. Just a switch.

What I am just not understanding is how what appears to be an on/off signal from the 262 will properly manage the operation of a variable speed condensing boiler. Things like water temperature and modulating. The 269 seems to input a DHW demand and heat/not heat. I am just not getting it.

I have searched extensively, but pretty much always get pointed to the documentation I do not understand.

Can anyone help me understand this chain of control to me. Or point me to some explanations not published by Tekmar or WM. I am clearly not understanding something. But simple on/off does not seem right.

Eastman

The ECO would have to accept a modulation rate or target water signal. Likewise the 262 would have to output one. The 262 does not, I don't know about the ECO, but I doubt that does either.

Eastman

You could probably coordinate the ODR curves and differential settings of the 262 and ECO, though. That way the 262 could initiate and terminate calls for heat, while the ECO tries to modulate the burner.

Eastman

Are you using indoor feedback with the 262? That would throw a wrench in my previous suggestion, as indoor feedback adjusts the Tekmar ODR curve up and down as needed.

flat_twin

An additional ODR input? Is that what you're trying to do?

Harold

I am not using indoor sensors. I am trying to figure out if a fifth sensor for the boiler will resolve anything. There is a fifth sensor outside, but I have been unable to find where it goes inside. It is documented as going to the boiler. I don't have the fifth sensor to do the Tekmars and boiler. If I take one away from the 4 Tekmars, Tekmar gets unhappy.

The ECO does have settings for temperatures and reset for DHW and heat. I am going to run through the settings. I have avoided messing with them. And it can be configured to not have ODR. But there are lot of settings that would rather have ODR. I think the 262 just does on/off. The ECO would probably be more effective with ODR input.

My thought on an additional ODR sensor would be to try to share an outdoor sensor. The way the sensors work is that the electronics in the controller passes a small current through the thermistor to create a voltage across the internal circuit and translate that into a temperature. As a last resort, I think I could build something to track that voltage as an additional signal for a Tekmar and use the freed up sensor for the ECO. I don't really want to try.

Eastman

What do you mean you have 4 tekmars? These are thermostats?

Harold

No. Three zone controllers (369) and a controller (262) for external interface.

Eastman

So the 369s are connected to the 262, right? And you must have a bunch of indoor sensors or RTU's, connected to the 369's, right?

Harold

Yes. The 369 zone controllers deal with powering individual actuators in the manifolds, has an outside thermistor, and looks at thermostats for demand. They are sequentially chained via a proprietary (I think) link to the 262. The 262 also has/uses an outside thermistor. The 262 manages the 369 inputs, performs some more magic, and feeds what I believe is two simple on/off commands to the boiler. It also has its' own outside thermistor.

All of these devices have computers in them. They are not dumb.

There are thermostats. They just look at the temperature of the room they are in. There are other devices and some thermostats that can deal with external sensors. The 063 has an air sensor and 3 more that can be used for distributed air sensors for large areas and slab heat control. One of my thermostats is actually a 063, but configured for air only.

Eastman

This system uses indoor feedback to adjust it's ODR curve. It calculates a target water temperature based on both external outdoor temperature and the required programmed internal room temperatures. Tekmar uses "indoor feedback" to correct the target water temperature. It ensures the water is just hot enough to meet the most demanding room.

Unfortunately, this particular model was intended for bang-bang boilers. The ODR curve on the ECO would have to be set just beyond whatever you think the highest requested temperatures might be requested by the 262.

Gordy

I think to much sensing ends up being convoluted. Really......

Eastman

Indoor feedback is good. It just needs to be an open standard.

Harold

Just some more info in the saga. The system was greatly overheating the house to the point I would need to be turned off and on. I believe I fixed that. There was a single valve motor that I had not clicked on completely when I finished purging. Even looking I did not see it. It fed a room with a thermostat. So the boiler kept plugging away.

The ECO lets target heating settings be entered from their control panel. So it has those parameters without needing anything from the Tekmar 269 except on and off. Still thinking about any unwanted interactions among the pieces.

I am trying to follow the heat through the system and adjust circulators. It appears my hand held IR detector is not working correctly.

I have to go now and build a condensate neutralizer that will fit in the limited space. The excitement never ends.

Gordy

When using an IR thermometer shooting pipes you need to put painters tape on the area you are shooting.

Eastman

@Harold
The way I see it, you need to configure the ECO to stay out of the way of the Tekmar. The Tekmar wants to use on/off bang-bang modulation to approximately control the water temperature. The target temperatures on the ECO needs to be higher than whatever the Tekmar could request. The differentials on the ECO need to be wider than whatever the Tekmar is set at. That way the Tekmar's aquastat will be in control. Any anti-cycling settings on the ECO should be disabled. However, if the ECO has any kind of ramp delay, or fire rate cap, that should be capitalized on.

Gordy

The only point I see in this is being able to use I assume existing third party control verses the onboard controls of the boiler.

Eastman

Pretty much. It's kinda a toss up to me as to whether to dump the 262. I mean, it's cool, it's got "indoor feedback", and zone syncing or staggering? (Can't figure if it syncs or staggers zone cycle calls.) I feel like if I were Harold I might find it fun to play with for awhile. Maybe I secretly want a Tekmar system.

Harold

The problem there is that the ECO can't deal with all of those (around 20 thermostats) inputs or valve control. It needs the Tekmar stuff to do that.

Tinman

It doesn't need a 262 though.

Harold

Steve - Why do you say it does not need the 262?

Tinman

I really like tekmar and I've used many of their products, including the 262 many times. I'll admit I haven't read every word of this thread but unless you have 2 boilers and an indirect water heater, I don't see the need. Are you using it strictly for indoor feedback?

Harold

It is for boiler and DHW control and interfacing the three 369s.

Gordy

Lol,I didn’t know you were dealing with that many stats.......

Eastman

I really want to know Harold, does this system stagger calls, or does it sync calls for heat????

Harold

I believe the 369s accumulate heat demands and feed the 262, which arbitrates what is going to be done for heat demand.

I believe that the thermostats contribute room air temperatures from their sensors.

Everybody wants an outdoor sensor. Rather primitive approach, but these are old devices. It would be nice to move everything to current products. But I don't think the expense would be justified. The Tekmar stuff is quite expensive.

The 369s have algorithms to stagger demand within their control domain. The documentation says they will spread out demand to level opening of valves. The 262 manages merging demands and triggering the boiler.

Eastman

What do you mean by "level opening of valves"?

Harold

That is the "stagger demand" in the preceding post. The 369s control valves and thermostats.

Eastman

Yeah, I know. But their marketing and I+O materials don't explain the particulars of it. Seems like one would want to sync, not stagger. I would think staggering would cause the greatest level of excessive boiler cycling.

Harold

From what I have read, I believe they are trying to minimize effects on the system flow from a bunch of valves opening at the same time. To minimize transient flow demand spikes by aggregating the demand before dealing with the next higher level controller. I don't think the intended issue is boiler cycling rather than just dealing with rapid changes in boiler flow.

Since systems of this vintage are likely (could be wrong on this) to use constant flow circulators, I am not sure why that form of staging would be useful. And if the circulators are variable speed with rational sensor/control based on some rational control device or algorithm, it would seem to be redundant.

My feeling for Tekmar is a lack of helpful and open explanation of a lot of things. I have quite recently found some protocol information; but not terribly useful for the casual observer.

Remember: I am a civilian. Actually an old engineer with a heating problem. Just my guesses/interpretations.

Harold

Just an added point with the Tekmar 26x. The "replacement" is a 263. The 263 fixes one issue; it can manage the modulation of the boiler instead of bang/bang from the 263.

However, the 263 does not appear to use the information from the thermostats to work the indoor and staggering of valve actions magic the 262 does.

The guy working on this with me has talked to Tekmar and they confirm the 263 behavior.

At this point I am not quite sure how to proceed. My current favorite approach is to let the 262 do it's thing and live with it.