Zone valve, RIB question

northlakes

Hello, 

New here. Already owe everyone thanks for all the information I’ve read here.

My question relates to a RIB (2401D) that a contractor added in order to be able to control two boilers, both of which used to run off of an old boiler control unit that now no longer has the internals, (last owner only used one boiler.) Plan is to have a backup boiler and maybe cycle them to lessen the duty. 

System has two old WM HEII boilers each with their own circulators and a system circulator. 

As it was wired, the RIB LED was lit (relay activated) with no thermostats on, causing a constant call for heat at boiler, with boiler circulator on, but main circulator for some reason remaining off. Activating a thermostat would then cause the boiler circulator to stop and the main circulator to run. 

Thermostats are wired to 3 Taco zone valves, which are then wired back to the RIB, which is wired to the boiler control. 

I couldn’t trace out what was causing the RIB to activate, but because it seemed like an opposite sort of behavior, I thought I’d change over and use the N/C output contacts, thinking that maybe the zone valve connections to the control are normally closed. 

It worked, meaning it ran both circulators so that hot water can get into the system, and it functions as expected with thermostat calling for heat. However the RIB still behaves opposite of what I’d expect, with LED off when the boiler is calling for heat, and on when it is standing by. 

I guess my question is am I right about any of this, or have I got it all mixed up!

mattmia2

You probably want some sort of staging and rotation control. It is hard to say exactly what you have without you tracing it out, but roughly ho you would want to set it up:

zone control controls system circulator and sends call to staging and rotation control
staging and rotation control calls one of the boilers and circulators as determined by its rotation algorithm

Some sort of staging trigger is set up for the rotation/staging control. could be length of call, could be return or supply water temp, could be outdoor temp. Could be number of zones calling. You likely only need both boilers on the coldest days of the year. I don't see how you do this with only a relay.(if they never need to run at the same time, some clever use of a relay or a couple relays could make it switch back and forth on every call for heat. Of course that would increase your standby losses since you are heating both boilers.)

EdTheHeaterMan

This is the simplest way to get what you want. https://www.watts.com/products/hvac-hot-water-solutions/controls/boiler-mixing-controls/261/261?utm_source=PrevSite&utm_medium=Redirect&utm_campaign=tekmarsiteupdate
All the rotating and staging (if you ever require both at the same time) are included in this control. Just wire your zone valve control (or end switches) to the input of the 261, then you can wire the separate boilers to the boiler 1 and boiler 2 outputs. There is even a spot to wire a system circulator (if you are piped with 3 circ. pumps... 2 boiler pumps and one system pump). I have serviced several systems with this set up!

You just need to be a little creative with the boiler demand input. When a thermostat calls for heat it should operate a zone valve with an end switch. When the end switch is closed it must send a 24 Volt signal to terminal 1 and 2 on the Tekmar 261 in order to start one of the boilers and the system pump (if you have one). This can be done with a taco ZVC control or with an inexpensive 20VA transformer in series with the end switch circuit. Details can be illustrated once you provide the wiring detail of the boiler and zone valve configuration you currently have.

The RIB is not necessary with the 261 control... but save it, it might come in useful for something else.

109A_5

Hello @northlakes,

If I understand your situation correctly, there is multiple thermostats and multiple zone valves and two boilers.

I would use the RIB (2401D) to provide an A/B selection of which boiler I wanted to use (automated and / or manual). I would suspect there is a switch (or was) that controls the RIB (2401D) somewhere, possibly using power from one of the boiler's transformers to power the RIB (2401D). That switch or switching equipment may be gone now and the connection was made to select the desired boiler permanently, so to speak. I would trace out the control side of the RIB (2401D). It could be 120VAC.

In other words when the RIB (2401D) is off boiler A is selected, when the RIB (2401D) is energized boiler B is selected. It steers the thermostat / zone valve control to the desired boiler.

The relay in the RIB (2401D) may help provide isolation between two different transformers (one at each boiler). Once the control of the RIB (2401D) is traced out or otherwise determined it could be automated, if desired. You may have to put the RIB (2401D) contact wiring back the way you found it or put the other boiler on the opposite logical contacts. Like boiler A = NC and boiler B = NO when the RIB (2401D) is off.

They may have used both sections of the RIB (2401D) to switch both TT wires.

Datasheet here https://www.functionaldevices.com/wp-content/uploads/2021/08/RIB2401D.pdf

northlakes

Thanks so much, this clarifies a lot. I’m going to dig into these options and will loop back. Sadly one boiler now appears to have a slow leak so a whole other can o’ worms just cracked open.

109A_5

Hello @northlakes, This part of your system's behavior does not quite fit into the model I described before.

northlakes said:

As it was wired, the RIB LED was lit (relay activated) with no thermostats on, causing a constant call for heat at boiler, with boiler circulator on, but main circulator for some reason remaining off. Activating a thermostat would then cause the boiler circulator to stop and the main circulator to run.

Also;

both of which used to run off of an old boiler control unit that now no longer has the internals

The old boiler controller may have been the A/B control switch and the RIB (2401D) may have been used to control system circulator so it ran with either of the boilers running. With the old boiler controller missing they apparently picked one boiler to use. The wiring now may be kind of kluged up as compared to when things worked as originally designed. Is there any Make / Model information on the cabinet of the old controller. If so it may help to understand the original configuration.

If you get both boilers up and running it may be a better plan to use a new controller as @mattmia2 and @EdTheHeaterMan suggested. You would have to figure out what controller best fits your needs. Lots of options depending on what you need or want.

northlakes

@109A_5 After all this head scratching absolutely agree when possible we are going to have to start again with new controls. 

109A_5

Hello @northlakes,

I looked at one of the new boiler controller's documentation that was mentioned above. It looks like it only gives 48 hours rotation. Assuming your boilers are redundant and you don't need both running for design day. For the cost of these controller units if 48 hour rotation is not what you want or need you may have to look into other alternatives for rotational control.

ROTATION
The 261’s Equal Run Time Rotation function is fixed at 48 hours. The firing order of the boilers changes whenever one stage accumulates 48 hours more running time than the other stage. After each rotation, the stage with the least running hours is the first to fire, and the stage with the most running hours is the last to fire. This function ensures that both stages receive equal amounts of use. When the Rotate / Off DIP switch is set to the Off position, Stage 1 is always the first stage to fire.

northlakes

Fan control relay burned up when I tried to fire it up today. Contractor was trying to fix wiring yesterday and he thought wiring on the transformer might have been reversed. According to the diagram it was backwards, it had tstats to C terminal, and the #2 on ZVs wired to the R terminal. (Return legs from tstats on #1)

After tracing it all out it did look like fan control 24v and common was wired backwards, maybe whoever wired it originally looked at the diagram and got it swapped? 

Seems maybe some other wiring was wrong and shorted/burned it up, not sure just yet.

RIB and outdoor reset are disconnected for now to simplify troubleshooting. Seemed like the zone valve was struggling to open all the way before fan control burned up, so maybe the ZV power head(s) got fried too :-( 

Will resume solving for two boilers when one is working correctly... 

109A_5

Hello @northlakes,

northlakes said:

Fan control relay burned up when I tried to fire it up today.

What part of the fan relay burned up, the contacts or the coil ? I'm guessing the coil.

I touched up your drawing, this is how I would wire this part of the circuit (first picture). And the second drawing is how I guess it was. Which is a bad way since it depends on how the fan relay and the boiler transformers are phased. When phased correctly 0 VAC across the fan relay coil with ZV End Switch open, phased wrong up to 48 VAC with ZV End Switch open depending on the boiler circuitry. Which may cause the fan relay coil to burn up.

They probably did not want the circulator to come on until the End Switch closed. The problem is you have to get the transformer phasing correct.

northlakes said:

Fan control relay burned up when I tried to fire it up today. Contractor was trying to fix wiring yesterday and he thought wiring on the transformer might have been reversed. According to the diagram it was backwards, it had tstats to C terminal, and the #2 on ZVs wired to the R terminal. (Return legs from tstats on #1)

After tracing it all out it did look like fan control 24v and common was wired backwards, maybe whoever wired it originally looked at the diagram and got it swapped?

northlakes

@109A_5 Wow, thanks, I think I am seeing the light. i assumed it was coil but I’m not positive how to test. It sizzled and smelled and I removed it from the system. In your 1st drawing am I correct that the circ relay is energized when TS closes, before zone valve opens? In my particular system this may not be as much of a problem as there is one always open loop on perimeter of bottom floor... I think you’re absolutely right, this circ-last objective would make sense as to why it was wired backwards. 

I’m now fully grasping why the RIB was the wrong solution for two boilers and so on... but now that the short-term goal is one boiler operating with three zones until more time and investment are possible, this makes me wonder if the RIB might have a temporary purpose in energizing both circ and boiler TT. Not taking into account curves and such, the RIB appears to support the load of this circ, at 215W guessing it draws +-2 amps. 

Maybe I’d just need a new transformer. Wired correctly even. 

109A_5

Hello @northlakes,

Obviously with me not being there it is hard to get the 'Big Picture' of the intent of how they originally made it work and you stated the original controller is missing so that does not help either. So some assumptions (that may be wrong) are made. Like were the two boilers staged or just rotated, are both needed for design day or will just one do the job. Circling back the RIB maybe was for boiler A/B selection, since if the fan relay controlled the circulator why would you need another relay ?

Some zone valves start to open almost immediately when power is applied. Some with Wax motors or charging Capacitors there is a delay. If the pump is running will it jam up a zone valve from opening ? maybe not. Is it bad for the pump to be dead ended for a few seconds on each call, maybe, maybe not, probably depends on the pump. In your case it may not be a problem. Doesn't the first floor get too hot ?

northlakes said:

I think I am seeing the light. i assumed it was coil but I’m not positive how to test.

Seeing the light is good (usually), seeing the smoke is bad in this situation. Substitute an AC Voltmeter for the relay coil with the original circuit. And then reverse one winding on one transformer for verification. I probally would just reverce the primary of the Fan Relay Transformer since it looks like the one wire for the relay coil is soldered to the 'C' terminal.

In your 1st drawing am I correct that the circ relay is energized when TS closes, before zone valve opens?

Yes.

I’m now fully grasping why the RIB was the wrong solution for two boilers and so on...

I'm still curiously confused of the intent of the RIB relay.

this makes me wonder if the RIB might have a temporary purpose in energizing both circ and boiler TT.

Maybe ?

Not taking into account curves and such, the RIB appears to support the load of this circ, at 215W guessing it draws +-2 amps.

So there is two relays basically in series to control the circulator ? The RIB and the Fan Relay, I'm not clear here. It is probably the multiple thermostat one circulator thing. Which is why they used the End Switch to control the circulator. This is where the modern controllers can sort this stuff out, but at a price.

Maybe I’d just need a new transformer. Wired correctly even.

Why ? Is one transformer now bad ?

109A_5

Hello @northlakes,

OK I think my head is in a better place now, as far as your system is concerned. No transformer phasing to worry about. You can add zones until the transformer is overloaded. For your present needs look at this drawing.

RIB NO Contacts Yellow & Orange, Purple & Brown.
RIB 24 Volt Coil Wht/Blu & Wht/Yel.

northlakes

@109A_5 I grabbed a new transformer and this is exactly how I wired it today minus fan control, with circ on one pole of the RIB and boiler TT on the other. Worked just as expected! 

For education’s sake when I get time I’m going to test the burned up fan control to see what’s what. 

Sorry for the puzzle on the RIB, it was an attempt a contractor made to manage two boilers on the cheap that just wasn’t the right equipment. Glad to have it leftover now though, as it’s exactly what I needed to put a band-aid on this system until the next step. 

In just a few days on this site I have to be honest I’ve learned more from people’s generous help than anywhere in a very long time. 

109A_5

Hello @northlakes,

OK great, that part now works for you.

If it were me, and if you get the 2nd boiler up and running, I would use another RIB 2401D and a timer (or whatever criteria you choose) to switch between boilers, as long as you do not need staging.

The burned up relay coil may still work if you caught it in time. Even if it does work, I'm not sure I would trust it.

northlakes

Makes sense. So maybe I’d have an SPDT timer from the end switch to the RIB coils, both RIBs output contact pole 1 to circ with RIB 1 output 2 to boiler 1 TT and RIB 2 output 2 to boiler 2 TT. 

(That would energize the output contact of the RIB whose coil isn’t energized)

109A_5

Hello @northlakes,

Yes, I drew it this way (first drawing). The only down side I presently see is a SPDT timer, and that may not be an issue.

Presently not sure about this "(That would energize the output contact of the RIB whose coil isn’t energized)"

The second drawing is what I originally had in mind but I like the first drawing better, less wear and tear on the circulator contacts and a 'Both' switch could be implemented and is simpler. The 'Both' switch functionality can be implemented on the second drawing by putting a DPST switch between the boiler's TT BUT the boiler's transformers would have to be phased correctly (just asking for more trouble), so I like the first drawing much better.

The 'Both' switch I thought may be handy in very cold weather and you would not have to fool with the Timer to service the currently selected boiler during the heating season. Just close the 'Both' switch and shut down the boiler to be serviced at the boiler's AC power switch.

Also if I was starting from scratch I probably would use socketed relays and not the RID 2401D style, easier to test, service and replace the relays, however that method may require an enclosure for the relays.




Second Drawing, too busy, too many issues, the idea originally seemed better in my head.

northlakes

@109A_5 the “both” switch seems like a great idea. 

northlakes

@109A_5 any idea what would be the benefit (or original design intention) of going beyond rotation and actually staging two boilers? It had an old gutted WM “System 1” control which I can’t find any lit for. It has what I assume is some kind of temp sensor running to a supply pipe, and I assume it was doing both some staging and rotating. 

hot_rod

here is an example of what a staging control can do, beyond a relay control only

https://api.ferguson.com/dar-step-service/Query?ASSET_ID=851838&USE_TYPE=PARTS&PRODUCT_ID=1439506

109A_5

Hello @northlakes,

Well, on Design day, is one boiler enough, so two boilers are just redundant, so they switch to even out the wear and tear. And if one unit failed the other could have been automatically fired up. They may have just wanted redundancy because or the building's type of use. Or on Design day is one boiler not enough so the other has to be run too. Maybe they could not get a bigger boiler into that room ? Your guess is better than mine since you are there living with it.

You can get more sophisticated controls as folks have shown above in the thread, but they cost a lot more than a few relays and a timer (assuming timed rotation control is all you need). Maybe by the end of this upcoming heating season you will have a better feel for the situation. The more sophisticated controls have benefits if you need them.

Without finding more info on the WM “System 1” control it is only a guess. If you get both boilers operational I would try to get a feel for the cycle rate on a colder day, you may not need staging, just rotation, unless some automatic fail-safe is desired too.

northlakes

It takes a while to get up to temp but does seem like it will do the job just rotating. Found an old Tekmar 252 for less than the cost of the rib+time delay SPDT, might read up on the subject and give that a whirl. 

109A_5

Hello @northlakes,

Sounds like fun, did it come with the sensors ?

Some documents here, if you don't have them already.
https://www.watts.com/products/hvac-hot-water-solutions/controls/252/252

northlakes

109A_5 said:

Hello @northlakes, Sounds like fun, did it come with the sensors ? Some documents here, if you don't have them already. https://www.watts.com/products/hvac-hot-water-solutions/controls/252/252

It didn’t come with sensors but seems they’re not too expensive. 

EdTheHeaterMan

@109A_5 Are you sure there isn't a short circuit making that smoke?

northlakes

EdTheHeaterMan said:

@109A_5 Are you sure there isn't a short circuit making that smoke?

There was a transformer wired backwards and an end switch wired wrong, and I believe it caused the transformer to get “backfed” but it’s sorted now.