Tekmar/Taco/Boiler wiring nightmare

ColdTaco

Hi all,
Disclaimer: I know little to nothing about HVAC systems and wiring--I've learned a bit out of necessity as everyone I've had out to take a look has suggested something different..
Family and I moved into a new house in August. Home inspectors were very thorough, inspection did not identify any issues with the HVAC system aside from stating that the cast iron Buderus Logano G234 (cast iron, 1-stage non-condensing gas boiler) was 15+ years old but could "go forever" if maintained. Previous owners had been there 20 years and designed and installed the HVAC and radiant flooring system, no reported issues.
Systems are (pictures below) Buderus Logano G234 (cast iron, 1-stage non-condensing gas boiler, 15-20 yrs old(?)), Buderus Logalux indirect hot water tank, hydronic radiant floor heating on the first floor and then on the 2nd floor there are air handlers in the attic that receive hot water from the boiler. Electronic/control systems are: an old Tekmar 369 Zone control which controls 2 hydronic floor heating zones, then a Universal Reset Control 364 which controlled the DHW tank, and then a newer Tekmar 402 House control system which controlled a *different* heating zone (total of 3 hydronic heating zones), then all of that is also wired to a Taco SR506 zone relay. The thermostats which control the radiant heat on the first floors are all Tekmar (some old, story below) and wired to the Tekmar systems. The thermostats (non-Tekmar) which control the air handlers on the 2nd floor are wired to the Taco relay, which is also wired to another Taco expansion zone control which controls the heat in the garage and one more hydronic flooring zone. If this sounds like a Frankenstein, mismatched system at this point, I agree. Did I know any of that 2 months ago? Nope.
The radiant floors are operated by a number of pumps and injectors, no valves as far as I know--putting the pictures in below which will hopefully make it clear.

Fast forward to Thanksgiving week and the temp starts to drop into the 30s overnight. Night before Thanksgiving day we suddenly have no heat or hot water in the middle of the day/evening. I called an HVAC service that I had already contacted to setup a service contract, and thankfully they sent someone over in the AM on Thanksgiving that we were incredibly grateful to have. He took a look and asked how old the fan in the can was, I had no idea, and he turned the power off to the boiler, put a jumper on the contacts in the fan in the can, flipped the power to the boiler back on, and everything turned on. He told us the problem was the fan in the can was blown (he didn't use a voltmeter on it, just jumped it) and replaced it the next day. The next three weeks things were fine, but it was warmer in early Dec and I noticed right before leaving for the holidays that I did have to go and cycle the power again to the boiler because it seemed like it has shut off again--should have called immediately but was busy and leaving town in the next few days.
We leave or a week, come back to a stone cold house with thankfully no burst pipes, but it was clear the heat and hot water had been off for awhile.
If I cycle the power to the boiler it fires back up right away most of the time UNLESS it's hot and just recently turned off, then I hear the clicking from the ignition module and without it firing up and it eventually quits. When I look at the Taco and Tekmar systems, both are calling for heat without the boiler firing up. Fan in the can is running no problem. Flu damper for the boiler has been disconnected at some point long ago and just fixed in the open position (no idea why).
I've had 2 electricians out to look at the wiring--both have said it's a mess and they can't make sense of it. The Taco isolated end point is not directly wired to the boiler but instead is spliced and wired to both of the Tekmar controllers 369/364. The Tekmar 369/364 systems are wired to the boiler but it's unclear how or what is actually making calls for heat or why it's potentially causing the boiler to short cycle (which I think is the term but I could be wrong) when the weather is cold. DHW has an aquastat that was disconnected prior to our move-in (no idea why, the wires are still sitting on top of it) DHW is controlled through a sensor on the DHW pipes which is wired to the Tekmar 402; DHW has priority but I've tried turning the priority setting off and it makes no difference with the boiler cycling.
The electricians thought it was the boiler ignition module--replaced that, no dice, sbut it now has an LED which shows that it's in lockout. Supply vents are clear (as best as I can tell). I haven't checked the flame sensor (don't know how) but I can ask the plumber to take a look?
Other than that, the way everything is wired seems odd. The Tekmar 369 Zone control and the Universal Reset Control 364 are wired to two old Temkar thermostats controlling two rooms, and the new(er) Tekmar 402 house control is wired to a newer Tekmar Tn2 thermostat in another room.
I was on the phone with a very helpful guy from Tekmar who let me know a few things:
1) The 402 house control should be able to control all the radiant floor heating zones without needing the 369/384 anymore, but
2) The two older Tekmar thermostats currently running into the 369/364 are not Tn2 and can't be hooked up to the 402 house control
3) He said that Tekmar and Taco really aren't compatible and he couldn't help me with that
4) The electrician pointed out that the Tekmar 402 is designed to control valves, not pumps, and my system uses pumps. He thinks the Taco zone relays are providing power to the pumps, and that the Taco is necessary in the system currently to power those pumps. Tekmar does make a house control 403, which DOES have control for pumps instead of valves, it just that in order to simplify down to that I would need to replace the two thermostats that are too old to be compatible with it, which I'm willing to do.

Questions:
1) Short cycling seems only to be happening when it's cold outside, so is it the Tekmar settings that are messing it up? I have every manual for every one of the controls I have and I have spent hours trying to adjust the settings--no joy so far.
2) If the boiler fires on without any difficulty AFTER the power has been cycled, so long as it's cooled down, could it still be the flame sensor? Does something need to be flushed, cleaned etc?
3) It is possible/likely this short-cycling is happening because the wiring is a mess? I ordered a Tekmar 403 and new thermostats so that the DHW and all radiant flooring zones can be run off that single unit once installed, but how do I handle heat calls from the 2nd floor thermostats that are hot water air handlers and not radiant flooring? Do I need to go "all tekmar", get a Zone extension for the upstairs zones and change the thermostats out to Tekmar thermostats? Those thermostats in the 2nd floor also control cooling, so I'm guessing I need to get thermostats able to do both.
4) Unclear to me why this seems to be happening now all of a sudden--I don't anticipate the previous owners were cycling the power to the boiler every 3 or 4 hours round the clock like I have been for weeks, and I don't think their gas bill was astronomically high like mine was last month, but who knows. I didn't change a damn thing when we moved in, so maybe were were just unlucky. But, if it's a wiring issue, that has stayed the same since we moved in.
5) I definitely do not want to be DIYing this because I don't know a damn thing--unfortunately, I have lost count of the number of people I have called (including the rep from the Tekmar website and all of the people that rep told me to call), and everyone backs out when they hear radiant flooring, Tekmar, wiring, etc.

Sorry for the length, thank you for reading through this and any help you can provide!!

STEVEusaPA

First of all, an inspector won't be able to do anything except look at that and say...hmmmm
Well it worked before, probably, right?
Forget a general electrician. Try to find the original installer.
:Unfortunately, it's going to be pretty hard to diagnose/fix over the internet. Gonna need boots on the ground, so to speak.
Either find someone on this site close to you to come out, or call Tekmar and see if they have someone with expert knowledge near you to come out.
Yes, the settings make all the difference but keep in mind with the logic, there is some 'learning' involved. It's usually not change a setting, instant comfort, everything fixed.
I played with my Tekmar boiler control for years to finally dial it in, making small changes at a time.

Zman

What you have is an older Tekmar system with injection mixing and DHW priority. From your description, it sounds like the Tekmar side of this is working just fine.

Your boiler is not "Short Cycling", it is failing to ignite intermittently. I would recommend you have a competent boiler tech come out and service your boiler. This service should include cleaning the boiler, replacing consumable parts like ignitors, checking gas pressure, performing a combustion analysis and tuning as needed. If the company you call cannot perform these services, keep calling until you find one that can.

Paul Pollets

While the boiler can last 25-50 years with proper maintenance, the controls and pumps tend to have a 10-20 year lifespan. I would start to consider a mod-con boiler replacement and a re-pipe that used 2 pumps instead of 11 (or maybe 12). The better mod-cons come with integral computers that can handle multiple temperatures. A 3 way motorized valve is used when there are more than 2 system temps required. It greatly simplifies the system and reduces electrical loads. As you've found out, heating systems tend to fail on the coldest Saturday night in January and not July. The cost of replacing the Tekmar controls is not worth the expense, considering they're part of a new mod-con.

mattmia2

As @Zman said, your issue is with the combustion controls or the combustion/draft of the boiler. The flue damper likely failed at some time and someone set it to manual and got it to open so it is always open now.

You could set a cell phone camera on the burners and the pilot burner and leave it recording until it locks out then see what it happening when it locks out. It could be the flame sensor is dirty or a bad ground from the pilot to the control or it could be a combustion or draft issue causing it to burn improperly or rollout. Does the control give you a code of why it locked out or just that it did?

Don't let anyone that doesn't really know what they are doing touch those Tekmar and Taco controls. If they are working when the boiler fires, any screwing with them could really screw them up and take the right person a day or so to sort out. I don't suppose there is a control drawing somewhere. I suspect they are all applied properly and some parts were changed over time but it works correctly if the boiler fires where it gets a heat call.

EBEBRATT-Ed

@ColdTaco

Your going off in 100 directions except the right one. The boiler isn't starting because you have an ignition problem. When you recycle the boiler your recycling the problem.


Your controls may need to have some fixing but everything works when the boiler runs. Don't overcomplicate things and get the boiler fixed.

Then come up with a plan to rework the controls in the summer.......if you even need to.


It's like worring about the paint on the car when the engine won't start

hot_rod

Paul Pollets said:

While the boiler can last 25-50 years with proper maintenance, the controls and pumps tend to have a 10-20 year lifespan. I would start to consider a mod-con boiler replacement and a re-pipe that used 2 pumps instead of 11 (or maybe 12). The better mod-cons come with integral computers that can handle multiple temperatures. A 3 way motorized valve is used when there are more than 2 system temps required. It greatly simplifies the system and reduces electrical loads. As you've found out, heating systems tend to fail on the coldest Saturday night in January and not July. The cost of replacing the Tekmar controls is not worth the expense, considering they're part of a new mod-con.

I see at least 10 circulators there X 78W each= 780W just to spin circs when several could do the job as @Paul Pollets suggested.

On mild days turn off the boiler and let the pump wattage heat the place

That was state of the art. 20 years ago.

mattmia2

Are those circulators actually drawing 78w in that application or is that only if they are at a certain worst case spot on their curve?

hot_rod

mattmia2 said:

Are those circulators actually drawing 78w in that application or is that only if they are at a certain worst case spot on their curve?

Just a guess not knowing the model or circuit they are attached to. Some could be 90W high head versions? Doubtful many, if any are working at the knee of their curve?

Even so, on a good day, running at their best efficiency a PSC circ runs at about 22% efficiency. Zone pumps connected to a 3/4" circuit shouldn't be flowing over 5-6 gpm, so down into the teens perhaps for efficiency. Not a good conversion of wire to water.

An ECM could be twice that or higher.

kevink1955

Your original post said

The electricians thought it was the boiler ignition module--replaced that, no dice, sbut it now has an LED which shows that it's in lockout. Supply vents are clear (as best as I can tell). I haven't checked the flame sensor (don't know how) but I can ask the plumber to take a look?

and as ebebratt ed said
If it's in lockout it's a boiler ignition problem

It has nothing to do with Tekmar or Taco controls, get the boiler fixed and the problem will be solved. Not that the other wiring does not need to be cleaned up and documented but get the boiler to fire reliably first

bucksnort

What's really amazing is with all those nipples, elbows and flanges that it looks like nothing leaks.