Activating Radiant Circ Pump via 24vac Output from Honeywell AQ251

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Old 10-17-13, 01:23 PM
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Activating Radiant Circ Pump via 24vac Output from Honeywell AQ251

Hi Guys,

New to the forum. Probably been a good 10+ years since I've posted anything in any forum, but I'm stumped by what should be a simple problem, and I'm hoping someone here can help. I recently purchased a 5 y/o 2 floor home with walk out partially finished basement. The home has a Buderus G115WS boiler controled by a Honeywell AQ251 boiler reset control panel. The system has three zones and DHW. The DHW and zones 1 & 2 are controlled by Taco 571-2 zone valves, and that part of the system is working fine. The problem is with the 3rd zone, and I believe something was designed incorrectly...

The 3rd zone is a radiant heating system in the basement. Instead of a zone valve, there is a circulator pump connected to it which is in turn connected to an Argo 822 relay which then connects to the 3rd zone output of the AQ251. When I first moved in I noticed the circulator pump was constantly running, so I called my oil provider for service. The first tech they sent out noticed the Argo 822 had been jumped at the T-T and that was why it kept running. He removed the jumper, which stopped the pump from running, but then it wouldn't activate when there was a zone 3 call for heat. He suggested I have one of their other techs out to figure out what was going on. The 2nd tech came out a few days later and was unable to get it working properly and suggested I call Honeywell for support. I called Honeywell and the tech asked me to check the output at the zone 3 connector during a call for heat, so I disconnected the zone 3 output on the AQ251 and ran a call for heat. I then checked the output, and it was around 25v or so (close enough to 24). AQ251 seemed ok. For the heck of it I check the wires that were coming from the 822 and noticed they also had about 24v coming off them. That's when I realized that the current setup was unworkable.

If I'm correct, the 822 has a transformer feeding 24vac to the T-T terminals expecting to be connected to a thermostat, which in turn would then close the circuit when there is a call for heat. The AQ251 on the other hand is putting out 24vac to close a valve. Assuming i'm correct, what is the easiest solution? I've looked for a simple 120vac relay which can be activated by the 24vac output from the AQ251, and I haven't found anything too straight forward (all the hydronic control have tranformers to feed a TT like the 822). Alternately, should I keep the 822 and try to get a simple 24vac relay which will close the T-T circuit on the 822 when the AQ251 calls for heat on zone 3? Seems like there should be a really simple fix I'm overlooking..

I'm really surprised that the system was designed like this, but luckily it looks as though everything else was designed fairly well. Thanks in advance for any suggestions.
 
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Old 10-17-13, 03:56 PM
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Hi Bob, welcome to the forum.

I need to study your post a bit more, but initial impression first...

Alternately, should I keep the 822 and try to get a simple 24vac relay which will close the T-T circuit on the 822 when the AQ251 calls for heat on zone 3?
Probably the easiest/cheapest way.

I would think something like this Tekmar relay would be a simple fix.

003 - Tekmar 003 - 24V Relay

Wire the AQ251 output to the relay coil, and one set of the relay "Normally Open" contacts to the T T input on the 822.

This relay would also be able to run the pump directly, but then because it is switching 120VAC, it would have to be mounted in an approved enclosure. so easiest would be just to wire it between the two panels. No need to enclose it because it's all LV wiring.
 
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Old 10-17-13, 04:02 PM
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OK, now picking out the bits and pieces I have questions about:

You said that the T T on the 822 was jumpered, but then you said:

an Argo 822 relay which then connects to the 3rd zone output of the AQ251
How so is the 822 'connected' to the 251 ? It sounds to me like since it was jumpered that it is NOT connected to the 251 and rather is jumpered... which was obviously a 'hack' when the installers realized their mistake and hoped that the homeowners did not.

so I disconnected the zone 3 output on the AQ251 and ran a call for heat.
Disconnected it from what?
 
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Old 10-17-13, 04:04 PM
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He removed the jumper, which stopped the pump from running, but then it wouldn't activate when there was a zone 3 call for heat. He suggested I have one of their other techs out to figure out what was going on. The 2nd tech came out a few days later and was unable to get it working properly and suggested I call Honeywell for support.
I sure hope that you didn't actually PAY for these 'so-called' techs inability to diagnose and correct the issue.

I'm really surprised that the system was designed like this
I'm not. Not at all....................
 
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Old 10-17-13, 04:18 PM
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I would like more information.

Please take a look at the Honeywell panel and tell me which 'communication module' you have, and which 'zoning module' you have... full model numbers please.

I may ask for pictures eventually...

On the radiant zone 3... is there ALSO a zone valve in addition to the pump?

Is the pump on the 'other side' of the piping to/from the boiler with a TEMPERING VALVE in between?

Once I know all the details, there MAY be an even easier solution...
 
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Old 10-17-13, 04:23 PM
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Did the installers / previous homeowners leave the manuals for the 251 / 822 / boiler / etc for your use?

You would do well to read and understand the functions of the 251 system. If the installers did what they did, they could well have screwed the pooch on the setup of the 251 system.
 
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Old 10-17-13, 06:06 PM
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Hi NJ,

Thanks for the quick reply and the info on the Tekmar 03- I will look into that!

To answer your questions, the AQ251 is an AQ25142B which has a AQ15100B communication module, and a 4 zone low voltage zone module (AQ15540B). The zone 3 N&L terminals of the AQ15100B were indeed connected directly to the T-T terminals on the Argo 822. So not only was the 822 back feeding to the zone module, but I believe there would have been a short at the zone module when there was a call for heat on zone 3 and the 822 terminals were jumpered. There is the possibility that the first tech that came out and removed the jumper also (re)connected the leads from the zone 3 N&L (they may have been fed into the 822 casing, but left disconnected when whoever realized it didn't work and hacked it with a jumper), so it may not have been in that configuration for long. Luckily the AQ15540B seems to be undamaged.

To answer your other questions:

No, there is no zone valve on the radiant zone 3, just the circulator pump, which along with the zone valves for zones 1, 2, and DHW, are all on the return side. There is a Honeywell AM-1 series valve between the supply and return side of the splitters for the radiant tubes before they disappear into the concrete. I'm not sure if that's the same a tempering valve.

When I said I "disconnected the zone 3 output" what I meant was that I pulled the wires that were coming from the T-T terminals of the 822.

Lastly, the previous home owner did not leave any documentation, but I have found all the brochures and manuals for almost all of the components in the system online, including the boiler, Aquastat, 251 unit and 822 relay. I have been studying them and have created notes on all of the existing settings and any changes I have made. I am extremely OCD when it comes to understanding and tweaking systems. There are many more questions I have, but I will keep this post on topic!

Lastly, no, there has been no charge thus far for the two techs who came out and checked the system, it was covered under my service contract. They were both really nice, but I find it difficult to understand how they didn't figure out the problem, yet when I finally dug in it took just minutes..

PS- I can post pictures tomorrow if you would like.

Thanks again!
 
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Old 10-17-13, 09:08 PM
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Excellent... and understood...

No, there is no zone valve on the radiant zone 3, just the circulator pump, which along with the zone valves for zones 1, 2, and DHW, are all on the return side. There is a Honeywell AM-1 series valve between the supply and return side of the splitters for the radiant tubes before they disappear into the concrete. I'm not sure if that's the same a tempering valve.
I'm not confident that the piping is correct... at least my visualization of your description doesn't sound right.

I would like to see a picture of this.

Yes, the AM-1 is a tempering valve.

What make/model is the boiler, and how does the pump for the other zones fit into this setup?
 
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Old 10-18-13, 01:30 PM
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The burner is a Buderus G115WS/5 with chimney venting, and the main circ pump is right near the boiler supply. You can see it in the picture below. One other thing to note from the below picture is that there are 3 supply lines going out, and 4 coming back it. That's because zone 1 & 2 feed from the same supply line, but then split before they exit the basement.

Here is the burner and main piping setup including both circ pumps:
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And here is the tubing and valves for the radiant:
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You may notice from the above image there is a set of tubes (one supply, one return) heading upwards. That is because there is radiant heating on the kitchen and bathroom floor for the first level. This is an odd design choice seeing as how the first floor is already served by base boards and the radiant is on zone 3 which I keep set to around 50, so it never gets used...
 
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Old 10-18-13, 01:39 PM
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Here is a clearer picture of the piping:
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Old 10-18-13, 03:33 PM
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Right off the bat Bob, I can tell you that the radiant zone piping is all whacked.

The tempering (aka Mixing) valve is wrong, the pump is wrong...

But to get the pump so that it only runs during a heat call, you could add that relay. I believe that it will still be usable if and when you decide to get the radiant piped correctly. You will still need that pump, but it won't be installed where it is!

That pump, judging by the way it is installed, was most definitely a complete afterthought hack job.

Let me look around and see if I can find a post a diagram of how it SHOULD have been piped.
 
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Old 10-18-13, 03:41 PM
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Now for more questions:

1. The green Taco pump, does that one run when there is a call from the radiant zone? (BOTH pumps run?)

The lower manifold, just above the AQ251 panel is your hot supply out of the boiler. I see only three 'take offs' on that manifold, yet the return manifold has four.

2. It appears that the first take offs on the left side of each manifold go around the corner to the water heater, correct?

3. So how do the other two take offs on the hot supply manifold feed two zones AND the radiant stuff?

I can surmise that one of the pex tubes running up the wall from the radiant manifold is going to the red Grundfos pump. But the other?
 
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Old 10-18-13, 03:43 PM
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Can you tell me what the writing on the tubing into the floor says? And also any nomenclature on the orange tubing as well.
 
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Old 10-18-13, 05:31 PM
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Thanks again for the advice on that relay- I'll get that ordered and wired in next week. As for your questions:

1- Yes, that Taco pump runs for any of the three zones and DHW.

1a- The main supply has a combined pipe for zone 1 and 2, which splits about 10 feet down from there. Hence why there is three supply and 4 return.

2- Yes, those takeoffs go to the SMART Triangle Tube water heater.

3- Yes, and I'm guessing that's not a good thing..

3a- The other orange tube comes from the supply take off furthest to the right in that picture.

Here is the text from the tubing:

Main orange: 315115FT Cash Acme PEX OT w/02 Barrier 3/4CTS cNSFu-pw-rfh ICC ESR-1852 U.P. Code B137.5 ASTM F876/F877/F2023(F1807/F2098/ASSE 1061) SDR9 PEX 3006 160psi @ 73F 100psi @ 180F 12/03/09 18 1 09:00 Reel # 860

Into Floor: WIRSBO hePEX Plus 1/2 IN SDR9 PEX-a 100psi 180F / 80psi 200F (NSD-rfh ASTM F876/F877) (ASTM F1960/F2080) ICBO ES ER5143 ER4407 NOT FOR POTABLE WATER UB04070922 22584

I look forward to seeing how this was supposed to be setup! Thanks again for all your help.

PS- Going to start a new thread soon about the settings in the AQ251 and why it will on occasion fire the boiler for 3-4 seconds, only to shut it down, and then fire it again for 30-90 seconds just moments later..
 
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Old 10-18-13, 06:51 PM
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3- Yes, and I'm guessing that's not a good thing..
No, not a problem, just want to see how it's all fitting together...

I look forward to seeing how this was supposed to be setup
I've been googling images to see if I could find a 'close enough' drawing but so far have not had any luck. I might have to draw my own.

Very basically though, the pump for the radiant floors needs to be on the 'outlet' of the AM-1 ... on that short section of tubing (where there isn't enough room for it!) where it feeds into the upper radiant manifold.

That part is a 'given'.

How to get the water in and out of the main manifolds is a little trickier...

The tubing looks fine! Just wanted to make sure they didn't use regular pex for domestic plumbing and used the correct stuff for heating. They did.
 
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Old 10-28-13, 03:52 PM
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Hi NJ,

I was able to wire up that Tekmar relay, and now the activation of the circ pump for zone 3 is working properly. I've tested the system for a few minutes, and the supply lines get nice and warm (with the exception of the line to the far left for some reason), but the return lines don't seem to be warming up. I guess this is due to the system not being setup properly as you pointed out..

I also found that the supply sensor for the AQ251 had gone bad, so I replaced that. The system (with the exception of the basement radiant heat) is now working perfectly. Thanks for all of your help!

-Bob
 
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Old 10-28-13, 08:41 PM
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Hi Bob, I'm sorry I seem to have gotten overwhelmed with other posts and forgot all about you!

Glad the relay is doing what is needed.

and the supply lines get nice and warm (with the exception of the line to the far left for some reason)
By 'supply lines', you mean the radiant tubing coming off the supply manifold?

Your manifold appears to have 'balancing valves' for each of the ports. Is the one that's not getting warm possibly closed?

but the return lines don't seem to be warming up
Depending on how cold the slab is, and how long each tubing is, it may take a while even with proper flow for them to get real warm.

I'll try and remember to find a diagram, or draw one for you, but basically what needs to happen is that you will need to install a zone valve for the radiant zone, and connect the supply and return lines together. On that connected together section, you will need a pair of 'closely spaced tees' to which the supply and return from the manifolds will be piped.

The pump need to be moved from where it is to that short section between the supply manifold and the mixed outlet of the mixing valve.

Let's see if this picture will link:


image courtesy pmmag.com

The 'hot from boiler' would come from your supply manifold, and the return would go to your return manifold through the zone valve.

It's still not the diagram I wanted, but it's a start.
 
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Old 11-11-13, 06:31 AM
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Thanks again for all this info NJ!

Your explanation and diagram make a lot of sense. When I do need to get that zone up and running properly, it doesn't look like it will be too costly a fix.

Having said that, you mention adding a zoning valve, which makes perfect sense to me. Right now the system is open, which means whenever there is a call for heat on zone 1 or 2, or DHW, some heat bleeds through that system. Seems like a costly waste of energy.. If it is safe to use a zone valve to block off that zone when not in use, than would it also be safe to just turn off the manual valve on that zone for now? My concern is that if there is no water circulating through that system, that there could be a chance of the in-concrete pipes freezing (which I'd imagine would be a nightmare..).

A little added info to the above. The basement "zone 3" zone has yet to drop below 63 degrees even with a few high 20s nights and low 40s days we've had.
 
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Old 11-11-13, 03:53 PM
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I doubt if it's really 'costing' you anything to have a little flow during other heat calls. Heat is going into the home anyway, right?

there could be a chance of the in-concrete pipes freezing
These are in the basement floor slab, which is well below grade? refresh my memory...

If they are I doubt if there's any chance of them freezing.
 
 

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