To start, here is my heating system info:
Weil-McLain CGM-4 boiler (nat gas)
Taco ZVC404
3 x Taco 571 zone valves

The heating system was originally a single zone, so no zone valves or ZVC. I added a second zone for a portion of the house and a third zone for raidiant floor tubing that was installed in the garage but never hooked up.

Currently, the two Tstats in the house run to the ZVC, which opens zone valves as needed and the main end switch activates the boiler gas valve and a single circ pump.

The zone for the radiant flooring has a zone valve plumbed, but is manually locked open (no wiring connected). The hot water from the open zone valve runs to a Sparco mixing valve then to a separate circ pump. When the radiant flooring Tstat calls for heat, the circ pump kicks on. However, since the Tstat/circ pump wiring are not connected to the boiler, if zones 1 & 2 are satisfied, the boiler will not flame.

I need to find a way to wire the boiler so it will flame when the water temp drops due to circulation in the radiant flooring, even though the ZVC has not activated the boiler.

I assumed I could just connect the radiant floor zone to the ZVC, but since it is on a separate circ pump, I don't know how to mix the low voltage transformer for the radiant floor circ pump with the low voltage transformer in the boiler.

After reading a few of the posts on this forum, I wonder if I need an aquastat. I don't really know what it would do, but I don't think I have one....

Any help would be greatly appreciated. Thanks in advance!

 

Since I can't seem to edit my prior post, I will add another. Upon further reading, I obviously have an aquastat on my boiler, otherwise it would not currently work. It is no doubt behind the cover where the transformer and gas valve are.

I guess I still need to know how to adjust my wiring or if a "brain box" is needed in order to solve my problems.

 

Phil, what pump are you running in the radiant circuit? You said something about "the low voltage transformer for the radiant floor circ pump" and I'm not sure what that means.

Is the t'stat for the radiant zone a LINE VOLTAGE t'stat that is simply turning the pump on and off?

Please explain in a bit more detail how the radiant pump and t'stat are wired.

I'm sure there's a reasonable solution.

 

Hello NJ and thanks for looking at this.

I am using a Grundfos UPS15-42F, I believe it is set on the slowest setting. Since I'm not a plumber, I may have used the wrong terms. The t'stat is connected to the transformer and is used to turn the pump on and off.

I'm not sure if this makes it a line voltage t'stat. The t'stat is connected to a transformer (or is it a relay?), as well as 110v power and the power supply for the pump.

I am trying to put together a complete diagram of the piping and wiring in hopes it will make suggestions easier. I should have them posted here shortly.

 

Phil, it sounds as though the circ is running via an intermediate 'relay'.

A 'line voltage' thermostat would not need the 'relay', because it would be able to switch the pump on and off directly, much as a light switch turns a light on and off.

Depending on the relay that was used, it could be an easy fix...

In addition to a diagram, pictures of the 'transformer', etc, would also help. Usually the more pics the better...

You won't be able to directly post the diagrams or pictures, you can set up a free account at Image hosting, free photo sharing & video sharing at Photobucket and upload them there. Place a link in the thread here for us to view the picture album.

 

Now I understand what 'line voltage' means, and yes the t'stat is running to a low voltage relay to act as a switch for the circ pump.

I have created (and plagiarized from images on the net) the following crude diagram of my heating system. There are isolation valves, relief valves, etc., I just didn't include them.



And here is the Taco ZVC as I currently have it hooked up. Zones 1 & 2 are both baseboard and work fine. The 'main end switch' connection which shows going to the boiler hooks into two wires that are coming off the relay inside the front cover of the boiler. I would assume that once either zone is activated and the ZV opens, the end switch turns on the circ pump and the gas valve (if the aquastat calls for heat).



This is where I don't know how to wire the radiant floor portion in. I am heading home right now and will post a couple photos soon.

 

If the relay for the circ pump has an extra set of contacts, it's gonna be pretty easy.

If you have an extra set of normally open contacts on the existing circ relay, you can wire those contacts to another 'channel' on the ZVC, and the zone valve to that same channel.

When the t'stat for the radiant zone calls, it will turn the pump on via the relay, as usual, and when the relay closes, the extra set of contacts will signal the ZVC to open the valve, and in turn, fire the boiler.

If the existing relay doesn't have the extra contacts, it would be a pretty easy matter to swap out the relay with one that did.

There may be a way around having to buy another relay though, because the 'zone 4 relay' in the ZVC is available for use. If you wired the radiant t'stat and zone valve to zone 4, you can use the zone 4 relay to switch the circ. Priority switch would be turned OFF.

Waiting to see pics, and what relay they used.

 

Thanks for the additional comments NJ; I figured it would be something simple, but without knowing what all the electrical connections do, I was not brave enough to try shorting something out...

Here is a picture of the relay used to turn on the radiant heat circ pump and the ZVC.



and here is a photo behind the front cover of the boiler, although it sounds like I don't even need to go there.



While I have done a lot of wiring, Im not much of an electrician. How do I know which contacts on the relay are normally open? Which two should I use?

 

Phil, what's the model number of the circulator relay?

 

The relay is a Honeywell; the only number that looks like it could be a model number is 'R8239 B1043'

On further inspection, there is a wiring diagram on the bottom of the relay box. Maybe this picture will help your thoughts.



I have been thinking about the possible solution you mentioned below. If I wire the relay to signal the ZCV when the t'stat calls for heat, it will then open the zone valve for this loop and turn on the boiler. The problem I see with this - turning on the boiler in this instance would also turn on the other circ pump.

If this happens, while the other two zone valves are closed, one circ pump would just be pushing right into the other. Would this cause a problem other than wasting electricity?

 

It appears that the relay center that is running the circ pump DOES have an extra set of contacts.

Referring to the schematic, your circulator will be switched by EITHER the BLACK and RED wires, OR the VIOLET and RED/YELLOW wires. These are two individual 'poles' on the relay, and either one may be used... the free pair is available to use for wiring to the ZVC... tape the unused ones up individually.

If you carefully remove the relay from the box by loosening the two screws on diagonal corners, take a look inside and first check to see that they didn't cut the extra wires off, and then which pair they used.

I see what you are saying about the main pump running. I need to think about that a bit... the main pump would run if say, one (or both) of the zones was calling at the same time as the radiant... but if the radiant was the ONLY zone calling, hmmmm... lemmee sleep on that and get back to ya.

I do have a thought before bedtime though... it looks like a 'DIFFERENTIAL BYPASS VALVE' would solve any problem that the main pump running might cause, and if you did have to add this, well, that complicates things a bit, because now you have to get out the torch and melt some solder...

Thing is though, I'm willing to bet that when ONLY the radiant calls, that you don't have enough flow through the boiler anyway... so you might benefit from installing the diff bypass anyway.

Google 'differential bypass valve' for more info on that, and in the meantime maybe someone else will have some ideas...

 

It am happy that you are getting me closer to an answer and really appreciate the brain energy you are burning.

I don't really like the idea of two circ pumps running, it just seems like a big waste. But, just as you commented, I was also wondering if there would be a problem with the boiler firing when only the radiant mixing valve is sipping hot water as needed.

I have looked all over the boiler and through the very limited info manual, but can not find a 'minimum flow' rating. Is there actually such a thing? Or would the boiler simply repetitively short-cycle if there isn't enough flow?

I have melted lots of solder and certainly don't mind installing a bypass valve. It's never pretty, but I've never had a leak...

Back to the wiring for now - I am wondering what the 'extra end switch' on the ZVC is for. Also, could I unhook the baseboard circ pump wires from the original relay wiring so the main end switch from the ZVC just activates the boiler? This would mean I would need to find a different way to energize the circ pump. Could it be done with some of the unused contacts on the ZVC (like the 'dry contacts' or 'extra end switch')?

 

Phil, I'm gonna answer a few questions, ask a few more, then I'm gonna 'backtrack' a bit...

Some boilers do have a minimum flow req, but I don't think yours does. And yes, I think the boiler would short cycle... in fact, doesn't it already do that if only the radiant zone is calling?

Might even short cycle on a baseboard zone call?

How many BTU your boiler?
How big are the baseboard zones?
What is the heatloss of your home?

For functions that use the 'extra end switch' take a look at the application drawings at TACO - HVAC for the 404/406 panels.

Yes, you _could_ run the main circ off the extra endswitch, but that won't really 'buy' you anything, that circ is gonna run just the same as if it was connected to the boiler.

The 'dry contacts' on the 404 are actually the 'zone 4 relay', and that relay only activates when there is a heat call on zone 4. Typically they would be used to run a circ to an indirect water heater (see the app drawings).

------------------

[backtrack mode on]

I probably should have asked this at the start:

WHY do you want to change the setup?

Is it not working to your expectation?

I always seem to get myself into system design situations, and frankly, I'm more of a 'fixer' than a 'designer', so I'm reluctant to suggest piping changes/redesign. I can design controls, but what starts as a simple control question often evolves into more... and while the controls I design might _work_, they might not actually be _appropriate_... so let's go back to basics for a bit and explore the reasons you want to change this setup.

[edit: I just went back and re-read your first post, and understand some of the reasons... but let's talk anyway, hopefully we can attract some ideas from others]

 

It doesn't currently short cycle when only the radiant zone is calling. This is because the 'radiant zone' is not really a zone at all; there is no 'wiring' hooked to the boiler for the radiant zone. All it is doing is stealing hot water as needed. The t'stat is simply turning on a circ pump.

I never noticed it doing so before, but last night while I was staring at the wiring hoping I'd catch a clue, I did notice the flame came on for ~20 seconds then back off. I will have to watch it more tonight and see just what is happening. Maybe an anticipator setting is wrong?

Boiler sticker says: input - 105,000 & DOE capacity 86,000
One zone heats ~1100 sqft; the other ~500sqft
I don't know the heatloss; I have never had it tested.

Because the 'radiant zone' is not 'wired' to the boiler, it has no way of telling the boiler to heat the water. If both baseboard zones are satisfied for a substantial amount of time, the radiant zone will slowly but surely sap all the heat out of the water and just keep circulating in vain.

I have a very nice and efficient wood stove in the house, but I can't run it right now because when it's on, neither baseboard zone needs heat, thus the radiant zone gets no hot water....

When the temp hits -30, the wife loves it when I cook up the wood stove and she can dance around like shes in Hawaii...but then the garage freezes... NatGas prices have nearly doubled in 2 years and I like splitting wood, but since all my utilities are in the garage, I can't let it go without heat. In addition to this, the garage floor slopes toward the door (long story) so if I don't have the floor heated, the garage door will freeze shut in addition to the pipes freezing.

Maybe I should put a third baseboard zone in the garage, running a Modine unit heater, and then slave the hot water supply for the radiant zone off the heat supplied for the Modine. This way water is always being circulated through the boiler & is always hot, when the radiant zone was wanting heat. Hmmm...

I have been putting this off since we moved into the house (several years ago) because I always new deep down there was no real easy answer.

 

The older I get, the more 'duhhhhhhh....' moments I have!
Yeah, of course.... duhhhhhhhhhhhhhhhh...

That's not even a short cycle! I think your boiler has the hiccups. I'd keep my eye on that... probably just an anomaly... could perhaps the programmable t'stat have picked that exact moment to setback for the night?

Your boiler may be oversized for your heat loss, but at least it's not disgustingly so.

Same here... except under certain conditions, my garage actually floods with about an inch or so of water. It's fun trying to drive the vehicles out on super slick ice... IF you can get them unstuck from the ice around the tires. And, it's unheated.

I kinda like the idea of even a short zone of baseboard, and this could be in lieu of the diff bypass valve.

Let's look at this diagram and see what we think:


[edited from first posting, added DP valve, might still want to add that]

With this setup, you achieve a few important improvements I think...

1. The return water to the boiler will be warmed up significantly, because the water through the baseboard will be mixing UP the water from the floor, which is probably too cold to send back to the boiler straight, no chaser.

2. The flow through the boiler is increased, and even though the cycles will probably be somewhat short, maybe not terribly so.

3. The main pump won't be pumping into a nearly closed mix valve, and your mix valve will probably work better.

4. With the mix of baseboard and radiant in the garage, the heat will be a little more responsive out there.

There may be other reasons too...

If you decided to do this, then I would have no hesitation in wiring that unused pole in the relay to the TT input, and the zone valve to the output on zone 4.

What temp are you running the floor zone in the garage? Since it's not really 'living' space, you could probably run it a bit higher than an occupied room.

Anyone else? Buehler? Xiphias, you think it's junk?

Beer 4U2

 

Didja get a chance to look inside the relay box yet to see if you have the wires available?

 

Yup, there are still wires on the back of the relay; brown, purple, red and yellow /w red IIRC. What would I need to do with the wires in the back of the relay? Do I hook them to something? I assumed that, doing as you suggested below, I would hook wires from the front of the relay to the ZVC. Is this correct?

Thinking about the re-plumbing, I really like the idea. I think the garage could use a little more heat and a faster recovery after the garage door cycles would be nice.

I doubt the boiler is over sized that this time, as I think my heat loss is atrocious.... But that is something I am remedying this weekend with a few dozen bags of cellulose!

I currently have the mixing valve set around 120 deg as I seem to recall someone saying too hot of water was hard on the concrete...Any comments on this one?

And I'm not sure I really have any free wall space for a baseboard. Space is precious in the garage; no doubt you know what I mean. Do you see anything wrong with a hydronic unit heater instead of a baseboard?

 

One more question - you mention hooking the unused pole on the relay and the zone valve to 'zone 4'. Zone 3 on my ZVC is currently empty; should I hook to there instead, or does it need to be zone 4?

 

Yes... looking at the schematic on the relay, you will see that there are two sets of contacts.

One set is BLACK, RED (N/O), and BROWN (N/C). I believe you will find that the BLACK and RED are used to switch the radiant pump, they are probably connected in series with the HOT 120VAC coming into the box. Double check that the BROWN wire is wire nutted and taped. You don't want that wire contacting anything, since when the pump is OFF that wire is HOT.

The other set, VIOLET (purple), RED/YELLOW (N/O), and YELLOW (N/C) should all currently be unused, and taped up. You are going to connect the (N/O) normally OPEN pair, the VIOLET, and RED/YELLOW to a piece of thermostat wire, and run that to the T T on the ZVC. Wire nut and tape the unused YELLOW wire.

Yes, you can use Zone 3 if you wish. The reason I got 'stuck' on Zone 4 is because I was thinking that we might use the 'zone 4 relay, dry contacts' to run the radiant pump, but that isn't going to be necessary.

If ANY of the three wires in the second set (VIO,RED/YEL,YEL) are connected to ANYTHING, STOP! and let me know what you've found. Also, before you continue, it is best to verify those wires are REALLY what we think they are... don't trust the schematic. If you have a multimeter, first check them for voltages (you shouldn't have any on them), and then switch the meter to OHMS, and verify that with the relay OFF, you have continuity from the VIO to the YEL, and with the relay ON, you have continuity from the VIO to the RED/YEL.

Wire the zone valve to the zone 3 valve output.

That's it for the wiring!

A unit heater is probably a better choice for the garage.

Are you hip to the function of the DP valve? You don't absolutely NEED it, but it is a good idea. A little explanation about it in case it's 'fuzzy'... When all three zones are open, the DP valve is going to be set to 'the edge' of opening. The full flow of the main circ will then move all of it's capacity through all three zones. As each zone closes, instead of the pump trying to force all the water through the remaining zones, _some_ of the water is going to go through the now partially open DP valve and back to the boiler. Pressures and water velocity in the zones are better controlled with it.

I would suggest that if you want to do the wiring and not install the unit heater right away, that you do install the DP valve right away, and set it so that when only the radiant zone is open, you have most of the flow through the DP valve and only what you need in the radiant. Yes, the boiler will probably short cycle... but it might not be so bad as to be unacceptable. If it IS 'that bad', this is one case where something like the Beckett Heat Manager might work wonders. It will widen the differential on the boiler cycles, let it cool more between firings, and then in turn be on longer when it does fire. In other words, instead of say a 180-170 burner cycle, you might have a 180-140 burner cycle.

Maybe... I'm not a huge radiant guru, so not sure about that one... I would think that if the concrete was very dry, i.e. vapor barrier underneath, no water running down the drive and flooding the garage , etc... it would be more tolerant of higher temps... but I doubt if kicking it up to 130 or maybe even 140 would hurt it... I wouldn't go any higher than that myself... but check with a real guru...

Is there insulation under the slab, and around the perimeter? (I hope!)

As always, I welcome, even encourage, any comments on my ideas, from anyone!

 

Thanks for the very specific and easy to understand wiring guide. Yes, the black and red are connected to 120v. The brown does have its own little wire nut on it. I will add a little tape so it never comes off.

All the other wires mentioned are there and nutted as well. Thanks for the tips on checking the rest of the wiring; I have a very cheap multimeter, this will be a good excuse to buy something better.

Since I am going to wire the back side of the relay to the ZVC, this makes me ask: Should the t'stat for the radiant circ pump be running to the front of the relay? Is that the proper way to do things? Or should all the wiring on a relay be on the back side?

Yes, the DP valve sounds like a great idea; like a nice easy addition to reduce wear & tear on the system. Since I'll have everything off and drained, it will be a perfect time to make the addition.

Thanks for your thoughts on the radiant water temp. There appears to be Z-flashing outside the garage covering over 2" blue board, so I know the perimeter is insulated but have no idea on the underside.

Thanks again for all your attention to this matter. Beer 4U2
Even though the answer requires considerably more work than I wanted, it feels great to have a plan. I'm insulating the attic this weekend, hopefully I'll get to the plumbing next weekend.

Please don't go anywhere! I may have more questions...

 

Marvelous. Have at it. The dP is a good thing. The load sharing with the one zone valve is a good thing.

Keep concrete slabs <135-140. If 120 does the job, keep it there. What you want to avoid is a strong temperature differential from one part of the slab to another. That can cause cracking due to differential expansion. (That of course is a design issue to its a bit late for that, but keeping the average temp as low as can do the job is a good thing.)

 

Not really! This doesn't require anything fancy... all you need to know is that it's working... el cheapo is fine, as long as it works.

Yep. Right where it is is where it belongs.

I'm willing to bet that if they insulated the perimeter, they also did the underside.

I don't plan to!

Thanks for the input on the slab temp Xiphias!

 

I second that, thanks for the slab temp info Xiphias!