I have a taco SR504-exp relay.It has a 24vac output.Can I power a Robert Shaw 9615,two stage therm ,this thermostat needs 24vac.

 

Hi Bill, If you are asking if there is enough extra power on those 24 VAC terminals on the SR504 to power your thermostat, the answer is yes.

Are you actually running a 2 stage heating system? and are you also running an A/C unit with this thermostat?

In other words, what are you controlling with the thermostat?

If they are individual heating and cooling units, you might be better off installing an auxiliary transformer. When you shut the heating system down for the summer, you won't have the power coming from the 504 and the A/C unit won't run...

Tell us a bit more about what you are doing.

There is a moderator on another board, Jay11J who knows a lot about thermostats, he is the guru of thermostats! I've moved your question over to the Thermostat forum, you might get better / more answers.

 

No, you won't be able to run this stat on the Taco board.

There is no "C" (common) hook up, and the stat needs it to work.

As NJ asked, is there other equipment tied or you wanting to tie to this? ALso, why two stage? The zone valve is a single stage.

 

Hi Jay, I'm pretty sure there is are 24 VAC supply terminals on the 504, above the transformer... ?

In any case though, I think an aux transformer is probably the best bet, especially if he's running two units, separate heat and cool...

 

I didn't see anything in the diagram for this? IF there's C then he could use it IF he don't have another system tied to this.

he could do that with use of a relay.. This stat don't have Rc to keep the A/C away from the other transformer.

 

My set up is that the first stage ran a radiant floor system(separate,had its own pump,expanstion tank,own board,etc) from the hot water BB heat(installed about 8 years after the radiant floor heat was installed).The radiant floor heat was powered by a domestic hot water tank.The second stage I hooked up to the BB boiler,to run two hot water recessed wall heaters (the radiant heat didn't cut it when temp drop to low teens or below,stone fireplace).The 9615 was powered by a separate 24vac transfomer and a relay (tried to keep tranfomer isolated) to turn on a pump and boiler.
Now I want to move the radiant heat to the BB boiler. Have to run through a heat excanger(didn't know about oxygen barrier 8 yrs ago),a mixing valve on the out (radiant side) of heat exchanger.So I was woundering if I could run the 9615 off the taco board and just install a expansion board so I might use two of the new relays to run stage one and stage two. I understand it might cost more but a cleaner setup for future problems if something goes wrong(if everything working through one board or one place).If not I figure I just need another relay or two (cheaper),not powering from the taco board .

 

NJ, your thoughts on this?

 

Jay, I'm not sure if all the flavors of the Taco boards have the terminal strip for the 24VAC, but it's not mentioned in any of the literature ... at least not prominently. But I have seen a number of them that do have a terminal strip in the upper left hand corner of the board.

It seems that Bill's post is drifting back into boiler territory though?

I think the answer to the question is YES, you can. But I don't have time right now to explore all the facts...

Jay, feel free to move this back, and we'll try to help Bill out... if I have any t'stat q's, we'll be back atcha!

 

Moved it back to the boiler NJ.

I'll be on stand by! :-)

 

I don't see a problem with your idea Bill... just to make sure I understand the whole thing I'm going to re-state your design goal.

You want to use the 2 stage 9615 to control the radiant as stage 1, and the convector cabinets as stage 2.

Stage 1 will run the circ pump for the radiant, stage 2 will run the pump for the other heat zone.

I need to look at the 9615 diagram again... I think you have W1 and W2 for the two stages of heat. I think what you are going to find is that ... how can I explain this? ... you will be able to use only one wire from W1 to only one of the thermostat terminals on each stage, because the fact that you are using the 24VAC from the 504 panel to power the tstat... does this make any sense? I'm finding it difficult to describe what I'm thinking.

OK, more questions, and a repeat of some others:

1. Do you already have the 504 panel, and if so can you confirm that it does in fact have a terminal strip for the 24 VAC supply?

2. Can you confirm that you will NOT also be running an A/C unit from this t'stat ?

 

Thank you for taking some time for me.The answer is no I will not have A/C running from this thermostat (have wall units).The other answer is yes I already have a SR504-exp relay and it does have a 24vac pin on the left lower side looking at it. I know it would cost more but I would have to get another SR504-exp relay to plug into the original one(taco tech said I would need the SR504-exp relay to plug (wire) into the original circuit board).Ringht now using all the 4 relays on board.

 

Bill, sorry but yer confusin' me again!

You already have a 504 hooked up and running four existing zones ?

I do understand about your radiant setup from the other thread... so I'm good with that.

You only need 1 more relay circuit? Maybe you can do this with a SR501 (cheaper) or even a Honey 8845 ?

Can you describe exactly how the system is currently wired?

 

The radiant (as is now,will be putting on the HE)side of the HE already has a circuit board with one relay for pump on radiant side.I will be moving from that circuit board to new taco board.So I will need two more relays(didn't explain the whole situation). Was with telco and we always added extra for future so I will put in a SR503 .Now I was told by taco tech that if I wanted to put in reset in future I would need SR503-exp board NOT SR503.Like I said I want to have every thing in the same place,instead all over(two different circuit boards,extra transfomer ,with relay. One of my main concerns was if the taco board would have enough power(transformer output only 24v 15va) to supply the RS9615 and the relays on the board.

 

OK, it sounds like you've got a plan, and I understand your thinking about having an extra 'channel' on your PBX, and wanting to 'clean up' years of organic growth. That's usually my plan as well, but often $$$ is not freely offered!

The transformer in the Taco definitely has enough extra power for the thermostat. If that thermostat drew 25 milliamps, I would be surprised.

I'm quite sure that the Taco tech is correct in that you can't 'slave' a non-EXP panel... but I haven't looked at those diagrams in a while, so we'll just have to trust the factory guy. There is a whole bunch of literature on their website about various connection schemes... some of it is in wacky places, but look for the PDF file that's called something like : "Zone Wiring Guide" ... it's about 25 pages or more of all different combinations of controls, multiple panels, etc... fun reading... at least for control geeks like me.

 

Found it for ya, more like 100 pages!

http://www.taco-hvac.com/uploads/Fil...ry/100-9.0.pdf

 

I understand what I want to do a little,my wifes uncle has been in the hvac business for years.He called taco and robertshaw tech support,more than once.Both of them said not to us the RS9615 with a taco board.If you do use it only use one stage not two stages,plus us a separate transformer with a relay to isolate it.They both feel that you might get some kind of back feed ,if two stages operated through the taco board.This is what my wifes uncle was afraid of too.Thanks for the help but,I guess I will just have to have everything all over.Yes it will be cheaper too.
PS:I did discover that article you found with the different wiring diagrams.Had shown to my wifes uncle.

 

I'm quite sure that you could get that thermostat to work with the Taco board... I understand what everyone is talking about, and I'll try to explain my thoughts here:

In an earlier post, I tried to write what I was thinking:

and I might not have a better time of it this time either... but I'll try.

The 9615 has a COMMON and a 24VAC connection, which the Taco panel would easily power. Then, there is the W1 and the W2 connections for the two heat stages. These two signals are probably what they call 'dry contacts' that use the COMMON as the RETURN, or second wire for the W1 and W2 terminals.

If I were to design the Taco panel, I would do it as follows:

ONE of each thermostat terminals is wired internally to the COMMON terminal, and the other thermostat terminal is wired to the relay coil for each channel, such that when the thermostat circuit is completed, the relay coil circuit in the Taco panel is completed and that relay becomes energized. In other words, you would be switching the COMMON side of the circuit.

If Taco designed it the other way around, with the thermostat switching the 24VAC HOT side of the circuit, then there might be problems... and Taco doesn't release the schematics for the panels, so the only way to tell would be to use a multimeter and make some measurements.

However, even if it WAS designed the other way around, the 'fix' would be to reverse the COMMON and HOT connections to the thermostat, because AC power doesn't care about polarity. Without checking FIRST with the multimeter though, by the time you got around to realizing what was going on, you might have already fried the transformer in the Taco board.

In any case though, what you would end up with would be only ONE wire coming from the thermostat W1 or W2 terminals and going to only ONE of the terminals on the Taco thermostat connections. The other thermostat terminal in the Taco board would have NO CONNECTION. This WILL work, because the circuit would be completed through the INTERNAL COMMON connection in the panel.

So, the bottom line here is that I know it is possible to use that thermostat, but it would take some fooling around with a multimeter to determine exactly how it should be wired.

And, the bottom bottom line is that if you were to wire up a small external 24VAC transformer to power the thermostat, you could use it in any case... because by doing so you would be 'isolating' the common and 24VAC. (This is much the same confusion that people often have when wiring up Taco zone valves, which only have 3 wires. When you look at the circuit, it seems that you are shorting the 24 VAC from the zone valves to the 24 VAC in the aquastat, but that isn't the case because of the 'isolation' that the transformer provides.)