Wiring Help - Swapping SR501 for SR502 to fix my broken setup

bhilton

Hello, to save a long story, I'll start by saying where I'm currently at:

Vitodens 100 boiler with DHW kit
Zone1 - main level hydronic in floor heat running with a single groundfos looped off the boiler
Zone2 - upstairs forced air hydronic lifebreath furnace with its own groundfos loop off the boiler

Two thermostats:
- One for Zone1 running on battery power, very basic only signals by room temp
- A second one for Zone2 running on power from the SR501

Right now everything works sort of:
- When zone1 calls for heat, boiler fires and groundfos infloor pump kicks in, voila hot floor
- When zone2 calls for heat, furnace blower comes on, it's groundfos kicks in, voila hot forced air - BUT because the relay is single zone, i believe the infloor groundfos pump also comes on when zone2 is running! No big deal, kind of a bonus to me since the infloor is kept cycling occasionally.

The other big annoyance is zone1's thermostat does not have a slab sensor and i really prefer to run my zone1 off slab temp. I've tried replacing this thermostat with better ones but i can't seem to get it wired to work properly - which I feel is all due to having a single zone relay.

My first question, if I swap the SR501 for the 502, can I accomplish a proper 2 zone setup?

If Yes, can anyone help me wire it up?



Thanks a lot everyone!

Bill

lchmb

how about a picture of your boiler? So you have two t-stats, one wired to the sr501 and the other to the boiler? The 501 has an end switch, where is this wired to?

Zman

First off, yes the 502 will do that and it should not be a big deal to wire it.
It would be less expensive and more versatile to get another 501 and keep the other one.
Are you running the same temp to the fan coil as you are to the in slab radiant? If so, it would be better to do a 2 temp system with outdoor reset than it would to install a slab sensor. The slab sensor will tell you that you are overshooting. Outdoor reset will prevent it.

bhilton

lchmb said:

how about a picture of your boiler? So you have two t-stats, one wired to the sr501 and the other to the boiler? The 501 has an end switch, where is this wired to?

It's actually more messy than that!

In short, both tstats are wired to the SR501. I believe the furnace tstat (zone2) is wired directly to the furnace with some wires jumped over to the SR501 to tell the boiler to turn on when it's on (the furnace requires hot water too).

Here are pictures of the wiring right now, but i don't think how it is right now is really important. I have an SR502 sitting here ready to be wired, just need to figure it out.

bhilton

Zman said:

First off, yes the 502 will do that and it should not be a big deal to wire it.
It would be less expensive and more versatile to get another 501 and keep the other one.
Are you running the same temp to the fan coil as you are to the in slab radiant? If so, it would be better to do a 2 temp system with outdoor reset than it would to install a slab sensor. The slab sensor will tell you that you are overshooting. Outdoor reset will prevent it.

Zman, I am not sure I understand exactly what you're asking.

One thing is for sure, for zone1; I want to set the temp based on slab sensor OR room temp, at any given moment. Sometimes I will prefer it on room temp, othertimes I will prefer it on slab temp. The big reason for slab temp is that the lady likes the gas furnace to take the edge off, she doesn't quite love the in floor feeling on her as much as traditional. Also I like to keep a couple ceiling vents open for the furnace to circulate air in zone1 when it runs primarily for upstairs zone2. Therefore in general, i have found room temp in zone1 can easily be skewed and then the slab itself gets way below temp, so it takes a while to kick back in when it needs to. Just seems more consistent when I manage it by the slab temp.

I already have an SR502... I'll stick with it.

Now, I'm sure i can hook both Tstats to the zone1 and zone2 on the 502, but how do i hook the boiler up to BOTH zone1 and zone2, since in reality both zones get heat from the same one boiler.

Zman

Usually air coils and slab heat run at different temps and there is a mixing device or other means to control the temps.

It sounds like you are running a 1 temp system and just want 2 t-stats and 2 zones.

What are your questions on the 502?
The boiler wires to TT.
The T-stats to RW
The common is clearly marked if the t-stats needs it

gschallert

bhilton said:

Hello, to save a long story, I'll start by saying where I'm currently at:

Vitodens 100 boiler with DHW kitl

Hi there, sorry to horn in on your topic and I don't have any advice for you but I do have a question or two if you wouldn't mind?

I noticed you have the same combi boiler my in-laws just had installed and I'm going to be visiting them soon. While I'm there I'd like to make sure the new system is optimized for them.

My questions are:

1. What # do you have your heating dial set to, and do you ever change it during the heating season?
2. For your non-slab t-stat zone how many CPH is set? Do you know offhand how many times the boiler cycles per hour for heating calls in that zone?
3. I think you are in a similar geographic area to my in-laws, do you heat with propane or nat gas? If nat gas, what is your avg monthly ccf during the cold months there? They just converted to nat gas from oil and have no idea what a reasonable usage should be yet and I'm using LP so neither do I really.

Sorry if I seem nosy it's just nice to find someone with the same equipment to ask questions of.

Eric_32

The SR502 has all separate terminals for each zone. Won't get any easier.

The end switch on the 502 will close for either zone, telling the boiler there is a call for heat. It use to be labeled X1 and X2 but may be different now.. may be called an isolated end switch.

FYI I think Tekmar just came out with a digital wifi tstat that can work off a room thermostat or a floor sensor... looked pretty nice. Think it's the #561

bhilton

Eric said:

The SR502 has all separate terminals for each zone. Won't get any easier.

The end switch on the 502 will close for either zone, telling the boiler there is a call for heat. It use to be labeled X1 and X2 but may be different now.. may be called an isolated end switch.

FYI I think Tekmar just came out with a digital wifi tstat that can work off a room thermostat or a floor sensor... looked pretty nice. Think it's the #561

What do you recommend if the SR502 won't help?

I have 2 zones (downstairs and upstairs). I want downstairs zone to run on slab sensor temp, and upstairs t-stat temp.

Both zones need to fire the boiler when calling for heat, so if I use the SR502 and wire both zones up to the boiler and they both call for heat do I end up with a voltage overload?

In any case, do you have any tips on how to handle this situation?

I attached several pictures of the current setup.

The top of the SR501 has 5 sets of wires connected.
1) Direct from the tstat that runs my infloor heat downstairs. (low voltage)
2) Comes from the LifeBreath furnace as it has to fire the boiler so it can blow heat upstairs. There is 2nd t-stat wired direct to the LifeBreath. (low voltage)
3) 110V power coming from through the Guarddog low pressure sensor
4) Goes from the SR501 over to the boiler (low voltage)
5) 110V power going out to the in floor Groundfos circ pump

The result, every time the t-stat calls for forced air (upstairs only) the LifeBreath furnace wire to the SR501 causes the boiler to fire and unnecessarily causes power to go to the infloor Groundfos. This is messy and I'm sure there is a better way.

Thanks for everyone's help, just trying to figure out how to wire this setup properly.

Regards,
Bill

bhilton

I included a picture of the SR502 that's not yet hooked up.

Zman

It sounds like you plan to keep it as a one temp system and you just want to run 2 t-stats control 2 circs and have it fire the boiler?

Wire line voltage power to the 120 VAC input
Wire your circs to zone 1 and zone 2 circs respectively.
Not sure if you need the "jumper" between ZC and ZR as shown in the manual but it can't hurt.
The t-stats are wired to their respective terminals. If you need a common, pull it from 24 vac common.
The boiler wires that used to be on NO and COM now go on isolated end switch T-T.

bhilton

Thank you! That makes sense.
2 follow up questions:
- The End Switch, I presume that will turn the boiler on for heat calls from both zone1 and zone2?
- Safe to wire two t-stats to the 24 vac common?

Regards,
Bill

bhilton

Zman, I forgot to mention, yes there is a mixing valve on the slab heat! He's mixing in the colder return lines from the infloor, with the hot direct boiler water, before pumping into the slab.

njtommy

I will check out the Life Breath wiring diagram tonight to see if I can help you out @bhilton.

On a side note how do you like the life breath unit?

bhilton

I love the LifeBreath! It's the one thing I have not pulled the cover off yet to follow the wiring. I know my Honeywell t-stat is wired to the LifeBreath (it's doing dehumidification and heat and cooling). But there is a set of wires coming out of the LB going over to the SR501, it's probably just the circ pump on/off, but im not sure until I open it up.

Any tips you have, definitely appreciated!

I hope with Zman's advice, I'll be able to get it working on the 2 zone SR502 relay.

Zman

bhilton said:

Thank you! That makes sense.
2 follow up questions:
- The End Switch, I presume that will turn the boiler on for heat calls from both zone1 and zone2?
- Safe to wire two t-stats to the 24 vac common?

Regards,
Bill

Yes, the end switch will close with either of both zones calling.
No problem with 2 wires on the common.

bhilton

Thanks again! If all goes well, I will try swapping in the SR502 this weekend.

njtommy

It should be very easy for you to do this I hope.

Ok so you want to make sure the wires coming from your Current Taco control to the life breath unit are landed on Contact #1 this is a set of dry contacts so you can have the new controller send power to it with no problems.

You will just wire R to NO terminal and W to Common terminal on contact #1from the taco zone controller. R and W can either be from zone 1 or zone 2 it doesn't matter unless you want the life breath unit to be a priority zone. Your other zone will just be wired to r and W as well.

The two wires coming from the boiler will just be landed on XX terminals / end switch.

Ok pump wiring is easy. Do to the life breath units pump is built into their controller and inside the unit. You don't have to worry about that.

Just wore the line voltage to the 120input terminals and the pump for your radiant floor system to the corresponding zone on the 120v side.

njtommy

Here is the diagram for the life breath unit.

bhilton

ok, thanks! I believe the lifebreath already has power wired directly to it. So I don't need to send 120 VAC, i only need the 24 vac wires that are already connected to the SR501 to hook into the SR502 somewhere.

bhilton

Those wires should just be from the t-stat, hvac guy has the tstat wired into the lifebreath, then a set of wire coming out of the lifebreath over to the SR501, I'll look and trace to confirm, but I'm sure they're just the R NO and W, so i will put them on Zone2 as planned.

njtommy

@bhilton Any luck?

bhilton

I didn't get to it over the weekend, too many New Year social events and pain the following days. I will give it a go this weekend and report back. Thanks!