About this time last year, the transformer part of the Relay/transformer died and with Trooper's help, I was able to get that replaced.

But I was bad and never got around to replacing everything ... now the Relay has died! So, if Santa does come tonight, all I can expect is a lump of coal in my stocking - and I can't even use that, because there is a burn ban on here!

Now that it's xmas and everything will be closed till Monday ... I'm wondering if ...

1. Can connections/wires be jumped/spliced to get the heat on? I realize this would be an, "always on" condition, but figure I can kill the power when it gets too hot and then power back on when things cool down.

2. Is it possible to just replace the relay?

3. Trooper's solution from when the transformer died had/does kinda confuse me and I just never got around to getting back here to get things clarified.

Although, after reading through it several times tonight I think I understand why it will work ...

What had confused me was in post #4 Trooper said ... Then in post #6 Trooper said ... So, when I looked at Trooper's diagram and did not see an external transformer, I was confused. What I missed was where he said the Taco ZVC panels would work - without an external transformer, right?

Below, all the info needed to solve this problem - hopefully ...

The Relay Transformer from April 2008:


The Relay Transformer top connections:


The dead relay:


Current wiring diagram for Zone Valves to Relay Transformer:


Connection/wiring info from Relay Transformer inside cover:








Any help getting the heat on before Monday ... the new year ... appreciated!

Happy Holidays and warm homes to all ...

 

There's two things you would need to do...

Fire the boiler. This can be done with a jumper (or a switch) across the S S terminals. This is a 24VAC circuit, and relatively harmless.

Run the circulator. This can be done with another jumper, or a switch temporarily wired in... between the TWO LEFT and RIGHT larger terminals INSIDE the RTU 100 relay box (the two with the black wires on them, they are labeled 1 & 3, but not to be confused with the 1 & 3 on the OUTSIDE of the box with the low voltage wiring to the zone valves). BE CAREFUL! This is 120 VAC POWER! It is NOT relatively harmless!

I believe that as long as the 'temporary' transformer is still functioning, the zone valves should still be operating normally. Before you do any of the above, make sure that is so.

Sequence of operation should be:

When thermostat is calling for heat, switch on circulator, and then switch on boiler.

Make sure to monitor system closely during these times, because if the thermostat satisfies, and closes the zone valve, the pump will be 'dead headed', and they don't like that. So, it might be best to push the t'stat way up so it doesn't satisfy until you can shut down the pump and boiler manually.

Please... BE CAREFUL! make sure you understand what I have suggested above. This is TEMPORARY! FOR EMERGENCY USE ONLY! DO NOT GO TO SLEEP AND LEAVE THE BOILER/PUMP RUNNING!

 

Let's see if I can clear up some of your confushment...

You CAN replace the existing relay box with an 8845, but you can NOT source the 24 VAC from the 8845 because the internal transformer is not big enough. You would still need to use an external transformer to run the zone valves.

This would be a reasonable fix... and it would work as it always has. At this point, this is your MINIMUM path.

Next are two upgrade paths...

The first one would use an additional 8845 to control the basement floor circ from the thermostat so you didn't have to have constant circulation there...

Next, you could also UPGRADE the system if you chose to do so by adding the Taco zone control panel. The transformer in the Taco panel WILL power the zone valves, with no need for the external transformer.

 

Some slight rewiring will be needed... note the (two) removed jumpers in the mark up of your zone wiring drawing. You don't want any other connections to terminals 3 & 4 other than the jumpers between them, and the two wires going to the boiler ( S S ).



and the 8845 will connect thusly:



I believe there was a mistake in the ZVC panel wiring... note that the main circ is wired to the NORMALLY OPEN terminals.

 

Thanks Trooper - for now, heat back on - I manually opened and locked both zone valves (no chance of them being satisfied/closing) - I disconnected and removed the wire for the main pump from the relay box and I used the wall mounted switch and wire for the basement pump to power the main pump. So now I have a "light switch" for on/off of the pump and a separate power switch for the boiler. So what I've been doing is ... pump ON - boiler ON ... boiler OFF - pump OFF.

If you recall, this is my parent's place. For the past year-and-a-half or so, it seems like I just go from one emergency/breakdown to the next, never having time to get anything properly finished - just good enough to get by, because by then ... another emergency/breakdown has to be dealt with.

Thanks for the clarification on the zone control solution/options.

My problem now is, I think it may be time to just replace the boiler. So, I guess I may need to know, if I get the Taco control, can it be used with a new boiler - or - if we are replacing the boiler, is there a better way to setup the zone control - re-do everything?

I've got to get a few more things to get together, then I'll start a new thread to address the possibility of replacing the boiler. Just not enough time tonight - got to get back out there and turn the heat back on!

Thanks again and hope you have a great New Year!

 

If you are thinking new boiler, I would just do whatever repairs needed to be done for the time being. Just rip out that old relay box, screw the 8845 in it's place, properly mount that temp transformer, a few minor wiring changes... a few hours and under a hundred bucks and yer up and running again.

Yes, very good chance the Taco panel could be used with a new boiler, but it's not NECESSARY... all it really does is clean up the wiring by providing a central location for all them wires to go to. There's no real 'benefit' other than that...

 

Got the Honeywell R8845u relay and wired it as described above, but I think the transformer is dead.

I didn't think to check the transformer when the relay died. I did check it after I made the temporary wiring changes to get the heat back on - I got zero volts - but I thought maybe it was the way things were wired.

Now that the R8845u is installed, I've got 120vac going in and zero volts coming out of the transformer.

If the transformer has power coming in and no power going out - is it dead? Is it more complicated than that? Is it "switched on/off" some how? If so, how can test it?

Currently, if I manually open the zone valve(s), the circ pump and boiler will come on - close the valves and pump and boiler shut down. So I think the R8845u is working - there just isn't any power to run the zone valve motors.

 

If you've got 120 on the primary, you should have 24 on the secondary... if you don't, then I would agree that transformer is fried...

Disconnect power to transformer. Set multimeter to OHMS scale. Check resistance across primary, then across secondary. You will find that one or both are open circuit... no resistance.

 

Tested the transformer - open circuit across 24v - so fried.

Before replacing, thought I'd make sure I know why it died after just a year. When the original transformer died, Trooper said ...

Is that what happened again, with the relay dead, no heat, so the thermostats just kept calling until the transformer gave out?

The transformer that just died was a - Honeywell AT140A1018 - 120/208/240 - 40VA - was this the right transformer? Can you recommend a better replacement?

I hadn't given much thought to how the transformer worked before, but for some reason I was thinking that it was switched on/off somehow. After looking at how it is wired ... now I'm thinking that it is "always on" - but kind of idling until a heat call, then it has to work harder to power the zone valve motors - is this right?

After having two transformers die in just over a year, I'd just like to know a little more about them and make sure, that if I got the wrong one last time, I get the right transformer this time.

 

I think that what probably happened this time is that when the relay coil burnt up, some of the turns shorted out, and put almost a dead short across the transformer.

Maybe the relay coil was _starting_ to go back then... and took out the old transformer too... although from the looks of that old one, it was nowhere near enough for three zone valves at once.

A 40 VA transformer is fine for 3 valves... can probably even do 5 if ya wanted to push it.

Yes, exactly. With no load on the transformer, there is very little current flowing...

Many of the newer transformers these days have a non-resettable thermal fuse imbedded inside. If the transformer gets hot enough, that fuse opens, and transformer becomes a paperweight. It's a U.L. thing. Your coffee maker has the same thing... as do 99% of the 'wall wart' transformers.