Furnace is not kicking on when any thermostat is turned on

Stylez777

Hey all,

I'm having some issues and not sure if I can fix it or if I need a pro.

I bought this house a few months ago, when I did the walk through I checked all 3 thermostats and they worked and called for heat and the furnace would kick on and the baseboard heaters would heat up.

During some renovations to the kitchen, power had to be turned off and on a bunch of times and one day I had no hot water. Electrician put in a new transformer down by the furnace, said it shorted out stopped working. I got hot water back thought all was good.

Yesterday I replaced a 30 year old Honeywell Thermostat on my main floor with a new T5 with batteries. At one point it def was line voltage in there as it had an electric box and the electric wires (white and black). I get it all hooked up and test it out, get no call for heat, left it on heat mode and auto fan and temp set at 80 and no heat ever came up. I went to my basement and my 2nd floor and did the same with those thermostats and same issue no call for heat.

Now...I don't understand how any of this is wired, as there is a lot of splices, twists etc but the one thing I can tell is that the voltage at each thermostat is only 10v. The Transformer is a Supco SXT150 24v. I went down to the furnace and I tested the volts of the wire out the transformer and it saying 10v as well and not 24v. Could this transformer be the issue? Should I try and change the Transformer with a new 24v one and see if it resolves the issue before calling a pro and possibly spending $$$ for a simple transformer swap.

Lastly, if it is the transformer, this would be 2nd time replacing in 2 months. With all this frankenstein wiring (See the Pictures below)...should I call a pro anyway to checkout and help me figure out how this is wired, and if it is done correctly? Thanks!

mattmia2

Is your meter measuring AC volts?

Stylez777

@mattmia2 yes i have the meter set to ACV setting o measure. It getting 10v.

When i measure the transformer I use for my Ring Doorbell, that is a 16v transformer, same setting on meter I get 16v off that.

That why I am wondering if here something wrong with this transformer...I could be wrong though

JUGHNE

Your electrician may have unknowingly installed a doorbell transformer instead of an HVAC 24 volt one.

But I see you stated a 24 volt one above. It looks a little small for the job.
Is there a VA rating on it...something like 20 va or 40 va.

mattmia2

What if you disconnect one lead of the transformer and measure its open circuit voltage? What does the transformer say it is rated for? A picture of its ratings plate might help. Maybe it is a universal 120/240v transformer and they used the wrong taps or it is too small for the various loads on it.

STEVEusaPA

Why not get the person who services your boiler there, someone who knows the controls and how they work, instead of an electrician?
It's a universal 120/208/240 50 VA transformer. Let's hope you didn't let the smoke out of too many components.

Stylez777

@STEVEusaPA I don't have a service company yet. I just bought the house 2 months ago, and the old people who lived here used Sloeman's.

I was going to get into a service contract with a company, but all these issues started to come up and it has been over 70 here for longer than expected. When thehot water was out, I had a GC doing work on the house, so I kinda blamed his guys and put it on him to fix. Everything worked prior to his guys turning things on and off. So his electrician put in that transformer. Is that the incorrect Transformer, cause if he caused all this I want to take it up with the GC if that transformer caused other pieces to fail.

What would a correct transformer been rated for?

Stylez777

@JUGHNE

JUGHNE

The 120 volt side of that, inside the steel box, should be connected to the black and white of the transformer primary. The other 2 wires taped off.

Do you have another transformer in the system somewhere?

That is a 50 VA, should be able to run a lot of things.

It looks like you have 4 zone valves, is that right?
They have a VA required rating on them. The 4 added up should not exceed the 50 VA.

Jamie Hall

Too many cooks. I'd get a quality HVAC man or woman in there, take out that spaghetti bowl you have for wiring, and rewire everything neatly and cleanly with labels. I think you are putting patches on patches, and there's a very limited future in that.

EBEBRATT-Ed

Well usually you can run 3 zone valves on a 40 va. Looks like he has a 50 vaI see at least 4 zone valves in the picture. 40va/3=13va each 4 valves X 13 va= 52va

So the transformer and fuse could be too small. Putting two 40 va transformers in would be the cheapest way out

Check the voltage and check the fuse coming off the transformer (inside the white plastic inline thing) Should be at least a 2A fuse.

Stylez777

@JUGHNE On the other side of the Transformer the black and white are hooked up, the orange and red are capped off. On the outside the Blu and Yellow are connected to the wires that lead to the zone valves.

The BX cable comes out of the furnace box, hits the oil burner turn off switch, then to the transformer. Nothing else in between.

There is 3 Zone Valves, only 1 shows that is is 7va, the other 2 just say 24v, no va rating.

The last box there is a honeywell, can't really see much info but seems to be something with hot water.

Still very weird only 10V off the blue and yellow wire out of the transformer.

Stylez777

@EBEBRATT-Ed There was 1 transformer there when i moved in and probably 1 there forever and the system worked. I don't think 2 transformers should be needed, I would assume the prior service company would have been called out numerous times for issues and rectified it.

I'm thinking it has to be something off with this transformer, direct off the blue and yellow wires, it still reads only 10v and not 24

JUGHNE

Is that 10 volts with nothing connected to the transformer?

mattmia2

It is always possible the wires got connected to the wrong taps at the factory. The resistance between white and black should be about half of the resistance between white and orange.

Stylez777

@mattmia2 and @JUGHNE I think I disconnected the wires and tested the 2 wires bare out of the transformer. I'll go down and test it again shortly and report back.

JUGHNE

If you have only 1 pump and 3 zones plus hot water tank, then you most likely have 4 zone valves.

Stylez777

@JUGHNE @mattmia2 I tested just the transformer, nothing hooked up to it on the low voltage side, the blue/yellow wire. It read 10v. So I have to assume, this Transformer is an issue? Should I pickup a 24v 40VA Transformer and give it a try, see if I can get it working? It is the only logical thing I can think of trying at this point (outside calling a tech) and I think a tech would probably try to replace the Transformer.

mattmia2

You can safely replace it. If you can find one that is a little bigger than 40va (since you seem to have just a little more load than they would like to see on a 40va transformer) and has a circuit breaker I would recommend that.

Zman

I would go back to your original idea. Get rid of that spaghetti mess excuse of a wiring job and install one of these. https://www.supplyhouse.com/Taco-ZVC405-4-5-Zone-Valve-Control-Module-with-Priority
You will gain DHW priority and will be able to troubleshoot at a glance by simply looking at the LEDs

Stylez777

@mattmia2 I can get the same type and brand locally 24v 50VAC, same store has a 24v 75VA transformer that has a breaker. It says it is a foot mount, so not sure how I can mount that to the box. Should I give the 75VA one a try? Can't hurt right?

Stylez777

@Zman I would love to put that in and get rid of that birds nest! Not sure if I could do it all myself, but I prob will just have a guy come out and put one of those in. Right now, I just want to get it up and running power wise and then have a guy come in and sort out the rest of he wiring mess.

Zman

If you can troubleshoot that mess, you can install a controller. The valves and t-stats are plug-and-play. From there, you just need line voltage to the controller and the enable switch to the boiler. You could mount it in place of the existing transformer. The switch to the boiler is the wire that all the red zone valve end switches are tied to.
Put the DHW on the zone labeled priority.

EBEBRATT-Ed

@Stylez777

Your old transformer is a 50va. It's not just the VA load on the transformer there is INRUSH when everything starts at once......call it a surge if you want.

Again, did you check he fuse to see if it was blown?

Make sure you have a fuse or circuit breaker on the new transformer or you might let some smoke out

Stylez777

@EBEBRATT-Ed I tried to open the plastic to check the fuse, but I couldn't get it open. I'll check it tomorrow. The new transformer I get will either have a fuse or breaker as well

Stylez777

I checked the fuse and it looks fine. It is a 3a fuse