Transformer oddity...

Hvacman

I'm certain on each transformer and it's set of valves that I did not mix 24v and common, that would be a dead short, mine is overloading the transformer over time.

Hvacman

Transformer oddity...

I have a total of 8 Taco zone valves wired to 3-50va transformers. 3 zone valves to transformer 1, 3 to transformer 2 and 2 to transformer 3. Per Taco, 50 va is plenty big enough to power 3 zone valves but I keep losing transformer 1. I use transformers with circut breakers, initially the transformer is ok for 1 to 2 months, then there is no 24v but the circut breaker is not tripped, if I take a small pointed object and push the circut breaker button way in it will then trip fully the next time on a call for heat. Transformer 2 which also has 3 zone valves on it has always been fine. The valves are on a manifold and I've gone over all the wiring carefully for shorts. Should I go up to a 75va? All the power heads are new, the problem occurs after the transformer is a few weeks to 2 months old. Ideas?

Unknown

Amperage

You'll need to take the amp reading for each zone valve circuit alone to see if one is malfunctioning and drawing more amps than the others and then read the draw when all three are operating at the sme time and see if it exceeds .5 amps or the rating on the circuit breaker.

Mike T., Swampeast MO

Are both wires from each zone valve leading to same transformer? Both hot and neutral from each electrical consumer MUST lead back to the same transformer and you cannot use a common neutral connection among multiple transformers.

Leo_16

Use three

Use three identical transformers. Wire the hot side exactly the same on each. On the low voltage side wire number 1,A,H or whatever it is marked all to the top terminal on the zonevalve. Wire the other terminal to the middle zone valve terminals and be sure they all wire to the same T on the TT terminals at the aquastat. Wire the bottom terminal on the zone valves to the same side of TT on the aquastat. Now everything is in phase. If you have T 87 thermostats make sure the anticipater is on the high setting.

Leo

Unknown

Ground control to Major Tom...

Oops, wrong oddity.

Ken Field

Your circuits dead theres something wrong

Not too far off.

I agree with the use of identical transformers, all wired from the same line and neutral wires and all parallel wired R & C. Then feed the zone valves from one transformer just like there was only one. I ran a 12 Taco zone valve system that way for over 15 years and never lost a head or a transformer.

Ken

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Larry C_17

I agree that there is probably an overload on Transformer 1

I agree that there is probably an overload on tranformer 1. I would suspect a bad head or a miswire on the end switch.

Is the length of the wire to the heads on #1 long (greater than 50 feet)? If so, a direct short will not necessarily trip the circuit breaker but will overload the transformer. Is transformer #1 subjected to excess heat from another source like sunlight, a dryer vent, or a hot water pipe? Excess heat will also shorten its life.

Larry (NOT from OSHA)

Hvacman

Ah...

Had not thought of this, if I can isolate one of three with higher load then fix won't be far behind.

Hvacman

Yep...

I've done this exactly... It does seem though that when the transformer is at the end of it's life the trip occurs just as the end switch is making on one or more of the valves on transformer 1. I've swapped the heads around and the problem does not move, stays with transformer 1. The stats I'm using are digital "Rite-Temp"s or the new digital version T87 with no anticipators.

Hvacman

am I floating round my tin can?

If I have this right... You say to take load side of all 3 transformers and wire together in parallel? This would simulate 1 single 150va transformer, then wire as normal?

don_185

Check

Check for loose connection on primary side of transformer.

I find alot of blown transformer where they stab the wire into the emergency switch instead, of wrapping the wire around the screw.

Hvacman

Wire lenght...

From transformer to heads is less than a foot, longest run from t-stat to transformer is 40 or so feet. Transformer 1 is directly above 2 and 3... 3-4x4 boxes vertically in a row, transformers mounted to 4x4 plates w/center KO. Incidentally, #1 is warm to touch even with 0vac at terminals, no warmer or cooler than 2 or 3.

Hvacman

Oh, hey...

But wouldn't all 3 transformers be affected?

Hvacman

And the winner is...

Anyone who said "Transformer Phasing"... Although I was certain I had not messed up(famous last words), I was nagged by this. I had gone over the transformer load side many times with a fine tooth comb, and neglected the line side where I found transformers 2 and 3 with the common wire to hot. Why this affected transformer number 1 in this way I have no idea...

This is why I like the board so much, a gentle nudge in the right direction makes all the difference.

Thanks to all who posted.

Ken Field

Stuck in the 70s

Glad to see I'm not the only one.
Yes. Looking at it like one giant transformer is exactly what I meant. And then you don't have to separate zone valves into banks.
I see you already found the problem.

Ken

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zeke

I disagree with any idea of paralleling 3 transformers, since a single failure will result in no heat/cool for the whole house.
You should get a current reading on the faulty transformer feed line and if it reads correctly, I would change out the circuitbreaker since IT may be the problem.

ChasMan

Why Not Just.

Order one high quality transformer. Or one with three windings or three matched ones from a quality transformer maker. Im so sick of buzzy cheap transformers in my home. I replace them all with ones from this company.

http://www.toroid.com/

They will make anything you want.

steve_29

Why not just put in a couple of control panels?

Bet it would look alot nicer and probably stop the problems.

Barbarossa

Careful now

Be werry werry careful paralleling transformers not only the phase matching but if the impedances are not identical then the load will not divide out equally. The one with the lowest impedance will carry the highest load.

Rollie Peck_3

Transformers

There is another problem with paralleling transformers or using heftier transformers: Transformers designed to work with thermostats and zone valves are built to limit current to a value that won't overheat the low voltage wire going through the walls and cause a fire. Not a problem that I would want the fire investigators to trace
to me.

Rollie Peck

Homeowner

joe p_3

taco zonevalves

all issues of phasing, etc, aside... as a heat tech, i have found that the new t-87 replacements don't work with the taco motor due to the fact that the stat "robs" power from the line that it is switching. the taco head turns power to the stat on and off during a heat call as its piston heats and cools. this is also why you get little or no heat with the anticipator of a mechanical stat set too low - it satisfies before the slow-acting taco has a chance to open. long story short - i'll bet that the electronic t-87 replacement is on one of the heads powered by your persistently popping power part...