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Actuators, T-Stats, & VA's oh my.

Member Posts: 417
Can anybody help me with the math here.

Uponor Actuator 3023552
Start Current: <300mA
Working : 1W
End Switch: 24VAC, .05A

Honeywell Pro 1000 non-programmable
Heat: 20-30VAC, .02-1.0A

Floor 1: 8 Actuators, 3 T-Stats
Floor 2: 8 Actuators, 5 T-Stats

So this is for a friend who is an hour outside of town and was wiring it last week and blew a transformer.
Uponor told me when I called (I couldn't find the document using my phone today so I called) that 4.5VA is what I should use to size this. So I do not know if my buddy has a shorted wire or somewhere or not. But he only tried Floor 1 thus far. My math says 36VA for those 8 Actuators. If the 1A on a T-stat really equates to 1VA then it still should have been only 39VA on that transformer that blew. Actually thinking now, the T-stats are not installed yet as the painting isn't complete so the wires would have been twisted together. Either way I have time to go help them out tomorrow but I want to know that I'll going to be safe with a 40VA transformer, since I know there are none available in my area bigger than 40. But if I have to I will bring out a few and try to break them down a little more.

Thank you for sitting through this.

• Member Posts: 17,009
The devil is in the start current. Uponor is quoting you the hold rating -- 4.5 VA, which is just under 200 milliamps. However, the start current -- the surge when the circuit is first closed -- is half again as much; about 7.2 VA at 24 volts. I don't know how long that surge will last, but it may be significant. Perhaps while they are changing state -- and if more than 5 of them are drawing the start current at once, you will fry a 40 VA transformer.
Br. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
• Member Posts: 417
Uponor pdf states the following for total number for Actuators per Transformer. So I really don't know how a transformer could have blown on start-up with merely 8 installed. Could there be an 6 being installed in series maybe? I really don't want to go out there a blow a fuse. Maybe I will bring a few and just break them up into smaller sections. Although I know 6 will be the smallest because there is some RFH w/ 6 loops on one t-stat.

A3010522 Thermal Actuator, four-wire 12(50VA) 18(75VA) 25(100VA)
• Member Posts: 10,213
Yeah, sounds like he may have wired something wrong.
The uponor spec sheet says 300ma (or .3amps) is the inrush as you mentioned so ,3 x 24volts=7.2va (like @Jamie Hall said) so 40va/7.2va=5.55 actuators

so I would put 5 on a 40 va transformer.

Problem is I dont know how many actuators you putting on 1 stat but 3 will be pushing it on the stat amperage.

Since you have several actuators on 1 stat I wouldn't ignore the inrush current of .3 a each as all the ones on that stat will be on at the same time.
• Member Posts: 417
edited February 2017
There is one zone that is 6 actuators and 1 t-stats. That's is the biggest, with the added fact that I really don't think I'll find bigger than a 40VA tomorrow morning. I do have a two electronic suppliers that a couple of local guys said I should try. Honestly I'd feel much more comfortable with a couple 50 or 75's. Hour drive each way, I don't want to get it wrong.
• Member Posts: 17,009
edited February 2017
Find a quick acting 1.5 amp fuse -- electronics supply places and some auto parts stores have them (Amazon does too, but that won't help you tomorrow!) -- and get hold of a few and a fuse holder to put one in. Wire that in series with your transformer. That way you will only blow the fuse, rather than the transformer.

And @EBEBRATT-Ed mentioned the load on the thermostat -- it's not likely to blow the 'stat right away (although it might), but 6 actuators running through one 'stat is an overload even on the hold current, and it may not last long -- especially if it is one of the newer solid state ones (You could put a lot more than that through an old mercury Honeywell T-87, but those days are gone).
Br. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
• Member Posts: 417
I'll see if I can get some fuses in the morning. I assume I just wire it in series on the "r" of the secondary side. I know I've used a white Rogers before that didn't label R/C.
• Member Posts: 15,004

It may be the inrush current getting you, If they all hit at the same time.
Our low current draw 250mA has a 6 VA inrush
the TwisTop is an 800ma 19VA inrush.

We just released a low current TwisTop, 250mA.

The amount of time at high current draw depends on how cold the actuator is, as the heater needs to warm that wax pill.

This graph show the current draw of various zone valves. the thermal type, motorized flapper and motorized ball. The ball valve current drops off when the valve is fully open.

Motorized valveslike Z-one, HW, Erie, etc draw the same current as once they open the motor stalls and becomes a resistance heater

Missing from the graph is a 250mA type actuator.

Ideally you wire through a zone valve relay box to eliminate all the current draw through the stat.

Another method with a relay box is to use the end switch to open successive actuators so the high current draw of a bunch doesn't hit all at once. But it will take a few minutes for all to fully open.

Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream
• Member Posts: 417
Thanks so much guys. I really appreciate the depth. Thanks for the detail all around you three. It will help a lot.
@hot rod if I cannot get anything bigger than a 40VA. On the 6 setup your saying I could wire up four and then use the end switch on one of those and put it through a 24v relay and then send the signal to the other two. Essentially two zones would be "on delay".

I think I'll fly in a 75va and wait a day or two.

Again all three of you, I appreciate the detailed info on the actuators and some work arounds. In the future they'll be able to pipe it differently to prevent specialty situations like this too. I also learned lots that will prevent me from making this mistake too.
• Member Posts: 417
Just thinking. Can I hook up two equal transformers. Then wire the secondary sides in parallel? My 2 40VA's then equal 80VA @ 24V.
That would be more than enough with breathing room.
• Member Posts: 2,217
Yes you can wire 2 transformers together and get double the capacity. You have to correctly phase the transformers or you will blow out whichever one happens to be weaker.
• Member Posts: 15,004
Hilly said:

Just thinking. Can I hook up two equal transformers. Then wire the secondary sides in parallel? My 2 40VA's then equal 80VA @ 24V.

That would be more than enough with breathing room.

Yes. Also the Caleffi relay boxes have the 2- 40VA transformers in parallel, so you have 80 vA across the valve connections.
Hilly said:

Thanks so much guys. I really appreciate the depth. Thanks for the detail all around you three. It will help a lot.

@hot rod if I cannot get anything bigger than a 40VA. On the 6 setup your saying I could wire up four and then use the end switch on one of those and put it through a 24v relay and then send the signal to the other two. Essentially two zones would be "on delay".

I think I'll fly in a 75va and wait a day or two.

Again all three of you, I appreciate the detailed info on the actuators and some work arounds. In the future they'll be able to pipe it differently to prevent specialty situations like this too. I also learned lots that will prevent me from making this mistake too.

You would not need a relay, wire 4 to theet-stat, then send the 24V to the end switch to switch additional ones. most end switches are 1- 5 amp rating.

Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream
• Member Posts: 417
I explained to these guys today that they need to price in the control panels. I said the cost of 2 75VA's and 2 blown 40's would pay for the first one. And the time it would take to install them would pay for the second. I think after this job they will start incorporating them in their pricing. I haven't turned back since being introduced to them. I was happy to learn a few of the finer points of it all though. Thanks to you guys I got to be the hero today.
• Member Posts: 417
Well this is how it turned out. Manifolds were not near each other, nor were they near the boiler. I have to get going to hockey but this was what I was able to through together in Visio. My first crack at it, I think can see it really being a quick learning curve with a few YouTube videos. Let me know what you think. Would you have wired it differently? I think I have these contractors sold on ZVC's in the future. It wasn't a fun day, but at least the house was empty and I had just me and my mind to deal with. Sometimes those days are the most peaceful. Certainly get the most work accomplished anyway. Thanks again guys for your insight.

• Member Posts: 17,009
I see one problem -- but it is probably in the drawing. The black wire shown as connecting the blues from M1 A6, A7, and A8 back to the left hand transformer should connect to the blue from M2 A4, not the brown from M2 A4. Otherwise, looks good.

One wonders if there was a more complicated way to zone and valve the thing, though...
Br. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
• Member Posts: 417
Great eye Jamie and REALLY, thanks for taking the time to really look through it. And about the zoning/manifold/piping... It was interesting. The basement had some old cast irons stand-ups. Man that heat makes my heart sing. The money they could have saved in actuators alone would have paid for a ZVC. Blow transformers would have paid half of the 2nd one. And the cost of the new transformers would have balanced it all out. It's crazy how the minds work sometimes. They are good guys and I think they will think twice about control panels moving forward cause I might not have a free day next time it comes up. Sad part is the "Wholesaler" guided them on this one.
• Member Posts: 417
edited February 2017
@Jamie Hall I just crunched some numbers briefly for fun. If they piped it with three manifolds, 6 actuators on one and 2 zone valves for the other two and then used 2 ZVC controls panels they would have do it for almost a couple hundred dollars less. Except they would have had nice tidy clean control panel boxes and they would have been able to wire it themselves. I actually had to double look.
• Member Posts: 17,009