electric boiler 3 phase vs 1 phase

I have built a new shop with in floor radiant heat and am going to heat with an electic boiler. for now anyway.
I am bringing 3 phase in to power lathes and other misc. equipment. I was going to put a 240 volt 3 phase boiler in but a couple of road blocks. most smaller 3 phase boilers come in 208 volt or 480 volt so I have to go up to 27k boiler all of a sudden boiler cost goes from $1200 to $3000 now my question is there any electical savings by going to 3 phase vs single phase or is a kw a kw and running a 27kw 240 volt boiler on 3 phase cheaper or the same price as running a 27kw 240 volt single phase. any help would be appreciated for this electrical dummy and his helpers. Paul

A KW of heat is a KW of heat, single or 3 phase.
It's easier to balance the voltages and current on a 3 phase service if major loads are 3 phase.
I'm not certain of your concerns about 230 or 480V and 27 KW boilers?
Are you saying you have to go to a large boiler to get into 3 phase?
If you want to reduce the capacity of a way over sized electric boiler that is cycling on, off, on off etc. Connect the 480V boiler to 230V. It will drop a 40KW boiler to 10KW.

I would try to buy a boiler that matched the phasing and voltage of the service and size the wattage to what is needed. Lowering the voltage increases the amperage making it more expensive to run as is stated a KW is a KW it does not change. A 480V unit would draw less amperage than a 208V unit sized at the same wattage which would reduce conducter and breaker size.

480 volt. Better have a licensed and certified electrician. Also might affect your insurance costs. 480 will grab you and not turn loose. I have been there not done that but seen it happen. Lotta guys called "3 fingers" or "no thumbs" Additional expense of across line magnetic starter unless built into unit.

First I was led to believe that there are 3 different possible ways to bring 3 phase in #1 480 volt#2 208 volt #3 240 volt the 240 vs 208 has to do with wye and delta I am really unsure of this. the whole place will be on the same line so I was unwilling to bring in 480 volt and buy transformers to step it all down to single phase.The licensed electricion won't answer his phone either by the way.basically boils down to this I can buy a single phase boiler 24-30 k for $1000 give or take. the smallest 240 volt 3 phase that I can find isan idustrial 27k and is $3000. what will I gain by buying the 3 phase boiler? will there be a smaller electric bill at the end of the month? there are some other 208 volt three phase options out there but they all run about $2500 and up as well . any help again appreciated Paul

As far as the electric bill is concerned, KW is KW.

As for as the wiring is concerned, it will probably be cheaper to wire the 3 phase boiler.

You can hang a 1 phase boiler between two legs of the three phase supply, probably 208 three phase is handiest because it gives you three 120 legs. Though 240 three phase with a wild leg gives you two 120 volt legs and runs motors on 240 OK.

The boiler for single phase probably has one or two heating elements. The boiler for three phase will have at least three, maybe 6.

Wiring, breakers, and service tend to be more expensive for three phase because there are three circuits instead of two, and there are no home grade three phase products. There is much more single phase electrical service equipment made than three phase industrial, which lowers the cost of single phase equipment.

480 volt breakers and switches and contactors are several times the price of 240 volt because its harder to get the 480 interrupted. And the consequence of not stopping the arc is that the panel burns down completely.

Three phase is nice for motors, they are smaller for the hp and run quieter and if they are built into machinery its hard to change to single phase, but the modern Variable Frequency Drives, a solid state box make that a lot easier.

You won't get any more heat per KWH from three phase or single phase, but you will pay your utility more for three phase service than for single phase though the rate per KWH after the monthly fixed charges will probably be the same.

Gerald J.

I would stay away from those tapped delta systems.
Having more data now. Go with a plain simple 120/208 wye, three phase service if that is what your machines use.
With the difference in price go with the single phase boiler. Or........
There are reasonably priced ordinary everyday three phase water heaters that can be used as heating boilers too.

Yes, the tapped delta systems can be a pain because of impedance unbalance leads to current unbalance in the three phase motor. The worst is an open delta with the wild leg transformer too small, its size chosen by a new kid in the shop.

But that being said, sometimes that is all the utility will supply and we have to use it or not buy power at all.

Gerald J.

Yes, the new and even the old often forget that 57% rule.