Installing 24v DC Heated Floors in RV....how to connect??

[skimedickc]

I am installing 24v heated floors in our 40ft motorhome. They will pull a max of 1800watts at powerup, and drop to about 1100 watts after the floors are at temperature. I need to run two separate circuits of 900watts each to the control units (1 circuit to each) with a distance of about 20feet from the power supply center.

Here is my setup:

• 1 12/120 3000 Victron Multiplus II
• 6 206Ah SOK 12v batteries
• approx. 1650 watts Solar (will be expanding to 2k)
• Batteries connect to Lynx PowerIn, then to Lynx Smart Shunt, then to Lynx Distribution Hub which connects to MultiPlus, MPPTs, and 12v House Load.
• I have two Orion 12/24 50A, one for each floor circuit to increase the voltage from 12 to 24.

My questions:
1. What size wire do I need to run the 20ft from the Orions to the controllers (24v, 37.5A )
2. What size wire do I need to run the 5 ft from the Lynx Distributor to the Orions (12V, 75A)
3. I have heard that it may be better to run the positive from the most distant battery in the series (battery the negative is connected to) rather than from the Lynx Distributor due to the wattage draw on the system, any thoughts on that?
4. I plan to add a second multiplus, but should I do it sooner than later due to the wattage draw of the floors? Our microwave, airfryer, refrigerator, etc. all run on the inverter circuit but rarely draw more than a five hundred watts at a time unless we are using everything at once.

Thanks in advance!!

 

[Rocketman]

What is the heat system you are using?

1. 37a wire would normally be 8ga.
2. 75a wire would probably be 4ga.
3. I would connect it through the Lynx distribution, KISS principle. Also I think your description in #3 would bypass the shunt - thus giving you inaccurate state of charge numbers.
4. ???

One idea I had was because of the potential to run down the battery with the heat system, you may want to put a Battery Protect BP-100 between the distributor and the Orion - that way you can use a cutoff of like 12.3v - so the heat system gets cutoff first - well before other items run out of power. (The Orions may also be able to do that- I don’t know).

Good Luck with the project!

 

[skimedickc]

Thanks Rocketman , I am using the step warmfloor system for rvs https://stepheat.com/warmfloor/rv/. Great idea on the BP-100, I will definitely do that. I didn't know they had that product. I think to save space on the lynx dist I will get the BP-220 and split the two loads from there, running just one line from the dist to the BP.

 

[John Frum]

Don't step up the voltage from 12 to 24
Go the other way instead.
Use 24 volt batteries instead of 12 volts so you don't have voltage drift in the battery strings.

 

[John Frum]

This will help

Interactive Wire Size Calculator

Battery Chargers, Inverters, Solar Components, and Wiring Supplies for Boats, RVs, and Off-Grid Applications.

baymarinesupply.com

This calculator wants round trip length so remember to double your distances.

 

[John Frum]

The warm floor seems to work at 48 volts.
The would help with the distance induced voltage drop.

 

[Rocketman]

Interesting chart - the 37a 40’ run may be better with 6ga - 8 was just above the 3% voltage drop.

Also, may want to bump up one more size for even less voltage drop- which will make more floor heat.

Just goes to show - double check the charts.

 

[John Frum]

@skimedickc does your RV have have 30 amp shore power or 50?
Also do you have slides and/or levelers?
What is the amp rating on the ac/dc converter in the combo distribution panel?

 

[skimedickc]

@John Frum Its a 50A shore power, 4 slides and levelers. It says 50amp service distribution panel at the combo breaker panel if that's what you mean. I already have everything set up as 12v, had thought about going to 24 or 48v but was told by several victron distributors that since I'm already at 12v and have the battery bank set up that way to just stay at 12v and step up for the floors to 24v. (I had been considering going to 48v and switching to server rack 48v batteries, but I would have to sell all my current batts and multiplus to do that)

 

[John Frum]

@John Frum Its a 50A shore power, 4 slides and levelers. It says 50amp service distribution panel at the combo breaker panel if that's what you mean.

Inside the combo panel there is typically an ac2dc converter.
I was looking for the amp rating on that.
Since you have 4 slides plus levelers you will need lots of 12 current.
This usually means keeping at least one 12 volt deep cycle battery.

I already have everything set up as 12v, had thought about going to 24 or 48v but was told by several victron distributors that since I'm already at 12v and have the battery bank set up that way to just stay at 12v and step up for the floors to 24v. (I had been considering going to 48v and switching to server rack 48v batteries, but I would have to sell all my current batts and multiplus to do that)

I had a look at the link you posted.
From memory It mentions 500VA as a planning number for the secondary side of the transformer.

 

[skimedickc]

Inside the combo panel there is typically an ac2dc converter.
I was looking for the amp rating on that.
Since you have 4 slides plus levelers you will need lots of 12 current.
This usually means keeping at least one 12 volt deep cycle battery.

I had a look at the link you posted.
From memory It mentions 500VA as a planning number for the secondary side of the transformer.

I think, but not sure, that my slides and levelers operate on the chassis batteries rather than house batteries.

I think the only ac to dc converter on my rig is the multiplus. It originally had a magnum but I switched it out a year ago to the victron 12/120/3000 multiplus II.

 

[John Frum]

I think, but not sure, that my slides and levelers operate on the chassis batteries rather than house batteries.

Usually they run off the house batteries but are terminated at a separate distribution block close to the batteries.

I think the only ac to dc converter on my rig is the multiplus.

The multiplus is a dc to ac converter.

It originally had a magnum but I switched it out a year ago to the victron 12/120/3000 multiplus II.

The multiplus 2 has that really awesome automatic transfer switch.
The only other inverter/charger to have anything comparable is this one https://xantrex.com/products/inverter-chargers/freedomex/

 

[John Frum]

@skimedickc Since you mention that the slides and jacks might be powered by the starter battery does that meain your RV is not a trailer?

 

[skimedickc]

@skimedickc Since you mention that the slides and jacks might be powered by the starter battery does that meain your RV is not a trailer?

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