Low energy heating

[boathealer]

Now that the chill has set in in N. Florida, time to start talking heat.

One way to heat yourself (literally) overnight on battery power is with a heated mattress pad. We have a queen pad with separate left-right controls.

I did an experiment last night and measured the power consumption of the pad. It was amazing to me. Outdoor temps got down to 38F. Morning inside the boat was 50F with no boat heat running. Double quilt/blankets on the bed.

The mattress pad ran for 10 hours at #1 (of 10) setting on left side and #3 (of 10) setting on the right side. The bed was downright COZY. The warmth from the pad was very noticeable. For all that time, we consumed a total of 120 watt-hours of energy at the inverter-supplied outlet. This is a mere 10Ah at 12V plus inverter inefficiency - say 11-12Ah total. For TEN hours of sleeping warmth! Wow!

Now,

• Yes, the boat is cold when you get up to pee.
• Yes, the boat is cold when you get up in the morning.
• You need an inverter.
• I would guess manufacturer's products vary - ours pulses the heat on and off over time to the setting selected.

But, WOW, an entire night of heat for 12 amp-hours!!! The comfort-to-power ratio is so good because the heat is applied directly to your body instead of heating up all the airspace in your cabin and having to have it make its way to you.

Just another option/data point for anyone who occasionally needs low power options on battery-only.

Cheers

 

[Portage_Bay]

Been using 'em for years. Great way to keep the chill out of the bed. Start it 30 min before going to bed and you crawl into a nice warm bed, no need to curl up in a ball trying to warm the sheets with body heat.

 

[Dwk]

Good observation. I'm certain my wife will be shopping for a heated mattress pad after reading this post! O C Diver has talked about using a electric blanket..are they the same?

 

[O C Diver]

Yes, I use an electric blanket through the inverter for heating on cool or cold nights.

To avoid confusion, it may be easier for readers to understand how little power it consumes if you convert it to watts either as an hourly consumption or over the course of the whole night.

Ted

 

[boathealer]

Yes, I use an electric blanket through the inverter for heating on cool or cold nights.

To avoid confusion, it may be easier for readers to understand how little power it consumes if you convert it to watts either as an hourly consumption or over the course of the whole night.

Ted

I put in there that it was a total of 120 watt-hours for the 10-hour night.

 

[O C Diver]

Good observation. I'm certain my wife will be shopping for a heated mattress pad after reading this post! O C Diver has talked about using a electric blanket..are they the same?

A mattress pad is underneath you, the twin size electric blanket on a queen bed, is above you. I use the electric blanket over a light blanket and under a bedspread or comforter. Both should be frugal on power consumption.

Ted

 

[O C Diver]

I put in there that it was a total of 120 watt-hours for the 10-hour night.

Sorry, I saw AH. Watt-hours is redundant. Watts are an absolute commodity like gallons or miles.

Ted

 

[boathealer]

Sorry, I saw AH. Watt-hours is redundant. Watts are an absolute commodity like gallons or miles.

Ted

It's still a valid measure of battery capacity required. 120W for an hour, or in this case 12W for 10 hours....

 

[rslifkin]

Sorry, I saw AH. Watt-hours is redundant. Watts are an absolute commodity like gallons or miles.

Ted

Watt-hours is absolutely a valid unit of measure. Electric bills typically come in kilowatt-hours for example. If something is drawing 120 watts and runs for one hour, it consumes 120 watt-hours. Assuming 12 volts, that would also be drawing 10 amps, which over the course of an hour would be 10 amp-hours.

 

[boathealer]

Watt-hours is absolutely a valid unit of measure. Electric bills typically come in kilowatt-hours for example. If something is drawing 120 watts and runs for one hour, it consumes 120 watt-hours. Assuming 12 volts, that would also be drawing 10 amps, which over the course of an hour would be 10 amp-hours.

Yep.

 

[tiltrider1]

I used electric blankets for years. Up until the market placed changed the design to the auto on feature. Now electric blankets only turn on after they sense the heat of a human. No more coming to a preheated bed. Are he heating pads the same or can you turn it on early and then climb in to a warm bed later.

 

[boathealer]

I used electric blankets for years. Up until the market placed changed the design to the auto on feature. Now electric blankets only turn on after they sense the heat of a human. No more coming to a preheated bed. Are he heating pads the same or can you turn it on early and then climb in to a warm bed later.

Not the one we have - no "human detector". It even has a "Preheat" setting just for that. Also has a10-hour auto shutoff.

 

[MurrayM]

How about 12 volt options?

https://www.12volt-travel.com/12-volt-electric-blankets-c-90.html

 

[DavidM]

120 watt hours for ten hours of use is great. But what is the instantaneous wattage draw when it is cycling on? You will need that to size a dedicated inverter.

David

 

[OldDan1943]

Alas, the mattress on my bed is non standard so electric sheets are not available.
I stay warm by using blankets, the heavy spread and my sweet beautiful bed partner. We stay VERY warm.
Now if I can just convince her to warm my side of the bed for 15 min before I go to bed. Hey, fair trade. I warm the toilet seat for her. LOL

 

[boathealer]

How about 12 volt options?

https://www.12volt-travel.com/12-volt-electric-blankets-c-90.html

I think most of these are full-on, or off. 4-5A when on. That would be 50Ah over 10hours.

The thing that makes the pad we have so efficient is the pulsing of the heating elements when set low - averaging out the power consumption.

It looks like the $100+ model in you link has varying heat settings - I'd like to see more specs on that function.

 

[boathealer]

120 watt hours for ten hours of use is great. But what is the instantaneous wattage draw when it is cycling on? You will need that to size a dedicated inverter.

David

I think I saw it peak at 1.2A @ 120V when in the "on" state - so 12-15A at 12V. Still not much.

 

[boathealer]

Alas, the mattress on my bed is non standard so electric sheets are not available.
I stay warm by using blankets, the heavy spread and my sweet beautiful bed partner. We stay VERY warm.
Now if I can just convince her to warm my side of the bed for 15 min before I go to bed. Hey, fair trade. I warm the toilet seat for her. LOL

Our mattress has the top two corners cut down just a bit. We end up just tucking excesses underneath.

 

[psneeld]

I had a nice foam mattress go bad in just a few years...I chalked it up to not being a brand name.



The replacement name brand mattress had a warning DO NOT USE WITH MATTRESS WARMING PAD as it deteriorates the mattress faster.


I dunno...maybe after my first experience I just am worried about destroying a more expensive mattress ....and I miss the sucka right about now...


.....but I haven't hear of others reporting the same problem.

 

[O C Diver]

Watt-hours is absolutely a valid unit of measure. Electric bills typically come in kilowatt-hours for example. If something is drawing 120 watts and runs for one hour, it consumes 120 watt-hours. Assuming 12 volts, that would also be drawing 10 amps, which over the course of an hour would be 10 amp-hours.

We must have different electric companies. My bill tells me how many killowatts I consumed last month. A killowatt is a measure of power consumed. A consumption or production rate such as a generator is measured killowatts per hour.

Ted

 

[DDW]

Watts are a measure of power. Watt-hours are a measure of energy. Power is energy used or delivered per unit time. Your power company is being less than rigorous with their units. The production of a generator is usually spec'd in kilowatts (instantaneous power delivered). How many kilowatt-hours it produced depends on how long you run it.

 

[boathealer]

Everyone is right.

watt /wät/
noun
- the SI unit of power, equivalent to one joule per second, corresponding to the power in an electric circuit in which the potential difference is one volt and the current one ampere.

watt-hour /ˈwädˌou(ə)r/
noun
- a measure of electrical energy equivalent to a power consumption of one watt for one hour.

 

[STB]

For whatever it is worth, I am a big fan of electric blankets. I started using one on my old boat in SoCal during the worst of the "winter", then I switched over to using them at home in the northeast -- and saved a ton of money by lowering the thermostat for the whole house by a ton.

At one point, I tried heated mattress pads. Some people suggested they'd be better, because the heat would rise to heat the blanket in addition to simple conduction (which is how the blanket heats the bed).

I can't say I noticed any efficiency there. But, I did notice that I, personally like the blanket better. It makes more contact with me, so I am able to use a lower setting and be more evenly warm, versus a higher setting and getting more warm where I was making direct contact with the mattress pad, and less on other places.

 

[catalinajack]

Similar to Old Dan what does, we use nothing but flannel pajamas and a down comforter over a top sheet. We live aboard just south of Annapolis. From November to March, the cabin temp drops down to 48 - 50 degrees by early morning. We have NEVER been cold, not one single night. We do not put the reverse cycle heat on overnight unless the outside temp dips down into the teens. Having a foam mattress helps and, no, it does not sleep hot in the summer. It is 1:30am as I write this. The outside temp is 32 degrees. Inside it is now 51 degrees. By 6am it will go to maybe 48 degrees at which time I will switch on the reverse cycle heat. By 7:30 the boat will be approaching 70 degrees.

Alas, the mattress on my bed is non standard so electric sheets are not available.
I stay warm by using blankets, the heavy spread and my sweet beautiful bed partner. We stay VERY warm.
Now if I can just convince her to warm my side of the bed for 15 min before I go to bed. Hey, fair trade. I warm the toilet seat for her. LOL

 

[catalinajack]

Update. At 7:00am this morning the outside temp was 29 degrees and the inside temp was 45 degrees. We were still toasty warm under the down comforter. The inside temp increased by 15 degrees in one hour with the reverse cycle heat. The bedroom output temp from the heater is 53 degrees warmer than input temp. The main cabin heater not nearly as effective, just 16 degrees warmer. Skim ice on the some water surfaces

Similar to Old Dan what does, we use nothing but flannel pajamas and a down comforter over a top sheet. We live aboard just south of Annapolis. From November to March, the cabin temp drops down to 48 - 50 degrees by early morning. We have NEVER been cold, not one single night. We do not put the reverse cycle heat on overnight unless the outside temp dips down into the teens. Having a foam mattress helps and, no, it does not sleep hot in the summer. It is 1:30am as I write this. The outside temp is 32 degrees. Inside it is now 51 degrees. By 6am it will go to maybe 48 degrees at which time I will switch on the reverse cycle heat. By 7:30 the boat will be approaching 70 degrees.

 

[O C Diver]

Update. At 7:00am this morning the outside temp was 29 degrees and the inside temp was 45 degrees. We were still toasty warm under the down comforter. The inside temp increased by 15 degrees in one hour with the reverse cycle heat. The bedroom output temp from the heater is 53 degrees warmer than input temp. The main cabin heater not nearly as effective, just 16 degrees warmer. Skim ice on the some water surfaces

I have put in a request with mother nature for moderating temperatures on the Eastern shore. Will be up Friday to seatrial my charter boat Saturday for the buyer. Hopefully the conditions will extend to the Western shore on Saturday.

Ted

 

[FF]

"You need an inverter.."

Not so,, we have delighted with the truck 12v units for a few decades.

Instead of a warm groove where you lie , the entire bed is warm so a cold foot is simply moved to get it warmer.

Transiting 3 on 6 off is fine because one can actually sleep most of the 6 hours off.

In the early models the 120v house style plug was used with plug converter that had the 120v socket and was a cigar lighter shape when used with 12v. No longer sold .

Here is one brand,

electrowarmth.com › shop › 12-volts-bunk-warmer

12 Volts Bunk Warmer. Categories. All Products ... T36-12V Bunk Warming Pad Non-Fitted 36 x 60. $76.07. 4.5 star rating 4 Reviews. Copyright © 2020 Electro ...

 

[OldDan1943]

Forgive me please but, all these additional 12vt accessories we have been talking about require 12vt and X# of amps.

Just keep piling on the blankets and dont forget to put a blanket on top of the bottom sheet.
Dont really need electric mattress warmer or electric blanket. Snuggle close to your bunk mate. SMILE

 

[O C Diver]

Forgive me please but, all these additional 12vt accessories we have been talking about require 12vt and X# of amps.

Just keep piling on the blankets and dont forget to put a blanket on top of the bottom sheet.
Dont really need electric mattress warmer or electric blanket. Snuggle close to your bunk mate. SMILE

So why do you have a boat with an engine, head, and water heater? You don't need any of those things either.

My days of nautical camping in discomfort are over!

Ted

 

[OldDan1943]

So why do you have a boat with an engine, head, and water heater? You don't need any of those things either.

My days of nautical camping in discomfort are over!

Ted

yup, no camping for me.
I do like the weight of the blankets on me and the blanket on the bottom sheet makes my back feel better.
Of course my bunkmate and I share the heat from each other too.