Electric matress pad - issues with square wave inverters.

[tony_lee]

Can't stay in southern Baja forever and have to make the best of Christmas to New year in sunny Lancaster CA so need to prepare for a dramatic change of temperature.

Betty insists all her troubles would fade away if only she can get into a nice warm bed - so looks like an electric bed heater is on the shopping list - and maybe another electric heater so we can get our moneys worth out of a 50 amp hookup.

Question is - we have a 1500W vintage Trace modified square wave inverter that so far has not been found guilty of letting the smoke out of any appliance, including battery chargers, TV and other electrocics.
However, I am aware that some people have had problems with coffee makers and similar devices containing unwarranted amounts of fancy electronics and I wondered if anyone had had experience with say, the Sunbeam units with 15 hour timers and variable heat controls similar to this one http://www.amazon.com/Sunbeam-Quilted-Polyester-Mattress-Controller/dp/B00FHW8QI4/ref=pd_sim_201_3?i...

or would it be safer to get something with a bit simpler technolgy

[tony_lee]

I guess we have just about exhausted the topic of electic warming pads and i was surprised how little choice thdre really was for us dinosaurs who have old gear and are too mingy to upgrade

Thanks for all the pointers.

We'll try the softheat unit and hope we are one of the lucky ones who don't have failures every year until the 5 year warranty runs out

[tony_lee]

2oldman wrote:
The nice thing about PSW inverters is you never have to have discussions like this.

And you may consider getting a dual-control unit if the two of you can't agree on a setting. You know, the women are usually colder.

Yes, PSW is my preference too, but in this case the MSW invertsr charger has been working faultlessly for 15 years and im loath to double the value of the Airstream by installung a new unit. Cbeaper to get a heating pad that can cope.

Yes, it would be a cboice between separate beds or separate heat controls. Betty likes to run about twenty degrees hotter than me

[tony_lee]

Finally got a reply back from Electrowarm about running their mains units on MSW
?===================================+
Our units will only run on a true sine wave inverter.

If you have further questions please contact us.

Best regards,



Chris Billow

ElectroWarmth Products LLC
==============================

[eb145]

MSW inverter friendly heated mattress pad

[2oldman]

The nice thing about PSW inverters is you never have to have discussions like this.

And you may consider getting a dual-control unit if the two of you can't agree on a setting. You know, the women are usually colder.

[pnichols]

Here's another link to a 12V mattress heating pad ... but it would still require two of them for a queen mattress. I really like the idea of using two for a queen mattress so that each sleeper had their own control:

http://cozywinters.com/shop/ew-rvhmp.html

[MEXICOWANDERER]

After punching numbers until my fingers went numb, I came to the conclusion that a warm comforter like a THINSULATE LEVEL 3, plus a hot water bottle tossed into bed 20-minutes before retiring was hard to beat. No matter the manner of heating, once bed is exited at 0300 no pad or blanket is worth ten cents. A premium blanket retains warmth for 20-min, upon re-entering no thermal shock. A big comforter allows me to wrap my head and even my feet stay warm. Thinsulate level 3 is no joke - it's a low forties high thirties "lots of warmth" insulator and I lose not one amp hour in the process. When I am boiling water for the bottle I also make a cup of (caffeine-free) hot chocolate. Bottles available in larger FARMACIAS in Mexico. A heated hot water bottle will turn the bed into an oven. No worries.

Fond memories of Palmale/Lancaster (landscatter). Crazy Otto's at 4PM when the crude oil train rumbled past from Bakersfield. Dishes danced off the tables...

[NRALIFR]

tony lee wrote:
pnichols - I had a better look at that site and realised that the 12V pads are 36" wide so not useful if we need individual controls on a queen bed. Couldn't find any other sizes.
I've emailed to ask if their short queen size model is ok on MSW supply but I imagine their reply will be "maybe" since they do mention using it when connected to shore power.

Tony, I have an 12v Electrowarmth mattress pad and would recommend them highly. When I bought mine several years ago, they made a Queen size 12v model that was designed to put more heat in the leg/foot area than the chest/head area.

If my pad ever stops working, what I intend to do is this: buy two of the twin size bunk warmers and lay them across the width of the mattress, which would perfectly cover the top of a Queen mattress. That would also give the ability to control the heat of the two pads independently.

That may or may not be useful to you, but wanted to throw that out there. That's how much I like their product.

:):)

[tony_lee]

pnichols - I had a better look at that site and realised that the 12V pads are 36" wide so not useful if we need individual controls on a queen bed. Couldn't find any other sizes.
I've emailed to ask if their short queen size model is ok on MSW supply but I imagine their reply will be "maybe" since they do mention using it when connected to shore power.

[tony_lee]

pnichols wrote:
Many of the posts above seem to be ignoring 12V heated mattress pads - an example of which I gave a link to in a post of mine earlier - also other posters above mentioned 12V heated mattress pads and their power consumption advantage over a 120V pad.

If one already owns a MSW inverter and a 120V heated mattress pad that won't play together ... then they have to decide whether to buy a PSW inverter, another 120V heated mattress pad that will work with their existing inverter, or a 12V heated mattress pad.

No, didn't ignore it and I went over the web site until I found info on controls and power consumption and it is on my list. Depends on what I can get hold of when we get north of the border as to which way I go. 12v supply is available in the distribution centre at the foot of our bed so power is no problem other than a bit of messing around installing an outlet.
One thing I have found is that 12V equivalents of many household appliances are not very good value because of limited performance (microwaves, kettles) and usually at least 100% price premium - which applies in this comparison between the two 12v units - your suggestion and the one supplied from the mains. Certainly performance should not be a factor in this case because power levels are low anyway and because as has been pointed out a 60 watt load from 12V will draw 5 amps whereas via an inverter could be 7 amps or even more from a large inverter

[tony_lee]

Sam Spade wrote:

tony lee wrote:

Be more than happy to learn which are assumptions and which of them are wrong and why.

At this point, others seem more willing to just carry on a conversation that I am so......you failed to address my warning about Carbon Monoxide and that probably is the most important point in the whole discussion......unless you hook something up that starts a fire.

If all of the members of your party really DO think adhering to the "boondocking" plan is important......maybe an extra blanket or two would be a better solution all around.

I thought so. No facts.

As for the CO thing, I was thinking to satisfy your objections regarding getting off the topic - but since you insist.

** The motorhome has some permanent ventilation by design and a fair bit of incidental and accidental ventilation by virtue of construction
** the catalytic heater is supposedly fitted with a low oxygen cut off.
** Using one of my CO alarms with a digital readout I cannot detect ANY CO emitted from the heater in normal operation.
** we have THREE CO alarms and THREE smoke alarms and one Propane alarm. Basically the MH has three rooms and there is one CO and one smoke alarm in each room.
** the catalytic heater is in the living area so there are three detectors between us and the possible CO source.

I'm normally risk adverse but since the heater was in the MH when we bought it, I researched the dangers and modified things accordingly to the point where I have no problems running it all night. Some people drive their MH at 70mph with grandkids roaming around and wife cooking dinner, but not me. (BTW Neither is permitted in Australia, but this is America) To each his own.

[pnichols]

Many of the posts above seem to be ignoring 12V heated mattress pads - an example of which I gave a link to in a post of mine earlier - also other posters above mentioned 12V heated mattress pads and their power consumption advantage over a 120V pad.

If one already owns a MSW inverter and a 120V heated mattress pad that won't play together ... then they have to decide whether to buy a PSW inverter, another 120V heated mattress pad that will work with their existing inverter, or a 12V heated mattress pad.

[Sam_Spade]

tony lee wrote:

Be more than happy to learn which are assumptions and which of them are wrong and why.

At this point, others seem more willing to just carry on a conversation that I am so......you failed to address my warning about Carbon Monoxide and that probably is the most important point in the whole discussion......unless you hook something up that starts a fire.

If all of the members of your party really DO think adhering to the "boondocking" plan is important......maybe an extra blanket or two would be a better solution all around.

[tony_lee]

I think you are making a lot of assumptions and many of them are wrong.

Be more than happy to learn which are assumptions and which of them are wrong and why.


But to continue diverging (which is an inescapable aspect of forum topics especially once the original question has been answered, and which to my mind adds interest AND information)

One of the reference sources for suitability is http://www.electricblanketinstitute.com/heated-electric-blankets-with-inverters.html

Heated Electric Blankets with Inverters

We often get asked about using heated electric blankets or heated electric mattress pads with inverters. It seems that many folks have experienced problems with them in their campers or their boats. People like to use electric blankets in their RV or boat instead of running their heaters or furnace because electric blankets and mattress pads are more energy and fuel efficient. Obviously it costs less to heat one's bed than their whole RV.

ALL heated electric blankets and mattress pads (and heated throws) bought for the United States market will function as well with FULL WAVE inverters as they do with shore power. However most brands will not work consistently with MODIFIED sine wave (MSW) inverters due to the type of control electronics they employ. Some electric blanket controllers have even been known to “fry” when connected to MSW inverters.

There is only one brand of electric blankets, electric mattress pads and electric throws that we have found to consistently test well with MSW inverters. It is the SoftHeat Low Voltage™ line of heated products from Perfect Fit Industries in Charlotte, NC.

Perfect Fit has been producing these Soft Heat Low Voltage products since around 2003 and they are very safe, work well and generally receive good reviews for their comfort and ease of care. For more complete information on these products, see our reviews of their blankets or their mattress pads.

but of course you will have to decide how reliable it is since I guess anyone can set up this sort of web site. They do review all brands so seems to be reasonably impartial. To electric blankets can be added all sorts of electrical appliances ranging for refrigerators down to cordless tool chargers where plugging them in for the first time can be a bit of a c r a p-shoot.
Of course the other reference source - sometimes also highly suspect and getting more suspect by the year - is myself. Professional Electrical Engineer in areas requiring expertise in heavy manufacturing, food and beverage production and packaging and high speed materials handling including an assortment of different control systems both analogue and digital - design, construction and maintenance. And I have built a couple of RVs from the chassis up, and used them for some years, as well as owned other manufactured RVs.
That MSW inverters don't cause more damage is as much due to the excellence of the appliance design as it is deficiencies in the inverter design, but even right back at the beginning, it was widely recognised that sophisticated appliances of that period were prone to failure. Laser printers were one such. Over the years the problem has waxed and waned, but as one group of appliances is either fixed or shunned by RVers, another will soon come along. The huge variety of inverters ranging from a few dollars to hundreds hasn't helped either.

http://forum.solar-electric.com/discussion/14984/what-appliances-will-not-work-with-modified-sine-wa... has a couple of replies that are pretty representative if you ask the same question on many forums. Key point made is

In the end, probably 80% of the stuff you plug in will work fine, 10% will fail pretty quickly, and the other 10% it will be difficult to tell.

and nothing has changed over many years.

wa8yxm on this forum said

In addition MSW (Modified Sine Wave or Modified Square Wave) have a long list of things that MIGHT or might not work with them Radios, Epically AM Televisions (They are after all radios) Sat receivers (likewise) Audio amplifiers Clocks, timers and such Electric Blankets Coffee Pots (With electronic controls) microwaves Night LIghts (LED type, Incandascant work fine) And more.. the list is very long.

Yes, I could buy a PSW inverter, but all other things being equal, my choice is to buy a blanket that won't blow up if I power it from the inverter I have - which 16 years ago when the MH was built was fairly well regarded and is still going strong.