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What to use as supplementary heating? Inertia radiators, radiator-radiators...


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As some of you know, I am happy overall with my heat-pump-powered central heating. Not all rooms heat up to the same temperature, as is natural: I do not have a two-zone setup, and some rooms have southern and others northern exposure.

 

In particular, my setup includes a ground-floor, northern-oriented bedroom/studio that used to be 3 C colder than my living room/library. I've been working on improving the insulation in the studio to the extent I can (there's a metal door and it's unclear how to open it to verify it's insulated) - let us say that the temperature difference is now 2.5C. That's the case whether it's 0C outside or 10C outside.

 

The problem is that I sometimes let the room out as an AirBnB (mostly so as to get good reviews so that I can let it out during the Olympics). Now, there are three kinds of guests:

- the kind who like a studio at 18C with warm blankets

- the kind who tell me right away they are unhappy with the temperature - I gave one the thermostat, and she cranked it so far up that I was at 24C, but OK, five-star review,

- the kind that says nothing but leaves a four-star review (the kiss of death), telling me privately that it was because of the temperature (why not tell me before?).

So it seems that, while I will continue to work on the insulation (my girlfriend is horrified at my current plan to line the door with cork and covering it up with wallpaper), I really should install some sort of small electric heater with its own thermostat, to supplement the existing radiators. People like to be in control.

 

My main concerns are (a) safety, (b) efficiency. Because of safety issues, just getting a portable space heater is out. So, please guide me through the existing options.

 

What I have been able to find is:

(a) inertia heaters. The strongest claims for them have to be false (a COP of 1 is a COP of 1). Are they appropriate here? Are they safe? Is solid or liquid better in this context?

(b) radiators that claim to actually heat mostly by radiation, such as this one: https://fr.hudsonreed.com/radiateur-infrarouge-panneau-chauffant-electrique-intelligent-avec-cadre-blanc-300w-50-5-cm-x-59-5-cm-teplo-123659?_gl=1*15n7xc4*_up*MQ..*_ga*MTgzNTE1OTQ3NS4xNzA5NjAwMDgz*_ga_CTHXFM8H1V*MTcwOTYwMDA4My4xLjAuMTcwOTYwMDA4My4wLjAuMA..*_ga_K0QLN5D9SX*MTcwOTYwMDA4My4xLjEuMTcwOTYwMDA4My4wLjAuMA..&gclid=CjwKCAiA_5WvBhBAEiwAZtCU72oud3KU_3RPq59ciim3UbwEfB3oDoZVdm_C0yrlFbFsgpgVGGBf5BoCqJkQAvD_BwE&gclsrc=aw.ds

Well, it makes sense to heat the people before the air - but do these radiators get too hot? Are they safe? Can people get burns? Will they set the room on fire?

 

There's also the question of dimensioning. The space is 12.2m^2, of which 1.9m^2 are the shower and WC. I suppose that, since the question is how to bring the place up from 17.5C to 20C, 500W is actually overkill, and 300W is more than enough? This is just a wild guess; how would I actually do the calculation?

 

(Not sure the heat-loss spreadsheet would help me much (I can dig it out if needed). When the central-heating radiators in the studio turn on, everybody is happy. The problem is that, if it's 20C in my library, the system is happy and turns itself off, and the person in the studio may be unhappy.)

 

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I have never heard of an 'inertia heater'.

I suppose my storage heaters have inertia, in a way.

 

Infra-red seems to be only favoured by people that hate science and have already convinced themselves that they are the bees knees.

If they were so fantastic, why are so few fitted.

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Personally, if there is space, I would fit a small panel heater (IE electric radiator).  That's way safer and less likely to get damaged than anything portable and easy for your guests to understand.  You can get them with timers etc I think.

 

I certainly wouldn't bother with infrared, your guests will complain that the bed or chairs are cold even if they are warm.

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Posted (edited)

All right. A storage radiator it is (I think this is the same thing that gets called an "inertia radiator" in French: you heat a fluid or solid body, and it slowly releases heat) - with a thermostat and so forth. Is fluid or solid better? Some people say (in French) that fluid is better for bedrooms and solid is better for living rooms, but since this is a studio (bedsit) things are confused entirely.

 

Any recommendations as to brands? There's a bunch of things with 4/5 stars on Amazon, but I'd like something reliable and above all safe.

 

I suppose I'm right in thinking that 500W is more than enough? The place is already heated by central heating - it's just a matter of letting self-indulgent paying visitors have some control over the room temperature without changing the temperature of my entire house. (Friends and relatives have always been fine with 18C in bedrooms.)

 

I suppose I'll have to call an electrician (who will charge me as much as the radiator cost) - I need one to look at something else anyhow...

Edited by Garald
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1 hour ago, Garald said:

All right. A storage radiator it is (I think this is the same thing that gets called an "inertia radiator" in French: you heat a fluid or solid body, and it slowly releases heat) - with a thermostat and so forth. Is fluid or solid better? Some people say (in French) that fluid is better for bedrooms and solid is better for living rooms, but since this is a studio (bedsit) things are confused entirely.

 

Any recommendations as to brands? There's a bunch of things with 4/5 stars on Amazon, but I'd like something reliable and above all safe.

 

I suppose I'm right in thinking that 500W is more than enough? The place is already heated by central heating - it's just a matter of letting self-indulgent paying visitors have some control over the room temperature without changing the temperature of my entire house. (Friends and relatives have always been fine with 18C in bedrooms.)

 

I suppose I'll have to call an electrician (who will charge me as much as the radiator cost) - I need one to look at something else anyhow..

Since it needs to be responsive to your guests, is a storages radiator a good choice.  How can you know whether or not to charge it up?

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I think you are just after a low power panel heater.

They are basically just a heating element in a metal box that hangs in a wall.

Get one with just a thermostat and then they are basically just on or off.

 

Only thing is, how is your electrical supply? They used to be very small and limited in France (12 kW I seem to remember).

But Paris is more developed than Toulon, near to where I lived.

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32 minutes ago, SteamyTea said:

I think you are just after a low power panel heater.

They are basically just a heating element in a metal box that hangs in a wall.

Get one with just a thermostat and then they are basically just on or off.

 

Only thing is, how is your electrical supply? They used to be very small and limited in France (12 kW I seem to remember).

But Paris is more developed than Toulon, near to where I lived.

 

Oh, I used to get my electricity supply cut out all the time because the previous owners had a 6 kW cap. Took forever to get that changed - it's something done by a private monopoly run by the Three Stooges. I'm finally at 12 kW, and have no issues. 500W (or less) should be OK.

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1 hour ago, JamesPa said:

Since it needs to be responsive to your guests, is a storages radiator a good choice.  How can you know whether or not to charge it up?

 

I charge it up before they come! Then they will hopefully feel warm and forget about the issue.

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Just now, Garald said:

 

I charge it up before they come! Then they will hopefully feel warm and forget about the issue.

Except for those who like it cool, but I suppose they could open the windows.

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4 hours ago, Garald said:

Inexpensive, but is it safe?

In an airbnb, I wouldn't think so. 

 

Never underestimate the ability of the general public to do stupid things!

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1 minute ago, JamesPa said:

In an airbnb, I wouldn't think so. 

 

Never underestimate the ability of the general public to do stupid things!

 

Right, that's the only reason why I'm even considering something installed by an electrician (inevitably expensive).

 

OTOH, can you start a fire with 500W without deliberately trying to? Would 300W be safe?

 

Alternatively, I can just get a 500W heater, turn it on until the temperature is 20C, remove it from the room before guests arrive, and also remove the thermometer.

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20 minutes ago, SteamyTea said:

Yes you can.

It is 500 J/s, so a lot of force involved.

 

Well, it's a bit like starting a fire with a very low-powered electric stovetop (in a van?) - I'd think it would require some forethought. (Stick some very flammable and thin material into it, and then use it to light other things?)

 

Would a 500W electric radiator be safer? I suppose yes, but just because it's a larger area and it can't tumble or be put right against the curtains, no?

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1 minute ago, Garald said:

it can't tumble or be put right against the curtains

Basically yes.

Things that are fixed to a wall are generally better.

Saves the guests walking off with them as well.

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3 minutes ago, Garald said:

micathermic

Really.

Use an electric element to heat a stone, that then radiates heat, then dress it up with words that have little meaning.

 

A basic wall hung panel heater is really all you need.  They heat the air by convection.

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2 hours ago, SteamyTea said:

Really.

Use an electric element to heat a stone, that then radiates heat, then dress it up with words that have little meaning.

 

A basic wall hung panel heater is really all you need.  They heat the air by convection.

Quite so.

 

If you only need 500W you dont need an electrician even for the panel heater.  That's only 2.5A at 230V, which surely your sockets supply.  It's less than half the rating of a UK lighting circuit (I'm not suggesting you run it off a lighting circuit, but with LEDs there is essentially no other load).

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4 hours ago, JamesPa said:

Quite so.

 

If you only need 500W you dont need an electrician even for the panel heater.  That's only 2.5A at 230V, which surely your sockets supply.  It's less than half the rating of a UK lighting circuit (I'm not suggesting you run it off a lighting circuit, but with LEDs there is essentially no other load).

 

How many amperes do sockets usually provide?

 

There's a lighting connection that is essentially useless, and near to where I would have to put the panel. If an electrician somehow approved of that option, I suppose I could do it - I wouldn't do it myself.

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7 minutes ago, Garald said:

How many amperes do sockets usually provide?

 

There's a lighting connection that is essentially useless

In a modern French installation, 16A for power and 10A for lighting - you should be able to verify that on your consumer unit.

 

A 500W heater uses 2.2A, so no problem.

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