PIR to activate immersion heater

buzz11

I'd like to replace an on/off wall switch (which powers an immersion heater) to a PIR, so that when someone walks past the PIR will turn on the immersion for lets say 30mins (its a very small tank so will easily heat in 30 mins)

Most of the single gang PIR's that I've looked at control lighting, are they any powerful enough to control an immersion?

Thanks

2011

buzz11 wrote: »

I'd like to replace an on/off wall switch (which powers an immersion heater) to a PIR, so that when someone walks past the PIR will turn on the immersion for lets say 30mins (its a very small tank so will easily heat in 30 mins)

Most of the single gang PIR's that I've looked at control lighting, are they any powerful enough to control an immersion?

Thanks

None I have seen could switch a load that size. One way to deal with this is to get the PIR to switch a contractor which would bring power into the immersion.

I think you idea is nuts not great as it will cost you every time someone walks or the PIR. Remember heating water electrically is very expensive. It costs far more than heating it by other means such as gas, heat pump or oil.

buzz11

Its for an holiday apartment and electricity is the only option, no gas nearby and can't fit oil system.

There is a lot of wastage by having the immersion on a timer, guests could arrive anytime and they let themselves in and out by keybox, so its impossible to predict the pattern. My thinking with the PIR was that when they arrive in and trigger the PIR, they'd have hot water within 15mins or so, when they leave the immersion cuts out after the set time. If they were in the apartment all day, then the PIR would be triggered all the time but that would be a rare event.

Also the shower is electric, so the immersion is just to supply kitchen & bathroom sink.

davegilly

Turn it on and off yourself with this - https://www.amazon.co.uk/gp/product/B077NBZ3LD/ref=ox_sc_saved_title_5?smid=A3VC26QI8E5QU5&psc=1 - It's a WIFI controlled switch so you could turn it on yourself before they arrive and then setup a schedule for an hour a day until they leave?

cruizer101

You can get water heaters that heat on demand for just a sink. Similar to electric shower.
Here is example
https://www.ie.screwfix.com/triton-t30i-bq3a3034i-handwash-3kw-oversink-water-heater.html
There is probably cheaper and better units available.

More initial outlay but probably cheaper in long run to not have to run immersion at all.

DublinDilbert

Not the worst idea, although probably not great either. You could use a tank stat in series with the Pir, so it would only heat the water to a particular temp. I'd probably go the boost button route and print a label "press for hot water"

GreeBo

If the water will heat in 30 mins why not just install a timer with a boost button and have the user flick the switch 30 mins before they want it?

Risteard81

GreeBo wrote: »

If the water will heat in 30 mins why not just install a timer with a boost button and have the user flick the switch 30 mins before they want it?

It's not just me wondering that then.

No harm, but controlling it through a PIR switching the coil of a contactor is an extremely daft idea for this application. I really can't understand why that would be desirable.

buzz11

Thanks for all the replies

GreeBo wrote: »

If the water will heat in 30 mins why not just install a timer with a boost button and have the user flick the switch 30 mins before they want it?

Because its a holiday letting (airbnb) lots of guests won't spot this and will call up and complain or worse still leave a bad review, so whatever system controls the hot water heating has got to be automatic/automated.

Upto now its been on a timer but at this time of year the apartment is vacant mid week and some weekends so the immersion is on with nobody there, hence the idea of the PIR.

I'm familiar with the wifi immersion controller as I have one at home, really simple piece of kit but if I forget to switch it on before a guest arrives, then the phone will ring and I want to avoid that.

2011

buzz11 wrote: »

Thanks for all the replies




Because its a holiday letting (airbnb) lots of guests won't spot this and will call up and complain or worse still leave a bad review, so whatever system controls the hot water heating has got to be automatic/automated.

Upto now its been on a timer but at this time of year the apartment is vacant mid week and some weekends so the immersion is on with nobody there, hence the idea of the PIR.

I'm familiar with the wifi immersion controller as I have one at home, really simple piece of kit but if I forget to switch it on before a guest arrives, then the phone will ring and I want to avoid that.

I believe that post #6 ticks all of the nieces for you. It makes it impossible for the immersion to be left on, it ensures that there is as much hot water as is required, it is simple to use and it prevents wasteful overheating of water.

Your idea actually increases the chances of no hot water and therefore bad reviews as the immersion is more likely to fail from overuse.

EdgeCase

I never understood why Irish and British water heaters of that era are so poorly insulated. They make absolutely no sense.

With a proper electric water heater it's more like keeping a thermos flask on temp. Very little heat is lost to the air so the water heater can be left on and will basically only heat water that's used.

If your hot press is hot, that's where all energy is going. A proper water heater would leave the hot press cold. You'd have no idea it was on.

Why are hot water heaters here often just an uninsulated or very minimally insulated copper tank? And why are hot water pipes often not lagged? I don't get it. Is it just some kind of irrational fear of insulation? It's not that expensive!

These two places have to be amongst the only developed countries where hot water on demand is still seen as a luxury. It's no wonder that guests leave bad reviews. If you're from a country with plumbing that is based on science as opposed to 19th century notions about things, then you turn a mixer tap and get hot water.

If you're in Ireland or England you often have to preplan showers and you've one scalding tap and one freezing tap for no logical reason.

2011

EdgeCase wrote: »

I never understood why Irish and British water heaters of that era are so poorly insulated. They make absolutely no sense.

In many cases you are 100% correct. Believing in insulation and more energy efficient heating systems is a comparatively recent phenomenon in this part of the world.

In 1970’s homes were drafty and poorly insulated but they were warm because the heating system ran constantly. People didn’t care as fuel was relatively cheap.

But things are slowly changing. We now have triple A rated homes and even passive houses.

GreeBo

buzz11 wrote: »

Because its a holiday letting (airbnb) lots of guests won't spot this and will call up and complain or worse still leave a bad review, so whatever system controls the hot water heating has got to be automatic/automated.

Laminate a card and stick it in the kitchen or wherever you have your "welcome pack".

Otherwise install a combi boiler and be done with it.

It comes down to budget and effort.

tbh, the approach you are taking is the most effort for the least reward.:o

buzz11

2011 wrote: »

Your idea actually increases the chances of no hot water and therefore bad reviews as the immersion is more likely to fail from overuse.

Im not an electrician and would like to understand this more... is there a difference between

• the PIR activating the immersion, say every 30mins for a whole day
• and having it on via a manual switch with thermostat kicking in and out over the course of a day?

dathi

how about an electrical key card like they have in hotels but only have it turning on hot water

Idbatterim

A dafi or similar instantaneous water heater would do the job... no waste...

2011

buzz11 wrote: »

Im not an electrician and would like to understand this more... is there a difference between

• the PIR activating the immersion, say every 30mins for a whole day
• and having it on via a manual switch with thermostat kicking in and out over the course of a day?

Both of the above are uneconomical solutions.

My prerefrence would be what DublinDilbert suggested. The occupant simply presses a boost button when hot water is required. This button switches on the immersion for a maximum of 30 minutes. This means that not only can the immersion not be left on for protracted periods of time but it can only be deliberately switch on unlike the PIR solution.

This can be further enhanced with the addition of a stat as this will prevent overheating of water saving more money. A well insulated tank will increase the efficiency further.

An immersion element will not last indefinitely, if you want to extend its life then switch it on less. If guests constantly switch on the immersion inadvertently just because they walk past the PIR it is more likely to burn out simply because it is on so much of the time.

EdgeCase

To be honest, if you're running AirBnB and you've no hot water on demand you are going to get bad reviews. That's just the reality of what people expect from accomodation.

I think that only solution is to upgrade your hot water system with a modern, heavily insulated, system. Or, install a gas combination boiler or electric shower.

At the end of the day people are paying for accomodation and would expect some basic minimum standards.

I genuinely do think Irish and British people have very low expectations of what is normal for a hot water system in a house. There are a lot of homes in these islands with very basic plumbing compared to what is normal on the continent and in the US.

2011

EdgeCase wrote: »

To be honest, if you're running AirBnB and you've no hot water on demand you are going to get bad reviews. That's just the reality of what people expect from accomodation.

An abundance of hot water can be supplied from an immersion.
There are a variety of cost effective effective options that can guarantee this (although an immersion is an expensive way to heat water).

I think that only solution is to upgrade your hot water system with a modern, heavily insulated, system.

Once tenants have hot water they won't care how modern or efficient the heating system is.

Sometimes is is not economically viable to spend so much on a rental property. It is all about return on investment. Just getting a gas supply to a house can be very expensive thats before you gent into buying a boiler, plumbing, servicing the boiler, paying a standing charge etc.
I guess it will come down to the margins and how much of the time the property is rented.

EdgeCase

What I'm saying is you can't expect good reviews if you've hot water that's not available on demand. Airbnb basically competes with hotels for short term accomodation.

And yes a lot of Irish people live without hot water on demand. That doesn't mean it's how people live in most of Western Europe or North America.

It's one of the things that absolutely baffles most people about Irish and British houses - lack of easy availablity of hot water, hideously complicated plumbing and then things like non mixer seperate taps.

The reality is our plumbing is often like something from a bygone era or the developing world.

It's also not about energy use. A typical immersion system uses a 3kW heater to heat the air in the house. There's so little insulation the tank will lose all the heat in a couple of hours. So it's a total waste of energy.

They're just totally inconvenient and inefficient.

Things are getting better, largely due to more continental style heating systems appearing.

There are a lot of plumbing things here that seem to be about unchanging plumbing traditions rather than anything about science or technology.

It's not a criticism of the OP, just pointing out that there's a major difference in expectations between your average Irish or British person familiar with the quirks of plumbing in these islands and tourists who are confronted with some contraption that looks like it belongs on a Doctor Who set.

GreeBo

EdgeCase wrote: »

What I'm saying is you can't expect good reviews if you've hot water that's not available on demand. Airbnb basically competes with hotels for short term accomodation. .

That's clearly not the case considering the thousands of airbnb offers in Ireland.