Old Heating System

[NewhouseOldhouse]

That all depends whom you ask. It's a bit subjective, like saying I want to replace my car. What should I replace it with? Personally I would go for a digital, battery operated, Drayton, Danfoss or Honeywell thermostat (wired, non programmable version) generally, as with most things you get what you pay for.

Do you have a link for any type?

 

[stem]

Drayton Digistat

 

[NewhouseOldhouse]

Thanks for all the info and advice Stem, I was thinking more of this Drayton.

Very tempted to install new boiler might be better in the long run!!

 

[stem]

The RTS8 is OK. It has an old fashioned bi-metallic strip temperature sensor, so won't be quite as accurate as the modern electronic versions, and being a mechanical mechanism it will wear over time and become less accurate [like the one you have now] but they are still pretty good and about the best of that type IMHO.

I think you would be wise to get someone in who is able to survey the current installation as a whole and make recommendations.

 

[NewhouseOldhouse]

I am trying to replace the room thermostat please see pictures of old one and new one. I thought it was a direct swap but when I put live to live and neutral to neutral then earth the new one heating will not come on. I have to have to old one set to max for heating to come on so I thought old thermostat was buggered!!

 

[stem]

From what I can see in your photo, the original thermostat is not wired up correctly. There is a wire missing. Apart from the earth...

There should be a Live (this is probably the existing red wire)
There should be a Switched Live (this is probably the existing black wire)
There should also be a Neutral (can't see one)

If the Neutral is missing the RTS8 can be wired as shown below using the 'L' and Terminal '3' But it won't be as accurate as it could be, because the neutral is required to operate the accelerator (Acc in the drawing)

So I would either wire it correctly using a neutral, or swap the thermostat for a battery powered one that doesn't need the neutral.

I have to have to old one set to max for heating to come on so I thought old thermostat was buggered!!

It is.

 

[NewhouseOldhouse]

All wired and working thermostat cuts out when temperature is reach brilliant.

Another thing I have a immersion heater switch see picture. I want to replace it with this

https://www.screwfix.com/p/greenbro...0v/7643g#product_additional_details_container

Would this be feasible? Just want the ability to set heater to come on in morning to heat water, also don't think I have thermostat at hot water cylinder could this be installed?

 

[stem]

The immersion will have a thermostat otherwise the water would boil and be very dangerous. It's under the immersion heater cap.

You can add a timer such as the one you have provided a link to. But if you need any help with that, I suggest that you start a new thread in the electrical section, I'm not going to be around the forum much (if at all) for the rest of the month.

 

[NewhouseOldhouse]

Thanks for all your help Stem.

I take it this is the thermostat?? Should his be set so high or is this normal?

 

[stem]

Yes that's it.

The setting is really your personal preference. But generally those that use off peak tariffs (eg economy 7) to heat the water tend to set it high to store as much hot water as possible during the off peak time, the hotter it is, the less quickly you will empty the cylinder because you will be mixing it with cold water.

Those that use normal full rate electricity tend to set it to the temperature they are comfortable with, but with a lower temperature, you can run the risk of running out of hot water when filling a bath as at a lower temperature you won't add so much cold water. In your case, if you can heat the hot water with oil it will be cheaper than full rate electricity.

 

[MeldrewsMate]

I was over in 'Non-iron' a few years ago, when gas fired heating was relatively new. Many houses used oil to heat the radiators, but an immersion heater to heat the water, it being cheaper to use electricity than to use oil. Some of these houses had an ingenious external immersion heater added beside the hot water cylinder. It is called a Willis heater, invented by a company in the Belfast area. Essentially this was a 3kW 12" electric immersion heater mounted in a copper enclosure, similar to a piece of large bore copper pipe with a 2 1/2" boss at one end (to mount the heater), a pipe tapping point to the side (near to the boss), and a second pipe tapping at the other end. Cold water from the bottom of the cylinder was piped to the boss end, and the second tapping point was oriented higher than the first to allow the heated water to rise and connect to the cylinder open vent pipe close to the top of the cylinder.
The claims were that the heated water would stratify and the cylinder would heat from the top down. The instructions indicated that, from cold, this heater would produce enough hot water for a shower in 5 minutes, and a bath in 15 minutes.

So, OP, if you're considering replacing your hot water cylinder, you may benefit from adding a Willis heater. I believe an unvented cylinder version is also available. Bear in mind that most modern cylinders are designed for pumped primaries, so may not work very well on the gravity circuit you have at present. It may be quite simple to alter your gravity pipework to incorporate a circulating pump, in which case you may get a full tank of hot water and not need to change it. You will be wise to add some safety features, such as a tank thermostat, and a 'normally open' zone valve, to prevent overheating of the hot water.

MM

 

[stem]

Many houses used oil to heat the radiators, but an immersion heater to heat the water, it being cheaper to use electricity than to use oil.

Wow! oil must be expensive in Ireland (or electricity cheap) a recent course I was on here in England presented figures that showed the average cost of heating with an oil boiler is around 50% cheaper compared to LPG, and about 75% cheaper than electric.

 

[NewhouseOldhouse]

I give £330 for 500ltrs of 1202 oil last week

 

[JohnD]

The instructions indicated that, from cold, this heater would produce enough hot water for a shower in 5 minutes, and a bath in 15 minutes.

that shows you can't trust people.

A 3kW immersion heater takes about 1 minute to heat 1 litre of cold water to bath temperature. So unless you want a three-gallon bath, it is simply impossible for 3kW to heat it in that time.

A typical bath will take about 100 litres of water. Depending on the temperature you like it, and how cold the incoming water is, it will take about an hour and a half.

 

[MeldrewsMate]

that shows you can't trust people.

A 3kW immersion heater takes about 1 minute to heat 1 litre of cold water to bath temperature. So unless you want a three-gallon bath, it is simply impossible for 3kW to heat it in that time.

A typical bath will take about 100 litres of water. Depending on the temperature you like it, and how cold the incoming water is, it will take about an hour and a half.

Oh boy! Worms, can, open.
SHC of water is about 4kJ/kg/C 3kW = 3kJ/second, therefore in 300 seconds will supply 900kJ, raising the temperature of 1kg of water by 300/4=75C. By inferrence this is the same as raising 3kg by 25C, or 3 litres from 15C to 40C. Now I would expect the manufacturer to maximise any claims about his product, and whilst 3 litres of water would give about 30 seconds of use in my shower, it is perfectly possible to have a quick shower in a minute if you turn off the flow while shampooing/soaping. So there you have it, the revelation is that some manufacturers stretch the truth. Please resist the temptation to divert this thread into an argument about how long it takes to have a shower (or how much water is needed for a bath).
MM