Room Thermostat v Valve Thermostats

[tonybhoy]

[

yes that would be obvious less energy is used, but the point i am trying to make is the room with stat gets up to temp, boiler shuts down, but every other room might still be cold and calling for heat. And surely the boiler does not run constantly, if the return water comes back hot still i'd pursume it shuts down otherwise the water would boil? Im not disagreing i just want to understand it.[/quote]

Every time the gas valve opens you lose about 20% of unburnt gas out of the flue. You can't do anything about this it's a physics thing therefore the way to save fuel is to ensure that the boiler doesn't cycle and the way to do that ,amongst other things,is to install some sort of electrical control to control the house temp and thus the gas valve opening and closing.

Bottom line is house warm and boiler off saves money. House roasting and boiler/gas valve constantly on and off costs money or even worse house cold and boiler constantly on and off = throwing money away.

 

[D_Hailsham]

Every time the gas valve opens you lose about 20% of unburnt gas out of the flue. You can't do anything about this it's a physics thing therefore the way to save fuel is to ensure that the boiler doesn't cycle and the way to do that ,amongst other things,is to install some sort of electrical control to control the house temp and thus the gas valve opening and closing.

An even better way is to have a modulating burner which adjusts the heat produced by the boiler to match the heat lost in the house.

 

[tonybhoy]

An even better way is to have a modulating burner which adjusts the heat produced by the boiler to match the heat lost in the house.

Presume you mean modulating gas valve? Nope they still lose the initial volume of unburnt gas out of the flue.

Zero governor gas valves may be able to burn that initial (lost/unburned) gas more efficiently but I don't think so,think the physics doesn't allow that to happen.

Most effective way to save money is to have the boiler off. This is what weather compensators do and to a lesser extent programmable room stats and simple room stats also do that,these devices ensure the gas valve is open for longer and closed/off for longer.

What your trying to achieve is to use the gas as efficiently as possible when the gas valve first opens,the only way you can do that is by heating a cold system for a long on period rather than topping up a hot system for a short period.

The modulating gas valves simply turn the gas down or up as required by the system load,previously this would have been done by 'rating' the boiler to suit the load.

For example a 35 KW combi might only require 15 KW for the heating so you rated the boiler accordingly on the boiler PCB/gas valve so that it was only producing the required amount of gas to heat the rads however the boiler would revert to full power for the hot water and then modulate down to low flame once the water temp was reached so that the temp was maintained indefinitely if you continued to run a hot tap.

Modern combis modulate on both heating and hot water these days and WB CDI boilers can be adjusted to start on a lower output for heating rather than the full 100,000 BTU the boiler is set for when it comes out of the factory.

 

[Bowness72]

Am I right in thinking from all this that it would eb a good idea for me to have it done to save on gas bills ?
Also, it sounds like it might be a bit too complicated for me to do properly. Any idea how much I should be looking at for someone to supply and install ? (ball park figure only)

 

[tonybhoy]

Am I right in thinking from all this that it would eb a good idea for me to have it done to save on gas bills ?
Also, it sounds like it might be a bit too complicated for me to do properly. Any idea how much I should be looking at for someone to supply and install ? (ball park figure only)

Absolutely!

Quoted figures for savings from TRVs is around the 10% mark,if you use them properly that is. I never have and have always had them fitted to 90% of my rads. Most people leave them set on number five,me included.

Roomstat on the other hand will pay for itself in about a year. Typical install cost should be less than £100 including the stat however if you go for a Honeywell CM927 programmable RF roomstat with optimum start expect to pay about £200 including fitting by a decent electrician,the stat you can get online and delivered from about £98 from here,

http://www.heatingcontrolsonline.co...reless-programmable-room-thermostat-p-68.html

 

[Bowness72]

Thanks Tony. Who would I get to do the work, an electrician or a vokera service engineer ? (not going through Vokera though)

 

[JohnD]

I turned down a programmable RF roomstat , seems to me more complicated, more to go wrong, more expensive.

 

[tonybhoy]

Thanks Tony. Who would I get to do the work, an electrician or a vokera service engineer ? (not going through Vokera though)

An electrician. Very easy to install though. Two wires to the boiler terminal block for the receiver unit block it says link for external controls,one and three I believe however I do installs and always employ an electrician to wire the boilers and stats to ensure everything is legal and above board so to speak.

 

[tonybhoy]

I turned down a programmable RF roomstat , seems to me more complicated, more to go wrong, more expensive.

Got to agree with you here John however the Honeywell one is idiot proof and is excellent. Have one myself although I'm now installing the WB ones purely for the extended warranty available on them in conjunction with the boiler.

I'm fitting ones such as the DT10RF which also allow you to programme the Eco feature (hot water) up to three times per day on the CDi combis in addition to programming the room temp with delayed start times of up to one hour.

Effectively a double channel programmer,one RF and the other wired, for a Combi. Now that is complicated


http://www.worcester-bosch.co.uk/ho...ems/greenstar-37cdi/optional-plug-in-controls

 

[D_Hailsham]

An even better way is to have a modulating burner which adjusts the heat produced by the boiler to match the heat lost in the house.

Presume you mean modulating gas valve? Nope they still lose the initial volume of unburnt gas out of the flue.

OK, I used the wrong term, but you knew what I meant.
I am not familiar with the physics to question your assertion that unburnt gas is lost every time the boiler ignites; but a modulating gas valve adjusts the gas flow to match the current requirements, so it will not ignite as frequently as an on/off gas valve. The loss will therefore be less.

Most effective way to save money is to have the boiler off.

I agree - wear jumpers and leave the boiler off permanently.

This is what weather compensators do

They do more than just turn the gas valve on and off.

The modulating gas valves simply turn the gas down or up as required by the system load,previously this would have been done by 'rating' the boiler to suit the load.

Rating a boiler sets the output to a fixed amount. Are you saying that a modulating gas valve is just a fancy way of achieving the same? If so, you are wrong.

 

[tonybhoy]

.

OK, I used the wrong term, but you knew what I meant.


Nope,stopped doing mind reading when I was ten


I am not familiar with the physics to question your assertion that unburnt gas is lost every time the boiler ignites; but a modulating gas valve adjusts the gas flow to match the current requirements, so it will not ignite as frequently as an on/off gas valve. The loss will therefore be less.

Is it me?

This is what weather compensators do

They do more than just turn the gas valve on and off.

Yeah,er, well yeah so they do but essentially they control the boiler firing or they did the last time I checked.

The modulating gas valves simply turn the gas down or up as required by the system load,previously this would have been done by 'rating' the boiler to suit the load.

Are you saying that a modulating gas valve is just a fancy way of achieving the same?

Nope.


If so, you are wrong.

:

Am I indeed. Gosh thanks for that