fitting a system

[dave knight]

i really appreciate all the advice guys.

like i said before, i'm on no deadline to finish the job, so i will be taking it step by step. i have yet to talk through with my landlord about the details as he has been on hols, but i will raise the point of liability etc with him.

i have done the heatloss calcs and worked out size of rads needed for each room. however, i am struggling to find rads that will fit in the spaces required, and provide enough btu's according to the heatloss.

in regards to the boiler; i wasnt going to touch any of it tbh. especially if it requires electrics and wiring through the house. its not a question of me not being able to do it, but more the fact that the landlord should have proof to show the instal was correctly done, incase someone gets a shock etc when we have moved out. the gas multi point instantaneous water heater that we currently have is boiler sized, and located where i would like the combi to go. it is already wall hung and room sealed with a balanced flue through the rear wall to the garden.

so, with a combi, i will reguire a room stat, prob in the front room, and trv's on all rads except the front room? i'm unsure about the timer situation tho!

thanks again for all the advice. places like this forum are invaluable to me.

 

[doitmyself]

If you have no room stat your boiler is on for the entire timed on period, your flame might go out but your pump is still running , your radiators cool the water (relatively quickly) the flame comes back on and the "cycle" continues.

With no room stat, the boiler will be turned on and off by the boiler thermostat. If the pump is controlled by an overrun device I would have thought that the pump would also be connected to the boiler stat, so it would not run continuously.

Avatar, if all trv's are shut room temp will not be going up and room stat will not shut down boiler.

Firstly, TRVs do not shut, they just reduce the flow through the radiator. Secondly, a TRV should never be on a radiator in the same area as the room stat because it could prevent the room reaching the temperature set on the room stat.

Lastly, "constant circulation" systems are possible and are quite common on the continent. They are usually used with weather compensation controls.

 

[Toddyplumb]

The boiler is not turned on & off by the boiler stat, only the burner , that is the point .
They have tried to help this with anti cycle( which is just burner off time) , but it still needs a room stat as mechanical interlock.
Try watching a couple of different systems, you may be surprised.
And yes you can use a flow switch as the mechanical interlock, before thats thrown in😉

Trv s do not shut, new one on me . As we speak (type) I have a TRV on 2 no flow !

Avatar , re reading your post if the stat is in an room witout TRV then yes it would shut boiler , sorry. I missinterpreted as a fully TRVd system

 

[easyt]

As a retired highways engineer, why are you proffering advice to people on a subject that isnt your speciality? My issue with your advice is that it is wrong and doesnt meet modern regulatory standards, so you are introducing your opinion and not factual information which then causes confusion. If theres a question on sub base depths etc then go ahead and answer but on issues of central heating wouldnt you be better off observing rather than advising?

Whoaa. Steady on Oldplumber.

I was very careful to preface my post with the words 'I'm not saying that it is right or wrong'. I was not Offering advice, If it seemed I was then I apologise unreservedly.

I merely commented that I was happy without a roomstat and was content with my with my present system. I recently updated my details in order that people were aware that I was not a plumber but a retired highway engineer.

I think that you were a little sharp with me. 😉

 

[Toddyplumb]

He was a bit sharp wasnt he 😉😉
Fully TRV,d system with flow switch works 🙂

 

[Spudhater]

Go for a RF programmable room Stat like the Honeywell CM927 dont go near Salus as they stop working with in a year !!

For Timer and roomstat i would use a programmable RF Honeywell CM927 stat

Dont fit Salus because they are rubbish !!!

 

[tamz]

Fitting a thermostat is really a no brainer. It will reduce running costs. Wireless stats are available relatively cheap so there is really no excuse for not fitting one.

Easyt
Although you may be happy enough with your current set up try sticking a thermostat on and you will notice the reduction in your fuel bills, i promise you. It will pay for itself in the first year.

 

[easyt]

Thanks for the advice Tamz. I will give it some consideration. I am doe to have some work carried out in September. Which room would be best suited?

Many folk seem to have them in a hallway. Our hallway is never open to the outside world, Always use back door. Is the best place the main lounge?

 

[dave knight]

Fitting a thermostat is really a no brainer. It will reduce running costs. Wireless stats are available relatively cheap so there is really no excuse for not fitting one.

Easyt
Although you may be happy enough with your current set up try sticking a thermostat on and you will notice the reduction in your fuel bills, i promise you. It will pay for itself in the first year.

wireless? really? awesome stuff.

 

[Spudhater]

In my experience "Cheap" is not good regarding RF Stats.
I only fit Honeywell CM927 stats now as opposed to the Salus i fitted previously ( which dont last more than a year..)

The landing might be a good place..

 

[tamz]

wireless? really? awesome stuff.

Wonderful some of the stuff they come out with nowadays 😛

 

[dave knight]

Wonderful some of the stuff they come out with nowadays 😛

lol. well i was aware of wirelessness. just didnt know it had spread so far. would i need to get one from boiler manufacturer or are they all univesal?

 

[doitmyself]

The boiler is not turned on & off by the boiler stat, only the burner , that is the point .
They have tried to help this with anti cycle( which is just burner off time) , but it still needs a room stat as mechanical interlock.

But if the burner is off the boiler is off. What else is there to turn off?

Trv s do not shut, new one on me . As we speak (type) I have a TRV on 2 no flow!

So you have your heating on at this time of the year? How do you know there is no flow?

I agree that, if the TRV has a positive OFF position, it can be turned off so there is no flow though it. It is a flow control, just like the accelerator of a car, which varies the flow through the radiator to maintain the required room temperature. It is not open/closed, like a light switch is on/off.

 

[Plucky]

I have also seen TRV's on 1 or 2 and stay absolutely stone cold. I.e. No flow what so ever.

Also when a boiler stat is satisfied it does not switch the pump off. Pump overrun or not it will keep on running. Combi, system or heat only boiler the pump keeps going. The pump is controlled by the switched supply from zone valves/programmer. Even with a boiler with pump over run it still takes its supply from the switched live and just runs on a timer relay.

On a combi the pump will be wired into switched supply, be it from timer or a roomstat. It has no direct relation with boiler thermostat.

 

[tamz]

lol. well i was aware of wirelessness. just didnt know it had spread so far. would i need to get one from boiler manufacturer or are they all univesal?

They spread to Scotland a good few years ago, probably all over the world by now 😀

But if the burner is off the boiler is off. What else is there to turn off?

The pump

So you have your heating on at this time of the year? How do you know there is no flow?

Because i just know. Try turning your TRV to 1 and disconnectiong it. It should be warm enough to be closed completely.

I agree that, if the TRV has a positive OFF position, it can be turned off so there is no flow though it. It is a flow control, just like the accelerator of a car, which varies the flow through the radiator to maintain the required room temperature. It is not open/closed, like a light switch is on/off.

Not quite. If the valve head pushes on the pin enough, it gets to a stage where it completely closes.

 

[Toddyplumb]

Do it myself, I leave my heating on all year but at different temps on the prog stat. Do you really want me to tell you how I know there is no flow 😕
What else is there to turn off 😕 The pump, which leads to cycling
If you want to know more might I suggest an Energy efficiency course
Are you working in the trade or are you as name DIY ( this is a genuine question)
Damn , plucky and Tamz answered first !

 

[doitmyself]

I have also seen TRV's on 1 or 2 and stay absolutely stone cold. I.e. No flow what so ever.

I agree that can happen. But it does not negate my statement that a TRV is like a car accelerator and not like a light switch. If you want to maintain a speed of 70mph you do this my making small adjustments of the accelerator. What you do not do is put your foot flat down until you reach 71 then take it off until the speed drops to 69 and then repeat the sequence.

Similarly with a TRV. A rise in room temperature will cause the valve to close slightly and a drop will cause it to open slightly. The total travel of the valve from fully open to closed is about 2mm and the movement is about 0.2mm per degree. What does not happen is the valve opens completely if the temperature room is low and closes when it high.

At a high setting the valve will fluctuate between, say, 1.5mm and 1.9mm with a midpoint of 1.7mm. At low settings the valve could close as the midpoint is much lower, but the fluctuation will still be the same.

Also when a boiler stat is satisfied it does not switch the pump off. Pump overrun or not it will keep on running.

Thanks for putting me right about this; I can now see the logic of this.

My name says it all, but I know my limitations. 😉

 

[Plucky]

I understand what you mean the TRV is slowly opening and closing all the time. I completely agree. For some reason I thought that you meant a TRV was never closed unless it was in the 0 position.

 

[Avatar]

Nice debate about room stats guys!

Of course the stat is supposed to be in a central hall area, without a trv - any of you actually read the building regs on this.?

They do teach this on the courses C & G level 2 you know (although I actually do this kind of work - got one next month in a council flat!)

 

[Toddyplumb]

Ive read the building regs .
There are a few ways to comply with them, what you propose is one of the ways , and is propably the best known. However it does not say fit the stat in the hall (this is my preferred option also). There is a case for having the stat in the lounge , or most used room . why heat the whole house ? Especially the elderly who retreat to one room and wont use the fire .
The building regs actually allow fully TRV'd system with a flow switch.
You are far better following Energy Efficiency For Domestic Heating

 

[dave knight]

Ive read the building regs .
There are a few ways to comply with them, what you propose is one of the ways , and is propably the best known. However it does not say fit the stat in the hall (this is my preferred option also). There is a case for having the stat in the lounge , or most used room . why heat the whole house ? Especially the elderly who retreat to one room and wont use the fire .
The building regs actually allow fully TRV'd system with a flow switch.
You are far better following Energy Efficiency For Domestic Heating

i dont have a hall because of the lay out of this old cottage, so i was thinking of putting the stat on wall in lounge. there is no door between lounge and kitchen (there should be but it fouled on sofa so was removed) so should stat be as far away from the opening as possible to allow it to operate more efficiently?

regards

 

[Toddyplumb]

Away from the rads , away from the sun, away from the fire

 

[stevetheplumber]

Cant see why you would want to take heating into the loft one of the advantages of a combi is a "dry loft"
if its only 5 rads id come of the boiler in 22 pair of 15s going up 22 to the first rad downstairs then 15
sounds like a small place id use copper where its exsposed and hep under floorswith copper tails from the rads
gas size is dependent on distance from meter to combi as a rule of thumb if its over 2 meters you need 22 DONT ASSUME THE RUN TO THE WATER HEATER IS CORRECT LOTS WERE FITTED BADLY

 

[easyt]

Depends whether it is single storey with a solid floor or two storey with solid floor and thick stone walls. If it is a more usual build it would be common practice to run under first floor floor boarding.