Zoning education.

[Dan Masey]

I'm still trying to get my head around central heating zones. I understand the practicality and that each zone has its own thermostat or programmer. But someone asked me today, how is having a separate thermostat upstairs any different than setting all the upstairs TRV's to 3 or 4??

Wasn't really sure on the best answer to this. Obviously a separate programmer makes sense but is it really worth it just having a thermostat controlling that zone?

 

[Killy Bing]

Ermi,

The process for replacing the air bubble in a Megaflow entails manually opening the PRV, it's a standard procedure that you may need to do twice a year,
they don't leak after, its good gear.


Tony

but that's half way up the cylinder and its not filled with sludge!!!

 

[happyflyer]

but that's half way up the cylinder and its not filled with sludge!!!

What you are both saying is a boiler PRV is only good for one blow off, jeeez what are they ever making them of, plastic

 

[Killy Bing]

And when you get crud in the seating, prv is dripping, do you leave it or change it?

do you charge the customer or reach into your own pocket?

 

[Nostrum]

What do you size the rads on? If upstairs is off then the rads downstairs will be undersized taking into account the unheated space above, or the rads will be sized in that manner and be over sized when upstairs is heated?

 

[Gray0689]

What do you size the rads on? If upstairs is off then the rads downstairs will be undersized taking into account the unheated space above, or the rads will be sized in that manner and be over sized when upstairs is heated?

Size rads on room as normal

 

[Nostrum]

So what happens when the customers phones you up saying its cold downstairs? Tell them to turn the heating on upstairs? Goes against the reasons for doing a detailed heat loss calc.

i can kind of understand in new build where the insulation between floors is good but for retro?

ive heard the zoning requirements are going to be amended

 

[Gray0689]

So what happens when the customers phones you up saying its cold downstairs? Goes against the reasons for doing a detailed heat loss calc.

You tell them to turn the stat up in that room

 

[Nostrum]

But it could be that the radiator isn't capable of raising the temp as the design heat loss is less than the actual losses because of the unheated areas?

i know this is worst case, but weather compensation could cause this to happen more often.

 

[Gray0689]

But it could be that the radiator isn't capable of raising the temp as the design heat loss is less than the actual losses because of the unheated areas?

i know this is worst case, but weather compensation could cause this to happen more often.

The zones are heated to whatever the temp is set to on stat simple
Your heat loss is per room

 

[Nostrum]

But the emitter is matched to the heat loss of that room based on fabric losses including the surfaces above and below. A colder room upstairs will promote a greater loss than if it were heated. So if you deign the system correctly, and choose a radiator to suit the heat losses of a room with a heated room above. Then run the system with an unheated space above. At the specified outside temperature the emitter will technically be undersized.

How much by will depend on a lot of factors so I'm not sure how much effect it would have, but from a theoretical point of view I struggle to see how you can zone a system and design it to operate in the conditions you have designed it for effectively.

i suppose most people don't give a toss but I like to be given a logical explanation for these regulations that are introduced by some pen pusher.

 

[Gray0689]

Your designed temp is 21 living and 18 bedrooms
But as we all know some people like it higher some lower
Do you factor that into your design no we aim for a set point only
So the room will be heated to that desired temp on stat
If the room above to side or underneath is at a lower temp it may and only may as depends on a lot of things ie insulation even to if the person leaves a door open or closed
We can't factor that fine a detail on it nor would I want to

 

[basildog]

What do you size the rads on? If upstairs is off then the rads downstairs will be undersized taking into account the unheated space above, or the rads will be sized in that manner and be over sized when upstairs is heated?

That asumes conventional construction and have found these days more and more floor spaces are being insulated either for soundproofing or heat loss !
Drives the sparkies mad as cables have to be uprated if insulated !

 

[Nostrum]

I see what your saying but if you look at it on a larger scale, say an older style large detached house, the whole of upstairs could be off on a zone. Therefore you've effectively halved the heat output but the heat loss remains the same. Ok there are surfaces in between these two zones that would reduce the heat loss rate but it is still going to have an effect surely? I struggle to see how the zoning will save any significant amount of energy after factoring the cost of the extra controls in a retro fit. A good idea in principle but flawed in my opinion. A well designed system with correctly sized radiators would be much more beneficial pound for pound.

 

[Gray0689]

I see what your saying but if you look at it on a larger scale, say an older style large detached house, the whole of upstairs could be off on a zone. Therefore you've effectively halved the heat output but the heat loss remains the same. Ok there are surfaces in between these two zones that would reduce the heat loss rate but it is still going to have an effect surely? I struggle to see how the zoning will save any significant amount of energy after factoring the cost of the extra controls in a retro fit. A good idea in principle but flawed in my opinion. A well designed system with correctly sized radiators would be much more beneficial pound for pound.

On a retrofit the best money spent is on insulation before anything else

 

[Nostrum]

That asumes conventional construction and have found these days more and more floor spaces are being insulated either for soundproofing or heat loss !
Drives the sparkies mad as cables have to be uprated if insulated !

yes and I would completely agree with this in a new build as said before, I'm questioning its effectiveness in a retro fit scenario as they try to imply in part L.