Central Heating Control approaches for replacement gas boiler installation

Hello, I'm finally getting near to replacing the dreadful Keston C25 that I've had for a number of years now and am getting a couple of quotes from two local installers both of whom are proposing Worcester Bosch - most likely Greenstar 30 or 40 CDi Regular or the FS models.

The existing system is 2 zones (upstairs and downstairs) plus water heating - the system is open vented. The existing controller is Horstmann ChannelPlus Xl controlling the three zone valves. The zone valves are old and will be replaced and an automatic bypass installed but otherwise the radiator/pipework will remain much the same.

All the radiators have Drayton TRVs except for 3 upstairs (bathrooms and landing) and one downstairs (hall) and I'm told that I will need to have two room thermostats - one for each zone. These TRVs will probably be replaced except for a couple which are very recent because they are/have shown signs of sticking over the recent years.

I would like to improve the temp. control throughout the house, at least by having all radiators controlled by TRVs but feel that I can probably save energy consumption by having some more specific controls - e.g three of bedrooms are only used a few times a year for guests and the bathrooms get too hot when the heating generally is running all day in cold weather.

So I'm looking for suggestions for a control approach that it would make sense installing at the same time as the new boiler and that would work sensibly with the existing system. I'm wondering about controlling some of the radiators with wireless/programmable TRVs and linking groups of radiators (living room, hall, kitchen for example) to a single thermostat and similarly upstairs.

I would appreciate ideas and/or pointers to helpful discussions elsewhere that I can consider whilst we wait till April/May time (assuming the Keston doesn't fail completely before then). I have tried to review threads on this newsgroup and via google but feel that I need some practical and current inputs if poss. Sorry for verbosity but have tried to cover questions that might be asked of me in advance.

Regards, Colin

Reply to
Colin Brook
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I have been looking at the LightwaveRF remote heating control stuff

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and was going to try out their current remote rad valve but it seems as though they are about to launch a replacement (see bottom right of the linked page).

It looks as though they are in the process of setting up their own sales operation - until now their products have been available have been available via Amazon, Vesternet and rebadged as Siemens through outlets such as Screwfix.

I have recently installed a couple of their wireless inline relays with a remote switch and a hand held remote control to switch a downlighter setup, all of which seem to be functioning well.

Reply to
rbel

The only way to get proper room by room temp control is to have a thermosta= t in each room. TRVs control the water return temp, not the room temp, they= can only improve things some.

With the low cost of bimetal stats I would have thought this approach would= pay back well over time in a house where room temps vary noticeably betwee= n rooms.

The easier option is to plumb it all as now but let the thermostat control = a valve on each rad. You might cut corners further by having the stat contr= ol a few watts of resistor stuck onto the TRV instead. One plus of this is = you can take the extra controls off easily at sale time, buyers get nervous= about anything nonstandard.

NT

Reply to
meow2222

tat in each room. TRVs control the water return temp, not the room temp, th= ey can only improve things some.

ld pay back well over time in a house where room temps vary noticeably betw= een rooms.

l a valve on each rad. You might cut corners further by having the stat con= trol a few watts of resistor stuck onto the TRV instead. One plus of this i= s you can take the extra controls off easily at sale time, buyers get nervo= us about anything nonstandard.

I believe at least one radiator must not have a TRV to prevent the system overheating - more knowledgeable people can confirm or refute this.

Jonathan

Reply to
Jonathan

On Monday 07 January 2013 07:56 Jonathan wrote in uk.d-i-y:

That is mostly correct if the boiler is driving the rads directly but you can have a bypass valve instead.

Reply to
Tim Watts

in each room.

Agreed

things some.

Not strictly true. They do sense room temperature - but only near the radiator, rather than where you might mount a room stat. Having said that, you can get some with remote sensors.

They don't control the return temperature - mine are all on the flow side, but they still work. What they do is progressively restrict the flow as the set (room) temperature is approached.

Reply to
Roger Mills

The radiator heating the area where the room stat is located shouldn't have a TRV because only one will be effective. If the TRV shuts down the rad before the room stat's set point is reached, the heating will run all the time and you won't achieve boiler interlock when all demands are satisfied. If the room stat shuts down the system before the TRV closes, the TRV won't do anything - but won't actually do any harm.

Reply to
Roger Mills

each room. TRVs control the water return temp, not the room temp, they can only improve things some.

back well over time in a house where room temps vary noticeably between rooms.

valve on each rad. You might cut corners further by having the stat control a few watts of resistor stuck onto the TRV instead. One plus of this is you can take the extra controls off easily at sale time, buyers get nervous about anything nonstandard.

What I am hoping to achieve, hopefully with some LightwaveRF kit, is to have wireless remote TRVs ie a TRV on each radiator which has a overriding wireless on/off function that can be individually controlled from a pc. In effect it would be multiple zoning.

Reply to
rbel

Just had a look at that. I'm in the market for something similar. They don't seem to have much in the way of useful information on their site do they? And what is with the 'request a brochure' Haven't they heard of downloadable pdfs?

How very 20th century.

Reply to
Andrew May

in each room.

things some.

The typical TRV has a metal body in excellent thermal contact with the water and the wax capsule. Its insulated from room air by a plstic cap. Thus room temp has little effect on it, it effectively responds almost completely to circulating water temp.

That doesn't mean you cant improve room temp control with them, but it happens by improving system balancing, not by sensing room temp. Regrettably.

There are TRVs that improve on this design with lots of cap ventilation, but still they're in intimate thermal contact with the water, and have far lower thermal conduction to the air, so are still mostly controlled by water temp.

NT

Reply to
meow2222

in each room.

things some.

and the wax capsule. Its insulated from room air by a plstic cap. Thus room temp has little effect on it, it effectively responds almost completely to circulating water temp.

by improving system balancing, not by sensing room temp. Regrettably.

still they're in intimate thermal contact with the water, and have far lower thermal conduction to the air, so are still mostly controlled by water temp.

So why don't mine - which are on the inlet side - shut down immediately hot water starts to flow through them?

And I did mention that you can get some with remote sensors.

Reply to
Roger Mills

In message on Sat, 5 Jan 2013, Colin Brook wrote

Thanks for all contributions in this thread which have given me some pointers that I wasn't at all thinking about - especially the overlap with home control systems etc. Combined with the related thread "Relocating thermostat - wireless?" I have some very helpful inputs.

Colin

Reply to
Colin Brook

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