Is a rad return stat instead of room stat a sensible option?

[Ookysoft]

I have a typical 2 zone [ upstairs & downstairs ] zoned radiator based central heating system.

Both are on seperate timers / room stats...... the room stats for both the upstairs and downstairs are in the hallway and landing respectivly.

I'm putting thermostatic valves on the bedroom radiators in an attempt to regulate the bedrooms temperatures. I want to dispense with the upstairs room stat as it's clearly not efficiant in allowing the rooms to warm due to the interferance from the downstairs heating - equally when the rooms are warm it will rely on the upstairs hallway radiators to 'tell' the stat that all is warm enough.....

So.... can I dispense with that upstairs room stat and control the upstairs flow from a thermostat on the return water temperature from the upstairs heating water. If so, would a cylinder stat do the job or maybe cobble something from a combi spare or......

I'm guessing that 1 rad upstairs mustn't be thermostaticly controlled so the IS a minimum return? Or maybe I should put a flow to return loop in the boiler room to stop the pump straining.

Any good books on designing central heating systems maybe?

Thoughts please?

 

[bengasman]

ROOM-stat should not be in hall or on landing. this used to be done in the old days but is outdated way of doing things. Only trvs is asking for trouble. your installer must have been asleep at the energy efficiency course

 

[Ookysoft]

The installer was a brickie.... this guy, I discovered, put fittings [ lights etc ] on walls THEN plastered, didn't tape plasterboard so I have nice rectangular cracks in all ceilings, didn't bother marking switched lives cables.....and on! - No problems with the brickwork though!!

Anyway, how is this conventionally done? If I put a room stat in 1 bedroom, then all rely on the temperature preference of that rooms occupant. I could rely on the boiler stat as, whether the downstairs heat kicks in or not, the thermostatic valves still control flow into each rad.... Just doesn't seem like enough?

 

[ChrisR]

LOADS of ways to crack this one, depending on what you want exactly.
Best and most expensive is (eg) the Honeywell system with radio , programmable trv's so each room is its own zone.

Putting a room stat in one bed room is a reasonable way to do it - as long as you close all the doors.
Using the downstairs room stat is ok for "open loop" control, with just a timer on the upstairs zone valve. You could add a stat in a bedroom to override the timer if the room gets below say 16 degrees.

Stats on the return pipes don't do it, they only tell you the pipe temp not the room temp.

Oh yes, you can also get electricaly operated rad valves, so again, a prog stat control in each room is possible for less than £50 a room. Payback period would be long though!

 

[bengasman]

Long story with loads of variables, read up on the subject if you want a clear understanding.
In short; hypothetical setup of bogstandard house: lounge, 3 bed, kitchen, bathroom corridor, mum and kids at home most of day.
Lounge centre of household therefore centre of heat demand. Average comfortable temp 21 C. Secondary rooms can be cooler as they do not need to keep people comfortable for sustained periods of time.
Assuming that all rads are adequately and relatively sized, all rooms heat up at same speed. Secondary space upon reaching required temp, will be shut off by trv, saving energy. When lounge reaches required temp, roomstat turns boiler off saving more energy again. It ALSO stops the boiler from cycling which extends the life expectancy of the boiler.
If the roomstat is in the hall, it would turn the boiler on every timer the door is opened, even though the rest of the house is warm enough, making the lounge too warm, the bill too high and unnecessary strain on the boiler. That is why a roomstat in the hall is a dumb idea.
In the old days it worked fine because we could not afford more than an hour in the morning and an hour at nite, so it did not matter how many times the door would open as the boiler was off anyway.
2 zone heating: master bedroom is lounge would be workable way of doing it

 

[jpdw]

Oh yes, you can also get electricaly operated rad valves, so again, a prog stat control in each room is possible for less than £50 a room. Payback period would be long though!

Could you post some links to these? Been looking for this kind of thing (other than the £££ honeywell). Thanks.

 

[Ookysoft]

Long story with loads of variables, read up on the subject if you want a clear understanding.

*Wonders where I read up on the subject.*

Thanks for the input - I kinda think a wireless control from each valve would be a nice idea - just the cash impication and keeping the lodgers fingers off might be a struggle.

I guess regular thremostatics valves and a roomstat in the 'warmest' bedroom may do - not the master as I like to sleep in the cold.

I can see no bypass in the boiler room so I reckon I need to pop 1 of those in there.... or the pump may suffer - I'm guessing the boiler will be ok as it has it's own stat!

I think this place should have been zoned to 'bedrooms' and 'downstairs & landing' and 'bathrooms' - but I appreciate each house is different!

 

[bengasman]

don't know by heart, google should do the job