Conservatory Heating - exploring the possibilities

[mungoh]

Hi Folks, Just mumbling out loud here to see what others think:

Our builder has (unusually?) told us that he's happy to erect our new conservatory over the Christmas holiday period, providing that the brickwork can of course be put in place by then.

This has caused me to think seriously about heating the new space. I've never owned a conservatory before, so it's all new to me.

Present proposition is to add three wall radiators to the dwarf-walled conservatory and run these off my mains gas wet central heating system.

Being careful with the pennies, I was thinking of adding a two-port valve to the feed for these radiators, and then controlling this valve from (say) some sort of timer such as an immersion-heater-booster device as per shown on the TLC web site here:

to using the space, I merely press the button for (say) a two-hour duration and this opens the valve for that time. I'll leave the house stat to decide whether the boiler needs fired, and also I'll add Thermostatic Radiator Valves to the three radiators too.

Of course, this arrangement does not guarantee that the boiler will fire when the conservatory needs it, but I'm hoping that that will not be a problem (fingers crossed; this is where your opinion is sought).

Instead of fancy Frost Stats I was thinking of adding an electric panel radiator to the conservatory whose thermostat is set quite low. Thus when the outside temperature plummets and there is a risk of the conservatory radiators freezing, the electric panel cuts in and lifts the temperature to avoid this.

Perhaps another immersion-heater-booster switch could be wired to override the thermostat to kick the electric panel in if required.

Any problems with my scheme?

Any source of an electric-booster switch with more flexibility than that shown on the TLC site?

Advice requested; thanks in advance.

Mungo

[Andy Hall]

This meets the building regulation requirements in that there is separate control for the conservatory.

In effect here, you are connecting the new zone valve in series. I can see that it might be easier than running pipes all the way back to the existing diverter or zone valves.

You might get away with this approach (mostly) if you arrange for the conservatory to reach temperature before the rest of the house. This could be achieved by oversizing the conservatory radiators (may not be possible in the space) or by deliberately distorting the system balance so that the bulk of the heating water goes to the conservatory radiators and then to the house when the conservatory is warm. The trouble is that the time for the house to warm up may then be quite long and variable.

[Set Square]

> Prior to using the space, I merely press the button for (say) a

How is the existing heating system zoned? If you already have an S-Plan system, you could add another zone - but you'd have to connect in at the current split point rather than tapping into an existing heating zone. You could then use the secondary contacts on the new zone valve to bring the boiler (and pump) on when required - independently of the other zones.

I would control the valve with a programmable room stat such as the Honeywell CM67. This acts as a frost stat in its 'off' state and will turn the heating on in the zone it controls when necessary to prevent freezing. You can normally leave it on a low setting, and then use it's 'party' setting when you want it hotter for a period. This lets you specify a higher (or lower!) temperature for a specified number of hours.

[mungoh]

Ta to Set and Andy for their replies.

Conventional arrangement in the house: hot tank upstairs with thermostat; programmable thermostat in hall downstairs; three-port diverter valve midships in the house. The conservatory will be tacked on to a gable wall - the route from the existing three-port valve locus to the gable end would be tortuous (not impossible, but just outside my "contemplated" range just now! :-)

Mungo

[Doctor Drivel]

> Prior to using the space, I merely press the button for (say) a

Don't put rads in. Install a dedicated Myson fan convector heater.

probably could take this off the rad circuit. You may want to fit a pump with non-return valve in front of the pump, just for the unit to get the flow. Have an external stat which switches on the fan and pump.

This is far better than rads.

[Set Square]

OK then, Plan B!

I assume that CH is set to Constant on the programmer and *actually* timed by the programmable stat in the hall?

If so, how does this grab you? Have a programmable stat in the conservatory to control your new zone valve. Wire the secondary contacts of this zone valve in parallel with the prog.stat in the hall. Then, whenever the conservatory is calling for heat, it will bring on the house heating even if it isn't otherwise scheduled to be on. If the house rads have got TRVs, having to have the house heating on to heat the conservatory shouldn't be too much of a problem.

[Peter Parry]

When sizing the radiators bear in mind a double glazed conservatory will have a heat loss about 8 times greater than a house room of the same size. Basically your conservatory requires as much heat as the rest of the house in total to maintain the same temperature. You might find fan assisted radiators useful as they get the temperature up somewhat quicker.

Depending upon the temperature you want to achieve you will need to plan ahead by 2 hours or more anyway!

If the house is warm and the conservatory cold this isn't going to produce any heat.

Bit of a waste, you would be better putting a single thermostat in the conservatory controlling the heating to it.

It will be as the heat loss from the conservatory is vastly greater than the heat loss from anywhere else in the house.

Unless you leave it unheated for days on end in very frosty weather it's unlikely the radiators would ever freeze as even in winter conservatories collect enough solar gain to keep above freezing. A better, and cheaper, solution would be to put a frost stat across your push to start switch.

[Andy Hall]

Plan C......

This is a bit more work than SS's plan B and assumes that the boiler is closer to the conservatory.

Change the diverter valve to 2 two port valves.

Move the pump to a point closer to the boiler - taking account of feed and vent pipes if an open vented system.

Connect conservatory circuit via zone valve to a point close to the pump.

If you give this some thought in the initial stages, you might be able to do a part job to begin with (like you planned) that is easy to migrate later.

[somebody]

In message , [e-mail] writes

[snip]

[snip]

I don't know the size/makeup of your proposed conservatory, but please bear the following in mind....

In our 2.5m x 7m conservatory, using our radio thermostat (cm67), it could take up to four hours to get the conservatory to a reasonable temp (not warm, just liveable). That's with a nice big double rad in there.

During those fours hours, the boiler would be running non stop. If you fancied just popping in there of an evening at this time of year... forget it. On a seperate note, the rest of the house would be cooking at the time.

In the end we bought a 1.8Kw ceramic fan assisted heater from Argos (30 quid) and it now takes 10 to 15 minutes to bring it up to 22 degrees (our stat temperature in the house).

To be honest, I think using one of them 'as and when' may be your better bet. Someone

[Doctor Drivel]

That is why it is best to use a Myson Fan convector heater, they can pour out up to 9kW. Circulating air is the best method in a conservatory as convection just rises to the glass ceiling and the heat floats out the top. But it must have water flow through it. Tapping into 15mm rad pipes at the end of a line will not be good enough. Installing a pump just on the fan convector increasing the water flow through the heater is an option.

[Christian McArdle]

OK, but replace the timer with a programmable thermostat. This mean that you needn't bother with TRVs and you have much better control of temperature. Finally rather than radiators, consider a fan convector. These are superb for conservatories because they are a fraction of the size of radiators and can heat the room up in a fraction of the time, making it very suitable for an hour boost etc.

I would recommend a Myson Hiline above the door, so it doesn't waste valuable wall or floor space at all.

I wouldn't bother with the electric heater. However, if you are worried about frost protection, stick a frost thermostat in there which turns on your boiler/pump. Almost any programmable thermostat will have built in frost protection and will already be calling for heat for the conservatory, so the zone valve will already be open.

Christian.

[mungoh]

Many thanks for all the kind replies to my query.

As I said in my opening gambit, I have no experience of owning a conservatory hence I am torn between wanting to install sufficient heating facilities (just in case the new room is well used all the year round) versus not wanting to have added a "heat sink" to the house to waste valuable pennies when the room is not in use!

I know, I'm being awkward. I'm just hedging my bets.

Having read all the generous replies I'm now swithering over delaying a full installation for a season or two and just relying on an electric fan-assisted heater meantime.

Thus if the room gets well used (beyond the initial "novelty" stage) I can trade up to the thoughtful suggestions outlined by the repliers above, or chicken out and leave it with fan-assisted heating.

Not trying to irk the group's kindness, but I may take some days mulling this over and might revisit the topic later.

Regards

Mungo

[Doctor Drivel]

With a Myson fan heater it is a quickish heat up and when turned off no heat, unlike UFH and rads.

[Andy Hall]

Actually, I think that that makes a lot of sense.

Obviously the cost of electric heating is relatively high. OTOH, it is an easy way to determine exactly what heat is required and when.

What you may want to do is to provision pipework as the build is done, so that you can add later.

[mungoh]

Thanks Andy. I was always planning to build some sort of "trap" access into the floor of the conservatory (away from the normal foot traffic) just in case there is a need at a later date to run another cable or so. I'll now also drill a couple of holes through the gable wall for any future pipework.

Regards

Mungo

[Pete C]

IME if the house is on the small side and you have kids it WILL get used or cost some sanity not to! If not and you have equally usable space for dining/lounge etc it's not so bad.

Maybe get a £12 plug in meter from Maplin to monitor how much elec. the heater is using, bearing in it will cost the same as using gas for the next 4 years (electric being ~4x the cost of gas).

cheers, Pete.