zoned heat with a combi

[Steve]

On thinking about the type of heating I want, I know its gotta be a combi - stored HW isnt an option - its expensive for me and I dont have space for it in this house (2 bed+bath up, kitchen and lounge down).

Anyway, I have been sat on my sofa all night. While the whole house is heated by the radiators. I dont like this. I only want downstairs to be heated while I'm downstairs. What I'm thinking is to install programmable thermostats both upstairs and downstairs. So at the times I'm occupying the spaces they are heated to 21 deg, but at all other times, the temp is maintained at 16-18 deg. This should result in good savings (I live alone).

I also want a zone for the bathroom radiator alone, which would be simply controlled by an electronic timer. This rad will be changed for a towel rail in due course. (rad is currently fitted upside down for some bizarre reason)

So I'd need 3 zone valves and 2 programmable stats, and a timer.

Does this sound feasible? I know all combis have a pair of terminals for a stat - would I just use this for my zone valve switches and wire them in parallel? And set the combi to run "constant", so that its always ready to fire up on a zone opening?

 

[petit_pablo]

Yes its possible to wire up a combi like that.

Towel rail on its own timer seems excessive but each to their own.

 

[Steve]

Towel rail on its own timer seems excessive but each to their own.

Doing this, I could have the towel rail heat up in summer, without the rest of upstairs heating up. Would your average combi be able to regulate such a small circuit with one rad running? Or would it induce extra wear and tear on the pump etc? I'm going to get a quote from a local company who I know use worcester boilers (it'll probably be a greenstar junior 24)

 

[petit_pablo]

The boiler wouldnt be able to modulate down enough for just one towel rail without it short cycling and probably a bit of noise to.

Would a towel rail with added electric element not be sufficient?

 

[Steve]

The boiler wouldnt be able to modulate down enough for just one towel rail without it short cycling and probably a bit of noise to.

Would a towel rail with added electric element not be sufficient?

Probably. I'm trying to make this house as economical as I can. I'll probably have the electric element. I guess these have some sort of thermostat on them that prevents them working while the boiler is on, and thus the water is hot enough?

The thing is, the fuel bill for my 20 year old baxi solo 40/4 are gonna cripple me this winter, so come next year I want to go to the opposite extreme, and be as efficient as I can! I already have CFLs in ALL lights.

I'm going to have the back bedroom rad replaced (its the only old one left), and the boiler moved so its pipework no longer has to snake across the loft.

Would new pipework to all rads be a good investment or not nessecary if they are flushed out? Its all 15mm and 22mm at the moment.

 

[ajrobb]

I have a house like yours; kitchen and lounge downstairs and 2 beds + bath upstairs. The stairs are in the lounge. I have only just installed central heating. Prior to that, I only heated the lounge with a 3kW gas wall heater and this kept the whole house warm.

My point is that it can be difficult to keep heat out of the upstairs rooms and zoning might cost more than you save.

If you just want to warm your bedroom before a regular bedtime, you could replace your manual TRV with a programmable one:

http://www.heatingcontrolsonline.co.uk/danfoss-randall-raplus-programmable-trv-p-317.html

Another thought is that you could control an electric towel rail element with a humidistat (also linked to a bathroom fan). When the towels are dry, the humidity drops and turns off the towel rail heater.

 

[Steve]

My point is that it can be difficult to keep heat out of the upstairs rooms and zoning might cost more than you save.

Indeed, if the stairs are open to the downstairs rooms, but my stairs are enclosed with a door at the bottom (though there is a rad at the bottom of the steps, supplied off the downstairs pipework, unsure whether i should split this off).

If you just want to warm your bedroom before a regular bedtime, you could replace your manual TRV with a programmable one:

http://www.heatingcontrolsonline.co.uk/danfoss-randall-raplus-programmable-trv-p-317.html[/QUOTE]
I had seen these, thought what a brilliant idea they were, but then realised that they run constantly but with no trigger to activate the boiler. A good point is that women (master tinkerers) wouldnt go near them and turn them all up! And they need batteries. Batteries cost money and harm the environment (goes against the point of this).

Another thought is that you could control an electric towel rail element with a humidistat (also linked to a bathroom fan). When the towels are dry, the humidity drops and turns off the towel rail heater.

Yes, this sounds like a plan! Though I'd have to monitor how successful it actually is. I guess the theory is that when the upstairs room temp drops the heating will kick in and heat the rail anyway. I'd want a boost override switch for the electric heater, so that I can switch it on for an hour or so if there is no humidity and no heating.