Tuning heating system

[Jonathan]

I am preparing to tune my heating system for the first time ever and have ordered a thermometer.

I have read the FAQs about balancing the radiators and that all seems pretty clear. I also want to adjust the temperature on my condensing boiler to get that to operate at best effiency. To do this I understand that the return pipe should be below 55C.

My question is, do I adjust the boiler running at maximum output and then do the radiators, or vice versa, or is it a question of a series of repetitions, gradually getting to the desired result? I suspect the latter but any advice would be appreciated.

Thanks

Jonathan.

[ransley]

Not the return, but its what you heat the water to. Easiest way is just lower the aquastat now so it doesnt heat above 55c, some models are higher but the less you heat the more you save. There is a point where it wont heat you or will run to long but 55 is a good place to be. Your manufacurer will know where peak efficiency is. You should have in writing efficiencies at different temperaturs. Condensing units drop in efficiency alot above maybe 59

[Jonathan]

Thanks for that. Presumably the thermostat on the cylinder should be set a bit lower to prevent the boiler staying on trying to reach the higher temperature.

Jonathan

[Andrew Gabriel]

OK, you're talking about two things here. Balancing the radiators is part of the story, and adjusts the flow through each radiator to be proportional to the radiator's power rating, so they're all generating the same temperature drop. When that's done, there's then the matter of adjusting the boiler temperature for most efficient system operation.

For best boiler efficiency, the system temperature wants to be as low as possible whilst meeting the requirements for heating the house. It depends how large your radiators are just how low you can get it. To operate in fully condensing mode, it should be below 55C. You might not always be able to do that, particularly if your radiators weren't sized large for a condensing boiler on the coldest days of the year. Even if you do end up running it hotter than 55C, a condensing boiler will still be running more efficiently in non-condensing mode than a non-condesnsing boiler can.

The most efficient boiler setting is running the system such that the room stat (assuming you have one) almost but never quite has to switch off the demand for heat. In that case, you have the boiler modulated down to match the heat loss exactly. There are two problems with this though. Firstly, that boiler setting will change depending on heat loss (e.g. outside temperature). Secondly, it would take forever to warm up the house from cold. So this means you'll need to adjust the boiler temperature up as the outside temperature drops, and you'd need to temporarily boost it up to heat up the house from cold. You can get weather compensation controls which do this for you automatically, or you can set it just a bit higher than the absolute ideal economy setting to cope with this, and adjust up by hand further if it's particularly cold outside.

(Note this is all only for condensing boilers -- you'll wreck a non- condensing boiler by running it this cool.)

For balancing the radiators, the important thing is that the boiler and radiators are running as stably as possible -- it's pretty impossible to do it if the temperature keeps changing, e.g. if the boiler starts cycling off and on.

[Big Les Wade]

Andrew Gabriel posted

Why, what does it do to it?

[Wolf Goetze]

It makes it condense. The condensate dissolves some of the SO_2 from the exhaust and becomes corrosive. A non-condensing boiler doesn't drain the condensate so this will corrode the heat exchanger.

Wolf