New combi boiler going in, how to run it??

spinningsheep

Hi, hoping someone on here can give me some decent advice on my new boiler. My landlady is replacing the heating from tomorrow, advised will take 2/3 days. We are having a Baxi DueTec28kw fitted and a total of 10 rads and a towel rail, 8 TRV's and a new thermostat in the hallway. I have not had a system with combi before, am used to a hot water tank and having to wait for it to heat up etc, so will be great to have hot water on demand. Have been told, not sure how true this is, keep the thermostat in the hall at 25 to 30 degrees, and control the room temps by the TRV's, that way the wall thermostat is not going to click the heating off even when the rooms have not warmed up properly? Also, I currently have the heating on for 2 hours in the morning and 5 hours at evening. So that the boiler runs efficiently am I best doing the same or leaving it on low 24/7 so it's always in "condensing mode" ? I heard that if you have your TRV's set too high it can mean the water return temop is too high and therefore the boiler never gets into condensing mode, or is this a myth?

Sorry if this sounds blonde, I am not one of these "is it cheaper to leave the heating on 24/7 crowd" I am just totally new to combi.

macman

25C room temp is far too warm for most people, try it at 21C and see how you get on. Control the zone temps using your TRV's if required.
Leaving the boiler on24/7 will greatly increase your gas bills, and it's a return temp too low that may prevent it entering condensing mode.
As far as the CH side is concerned, a combi is really no different to a conventional boiler. The only thing to bear in mind is that no CH heat will be available when the combi is responding to a demand for hot water. So if you run a bath that takes 20 mins to fill, the CH will in effect be off for that period.

Canucklehead

spinningsheep wrote: »

Hi, hoping someone on here can give me some decent advice on my new boiler. My landlady is replacing the heating from tomorrow, advised will take 2/3 days. We are having a Baxi DueTec28kw fitted and a total of 10 rads and a towel rail, 8 TRV's and a new thermostat in the hallway. I have not had a system with combi before, am used to a hot water tank and having to wait for it to heat up etc, so will be great to have hot water on demand. Have been told, not sure how true this is, keep the thermostat in the hall at 25 to 30 degrees, and control the room temps by the TRV's, that way the wall thermostat is not going to click the heating off even when the rooms have not warmed up properly? Also, I currently have the heating on for 2 hours in the morning and 5 hours at evening. So that the boiler runs efficiently am I best doing the same or leaving it on low 24/7 so it's always in "condensing mode" ? I heard that if you have your TRV's set too high it can mean the water return temop is too high and therefore the boiler never gets into condensing mode, or is this a myth?

Sorry if this sounds blonde, I am not one of these "is it cheaper to leave the heating on 24/7 crowd" I am just totally new to combi.

Good afternoon: excellent advice is available from the Energy Saving Trust and the HHIC.

HTH

Canucklehead

fred7777

"Have been told .. keep the thermostat in the hall at 25 to 30 degrees, and control the room temps by the TRV's, that way the wall thermostat is not going to click the heating off even when the rooms have not warmed up properly?"
That would work. But how well depends on where the TRVs are. You say you have 10 rads but 8 TRVs, doing this the non TRV rads may be blasting out full all the time which you may or may not want.
Ideally you want the thermostat in the room you want hottest without any TRVs on the radiators in that room, all the other rooms running on TRVs colder and you set the thermostat so the room is comfortable. Failing that the room with the thermostat should be around the temperature you want the other rooms heated to.

Problems tend to occur when you have the thermostat in room you want cold so the TRVs are set low and the room isn't getting hot enough for the thermostat to control properly. Or systems where everything has a TRV set low so the system is constantly switching on and off.

"Also, I currently have the heating on for 2 hours in the morning and 5 hours at evening. So that the boiler runs efficiently am I best doing the same or leaving it on low 24/7 so it's always in "condensing mode" ?"
Leaving it on 24/7 is not an efficient way or running it condensing or not.
The boiler will condense more if the heating water temp is lower. This is set on the boiler not on the TRVs or room thermostat.

"I heard that if you have your TRV's set too high it can mean the water return temp is too high and therefore the boiler never gets into condensing mode, or is this a myth?"
It could be true it depends on the radiators and the weather. On a really cold day the return temp could be lower with the TRV set high than on a hot day with the TRV set low.
What is certain however is that if you set the TRVs too low you are going to be cold no matter what the rest of the system is set to.

spinningsheep

Thanks for replies guys, the new system is in and fired, been flushed and the magnetic filter was full of black gunk this morning and the water in the system when they drained it down again was clear! The installer has set the radiator water temp to 60 so that it will be below 55 on return temp so it condenses as much as possible, have set wireless room stat in hall to 20 and turned the TRV's to 3 at max as it was getting way too hot, house is so warm now! We left it on constant overnight so it could flush properly and I used 4 units of gas between 8pm last night and 8am this morning, and according to the smartmeteruk site this cost approx £3.70 on my BG websaver6 duel fuel plan. Would you say that is good for a 12 hour run? The normal running will be 7 hours a day split between morning and night so I am looking forward to cheaper gas bills!

It is running 10 radiators and a towel rail, partial double glazed, wooden front and back doors and light insulation in loft, and I havent yet put things like the front door curtain and draught excluders back at the doors yet.

grumpycrab

Sorry to butt in but "keep the thermostat in the hall at 25 to 30 degrees"? Why? Do you live in the hall? The hall should be one of the cooler areas in the house, unless you're open plan. I suggest...

1. which is your main living area? assuming its the living room, turn all thermostats FULLON in this room.
2a. radiator(s) in hall (where thermostat is) must be FULLON
2b. with the boiler central heating on, play with the hall thermostat until you get a comfortable temp in the living room
3. adjust thermostats in OTHER rooms to suit

It'll be interesting to see what the termostat in the hall ends up at. If the hall is a cold room and living room warm then the thermostat will end up being quite low eg 17deg
Vice-versa, if the hall is a warm room and living room a cool room then the thermostat may end up being set quite high e.g. 22deg

EDIT: you said "have set wireless room stat in hall to 20 and turned the TRV's to 3 at max as it was getting way too hot"
Do you really need the hall temp at 20? If you reduce this to, say 18, and turn the TRVs in your main (living) room back up the boiler will be on less.

spinningsheep

Cheers, will try that, i did think 20 was excessive so will try 18 and turn the TRV up in the lounge

spinningsheep

Just an update, I turned the thermostat to 18 and I noticed it got quite chilly and the radiators did not seem to get as hot, so I turned the thermostat up to 21 and turned a couple of the radiator TRV's to frost setting in the rooms we aren't using, and the boiler radiator temp to 65 degrees, and so far the house has been toasty. Used the smartmeter power site and according to that, we have burnt 2 units of gas since yesterday and this has cost approx £2.09. VERY HAPPY!

grumpycrab

spinningsheep wrote: »

Just an update, I turned the thermostat to 18 and I noticed it got quite chilly and the radiators did not seem to get as hot...

Was that quite chilly in the lounge? Which rads did not seem to get as hot? Were the TRVs in the lounge set to MAX?

spinningsheep

Hi grumpycrab no the TRV in the lounge was set to 4 not 5, the bedrooms are on 2 or frost in the case of the spare back bedroom, same for the dining room which we rarely use. I thought if the radiator in the lounge was on max, it would make the boiler fire more and therefore use more gas? Sorry if I sound thick, I am just not used to a modern system with TRV's and an accurate room thermostat!

grumpycrab

spinningsheep wrote: »

I turned the thermostat to 18 and I noticed it got quite chilly

spinningsheep wrote: »

the TRV in the lounge was set to 4 not 5,...I thought if the radiator in the lounge was on max, it would make the boiler fire more and therefore use more gas?...

I'm sure there is more than one way to do this but my view (and I might be wrong) is that if it was chilly (in the lounge) then either :-
1. the TRVs in the lounge are set to low and/or
2. the thermostat is too low

1st ensure that the rad(s) where the thermostat is are always full on.

Then in your lounge this is the room you live in so you want to use the full efficiency of the boiler to get the room to a comfortable temp ASAP; the best way to do that is have the TRVS full on. Then the boiler is working at max efficiency and the rads should be nice and hot. At that comfortable temp you then want the theromstat to turn off.

THEN if the temp in the hall is HIGHER than your comfortable temperature we might have to do some tweaking but you need this baseline to work from before the tweaking begins.