New Boiler advice

Widescreen

Hi folks-we have a 20 year old boiler which is on its last legs. Also the system is micro bore and the two furthest double rads from the boiler in our large lounge both heat up more on one side of the double rad than the other.. If you turn up the temperature higher eventually you get an acceptable level of heat in that room but too much oil used. I am finally going to get a boiler-thinking of grant 90/120 as we added a couple of extra rads 3 years ago.Changing pipe work not an option due concrete floors expense etc-assuming we have the right pump etc should this new boiler improve things particularly in the room I mentioned? Heat is fine in other rooms thanks

sullzz

Widescreen wrote: »

Hi folks-we have a 20 year old boiler which is on its last legs. Also the system is micro bore and the two furthest double rads from the boiler in our large lounge both heat up more on one side of the double rad than the other.. If you turn up the temperature higher eventually you get an acceptable level of heat in that room but too much oil used. I am finally going to get a boiler-thinking of grant 90/120 as we added a couple of extra rads 3 years ago.Changing pipe work not an option due concrete floors expense etc-assuming we have the right pump etc should this new boiler improve things particularly in the room I mentioned? Heat is fine in other rooms thanks

A new boiler is only as good as the system it's serving , I'd really reconsider not replacing the microbore , when fitting a new boiler you should always powerflush the heating system before the boiler is fitted , with microbore its is very risky and a lot of lads refuse to powerflush , depending how dirty the system is it can cause blockages that some flushing machines can not clear , if I was you I would repipe , you can pipe on surface if you don't want to break the concrete floors , pipework on surface can be boxed in or even left exposed if a clean tidy job is done with it .

shane0007

sullzz wrote: »

with microbore its is very risky and a lot of lads refuse to powerflush

I have heard this before but I would completely disagree. I have powerflushed absolutely dozens of micro-bore systems & never had an issue. They are certainly restrictive but not a problem flushing with the correct machine.
Powerflushing is low pressure, high velocity so no strain on the pipe work.

For the OP, do not oversize the HE boiler, especially with micro-bore as you will just short cycle the boiler, wasting the gain of the HE boiler. Under-size if anything to ensure the boiler operates in full condensing mode as much as possible. Decent quality circulating pump is a must otherwise heat will back up. You need to force heat through the restriction as much as possible.

sullzz

shane0007 wrote: »

They are certainly restrictive but not a problem flushing with the correct machine.

That's the key , I know lads who are flushing with a week machine and are not even using chemicals , they might as well be just draining the system and refilling it .

shane0007

The same could be said for any size pipe system! If a poor machine & no chemicals is used in 1" pipe work, it's a waste of time anyhow.
I'm just curious why people think Powerflushing micro-bore is a no no. I've heard many people say this but nobody seems to say why.

Widescreen

shane0007 wrote: »

I have heard this before but I would completely disagree. I have powerflushed absolutely dozens of micro-bore systems & never had an issue. They are certainly restrictive but not a problem flushing with the correct machine.
Powerflushing is low pressure, high velocity so no strain on the pipe work.

For the OP, do not oversize the HE boiler, especially with micro-bore as you will just short cycle the boiler, wasting the gain of the HE boiler. Under-size if anything to ensure the boiler operates in full condensing mode as much as possible. Decent quality circulating pump is a must otherwise heat will back up. You need to force heat through the restriction as much as possible.

Thanks, so is what you are suggesting-getting the next boiler down and the better pump which may give us a chance of getting better heat in the lounge?

My plumber says go for 90/120( I have 13 rads including 5 doubles) he will run system for several days with the cleaning agent and put in descaler etc.

By the way mine is a sealed system with expansion tank beside boiler no 2nd tank in the attic.

Can you explain further why you suggest the lesser powered boiler? I am slightly confused and need to make the decision.

Thanks

shane0007

13 rads is not a calculation. You either size the boiler to the existing rads or you size to the rooms plus system losses & hot water demand.
Running a chemical round the system & a drain down is not a powerflush. It's just better than nothing.
The system should be sized accordingly but then unless you over-size the rads, you will need to under-size the boiler to drop the return delta T from 11C to 20C differential.
This thus keeps to the boiler in condensing mode for longer. More important for an oil boiler as they cannot modulate. Gas boiler modulate on return temps so keeping them in condensing mode for longer.

Widescreen

Not sure if you saw the bit about mine being a sealed system as I was editing my last post at the same time u posted your last reply!

Anyway, the technical detail in the last post is over my head!

For the last 17 years a standard boiler has been doing the job, can you still get the standard grant boiler or are they all condensers now?

If the old type are still available maybe it would make sense to get the next model up from the one I have now rather than get a condenser boiler which you seem to think would be a waste for me?

shane0007

Sorry for the technical bit but you did ask....
You would be mad to fit a standard efficiency boiler. It would be against regs anyhow.
What kw output is your existing boiler 26kw or 35kw?

Widescreen

No worries! I'll check tomorrow evening, I am not sure tbh.

U noticed my system is sealed btw? Expansion vessel by boiler.

Based on the 2 possible kw's can you suggest what boiler to get?

Reason for my confusion I think is the reference to a larger boiler not going into condenser mode- not sure what you mean by that.

Does that mean the boiler is not working properly or some other issue?

I am assuming a super new GREEN boiler is going to be easier on juice!

shane0007

Widescreen wrote: »

U noticed my system is sealed btw? Expansion vessel by boiler.

Yes. It makes no difference to the kw output required. It just means you will have a better system.

Widescreen wrote: »

Based on the 2 possible kw's can you suggest what boiler to get?

I could not possibly determine that without knowing your rad sizes or room sizes, water cylinder size & a bit more info for good measure. You installer should be able to size this accurately. It should not be guessed!

Widescreen wrote: »

Reason for my confusion I think is the reference to a larger boiler not going into condenser mode- not sure what you mean by that.

Larger boiler will have a higher return temp so the delta T will be closer to 11C rather than 20C. It needs to be around 20C to keep in condensing mode, i.e. flow temp of 70C return temp of 50C. Traditional SE boilers would be 73C flow & 62C return.

Widescreen wrote: »

Does that mean the boiler is not working properly or some other issue?

It will work properly but just not as efficiently as it could be.

Widescreen wrote: »

I am assuming a super new GREEN boiler is going to be easier on juice!

You would be assuming correctly.
Anywhere between 5% & 20% saving. The more the boiler is in condensing mode the closer you will be to 20% & the less it is in condensing mode, the closer it will be to 5%.

Also make sure the boiler is properly commissioned by an OFTEC technician & that the boiler passport is filled out & certified & returned to the manufacturer to instigate the warranty. Full print of the FGA must also be included.

Widescreen

Great information.thanks
+
Are you saying that if the boiler is installed by a none OFTEC registered engineer that the warranty would not be valid? And what is the FGA? Thanks

Dtp79

Widescreen wrote: »

Great information.thanks
+
Are you saying that if the boiler is installed by a none OFTEC registered engineer that the warranty would not be valid? And what is the FGA? Thanks

FGA is a flue gas analyses. You cannot set up the boiler properly without doing this. The installer should hand you a small printout showing all the combustion details after the boiler is commisioned. Insist on this. Non OFTEC can also fill out the passport and warranty will be valid.

shane0007

Dtp79 wrote: »

Non OFTEC can also fill out the passport and warranty will be valid.

There should be 3 copies of the FGA. One stapled to the customer's copy of boiler passport, one for the manufacturer's copy & one for the commissioning technician's copy.
It's all well & good saying that the warranty will be valid. Any warranty calls I come to & they do not meet the regs as per the boiler passport requirements & the building regs as explained by OFTEC, the issue is highlighted to the manufacturer & warranty is decided on a case by case basis. Many are not given.

You can get your non-registeredinstaller to install the boiler but get an OFTEC technician to commission it. I do a lot of commissioning works & rarely do they meet the standards. The regular installers that use me to commission have theirs to standard now.

Widescreen

Thanks for all help, well noted.

Widescreen

By the way I checked the spec of my existing boiler. It is Thermomec make.

It says on the side Termal power input 23.500 Kcal/h
Termal Power conv 22.900 Kcal/h
Termal power output 20.000 Kcal/h
Comb.Chamber Press 0
Exercise Pressure Max 4.

I also got another guy to evaluate the job. He measured all rads ,went away did his quote and said the most suitable boiler is the 70/90 26kw output. He gave the opinion also that the bigger boiler would not be condensing enough etc...

Based on this and the power of my current boiler does anyone agree the 70/90 wud be better option and give good improvement on current situation... thanks