Efficiency Of Pipework And Boiler...is This The Right Forum?

[brummydave]

Not sure if an electrician's forum is the right place to find info but as many of you have amazing knowledge I thought I'd ask!

My central heating is unconventional to say the least and I'm trying to find out which would be the most efficient way to improve it. And then the best value for money...

Currently a 13 year old Gloworm combi boiler is in the kitchen by an external wall, 6m away from the utility room where the 3 motorized valves, underfloor heating manifold, unvented tank, expansion vessel and wiring centre are. It has 22mm flow and return and gas pipes from the utility. It supplies hot water directly to the kitchen sink only which is adjacent.

(If anybody wants to know why we've that arrangement, that's another two paragraphs!)

Option one is replace the boiler with a condensing combi in the same location.

Option two, replace with a system boiler and run a new 7m pipe for kitchen sink hot water from the utility.

Option three, locate new boiler in utility with extended 6m flue to either front or rear of house, adding new hot water pipe for kitchen sink as well (or reusing c/h pipe).

Efficiency wise,

is it true that shorter runs from the boiler to the tank and valves is better?

A new boiler will be ninety something % efficient which is better than ours (81% at new)

Cost wise

Modern boilers can cope with long flue runs but not sure of cost of 6m flue!

Moving boiler location will mean a small amount of pipe jiggery pokery, and several metres of pipe no longer needed.

Running a new hot water pipe to kitchen is a relatively minor cost.

We may be eligible for the boiler cost under ECO/Affordable warmth, but doubtful any new pipework.

Our boiler is Category D and our house has an EPC of B.

Any tips, advice, or places to go looking for them is much appreciated!

 

[brummydave]

I guess it's not the right forum. Anyhoo, I've had advice from some plumbers along the lines of...

The length of c/h flow and return won't affect the system efficiency.

The length of flue won't affect the system efficiency.

They will affect the cost!

The length of a hot water pipe will have an impact on efficiency as if there's a large draw off, more water will be heated than strictly necessary.

All in all, it seems how much heat your house loses is what's important, not how the system gets it around the place.

Also, we're not eligible for ECO as the boiler's not inefficient enough and if it goes wrong, there's still parts available.

Mend and make do they say!

 

[Richard-the-Ninth]

Only just seen this. :Blushing

Surely in situations like this, the best person to ask would be the person who can see what you have and who is quoting to do the job.

 

[ProDave]

This is really an electricians forum, though there are a few plumbers lurking.

I would go with option 2, but because the run to the kitchen sink is long, I would use a small bore pipe.  I would be tempted to rig up a trial with 10mm pipe and see if that delivers enough hot water flow, if not try 15mm. I would be seeking to minimise the volume of water in that run so as to minimise how much cold water you have to run off before the hot gets there. It all depends on your water pressure how small you can get away with ans still have decent flow.

Do NOT under any circumstances re use an old bit of central heating pipe for your hot water. It will have been used for years with dirty horrible old CH water and if you try using that for your hot water I would bet you will have trouble fir a long time with dirty water coming out of your taps.

 

[brummydave]

Only just seen this. :Blushing

Surely in situations like this, the best person to ask would be the person who can see what you have and who is quoting to do the job.

Indeed Richard, trying to get our situation across in text or by phone is nigh on impossible. I just thought i'd try!

This is really an electricians forum, though there are a few plumbers lurking.

I would go with option 2, but because the run to the kitchen sink is long, I would use a small bore pipe.  I would be tempted to rig up a trial with 10mm pipe and see if that delivers enough hot water flow, if not try 15mm. I would be seeking to minimise the volume of water in that run so as to minimise how much cold water you have to run off before the hot gets there. It all depends on your water pressure how small you can get away with ans still have decent flow.

Do NOT under any circumstances re use an old bit of central heating pipe for your hot water. It will have been used for years with dirty horrible old CH water and if you try using that for your hot water I would bet you will have trouble fir a long time with dirty water coming out of your taps.

Thanks Dave, I posted on here more on the off chance as I know there's a wealth of experience in most fields. I also posted on a couple of plumbers forums but have had less response! (Apart from that I quoted above).

Good thought on the hot water small pipe and not using c/h for DHW use. Think i'd be better off weighing in all the c/h stuff and using small bore plastic for the hot water and probably doing the trial myself as i'll be lucky to find a trial-type plumber.

The heating companies I've spoken to so far have been frustrating and most only want to replace like for like. So when I point out a 28kw combi is overkill and a smaller system boiler would be better, they don't want to know. headbang

Today's development was a call from Help-link. They wanted quite a lot of information including tax credit notice info, and then wanted £65 for an EPC - even though we had one in July! (Apparently their company won't accept that...) Finally they said they'd need to take lots of measurements and photos (probably to gauge our financial circumstances) before letting me know how much of a discount they could offer for a new boiler. When I said ECO covers the entire cost, they backtracked and said it's 'potentially free'.. X(

Hey ho, time to fill in and EICR and stop worrying about heating.. :slap

 

[ProDave]

The heating companies I've spoken to so far have been frustrating and most only want to replace like for like. So when I point out a 28kw combi is overkill and a smaller system boiler would be better, they don't want to know. headbang

I know exactly what you mean about that.

My Mother in law's house had an old system boiler and hot water tank in a downstairs cupboard. They had it replaced by British Gas with a combi boiler.  It was the most shocking job I had ever seen.

Quite apart from the use of plastic pipe which looked awful as the runs up the wall don't lie straight like copper. They had piped the hot water from the combi to where the old tank was and left the old hot water distribution in place.  The result was although the boiler was very close to the kitchen, the hot water had to travel to the middle of the house and back again taking ages for the hot water to get to the tap.  but I guess they just did what was easiest for them, instead of what was technically best.

 

[Blue Duck]

She sounds lucky, mother in law asked BG if she can have hot water all the time and they gave her £12k worth in a 2 bed flat! Storage cupboard's filled with tanks, cant move in the loft as there are so many pipes and where's the roomstat? Above the radiator of course!

 

[binky]

IMHO  a new boiler will do more for efficiency, combined with proper pipe lagging, something many plumbers seem to forget. Most of my house has no pipe lagging under the floorboards, the mice must love it! Now a while ago I had all the floorboards up in the hallway where the pipes run (about 20m of flow and return for rads) and lagged them all where I could get to them, made a big difference to the performance of the heating system.

 

[OnOff]

Think yourselves lucky! My downstairs system is an old 3/4" nominal bore SINGLE pipe system with loads of unlagged sections under the floorboards. Where the rooms have concrete floors the pipe just runs at skirting level. Soon to change albeit gradually! Got a mate on the car forum runs his own firm specialising in UFH.

 

[binky]

I can tell where the pipes aren't lagged by where the cats sleep...