Central heating – creative thinking needed!

Is paulosoxo or Stoner around please, indeed anyone as I really don’t know what to do.

First Winter in house (20 years old) and central heating was not working properly. I’ve had some work done – changing bathroom radiators, moved CH programmer from upstairs to downstairs, new digital room thermostat.

There is a large ground floor extension that has increased the downstairs size by around two thirds. Standard boiler (Alpha) was put in yonks after extension was done.

Downstairs does not heat up and only gets to within around 5 degrees of what room thermostat is set to. I’ve spent a lot of money on having a power flush done (very hard water here), radiators being balanced etc. and there really is no difference.

Extension has three radiators, two of which are large. Virtually no heating is getting to the extension. The extension is the furthest point away from hot water tank in loft.

I have complete confidence in my plumber but he is now totally baffled and has suggested an Alpha specialist plumber to take a look. He did however say that micro-bore pipework is not good.

I’m almost thinking that the extension needs its own separate heating system!

Your insight would be most welcome. 🙂

So are the radiators getting hot, but the space doesn’t seem to be warming up or are the radiators not actually getting any hot water to them?

Do you know if the boiler has a high enough btu rating to meet the output levels of all the radiators that you have? We just had a load of original radiators in our house replaced with new ones that are able to put out much more heat. We had to be quite careful about how large we went with the radiators as we were getting close to what the boiler could achieve.

I don’t really know much about central heating systems. Only what I have gleaned from internet research and asking questions on here about my own problematic installation.

Do you have two different pipe sizes in your house? Perhaps narrower pipes in the extension? If so, could the water be taking the path of least resistance and tending to stay in the ‘original’ system, rather than going around the pipes in the extension.

Have you tried turning all the rads off in the rest of the house to see if the extension then gets hot?

I was just thinking the other day how you don’t see much microbore these days.

We rent an old farm house with terrible heating I have been trying to sort out. What happens if you close off all the radiators other than the extension to force the hot water to them? Was the only way we could bleed our house properly and get some heat to the rads on the ground floor furthest away from the boiler and tank. We had lots of air locks caused by the pipes running up and down and round and round – a bit of a mess really.

stumpy – thanks for the reply. One radiator in the extension, if heat gets through, only warms up halfway up and halfway across, if that makes sense!

Radiators in the extension have the vents above. Have had TRV’s put on all radiators. Even if I set the thermostat (in lounge) to say 30 degrees, room only heats to 25 degrees if I’m lucky.

I think there’s micro-bore everywhere and suspect, possibly incorrectly, that whatever boiler is there won’t actually make any difference.

I just don’t want someone to try and con me into replacing with a condensing boiler which won’t actually fix the problem.

I’d agree with stump01, follow the logical sequence. If the radiators are of appropriate size for the room, are getting hot but the room is still cold, we can dismiss the radiators as being the problem. Check that the rads are the correct size.
If so, then the room is probably poorly insulated and this will be the area to focus on. Is there a lot of glass in the extension? Does it have adequate double glazing? Is there cavity wall insulation? Roof insulation, if there isn’t another room above?

You say it’s been balanced but it sounds like a balancing problem or pump capacity problem, the water sounds like it’s not being circulated to that part of the circuit (the extension).

Try turning the balancing valves on some of the rads that get hot down, count the turns so you can set them back. this may force the water to the rads that dont heat up.

cinnamon_girl – Member
One radiator in the extension, if heat gets through, only warms up halfway up and halfway across, if that makes sense!

So the top half doesn’t get warm and the warmth only extends half the width?? If so, it sounds like that radiator needs bleeding? Do you have a bleed key? If so, it’s easy enough to bleed and see if you get loads of air out. You can get bleed keys from somewhere like B&Q. Bleed the radiator with the system off.

Radiators in the extension have the vents above.

When you say vents – do you mean the clip on cover, on top of the radiator?
Are these radiators double panels with convectors (wavy fins between the panels)? Or single panels with convectors?
When we were looking to replace the radiators in our systems – the output capacity of the double panel rads was massive.

As in my original post. Have you tried turning all other radiators off (via the TRVs) in the house and seeing if the extension gets warm? If you do this and the extension does get warm, then at least you know that this circuit has the ability to heat the area, even if there is something at the moment stopping it from doing so when the rest of the system is also functioning.

Another thing to try, is turn off all radiators completely via the TRVs. You should have one system that doesn’t have a TRV on it (usually hall or bathroom), so you can’t really shut that one off.
Turn the system on and then open one radiator at a time so you send almost all the flow solely through that radiator. If you have any air locks, this might purge them out….? This was recommended to me by someone on here a while back.

In the first instance are there enough rads to heat the room. To be sure a room is toasty I normally allow for 200 btu/hr per cubic meter, so how big is the room? Then measure your rads size and types (how many panels, double or single convector) and compare with output of similar size and type rads . It may be that the rads do not have enough max output.

If the design is right then look at boiler capacity does it put out enough heat to meet the demand of the whole house, it may be that its just not big enough.

If the room rads are enough and the boiler has enough capacity then look at the suggestions above.
If the calcs are too much then just measure the rooms/rads post here and we will help. Its only a few minutes work.

If the plumber is stumped then i would have thought he has already bled the radiators. It sounds like a circulation problem and if you have microbore you could have a blocked restricted manifold/s (where the pipes branch off to different radiators) also microbore is very difficult to powerflush and often won’t work if system very ‘sludgy’. if you have/have had a sludgy system there is sometimes a return filter on alpha boilers (which model is it?) that can be restricted or blocked and this will affect circulation.

Alpha boilers – Rubbish but shouldn’t be your problem.
Microbore – Rubbish and in a hard water area could be your problem especially if inhibitor was never put in or topped up.

Repipe to the extension.
Investigate pump size (what is it there should be numbers on the head of the pump)

How many rads, what size. Measure them up and refer to a table from Myson and Stelrad and tell us what the total output is and maybe also the output in different areas of the house.
What boiler is it and how much output.
What size pipework can you find and where?

Outputs in watts please.

As said above. Turn off all the rads except the ones that don’t work and see if it will force it round.

Likely scenario is old pipework then house extended and tagged onto the end of the old system then boiler replaced.

We had to have an old pump replaced as the impeller fins had worn down – pump was running fine but wasn’t moving much water. New pump made a big difference.
Just another thought

Thanks again. 🙂

As soon as I switched on the central heating, I bled all the radiators. Twice in two weeks. Plumber has tried forcing water around, has been very thorough in all his work.

Have had extra insulation put in upstairs loft and downstairs loft looks well insulated too. Also draught excluders on all downstairs doors. Double glazing is not brilliant and have on order some heavy duty curtains and Roman blinds to add to vertical blinds.

Lounge has two smallish radiators but has stairs in it. In fact one radiator is right by the stairs. Also one window on each of the three walls. Total of 12 radiators in house.

Plumber suspected system had never been de-sludged before and it did look pretty disgusting! Water rated as extremely hard by water company (chalky area).

tomlevell – plumber did hint that Alpha boilers weren’t brilliant nor was micro-bore. Would a condensing boiler work any better? Will check out Myson & Stelrad. Thanks for your help.

Worth trying to force the heat round yourself.

Turn all the TRV’s or wheelheads to off and your not messing with the balancing that has already been done.

A new boiler won’t sort anything if you can’t get the heat to the rads in the first place. Although if it’s got the pump built in to the old one it might fix it but changing the pump head in the old boiler would also fix it in that respect.

If the heats not getting to those rads it’s a pump/circulation problem first.

cg, measure the rooms and rads, and tell us the type of each rad (single or double panel, single or double convector) and the boiler model.

OK, some measurements and all these are single panel.:

Room 2.30m x 1m. Rad 48w x 60d.

Room 2m x 0.9m. Rad 48w x 60d.

Room 5m x 5m. Rad 112w x 60d. Rad 187w x 40d.

Room 5m x 3m. Rad 180w x 40d.

Room 4.5m x 3m. Rad 95w x 60d.

Room 3m x 3m. Rad 64w x 60d.

Room 3.35m x 3m. Rad 64w x 60d.

Room 1.85m x 1.85m. Ladder style rad 60w x 110d.

Extension with double convector in both:

Room 3m x 1.5m. Rad 90w x 60d.

Room 5m x 5m. Rad 140w x 60d.

Room 2m x 1.7m. Ladder style rad 60w x 110d.

Boiler Alpha CD18R.

I’m finding out that things are a little shonky in this house, corners have been cut by using cheap and cheerful. 🙁

Thanks again. 🙂

ceiling height I am assuming is regular 2.4m?
If so then at my 200 BTU/hr (or 58W) then the rooms go like this .
EDIT CHANGED TO WATTS
323.55
253.21
3516.85
2110.11
1899.1
1266.07
1413.77
481.46

633.03
3516.85
478.29

Total
15.8Kw

So thats 15.8kws and the boiler is an 18 kw. So just about good enough, although I would prefer more headroom on the boiler.

Just working out the rads for each room now.

Rads assuming double means doubl panel single convector all in watts from this website here. All in watts

490
490
1176 +1300
1764
1000
600
600
600

1211
1883
600

11714

Ok first thign is that the 2nd extension room (5mx5m) requires 3516 watts but the rad only outputs 1883 watts. So its about half the size required. Even if we go to a double convector at the same size its max output would be 2425, still 1000watts under your needs.. Fit a bigger rad in this room, like this one, which is 2 metres wide, and still a couple of hundred watts under. You could try two rads rather than one.

TBH I suspect this is the root of the problem, massive room, undersized rad..

NOTE there is also undersized rads in the other 5mx5m room, not the extension.
Edit doh, just seen you have said double convector.. Anyway its still undersized..

Hi I install central heating all day every day.
firstly boiler make and size. alpha is nt a bad make more than capable, secondly capacity. the current thinking to be energy effcient is to have smaller size boilers as they use less gas but take longer to heat a room ( worcester bosch actually now come with a replacement chip when new so you get full heat for the hot water and only half heat for the central heating .. basically put)
you ve twelve rads from my basic adding up which is a lot especially if all are piped on copper micro bore. simply the volume of water travelling to a radiator is very small compared to a std. 15mm copper or plastic pipe so the water will cool quickly and take significantly longer to heat a rad.
having said that you heat the water, which we assume the boiler is doing and you pump it round then the rads will get hot the water in them might reach 70 degrees c with all other things ben okay.

if a rad is hot all over something is wrong either it has air in it, sludge in it water is restricted entering or exiting itor it has no water in it.

i suspect that the later is the case. when cold does air exit the rad when you bleed it? i suspect that if its a conventional system boiler that the feed from the f and e tank is blocked and restricting the water getting to the system.

as always very hard to diagnose over the phone never mind lurched over a keypad..

toys – brilliant research, thank you so much. 8)

Yes, agree about the rad in the extension, really is too small although it’s obviously a kitchen but with 3 windows!

As regards the other similar sized room (lounge), I did express concern to my plumber that it wasn’t sufficient to which he said quite likely but see how it goes first. Might be worth getting a quote from him anyway.

During the evening, I keep all the doors to the upstairs rooms closed to ensure heat was not being lost.

Sounds as though it’s worth getting the boiler checked out to see whether the pump is the problem.

Thanks to all for comments and advice. I knew I could rely on STW! 🙂

Good info there toys. This could turn into a “How a woodburning stove solved my heating problems” thread!

I did express concern to my plumber that it wasn’t sufficient to which he said quite likely but see how it goes first.

That’s not the best reply – expensive way of doing things. Do it once and do it right first time. 😐

toys19 – a bigger radiator wouldn’t solve this though, would it?

cinnamon_girl – Member
…One radiator in the extension, if heat gets through, only warms up halfway up and halfway across, if that makes sense!

Should the radiator not heat evenly, even if it’s too small to heat the room?

Not sure if this refers to the rad in the large room or not though……

I’m just a lowly engineer, my brother is a plumber, he always starts with a sizing exercise, takes 20 mins to measure and calc and tells you what you need to buy..

So I have done the same thing with my 4 houses, fitted central heating in each one, by working out rad size for each room, and then boiler required. Easy peasy..

Stumpy, aside from the technical issues in the house, I just wanted to be sure that everything was sized correctly, it obviously isn’t.. Those bleeing/flow issues still need to be solved, but even if they are the room will still be cold because of undersized rads.

I agree that this

I did express concern to my plumber that it wasn’t sufficient to which he said quite likely but see how it goes first.

is bollocks from your plumber, he could have just done the calcs and specced the right size rad for the room. Job done.

Stumpy, aside from the technical issues in the house, I just wanted to be sure that everything was sized correctly, it obviously isn’t.. Those bleeing/flow issues still need to be solved, but even if they are the room will still be cold because of undersized rads.

Yes, of course. A sensible thing to do; check whether the system is capable of heating the house, all being well & good.

Does seem a bit lame that the plumber suggested to just suck it and see with the undersized radiator.
Perhaps speccing a larger one would have meant floorboards up & pipes moving? When we replaced our radiators, we tried to look for sizes that meant we wouldn’t need to move pipes.

Perhaps speccing a larger one would have meant floorboards up & pipes moving? When we replaced our radiators, we tried to look for sizes that meant we wouldn’t need to move pipes.

No reason to move pipes under floor boards, just elbow off existing pipe above floorboards and extend to new length.

“Even if I set the thermostat (in lounge) to say 30 degrees, room only heats to 25 degrees if I’m lucky.“

And I thought Madame was frileuse. How about buying some long Johns and a woolly pully.

The plumber was trying to be helpful. He didn’t install them and you may find that they do heat the room if the radiators actually got hot therefore saving them money.
Getting the rads hot being the main point.

You need to try and force the heat round. Just leave one rad open and then try opening the others in the same area and see what happens.
Then the pump needs investigating. If your brave you can open the head up and have a look at the impeller.

No reason to move pipes under floor boards, just elbow off existing pipe above floorboards and extend to new length.

Now who’s the cowboy ;0)

“Even if I set the thermostat (in lounge) to say 30 degrees, room only heats to 25 degrees if I’m lucky.”

And I thought Madame was frileuse. How about buying some long Johns and a woolly pully.

I missed that. If your talking celsius you have no chance. Most systems are designed to 21degC at a outside temp of -3degC

Now who’s the cowboy ;0)

Decent plumber can make a nice bend in the copper, happy days. Personally I like it, think its a nice feature. Nothing cowboy about it. Anyway I aint a plumber and just trying to help.

Have you checked the pump is running at full speed?
Have you played with the water ( rad ) temp on the boiler ?
Surely fitting a massive rad in the extension will then leave an undersized boiler ?
HAve you done the nails in a jar test to see if you have enough inhibitor in the system?
Do you have a non TRV rad / towel rail that acts as a bypass if all the TRV’s shut down ? and does this get toasty ( too hot too handle) hot ?
Not a plumber so std stw disclamier insert here . . .
trying to help
btw you dont switch it on as you get home and try to heat up the house instantly?

Surely fitting a massive rad in the extension will then leave an undersized boiler ?

Not if you have actually done the calculation..

If this problem is fixed, will it lead to wandering about in underwear?

I’m always on here in my pants – where do you want me to go ?

OK, thermostat was set to 20 degrees and a quick check of the downstairs rads results in the large kitchen rad having less than a quarter heated. Utility rad has no heat and shower room has a little warmth.

Not quite warm enough for me to sashay around in my AP. 😉

I will defend the plumber – he’s independant and, as tomlevell said, was being helpful. Not spending money if not necessary. Of course, if it had been British Gas or someone similar, I would need a new all-singing all-dancing boiler and all radiators replaced due to being dangerous! Plus a compulsory £50 per month service contract for naff all.

First step I think is to get an Alpha specialist to check the pump.

Huge thanks for all the helpful replies, the funny ones too.

To be continued…

you know, not mentioned anywhere above, but has the plumber had a look at the expansion vessel on the boiler, it this isn’t working right all the symptoms fit, anfd as long as the vessel is still ok may just need repressurising which can be done with guess what…………..a bike pump

WAYYYY to many generalisations going on here!

you can only heat loss a property correctly knowing room volumes, wall sizes, window sizes, no of outside walls, is area above heated, floor, ceiling, wall, window and door construction. Any open fires as that will increase ventilation losses. I usually draw a floor plan and note all the height and construction info on it. From that I can reasonably accurately heat loss the building.

After than you can come up with a schematic isometric line drawing from which you can start to pipe size the building.

Once you have done that you can work out the index circuit and therefore pump size.

From the radiator sizes and pipe loss figures you should be able to come up with a boiler size.

So your problem could be any one of several, but my first question is were the extra radiators added to an existing microbore circuit?

Oh and systems are designed with an outside of -3 and living areas at 21, giving a difference of 24. If the outside air temp was 6 then in theory 30 would be achievable. However we used to work with a -1 figure, so it might not……

Yes, I would assume that the extra rads were added to existing micro-bore system.

The hot water tank etc is above a bedroom at the front of the house. The extension is actually at the other side of the house, on one side not the back, so there is a distance.

I am just assuming that once again it has been done in a shonky manner to match the bathroom light that used to switch itself off when you were in the shower, the ceilings lights in the kitchen that don’t all work and it’s not the bulbs either etc etc.

So you now have 2 or 3 radiators running off a section of pipework that used to serve only one radiator? Also from the sound of things this pipework is a fair way from the pump in the boiler?

This could be your problem. The microbore pipework is not of sufficient size to deal with the extra load additional radiators are putting on it.

Bear – the boiler is in the kitchen which is the extension. My gut feeling (read female logic) is that due to this being a chalky area with extremely hard water, as you say the micro-bore is too small.

My 4 year old washing machine needed a new element and I’ve only lived here for 6 months! Even the (Miele) engineer was surprised.

The plumber spent a whole day power-flushing, he came back the next day to balance the rads.

It is very frustrating to be paying such high fuel bills when the house hasn’t even been very warm!!

My system was always slow to heat. It had microbore everywhere off the main vertical pipes. So runs of 20 feet or more.

Plumber replaced all piping with normal size (15mm?) and removed and renovated the existing 20 yr old boiler. Problem solved. Cost a few quid but system has been good ever since – 10 years or more.

He said anything over 6 feet was too far for microbore – and this is a soft water area.I think the microbore will be a large part of the problem.

Not read it all, as I need to go to bed.

Email in profile if needed.

+1 with Bear. Teeing into a 8/10mm run to add on never really works.