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Buffy330

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Hi

my really old large house used to be a real mess in terms of several old heating systems that were cobbled together and extensions to it.
Not to mentions redundant pipework from Back boilers and a Rayburn/Aga style device in the kitchen.

Now - I have the original gravity fed Potterton Kingfisher2 floorstander - and Im happy with this .
22mm flow/return from the boiler to the rest of the system - all new.
Downstairs - I have 22mm feeding 3 radiators off the flow / return.
Upstairs , I now have a new 22mm single run of flow/return with no spurs , just feeds to upstairs radiators and drops to the remaining downstairs radiators.

Total number of radiators is 18 !!!

The system is pumped by a Grundfos UPS 15-60 130 pump.

The only 15mm copper is is from the flow/return to the radiators.

Now I have bought a thermo gun ( Bosch ) to measure the temps of each radiator in order to balance them , but my problem is what seems to be a lack of flow.
At no point does the drop in temp across the flow and return pipes mirror what is acceptable , therefore I am suspecting poor flow.
In fact the return is pretty close to cold !!!

All new pipes , new valves , new radiators and a filter ..... but sometimes when I open a bleed screw , all I get is slight dribble.

Any pointers please ?
The pump is only a couple of years old and I bled that too

Many thanks for reading this

Steve
 
Your boiler will have its output on a data label somewhere,
Measure all you radiators then find there outputs by using rad size list (lots online if you look)
 
I’m guessing it’s open vent eg tank in the loft also ?
 
exedon2 said:
Your boiler will have its output on a data label somewhere,
Measure all you radiators then find there outputs by using rad size list (lots online if you look)
Click to expand...

I have added up the value of the radiators and it comes to 112609BTU
The picture is from the boiler


20191112_172318.jpg
 
Hmmm, I'm not an expert here, I've got 13 rads, pump speed is on 2, boiler output is 26kw. It could be a combination of not enough flow and an under-sized boiler. Yours is between 23-29kw which feels a bit marginal to me for 18 rads.

How about closing off all your radiators apart from the one at the end, then open the bleed screw and see what comes out, you should get more than a dribble that's for sure, mine hisses and spits and it generally Sodes out when all the air is gone. If you open the lockshield all the way you'll get maximum flow through the rad, that will prove that the pump has enough oooompf to push the water that far. Tighten the lockshield until you get your temperature drop. If that rad gets nice and hot with all the other rads closed then it might be a case of rebalancing them all.
 
On the face of it your boiler is undersized I take it it also heats your hot water? If so add 10000 btu.
Is the boiler set at maximum? (Needs a G S R engineer to check.
 
Just throwing this out there. You said it’s all new pipes. Who ran the pipes? Are you sure the 22mm flow/return are not joined at the furthest end?
 
Looks to me you have a heat load of around 36kW
With a boiler that can do 29kw tops (this is without allowing any sort of margin)
Most of your rads (15) are on a 22mm circuit you seem to be pushing the limits in all directions.
I'm not saying it can't be made to work but you will struggle with current layout.
 
Rad(s) outlet are "cold and if one assumes say 30C then with a flow temp of 65C the heat output is only 46% of a "50 deg" rads so, 112609*46%, 51800 Btu, 15kw. If the boiler is reaching its target temperature then boiler not at fault?.
If the pump is A rated then if a energy monitor available to measure the pump power in watts, the flow rate can be derived from the pump curves.
 
I would say that your pipework is undersized. Heating pipe sized at 22mm will only carry approx (very approx) around the mid 50,000 BThU's/hr in my experience on an open vented system. Obviously I have not seen this so I am imagining the system using your description.

We need to know the output from emitters to determine the provisional pipe size amongst other things. I would expect 28mm as a minimum with that boiler.

Like I say, I have not seen it but an experienced heating engineer will be able to tell you on site better than anyone who has not seen it in the flesh. If the pipework is undersized, there is no point looking any further.

Did your heating engineer not calculate these things prior to re-piping?
 
Last edited:
Last Plumber said:
I would say that your pipework is undersized. Heating pipe sized at 22mm will only carry approx (very approx) around the mid 50,000 BThU's/hr in my experience on an open vented system. Obviously I have not seen this so I am imagining the system using your description.

We need to know the output from emitters to determine the provisional pipe size amongst other things. I would expect 28mm as a minimum with that boiler.

Like I say, I have not seen it but an experienced heating engineer will be able to tell you on site better than anyone who has not seen it in the flesh. If the pipework is undersized, there is no point looking any further.

Did your heating engineer not calculate these things prior to re-piping?
Click to expand...

22mm at a DT of 20°c and a target velocity of .9 m/s will carry about 25KW.
It seems there's a lot wrong with this system, boiler size, pipe sizing etc. I wrongfully didn't read all of the above before posting my comment.
 
SJB060685 said:
22mm at a DT of 20°c and a target velocity of .9 m/s will carry about 25KW.
It seems there's a lot wrong with this system, boiler size, pipe sizing etc. I wrongfully didn't read all of the above before posting my comment.
Click to expand...
True story! I wouldn't do it though, would you?

I personally would have used 35mm provisional pipe size for a 33 Kw system even though the boiler is a bit undersized but that is just my opinion on it based on my experience. I would want to see an 11 degree temperature differential on that boiler and avoid unnecessary noise. We all do things differently though I know.

There are all manner of things that come into this but if the pipe size is too small then there is no point diagnosing anything else until it has been corrected. The pump should be sized accordingly once the pipe size is calculated out.
 
Last Plumber said:
True story! I wouldn't do it though, would you?

I personally would have used 35mm provisional pipe size for a 33 Kw system even though the boiler is a bit undersized but that is just my opinion on it based on my experience. I would want to see an 11 degree temperature differential on that boiler and avoid unnecessary noise. We all do things differently though I know.

There are all manner of things that come into this but if the pipe size is too small then there is no point diagnosing anything else until it has been corrected. The pump should be sized accordingly once the pipe size is calculated out.
Click to expand...

I agree totally with you, was just pointing out what 22mm could carry at those numbers, I hadn't realised at the time it was a standard efficiency boiler, which makes 22mm capable of less. Ultimately any size pipe can carry any amount of power, its just at what flow rate and DT.
Like you say, the boiler is undersized and the pipework is wrong. The installer really should have known this stuff, realistically one should rip out and start again.
 
SJB060685 said:
I agree totally with you, was just pointing out what 22mm could carry at those numbers, I hadn't realised at the time it was a standard efficiency boiler, which makes 22mm capable of less. Ultimately any size pipe can carry any amount of power, its just at what flow rate and DT.
Like you say, the boiler is undersized and the pipework is wrong. The installer really should have known this stuff, realistically one should rip out and start again.
Click to expand...


My sentiments entirely!

It is unfortunately something that happens too often isn't it? I just can't work out why it does.
 
Last Plumber said:
My sentiments entirely!

It is unfortunately something that happens too often isn't it? I just can't work out why it does.
Click to expand...


Unfortunately you are right. There's too many people out there who take on work like this without the neccessary training and knowledge and its both dangerous to the end user and the industry.
Unfortunately for the OP the resolution to this problem is not an easy or cheap one.
 
SJB060685 said:
Unfortunately you are right. There's too many people out there who take on work like this without the neccessary training and knowledge and its both dangerous to the end user and the industry.
Unfortunately for the OP the resolution to this problem is not an easy or cheap one.
Click to expand...
Yes and the temptation is to continue down the road of trying to make it work. Like everything else, the foundations are crucial to all that follows.

On a more optimistic note and hopefully to give a glimmer of light at the end of the proverbial tunnel to the OP. It will probably be the initial run from the boiler which needs upgrading. Once you get down to say 16 Kw or roughly 55000 BThu's, you could leave the copper alone and use the right size pump if that one doesn't cut it. I would have been tempted to look at a slightly larger bore pump with the same head but that needs calcs.

One other thing. I have been presuming all this is in copper tube which has a larger bore than plastic. If it is in plastic (apart from the 15mm copper mentioned) then it will need to be assessed with that in mind.
 
I just wonder why you would go to all the trouble of new (undersized) pipework and not bother having 2 or more zones? Yes more pipework but immediately cuts pipe size except close to boiler.
Also is the (undersized) boiler achieving its rated output ? it has after all a elderly cast-iron heat exchanger.
 
exedon2 said:
I just wonder why you would go to all the trouble of new (undersized) pipework and not bother having 2 or more zones? Yes more pipework but immediately cuts pipe size except close to boiler.
Also is the (undersized) boiler achieving its rated output ? it has after all a elderly cast-iron heat exchanger.
Click to expand...


I think its safe to say whoever did the work really doesn't understand the basics. I appreciate that's probably not what the OP wants to here but it's evidently true.
Personally I would advise the homeowner to rethink and consider upgrading the boiler and having someone capable to undertake the work.
 
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