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central heating heat loss

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Re: central heating heat loss

Postby 9fingers » 24 Jan 2018, 11:54

The sooner you get some pressure in that system the better Roger. Even 0.5 bar perhaps less will do the trick.
Soooo much easier and low pressure need not stress any old rad valve glands.

Mains water--1/4 turn ball valve--non-return valve--pressure reducing valve-- heating system. Disconnect output of header tank.
Add a pressure relief valve to your vent pipe. keep the header tank to collect anything from the prv and its overflow to the outside world if you like.

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Re: central heating heat loss

Postby RogerS » 24 Jan 2018, 12:46

Certainly food for thought, Bob. Are you suggesting that with this approach I wouldn't even need an expansion vessel?

Incidentally I've connected up the boiler heat control circuitry.

Image

Observations are as follows.

Initially when the boiler had been left to its own devices, the heat store was pretty much equal temperature top and bottom. About 73 degrees. After I switched the boiler off, I watched the temperature change and was surprised to see that top and bottom tracked each other to within 0.5 degrees or so. Not sure why that should be so.

As I watched the control circuit work, it became very apparent to me that it is the bottom stat that is really the control (I think). Anyway currently got it set to 65 degrees and the top to 67 degrees. Gradually want to reduce the temperature but doubt I will get to the point of running the boiler at 55 degrees due to inherent heat losses in the pipes. At least I'm now getting a long burn rather than the inefficient cycling.

Ideally I'd like another one of those sampling meters so I could track top and bottom simultaneously. Really crying out for an Arduino or Raspberry ( a very distant long term project so I'm after a quick win re tracking and the meter would do that....thinks...would I need a second PC though ?)


Taking up the chipboard on the landing reveals just how much of that 22mm and 28mm pipe is not lagged (and can't be as some of it was out of bounds as it were and inaccessible even when we had ceilings off etc. Tempted to have a hot air grille in the floor !

Question...how does the water at the bottom of the tank get hot ? I can't get my head round how this can happen in the absence of any 'stirring' device.
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Re: central heating heat loss

Postby 9fingers » 24 Jan 2018, 13:00

RogerS wrote:Certainly food for thought, Bob. Are you suggesting that with this approach I wouldn't even need an expansion vessel?



No sorry - I left that off my list. :oops: With all the pipe runs you have a decent sized EV would be needed but that can be dumped in the garage together with all other gubbins and the PRV outlet can just go through the garage wall. With a couple of 1/4 turn valves on the vent pipe and header outlet. you could even switch between pressurised and non pressurised at will.
However if you still have the "fresh airlock when restarting pump feature" then stick with pressurised.

In fact your old vent pipe fitted with the aforementioned valve would make a nice "bleeding" dead leg as discussed way back.

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Re: central heating heat loss

Postby RogerS » 28 Jan 2018, 12:52

Sorted ! :eusa-dance:

Plumber fitted a more powerful pump yesterday albeit much more expensive. Reasoning went that (a) we knew there was air in the system - from dissolved air in the fresh water being introduced when we hose-pipe bled but (b) the initial pump wasn't man enough to push the air out from wherever it had accumulated.

So...more powerful Grundfos pump and bingo...ran the pump at its highest speed and system worked just fine. Let it get back up to temperature and then switched it off for 30 minutes. Turned it back on and rads warmed up everywhere...upstairs and downstairs. This morning I turned it down to its lower speed and repeated the test. Again..all rads returned to normal working.

There are also several unexpected bonuses.

1) Any air in the system either goes up the vent pipe or accumulates in the top of that radiator I was using to hose-bleed. A doddle to bleed the air out now.

2) Because it's running the water through faster, means that there is less time for that central main pipe to lose heat in an unwanted area. The rads seem hotter as a result.

3) Saturday morning woke to find the trip in the garage gone. Further inspection revealed that the old circulating pump we'd pressed into service for the boiler primary circuit had burnt out. The pump we took out from indoors has now replaced it ! Just got to take the new one I'd bought Saturday morning back to see if I can get a refund. Plumber called me while I was on my way back...too late to avoid the purchase.
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Re: central heating heat loss

Postby 9fingers » 28 Jan 2018, 14:08

Good news Roger. Lets hope this is it now after a few false starts.

I've seen pumps rated at 5m head and others at 6m and wondered how much more powerful/faster they need to be for such a small change in head height.

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Re: central heating heat loss

Postby Malc2098 » 28 Jan 2018, 17:23

Great news.
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Re: central heating heat loss

Postby 9fingers » 28 Jan 2018, 17:42

Malc2098 wrote:Great news.



Seems a shame that Roger has just got it going when the weather is so mild that we hardly need any heating Eh malc? :lol: :lol:

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Re: central heating heat loss

Postby Malc2098 » 28 Jan 2018, 18:00

9fingers wrote:
Malc2098 wrote:Great news.



Seems a shame that Roger has just got it going when the weather is so mild that we hardly need any heating Eh malc? :lol: :lol:

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Re: central heating heat loss

Postby Phil » 29 Jan 2018, 07:05

Malc2098 wrote:
9fingers wrote:
Malc2098 wrote:Great news.



Seems a shame that Roger has just got it going when the weather is so mild that we hardly need any heating Eh malc? :lol: :lol:

Bob


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I see the swallows are already cleaning house and packing bags to head North in next few weeks :lol:
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Re: central heating heat loss

Postby Andyp » 29 Jan 2018, 11:23

Perseverance pays Roger. What are your opinions of the plumber now? Seems he stuck with it too, even if he was owed money.
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Re: central heating heat loss

Postby RogerS » 29 Jan 2018, 15:49

Andyp wrote:Perseverance pays Roger. What are your opinions of the plumber now? Seems he stuck with it too, even if he was owed money.



He's 'old school'. Total integrity. Hasn't even asked for the remainder. I'll remind him.
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Re: central heating heat loss

Postby RogerS » 02 Feb 2018, 14:37

The saga continues and I suspect that the solution - nay only solution - is the one that Bob has been advocating all along !

The good news is that the airlock problem has been sorted. The pump starts up and gets heat to all the rads every time. The only 'funny' as it were is that it makes a lot of noise when it first starts pumping. Almost as if its cavitation or air but then once the water is moving it goes quiet. Annoying, all the same.

The bad news is that we're getting pumping over. I came across this by chance as I popped outside and saw that the header tank was overflowing. When I went into the loft, the water was high and warm. The pump at this time was off.

So I fired up the pump to see what would happen. Lot of suction up the vent pipe, the water level in the header tank then dropped a lot ...enough for the ballcock to drop and let in fresh water.

I let the pump run for a while to ensure everything was at operating temperature and then switched the pump off. Hot water then rushed out of the vent pipe and filled up the header tank...enough for the overflow to kick in. The cycle then repeats. Obviously we are constantly introducing new water into the system which is not good, as you know.

My laymans' guess is that when the pump stops it acts as a brake to the circulating water flow and momentum in that circulating water then rushes up the vent pipe. This happens because the pump is upstairs and so there is not that much head in the vent pipe to stop this happening. If the pump was downstairs then the weight of water in the vent pipe would act as a damper and pumping over wouldn't happen. Is this a reasonable deduction?

So...solution ? I can't see how a bigger tank will help as we'll constantly be introducing air into the circuit by virtue of the water cascading out of the vent pipe in the open air.
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Re: central heating heat loss

Postby 9fingers » 02 Feb 2018, 15:33

I would try two things at the same time before more drastic action

1. Take the vent pipe as high as you can into the roof and then back down to drain into the header tank.

2. Adjust the ball valve to drop the water level as low as possible.

In combination these should help with the pump over (or lack of pump - overflow!)

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Re: central heating heat loss

Postby Deejay » 02 Feb 2018, 17:44

Afternoon Roger

Oh dear. I think your new pump, even on the lowast setting, is too powerful for the F/E tank and vent. Before you start, I'd bleed all the rad's in case any air in them is being compessed by the new pump. If it is, when the pump stops the air will expand and the easiest path for the water to go is back up the vent. If you bleed the rads, this can't happen.

The only 'funny' as it were is that it makes a lot of noise when it first starts pumping.

With the bigger pump on, when it starts, is it sucking air into the pump which it then sends round the circuit? ( see bleeding above )

If you turn off the pump as soon as the noise starts, can you hear air going back up the vent?

You could try reducing the flow with the pump isolating valves, to see if you can stop it happening, just to prove that it is sucking in air.

How much water comes over the vent when the pump stops? I see what Bob means about raising the vent, but if you're getting say about a litre of 'overflow', that's about the volume of a 3 metre length of 22 mm pipe. Besides that, you would really be treating the symptom rather than the disease.

If you measure the 'overflow' you'll get an idea of the additional height needed. That might save you a bit of effort.

+1 for lowering the level in the F/E tank, but overdo it and you might be creating another problem. If you fit a bigger ( longer and wider ) tank, for a given amount of water sucked down, the drop in level will be reduced, so the ball cock might not open. Again, you'd be treating the symptom.

If you can prove that the pump is sucking down air on startup, I'd do as Bob suggests, if only temporarily, just to prove that it will work. Gate valves on the feed from the tank and the vent and an expansion vessel.

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Re: central heating heat loss

Postby RogerS » 02 Feb 2018, 22:44

I think I will simply cap off the vent pipe. It is, after all, on a secondary circuit.
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Re: central heating heat loss

Postby Robert » 02 Feb 2018, 23:14

about the heat store.. What is the heating circuit connected to? Is it the bulk of water in the heat store (assuming it is a big tank of water) or just a coil like the one that heats my indirect HW cylinder? (you can tell I know little about heat stores)

Just wondering if the heat store could be acting as a pressure vessel to cause the volume change. If not that, do the designer rads allow expansion as in can they bulge and go back assuming there in now no air in the system.

Be interesting to see what capping the vent does.
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Re: central heating heat loss

Postby Deejay » 03 Feb 2018, 09:46

RogerS wrote:I think I will simply cap off the vent pipe. It is, after all, on a secondary circuit.


Morning Roger

If it all works as planned, I'd join the vent pipe and the feed pipe near to the pump, fit a bleed valve to the pipework and recover the tank etc.

My point about a temporary gate valve on the vent (which I think Bob suggested) was that it might be useful as you diagnose the problem.

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Re: central heating heat loss

Postby RogerS » 03 Feb 2018, 11:47

Deejay wrote:Afternoon Roger

Oh dear. I think your new pump, even on the lowast setting, is too powerful for the F/E tank and vent. Before you start, I'd bleed all the rad's in case any air in them is being compessed by the new pump. If it is, when the pump stops the air will expand and the easiest path for the water to go is back up the vent. If you bleed the rads, this can't happen.

......
Dave


I think that you're on the money, there. Capped the vent pipe and then turned the pump off. The water in the header tank gradually rose by virtue of it coming back up the feed pipe. So I agree that it has to be air in the system compressing. Trouble is that some of those rads refuse to bleed very well. I have those useless Aladdin self-bleeding valves wich are about as much use as a chocolate teapot. I do have some propoer ones but with everything else higher priority guess that fitting them will have to wait.

So it looks as if I have my own 'pressurised' system now as I've turned off the feed from the header tank and any air in the rads or pipes are my own expanson vessel. The other advantage is that when the pump turns on. it's a damn sight quieter.
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Re: central heating heat loss

Postby 9fingers » 03 Feb 2018, 12:04

RogerS wrote:
Deejay wrote:Afternoon Roger

Oh dear. I think your new pump, even on the lowast setting, is too powerful for the F/E tank and vent. Before you start, I'd bleed all the rad's in case any air in them is being compessed by the new pump. If it is, when the pump stops the air will expand and the easiest path for the water to go is back up the vent. If you bleed the rads, this can't happen.

......
Dave


I think that you're on the money, there. Capped the vent pipe and then turned the pump off. The water in the header tank gradually rose by virtue of it coming back up the feed pipe. So I agree that it has to be air in the system compressing. Trouble is that some of those rads refuse to bleed very well. I have those useless Aladdin self-bleeding valves wich are about as much use as a chocolate teapot. I do have some propoer ones but with everything else higher priority guess that fitting them will have to wait.

So it looks as if I have my own 'pressurised' system now as I've turned off the feed from the header tank and any air in the rads or pipes are my own expanson vessel. The other advantage is that when the pump turns on. it's a damn sight quieter.



I guess it is a bodge solution for now but with cap on the vent rather than the valve that both Dave and I suggested, if you ever have to drain down eg to fit the different bleeding valve, it will be a total pig to bleed as it will be come one dirty great airlock.

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Re: central heating heat loss

Postby RogerS » 03 Feb 2018, 13:53

When I say 'cap' actually it's a full-bore gate valve and so can be easily opened.

Not sure I follow you re replacing bleed vales etc. If you're talking about the ones on the rads then what I usually do is shut both TRV and lockshield. Open the existing bleed valve to relieve any pressure then remove it and replace..
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Re: central heating heat loss

Postby Deejay » 03 Feb 2018, 14:57

RogerS wrote:When I say 'cap' actually it's a full-bore gate valve and so can be easily opened.


Hello Roger

That makes sense. If I were you, until you get it sorted I'd leave the valve on the feed open a bit, just to allow for expansion / contraction when the system warms or cools.
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Re: central heating heat loss

Postby RogerS » 03 Feb 2018, 15:28

Well it's definitely going to be cooling as we seem to have run out of oil :oops: which is a tad concerning as I'd checked it not so long ago and thought I had half a tank. I'd smell it if it was leaking, I reckon. Hopefully I can get it back alight without waiting for the plumber.
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Re: central heating heat loss

Postby TrimTheKing » 03 Feb 2018, 17:00

Oooooh good luck with that! Let
Me know if you struggle as we had that issue when we first moved in and Jenx from the original Haven wrote me instructions for how to sort it.

If it’s anything like mine you have to bleed the oil through by removing the oil feed pipe...

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Re: central heating heat loss

Postby RogerS » 03 Feb 2018, 18:51

TrimTheKing wrote:Oooooh good luck with that! Let
Me know if you struggle as we had that issue when we first moved in and Jenx from the original Haven wrote me instructions for how to sort it.

If it’s anything like mine you have to bleed the oil through by removing the oil feed pipe...

Mark


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Got to get some oil first ! Just got back from a bit of ditch digging to try and get the water from off the hill. Freezes something rotten and we're running out of grit ! And the hill will need gritting for the oi tanker to get up it.
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Re: central heating heat loss

Postby 9fingers » 03 Feb 2018, 19:07

RogerS wrote:
TrimTheKing wrote:Oooooh good luck with that! Let
Me know if you struggle as we had that issue when we first moved in and Jenx from the original Haven wrote me instructions for how to sort it.

If it’s anything like mine you have to bleed the oil through by removing the oil feed pipe...

Mark


Sent from my iPhone using Tapatalk Pro



Got to get some oil first ! Just got back from a bit of ditch digging to try and get the water from off the hill. Freezes something rotten and we're running out of grit ! And the hill will need gritting for the oi tanker to get up it.


Not so much "the house in the bog" but "the house on the glacier" this time of year eh Rog?
Its quite mild dahn sowf :lol:
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