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Author Topic: GSHP UFH Circulation problem  (Read 13765 times)
StBarnabas
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« on: November 29, 2010, 10:32:24 AM »


As displayed on my greening of StB thread I have recently installed a 1000 Litre thermal store. I have about 50 square metres of floor fed by 4 ground loops and two oversize radiators. Sadly the system was installed by a plumber more used to traditional Central Heating and I have never been convinced that it was ever commissioned correctly. The flow rate through the UFH loops has never been very good but it is now almost non existent. It is currently 14.6 C in the kitchen and I am getting complaints! I have disconnected the zine controllers and opened the valves to the UFH loops wide open but with no success. The radiators are working fine and there is plenty of heat in the store.

Any ideas? Lightfoot did mention that as I am now running at 0.5 bar rather than 1.5-2 bar I might have balancing problems.

Any help welcome!

Sean
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Gestis Censere. 40x47mm DHW with TDC3. 3kW ASHP, 9kW GSHP, 3kW Navitron PV with Platinum 3100S GTI, 6.5kW WBS, 5 chickens. FMY 2009.
Ted
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« Reply #1 on: November 29, 2010, 10:48:11 AM »

Can you turn off all the rads (at least temporarily) to force the UFH as the only open circulation route?
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Stuart
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« Reply #2 on: November 29, 2010, 10:58:43 AM »

Had similar problem with my rads now that gas boiler is working.

Set CH pump to full and blasted each rad one at a time to clear any air. was working ok not great. Couldn't balance the system up.

Had a long Chat to Lightfoot, and decided to investigate the pump as i has wrote the wrong numbers down and thought it must be a dodgy weak model.
Turns out it was a good one, and luckily the TMV Had overnight packed up. reveling the problem. The filters were a bit sludged up, possibly debris settled in the boiler flow and return pipes and a drip of solder!

Left filters out, working like a good un now.
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SteveH
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« Reply #3 on: November 29, 2010, 10:59:43 AM »

 I suspect you have air problems...

 My DIY UFH install in Wales would show similar reduced flow every time I had needed to drain down for any work. it was well laid out, but the new water added would carry quite a lot of defused air in it & this would find just the wrong spot to settle.

 My solution was to selectively purge each individual UFH circuit with the pump on maximum speed... I could hear the air coming out...

 Always worked for me & worth a try....

 Steve...
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StBarnabas
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« Reply #4 on: November 29, 2010, 12:31:37 PM »


All thanks for replies
Ted I have tried turning off all the rads and it does not solve the problem. SteveH I am trying to flush the individual loops - getting all of 1 Litre per minute through one of them.


Have just spoken to Stuart and it was obvious that it would be best to post a few pictures.
I have 2 manifolds one in the garage serving the utility room and a larger one serving the kitchen


Kitchen Manifold



Garage Manifold



Pump


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Ted
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« Reply #5 on: November 29, 2010, 12:46:32 PM »

I'll try to ignore that wiring!  whistlie

How do you know the flow rate?
Is there a pressure gauge fitted on the UFH part?
Does the pump sound like it's under strain at all? 
Can you feel any heat along any of the pipes? Where does it change from hot/warm to cold?

An overall rough schematic would probably be useful.
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Stuart
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« Reply #6 on: November 29, 2010, 01:25:10 PM »

Labeled it up for you Sean,

Bet the pipes on the hot side are hot, and the flow will be low or even cold. The Gauze filters will be gunged up.

undo the big nuts 1st and the valve body will slide out (make note of the hot and cold sides! ), then the smaller nuts can be unscrewed. Mine had 2 filters.

should have took a photo when i had it apart!

I'll assume the pump gate valves are fully open  Grin

Stu


* 5217729976_087c01038f_b.jpg (113.86 KB, 1024x768 - viewed 696 times.)
« Last Edit: November 29, 2010, 02:04:00 PM by Stuart » Logged

8kw woodburner, Big piles of wood, 20 tube solar panel, custom tanks, back up gas boiler, North walls internally insulated
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Nr. Tow Law
StBarnabas
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« Reply #7 on: November 29, 2010, 02:36:11 PM »

Ted
as Stu said the flow side is hot or at least wam. The return seems cold. I attach a very rough sketch - need to find how to run PLANIX on my APPLE as all my drawings are in MS only compatible format. Yes the pump electrics do not look well connected! (Not my wiring I hasten to add)
Stu
Many thanks. Will give it a go. I also assumed the pump gate valves were fully open but will check!

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Ted
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« Reply #8 on: November 29, 2010, 04:23:07 PM »

OK, those photos start to make some sense now.

When you say the flow is hot/warm - up to what point? Just to the manifold?
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welshboy
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« Reply #9 on: November 29, 2010, 04:58:33 PM »

It might be handy to label the pics of the manifold etc to show the feed/flow to the radiators which you say are ok.
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StBarnabas
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« Reply #10 on: November 29, 2010, 06:29:15 PM »

Here is some annotation on the utility Room manifold. Hope it makes sense

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Gestis Censere. 40x47mm DHW with TDC3. 3kW ASHP, 9kW GSHP, 3kW Navitron PV with Platinum 3100S GTI, 6.5kW WBS, 5 chickens. FMY 2009.
welshboy
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« Reply #11 on: November 29, 2010, 06:37:14 PM »

Thanks for the pics.
Ours is a similar set up. ufh downstairs and rads upstairs. I balanced the rad flow by just turning the shutoff valve enough to get a flow otherwise it was starving the ufh. -taking the lazy way of least resistance. Ted suggested closing the shutting off valve - did that have any effect ?
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Ted
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« Reply #12 on: November 29, 2010, 06:59:37 PM »

I'm assuming that the 3-way valve with the red cap includes some sort of safety valve, to allow the hot flow to go straight to the return, bypassing the UFH.

Is the pipe directly above that getting hot?
Have you checked the filters in there (what a poor design!) for blockages as Stuart suggested?
What controls the internal setting of that valve? Could it have been inadvertently adjusted incorrectly? (I'm not familiar with that particular design.)
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StBarnabas
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« Reply #13 on: November 29, 2010, 08:02:01 PM »

Ted
the red mixing valve mixes some of the return with the flow reducing the temperature as there are some radiators on the system.

Have spoken to Lightfoot and he is in general agreement with Stuart that it is likely to be a blockage or airlock in the UFH sections. Though he is not at all impressed with the layout of the system!
Sean
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Gestis Censere. 40x47mm DHW with TDC3. 3kW ASHP, 9kW GSHP, 3kW Navitron PV with Platinum 3100S GTI, 6.5kW WBS, 5 chickens. FMY 2009.
knighty
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« Reply #14 on: November 29, 2010, 08:33:50 PM »

at the mixing valve is after the pump, will it not just allow the hot water to bypass the ufh circuit and go straight back down the return ?

how hot/warm is the return from the ufh ? (at the pipe just to the right/behind the mixer valve)



I think for a system like that to work, the pump should be between the mixer valve and the manifold.... so it sucks in water..... and some of the return water will re-circulate to keep the loop temperature down ?
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