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DIY CH/HW Design - Thoughts? Help?


Tin Soldier

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On 18/01/2018 at 12:35, JSHarris said:

It's a good idea to fit a pressure gauge on the port on top of the pressure vessel, just remember to remove the blanking screw in the bottom of the switch/gauge port first.

Pressure gauge not pressure switch ? 

Also, if there's a EV at the lower location and the local pressure is circa 1bar higher than at the house, remember to set the back ( pre ) charge pressure in the upper vessels accordingly. More pre-change pressure for the lower and slightly less pre charge pressure for the upper EV's. 

Jeremy, I remember the Zimlet 300l horizontal I fitted a while back had a 1/2" tapping at each end, which I simply blanked off. Iirc those trappings were somehow connected to the stored water, rather than the pre charge chamber. Is that how you found yours to be?

Edited by Nickfromwales
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25 minutes ago, Tin Soldier said:

Thanks for the advice guys, yes I'll leave the pressure switch at the bottom and set appropriately

 

I don't really mind if 32mm is overkill... I just wanted to know I wasn't causing issues using it.

None at all, and tbh it'll have lower resistance than 25mm so you would ( marginally ) benefit from going bigger. Marginally. ;)

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35 minutes ago, Nickfromwales said:

Pressure gauge not pressure switch ? 

Also, if there's a EV at the lower location and the local pressure is circa 1bar higher than at the house, remember to set the back barge pressure in the upper vessels accordingly. More pre-change pressure for the lower and slightly less pre charge pressure for the upper EV's. 

Jeremy, I remember the Zimlet 300l horizontal I footed a while back had a 1/2" tapping at each end, which I simply blanked off. Iirc those trappings were somehow connected to the stored water, rather than the pre charge chamber. Is that how you found yours to be?

 

 

The 300 litre pressure vessel is going at the top pump house, so having a gauge on the top of it gives an easy check on whether it's OK, without having to trek to the lower pump house.  I have one on one of my pressure vessels, behind the door in the pump house that is in front of the electrics, air drier (for the ozone system) etc,  to save me having to open the other (padlocked) door at the other end of pump house to check.  Every time I do a check that all's well I can just glance to see if the pressure is in the right range, which is handy.

 

All the larger pressure vessels have a bladder that has a large flange that connects to the ring, secured with loads of bolts, at the bottom, which is also used to pull the bladder in and out for replacement, and a smaller tubular connection that clamps under a tank-fitting like arrangement at the top, fitted with an internal screw and O ring seal.  This top fitting does three things.  It supports the bladder vertically, so that is cannot fall to the bottom and get creased and wear, it stops the bladder from twisting in use, again to stop wear and it allows access to the water inside the bladder, so that an accurate measurement of pressure can be made.  When you buy a replacement bladder there isn't a hole in this top tubular bit, you cut it to size after fitting.   There's a description in the replacement membrane fitting instructions that gives an idea as to what these things look like inside: http://www.zilmet.co.uk/uploads/documents/38/Membranes___Flanges_V5.pdf

 

Worth noting that the general rule is that blue tanks have potable water EPDM bladders, red tanks may or may not have potable water bladders - best to check, as some manufacturers use a different material for hot water EVS, that may not be suitable for potable water.  Having said that, one of my tanks is red yet has an EPDM membrane, so is OK for potable water.

 

You're right @Nickfromwales, the top fitting is usually 1/2" BSPF, with a sealing screw at the bottom and a plastic cap over the top.  It's also externally threaded on the bit that clamps the top of the bladder to the tank and maintains the seal.  I fit a 1/2" BSPM to 3/8" BSPF adapter to the top fitting, using PTFE tape, then screw the pressure gauge to that, again with PTFE tape.  I'll try and remember to take a photo later.

Edited by JSHarris
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That makes sense now, thanks. 

If one gauge is fitted at the lower station, and another at the upper station, then the system was commissioned at say 2 bar, it would then clearly show the differential in pressure between the two heights. Handy for then setting the pre charge values accordingly. 

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  • 3 weeks later...

so

 

I've been picking my jobs - as such I'm backing away from plumbing in the heating/boiler as I'm busy at work just now and this needs to go in before the main build starts in march

 

I have a quote back from one plumber - materials list below

 

Plumbing Materials list

 

Grant vortex 36-46 outdoor module boiler

Mag one central heating filter-  requires to be installed for 5 years warranty

Oil fire valve 

Thermflow cylinder type 500l

50l expansion tank and float

4 pumps for each system  plus pump valves – rads, underfloor, oil boiler and solid fuel

Rust inhibitor for complete system 

28mm pipework and fittings 

22mm pipework and fittings

 

 

Mcdonald engineering thermflow cylinder (which is circa 2,3k) , and what looks like a beast of a boiler

 

Is 500litres big enough? the reason I ask is that another plumber about to give me a quote has recommended a 750 litre store.

 

Also, is that boiler overspecced? I don't mind paying the few hundred pound extra for a more powerful boiler, but would I regret it in the long run?

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Haven't read the whole thread but the 500l tank is slightly overpriced. Comparison we bought 500l UK manufactured stainless pressure tank with a few extras (coils etc) for less than £1400. 

Edited by Alexphd1
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Grant boiler is fine, they're what I recommend. The size needs to be spot on, and 46kw in a system boiler would do a small nursing home. 

26kw tops for a regular domestic dwelling, and deffo a TS not an UVC. Heat needs to be pulsed into the house, rather than trickle in as heat is consumed, plus you can then dictate the flow and return temp then too ( to maximise condensing ) when you pulse the heat in. 

Heating and DHW come direct from the TS, and the boiler goes direct to the TS with the boiler demand controlled via the cylinder stat on the TS. 

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I have a turco combi boiler at the moment which all the local heating engineers are suspicious of for some reason, so I'm choosing the path of least resistance which is Grant - the local company which come and fix our boiler every winter are grant through and through

 

Thanks guys

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14 hours ago, PeterW said:

Small oil boiler run hard into a 500 litre thermal store will give you gallons of hot water. Newark Copper or Telford will make you what you want - you would get change from £2K from both. 

 

 

About £1.5k for the boiler and about £1-1.2k on the TS depending on spec. With pumps and valves etc you'll buy it all for change of £3k most probably. 

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Oil boilers run at 100% or nothing unlike a gas boiler which changes it power output (example5-30kw). So this is why you are better to size your boiler and put it under load for longer burning period rather than on off on short period. A thermal store will help short cycling. Also oil boilers normally come badged ie 15/21 but come pre set to the middle kw output ie 18kw but the power is easily increased or cut by changing the nozzle, air and oil pressure. Any decent oftec engineer can do this. I personally would stick to grant or worcester oil boilers but i would sway to worcester as they have good back up in the area but would happily have a grant. 

Edited by Alexphd1
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Sounds good gents

 

Alex I'm up north of Ellon in Quilquox, near Auchnagatt.

 

I've gone back to the plumber suggesting a smaller boiler and passed on my previous quote from Trevor @cylinders2go - I've asked him to make sure he's comfortable (he should be) with what I was sourcing,

 

The saving covers the woodburning stove that I'm after, so Its definitely been worth pursuing.

 

 

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