I have a 22mm "check valve" I will be installing in heating system this weekend to resolve an undesirable gravity circulation issue..
On the side of all such valves that I have seen there is a Hex bolt head.
What is this for? Is this some kind of adjustment? Or does it just stop the "gubbins" within the valve from falling out!
D
Not having one to hand, I'd guess it's just the gubbins housing.
That aside, are you sure this will help? What will differentiate between the situations where you want flow, and when you don't? When you do want flow, will the circulating pump be able to provide enough pressure differential to crack the check-valve open?
I used zone valves to stop gravity circulation on my system in my old house.
What type is it? Post a link to a picture. It sounds like a swing check valve, in which case the bolt holds the spindle/hinge in place. Look on the Hattersley website for a diagram.
I put one in to stop gravity circulation from a thermal store; no effect at all. You need to ensure you don't install it between the boiler and cold feed or open vent, if it's an open vented system.
Pic here.
My Christmas present to myself was a Xcel 2009 thermal store from
Got it commissioned last weekend and found 2 unexpected gravity flows: One in the boiler loop and the other in one of the radiator loops.
DPS have recommended a simple check valve to resolve so I have acquired a couple and will install tomorrow.
Will know in 24 if it's worked!
It isn't an adjustment.
None of the single check valves I've used are like that. Your's sound like double check valves as used to prevent back syphonage in potable water installations.
Might be worth adding a not to the d-i-y faq on this one, as I'm about to add a check valve to my thermal store because of exactly the same problem.
I have a two-port zone valve on each of the heating circuits (as there are two circuits - bedrooms & bathrooms/everywhere else) - so no gravity circulation there.
But the boiler circuit is very prone to reverse circulation, and there is only the pump in this circuit.
resistance in the forward direction for an ordinary central heating circulator pump - if it works at all it's likely to be very noisy with the pump making a buzzing noise trying to overcome the resistance of the springs. You need a swing-check valve, or my be able to get away with a spring-loaded single-check valve if you can remove the spring.
Nooooooooooooooooooooooooo!
Those are double check valves, to prevent back-siphonage of mains water. Almost certainly not rated for hot water, it'll probably melt the innards.
Postpone the job. it's a waste of time anyway. I tried a check valve on a thermal store. A complete waste of time and effort. I used a zone valve.
See;
The equivalent check valve to the ones you have are Fig 249, only rated to 65 degC.
My application was a thermal store on the ground floor and a hot water cylinder on the first floor with a 3-port diverting valve controlling flow to heating and/or cylinder. The swing-check valve made no impression at all on the nuisance over-heating of the DHW cylinder. A spring check valve (like fig 49) may have stopped it, but I opted for
2 2-port zone valves.Unless the flow is reversing when the gravity circulation is happening, I wouldn't bother with any check valves for such a problem.
Thanks for this. researching now.
OK my mistake (and I feel foolish for it) is in naively walking into the local merchants and simply asking for check valves.
Your point is completely taken on the plastic innards and temperature limitations.
Looking at
Will go back to the merchants tomorrow and see if they have other technology available.
Update tomorrow!
Not as foolish as you'd have felt after fitting them. Nor as daft as I felt after fitting the 'proper' swing check valve and finding it was as useful as a chocolate teapot.
In article , Vortex5 writes
I have used one of the BES swing check valves vertically to stop reverse flow through a boiler when another heat source is operating and they are surprisingly watertight for just a machine faced brass flap. I like the swing valves as they will open to full bore if the flow is high enough.
As Onetap implies, they wont do any good if the convection path is forwards (ie opening the valve) but will be fine if it is a reverse flow problem. My system has a strainer and I put the check valve just after it to avoid any clogging problems.
If the convection flow is in the wrong direction to be stopped by a check valve can you swap the cylinder or boiler connections so that a check valve will work?
For info, the BES ones use threaded connections which are a bit of a PITA, I used an oversize valve and strainer to avoid flow restrictions and had problems with leaks on the threads of the reducer and compression adapter. The thread sealant I normally use leaked a bit and I will change it to the sealant impregnated cord that loctite do when I get a mo.
A look through the Yorkshire "compression fittings" (Kuterlite) catalogue
------
Kuterlite check valve performance for central heating and water services applications
Size 15mm to 28mm, Service temperature Min 4=B0C =3D 16 bar, Max 100=B0C = =3D
10 bar------
A double check valve is, as you say, inappropriate.
But the Kuterlite part (a common check valve, with coil spring and nylon working parts) is within spec.
It may be within spec as regards operating temperature but a spring-loaded valve is still likely to be too stiff for the CH pump to circulate water through it without it making buzzing noises.
Spring-check valves are recommended by some installers to stop nuisance gravity flow, i.e., flow in the same direction as the pump, but with the pump off. The theory is that the spring will close against the 'low' pressure exerted by gravity circulation but will open when the pump starts and exerts more pressure. How much pressure the gravity circulation exerts depends on the temperature differential and the height between heat source and heat sink. You can adjust the spring pressure on some types, so it could be made to work. I didn't try it.
I had thought that the weight of the flapper on a swing check valve would work the same way; wrong. It made no difference at all.
Do you have a manufacturers figure for pressure required for correct operation?
Here's my back of an envelope estimate:
Looking at manufacturers data for a ch circulating pump (Grundfos
15/60), a typical performance figure is pumping 0.3l/s through a head of 3m (which corresponds to a pumping pressure of about 0.3 bar).Looking next at the Kuterlite graph of pressure drop through the valve v. flow rate (single check 22mm, same link as my previous post), for those pumping performance figures - the loss would be around 0.025bar
- i.e. around a 10% loss through the valve.
Well today I took back the double check valves and purchased 2 single check valves.
28mm is on the boiler primary circuit, and 22mm is on one of 2 heating zones.Initial impression is that there is no extra noise from this setup and heating circuit "forward" gravity flow is eliminated. Have not been able to check the boiler circuit (reverse gravity flow) yet but I have no reason to believe there will be a problem.
Now I have found another problem with the second rad. circuit. When circuit
1 is pumping, circuit 2 has reverse flow "induced" through some kind of venturi effect. I had not noticed that before. Looks like I need another check valve! D
No, just experience - BTDTGTTS.
If it works for you (or the OP) fairy nuff, but be warned that IME you might have problems.
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