Irish Heating Systems ... Question (s)

Billysven

Hello all. Ive been a plumber for 30 odd years, UK and then Australia. I'm now in Dundalk (don't ask :-) ). Not been on the tools for a few years but have been asked to look at a few jobs for friends and family.

My partners Mam has oil fired heating system. Open pumped circuit (always 'ON" ) to HW cylinder and a switchable 2 port valve to open up the heating.

No stats (apart from boiler)

Problem is 3/4" flow to Cylinder getting hot but not returning to boiler. Pipes go up vertical maybe 3m, across the roof void and then drop down to a new HW indirect cylinder . Checked for air locks , no problem. Apparently It has worked in past. Only thing I can think of is pump has lost its guts and can't get up and over the roof space... but I'm not convinced.

Any ideas?

The other thing Im having trouble understanding is there is a F & E tank fitted and also a pressure vessel in boiler room? The 1/2" cold feed to system from tank has a check valve on it?

Surely the F & E tank is there to take up the expansion, top up system and facilitate venting?

Back in the day I regularly Installed gas fired heating, 3 port valve (or 2 two port) with either a F&E tank or a sealed pressurised system with blow off valve ... but never mixed?

Any help greatly appreciated

Cheers

Bill

John.G

Hi Bill, welcome back?.

That semi sealed system is common enough in this neck of the woods, it should normally be set up as follows, Swing check NRV installed in cold feed, E.vessel pre charge pressure 0.3/0.5 bar, vent blanked, when system is cold then the system pressure will be at the static head, say ~ 0.3/0.5 bar, when the system heats up the system pressure will increase and the EV will take the expansion volume. I assume the F&E tank is higher than the pipes you refer to above? Check that the NRV is clear and not leaking back, I don't like poppet type NRVs (if fitted) I would suggest changing this to a swing check installed on the horizontal and see how you get on, also a pressure gauge installed near the boiler or EV wouldn't go amiss.

Should also have said that there must be a 3 bar PRV (safety) valve installed on the boiler, 2.5 bar on some boilers now, including Grant I think.

Billysven

Thanks John

That makes sense now but I can't figure the reasoning for this system? Why not rely on an FE tank within open vent and cold feed/exp? or Sealed system with a top up valve.

Anyway thats been a big help. I haven't been back to her house yet but if I remember the NRV is vertically installed. Is there anyway of telling with type it is without removing?

The FE tank is probably a metre or so above the highest pipe run and another metre above the NRV. I was thinking if 2 metres static head was enough to 'open' the NRV

Cheers again,

Bill

PS I'm a Londoner so not really 'back' , went out to Perth 2005 and ended up as a plumbing inspector. No heating there! During the summer up north they used the insulated HW storage tanks to keep the water COOL as the incoming mains would get so hot! Ive seen some crazy stuff ;-)

John.G

The open vented system works well in most systems like my 40 year old one but some suffer from vent pump over or cold feed pump back leading to air ingress and sludge & corrosion build up, sometimes caused when the circ pump is renewed as these are generally now more powerful. A sealed system with top up valve is probably the "right" way to convert but the semi sealed, as long as the EV pre charge pressure is kept at ~ 0.5 bar will give the lowest possible pressures which are not as hard on older plumbed
systems, some wouldn't dream of converting to semi sealed, only fully sealed.
The NRV is almost certainly the spring loaded poppet valve as the normal swing check would just hang down fully open and never close. 2 meter static head should be enough to open the existing one but I would certainly be inclined to renew it or be satisfied that is is tight.

Billysven

Thanks again John, very helpful