Non return valve failing?

johneym

Hello Lads,

Have oil and back boiler range. Heating worked fine but recently last radiators in house not heating at all. Either with oil or range.Also when oil is on it triggers the range circulation pump. If I turn off this pump the result is the same, the range heats up ie sending hot water to range. I suspect a non return valve but which one? The one on the oil or range pump?

Thanks for your help.

John.G

johneym wrote: »

Hello Lads,

Have oil and back boiler range. Heating worked fine but recently last radiators in house not heating at all. Either with oil or range.Also when oil is on it triggers the range circulation pump. If I turn off this pump the result is the same, the range heats up ie sending hot water to range. I suspect a non return valve but which one? The one on the oil or range pump?

Thanks for your help.

If you run both systems (if you can) together and if those last rads then heat up it may/might point to a problem with the stove NR valve, the fact that the stove pump (via its pipe stat?) is triggered by the oil system would also point to the stove NR valve. I assume you have checked all the obvious things like the header tank having sufficient water and bleeding the rads etc. If the stove NR valve is stuck partially open then you may find that all the rads are slow to heat up due to poor circulation with stove only i/s. Any pictures/schematic of your system would help.

johneym

Thank you John,

yes I have done all the obvious and simpler things. The rads that do heat up are indeed very slowly compared to a week ago. I have to double check today but I also suspect the boiler is heating up when the stove is on!
On a side note, would a replacement valve require a drain down of the system?
I will try and get a photo today.

Thanks again for your help.

John.

John.G

johneym wrote: »

Thank you John,

yes I have done all the obvious and simpler things. The rads that do heat up are indeed very slowly compared to a week ago. I have to double check today but I also suspect the boiler is heating up when the stove is on!
On a side note, would a replacement valve require a drain down of the system?
I will try and get a photo today.

Thanks again for your help.

John.

Fitting a replacement NR valve(s) would IMO certainly require a drain down. As you have a suspicion that both valves are suspect you might consider renewing both or at the very least checking them. You could also consider shutting off one of the oil fired boiler circ pump isolation valves with the oil boiler&circ pump isolated to prove/disprove that but the risk there is that the isolation valve seal might leak except that you have the gate type pump isolation valves.

johneym

thanks John,

just to update on this issue for anyone else with a similar problem
I changed both NR valves and seams to have done the trick. Luckily I didn't need to do a drain down as the previous plumber had fitted lots of valves including a balancing valve. Those combined with the gate valves allowed me to do it.
The little nuts on the NR valve I presume is for air? When and how is it used. I have the boiler on at the moment but I am sure both systems will now have air. It's an open vented system. Or is it better to allow air to escape by bleeding radiators when hot?
Thanks again.

John.G

johneym wrote: »

thanks John,

just to update on this issue for anyone else with a similar problem
I changed both NR valves and seams to have done the trick. Luckily I didn't need to do a drain down as the previous plumber had fitted lots of valves including a balancing valve. Those combined with the gate valves allowed me to do it.
The little nuts on the NR valve I presume is for air? When and how is it used. I have the boiler on at the moment but I am sure both systems will now have air. It's an open vented system. Or is it better to allow air to escape by bleeding radiators when hot?
Thanks again.

Glad to hear you are sorted and thanks for the feed back.
Don't know if you have poppet type or swing check type NR valves but I'm pretty sure that you can't bleed any air there. I normally bleed the rads, especially upstairs with the system off, both cold&hot as some of these rads (one in my case, in the attic conversion) can run with a negative head and actually draw in air if the vent is opened with pump running, at any rate if you vent them with the pump running and you get water out of them all then you are OK.
What was the condition of the NR valves?, the poppet type have a guide and if OK you should be able to push the shaft in/out and it should re seat under spring pressure, the swing check normally will close under its own weight but some are spring loaded.

johneym

john, I think it's poppet type valve. Spring loaded. One was very manky and getting stuck as it pushed in and out. A good clean might have done the trick but they are cheap anyway. The other, the plastic part had a crack in it. Only 2 years old so I am thinking I probably need to flush system in the summer and add some inhibitor like MB 30 or something. Might be lot of grit or something in system. I know radiator pipes were left uncapped for months as work went on here. Not good. You are a good help and I really appreciate it. Pic of screw on NR valve below.

John.G

johneym wrote: »

john, I think it's poppet type valve. Spring loaded. One was very manky and getting stuck as it pushed in and out. A good clean might have done the trick but they are cheap anyway. The other, the plastic part had a crack in it. Only 2 years old so I am thinking I probably need to flush system in the summer and add some inhibitor like MB 30 or something. Might be lot of grit or something in system. I know radiator pipes were left uncapped for months as work went on here. Not good. You are a good help and I really appreciate it.

Thanks, attached a few photos for anyone's interest.

John.G

johneym wrote: »

john, I think it's poppet type valve. Spring loaded. One was very manky and getting stuck as it pushed in and out. A good clean might have done the trick but they are cheap anyway. The other, the plastic part had a crack in it. Only 2 years old so I am thinking I probably need to flush system in the summer and add some inhibitor like MB 30 or something. Might be lot of grit or something in system. I know radiator pipes were left uncapped for months as work went on here. Not good. You are a good help and I really appreciate it. Pic of screw on NR valve below.

That,s interesting, if that,s a picture of the newly installed one I wouldn't chance opening it but if its the old one or the old one is identical it would be interesting to know if it is actually a air vent or to allow the internals to be removed.