Is it? Circulation pump / boiler stat / blockage / air?

[Ookysoft]

Further to :-

//www.diynot.com/forums/viewtopic.php?t=159928

I replaced the boiler stat which I don't trust as the old one would not consistently start the boiler when cold enough and was asked for. I have a 20yr old Camray 2 - the guys at Part Center gave me a stat which they say others use as the Camray part is not available. The 'bulb' fits the hole so I guess it's ok - however, the old one ranged to 88 degrees & the replacement max's out at 77 I think.

The old one was set to 88 even though I thought I ran it cooler.

The circulation pump wasn't pushing the water far enough to heat the cylinder within a couple of metres of it. I may well have cooked it while by-passing the thermostat to get some water warm [ got steam in the boiler & air rushing through the vent pipe ] - it wasn't a problem before.

I've ordered a new pump but in the meantime have stripped, cleaned and reassembled it & it runs better now.

Here's the question:-

Some of the downstairs radiators [closer to boiler] are hot & others are cold. Is this likely to be the water losing it as it's not starting out at a high enough temperature? [ Kinda think the cold ones would be tepid at least ]. The pump is no longer man enough to push the water far enough around? A blockage there somewhere [ all water seen so far is black ] or maybe air in a pipe somewhere [ kinda thought air would still be pushed around ]?

 

[crockett]

If you mean that you've stripped and cleaned the pump, as sure as night follows day you will continue to have problems with it until you replace it I'm afraid. Once a circulating pump starts to fail, it's on the slippery slope.

 

[Ookysoft]

Yeah! Kinda guessed that one.... So the pump's probably not pushing it far enough! If it's been in as long as the boiler, I guess it's not done too bad! Thank you for your reply!

 

[sambotc]

Water will take the path of least resistance so it's common for some radiators to be stone cold (and not tepid)

Make sure when you change the pump you drain as much of the water as possible from the system. Fit the new pump and refill adding sentinel x400 or similar sludge remover. run for up to 8 weeks and drain down again. i would repeat this process until the water is fairly clear then add sentinel x100 inhibitor or similar for protection.

There may be an underlying fault which is causing the sludge build up(incorrect pipework etc) so you may have to check over the install also.

HTH Sam

 

[Ookysoft]

When I moved in, I discovered the previous owners had never had inhibitor in the system - I drained out black water at that time and keep it topped up with inhibitor whenever I have to drain any - Draining this time I had and will have to do again, as the valves either side of the pump are not willing to close - worked them some but they don't seal. Will replace those too!

I fitted thermostatic valves to the rads upstairs [ downstairs still to do ] & feel I need to put a pressure relief loop/valve in as I see nowhere for the water to flow if the valves all close but the pump runs.

Lots to do now it's cold out! Grrrrrr!

Thank you for your replies!

 

[sambotc]

Hi,

You will need a bypass rather than a pressure relief valve. Leave one radiator without a TRV and to comply with building regs you should also have a room stat. This goes in the same zone as the rad with no TRV.

If you have motorised valves (2 or 3 port) you should fit an auto bypass valve before any of these valves but after the pump and link it into the return.

I would be questioning why the water is black if the system is being maintained correctly?

HTH Sam

 

[Ookysoft]

I've not re-dosed the system since the first set of valve replacements - so I guess it's eating away again where it was eating when I first moved in [ inside the boiler I'm guessing ]! If it looks like I'm not going to swap them out this side of the New Year I'll dose it again as it'll start getting stick in January no doubt!

Thanks for your reply!