No hot water - boiler not firing - cylinder temp 27 degrees

[Mark Hunter]

Hi all.

We have had a few issues with our boiler over a couple of years, which I'll try to keep concise. We have a condensing boiler in the kitchen, cylinder in a bedroom and water tanks in the loft. A running problem is that when the heating and hot water are on at the same time the hot water really suffers whilst the heating is fine. A couple of times there has been no hot water at all, to the point where it is now on continuously in all weathers. Yesterday however, with no heating on, the hot water was incredibly cold and the boiler wasn't firing. Plumbers came to look, turned the heating right down and replaced the thermostat on the cylinder which seemed to do the job (radiators were tested before and they were fine), but only hours later the water in the cylinder had dropped to 27 degrees and again the boiler wasn't firing. The plumbers say we need a new, larger cylinder for the size of house and an immersion heater too, although we stressed that, given finances, we're not worried about heating for the moment, just hot water. They still say we need these new items, but I want to see if anyone out there can suggest anything else that may be causing the hot water to fail. Pump and boiler have been tested and are working fine.

Any advice greatly received as we can't afford these new items but naturally need hot water.

Thanks!

Mark

 

[Simon F]

Hello Mark,:welcome:
if the boiler is not firing when there is a call for it,
suggests an issue with the wiring + controls - programmer /thermostat /motorised valve

 

[cjg]

motorised valve naff all to do with tank, its 90% chance just m/valve stuck or goosed, replace first, not a big job unless its hidden in the worste possible inacessable stupid place,

hope that helps
cjg

 

[Mark Hunter]

Thanks guys - I'll look into the areas you suggested and will read up on m/valves. Forgive my ignorance, would that solve the problem with the heating/hot water conflict or is that down to something more serious?

Mark

 

[JAP&H]

motorised valve naff all to do with tank, its 90% chance just m/valve stuck or goosed, replace first, not a big job unless its hidden in the worste possible inacessable stupid place,

hope that helps
cjg

Hi Mark

I agree with cjg probably valve problem (2 or 3 port). Motor, actuator or entire valve need to be checked possibly replaced.

Whether or not the cylinder is undersized has no bearing on water getting hot or not. Means you may run out of hot water if there are a few bathrooms and kitchen.

 

[cjg]

motorised valve controls the water flow, ie, ether to the tank only, or c/heating, if you have a 3 port then 1 tank 2 c/heating 3 both, not in that order .there should be a leaver on the motorised valve for manual control, but that may be stuck too! just have a look to see mybe you can (untill repair done ) use the manual leaver for a day or two regards cjg

 

[Mark Hunter]

Following a similar problem a year ago I actually had a look then at what I now realise is the m/valve but I don't know what it should ordinarily do. All I do know is that when I turned on/off the heating/hot water it made a noise like it was transferring from one 'flow' to the other but the little stick didn't move, it either locked in position where it was or was free to be manually moved. It didn't move automatically though, which I'm guessing it should.

Does that help clarify the problem?

Thanks,

Mark

 

[diamondgas]

Any chance of a picture Mark? Or is there 2 or three pipes attached to the valve in question? If two pipes there's a problem, three then it's working correctly

 

[Mark Hunter]

I'm at work but will take some pics this afternoon and post. According to the wife a 'family' plumber has come round and got it working by turning the boiler temp up and keeping the CH running but turning the radiators off and thermostat right down. He has also suggested to turn one particular radiator on if we encounter further problems and this should help. Can someone explain why this might work, given that we turned the CH off at the control panel and it didn't work? Not convinced that this resolution will last us until the autumn when we can look at larger-scale changes.

Thanks.

 

[diamondgas]

Really would benefit from knowing a bit more about your system designs and controls Mark! It could be as suggested a faulty 2 port motorized valve, 3 port valve or a wiring fault! Deffo nothing to do with the cylinder unless it had a blockage in the coil which isn't impossible ... All depends on pipework configuration for that one

 

[Mark Hunter]

Ok, thanks. Will post pics later. What pics would be helpful?

 

[cjg]

. According to the wife a 'family' plumber has come round and got it working by turning the boiler temp up and keeping the CH running but turning the radiators off

this is not good!!!! never turn all rads off as you will be fighting against the pump, and bu*** the pump,

i am out again now and poss not back till late but the lads on here will keep you informed I"m sure

regards cjg

 

[Mark Hunter]

Should we leave the radiators turned on then but knock the thermostat down to zero? Baby is sleeping in the relevant room at the mo, but I'll post pics/video of the setup when possible.

 

[Mark Hunter]

Please find some photos of the setup attached. Hope they make sense to someone! Let me know if further clarification is needed.



Mark

 

[M.Joshi]

Honeywell 2-port valves. Have you tried moving the manual lever across on the valve that controls hot water flow from the boiler into the tank?

Also, when was the last time you vented the system from the main vent? I presume that's why the radiator key is handy on top of the valve near to the vent (vertical pipe not connected to anything)!

 

[Mike Jackson]

You've got an S plan. The hot water should work brilliantly with the heating off. You've either got a faulty component or it's wired wrong. Naff all to do with the size of the cylinder. get a heating engineer in that understands system wiring/fault finding and they'll sort it.

 

[Mark Hunter]

M.Joshi: I tried moving it in the past but met with resistance so thought it shouldn't be touched. What is the difference btwn auto and manual as it says on there? Also, only ever bled radiators - anything else is new to me!

The current situation is as follows:

Cylinder temp is 55-60
Boiler temp is a stable 61 and properly firing
Heating is turned off at the control (as seen in pic)
Hot water is perfect

However, this is the exact same setup that was operating when the other plumbers left and by the evening the hot water had stopped working.

Mark

 

[Mark Hunter]

Sorry, tried to delete this post but don't know how!

 

[M.Joshi]

Re: Valves

M.Joshi: I tried moving it in the past but met with resistance so thought it shouldn't be touched. What is the difference btwn auto and manual as it says on there? Also, only ever bled radiators - anything else is new to me!

You will meet a little resistance when pushing the lever across to manual. There is a tiny hook which you push the lever behind to stop it returning back (spring return). Normally when the system is wired correctly the actuator (if working) opens the valve automatically. The lever allows you to manually open the valve and let hot water flow from the boiler through the cylinder coil. The valve you should be opening is the one with the radiator key on it in the picture.

When you have water flowing through the cylinder coil, you can open that vent (vertical pipe) slightly with the radiator key to let any air in the system out.

It does seem as though you have perhaps a stuck valve/actuator or loose wiring somewhere.


P.S. If you PM one of the moderators for this forum, they should be able to delete the previous post.

 

[jtsplumbing]

Hi just seem photo's of your cylinder !it looks like the cylinder stat is to high up ! needs to be about 12" from bottom of tank, yours looks more towards the top (Hot Area) try relocating stat lower down (Cold area)

 

[Gray0689]

Is the cylinder stat even
Cut in to insulation ?

 

[AWheating]

Is the cylinder stat even
Cut in to insulation ?

does not look like it to me?? its abit high up aswell.

 

[jtsplumbing]

Good question Gray, maybe he could put a better photo on here showing cylinder stat, but it looks like it is just strap'd on tank !!

 

[Simon F]

it does look like the stat is on the surface of the insulation, therefore serving no purpose, causing questions!
it could even be wired backwards
the only real solution is for someone with a multi meter and an understanding of the controls sequence to run the checks and see what is happening

 

[mountainman]

Just looked at this thread.
I agree that the cyl stat is in the wrong position, it should be 1/3 of the way up the cylinder from the bottom.
Disagree with the speculation that the stat is not cut into the insulation being the cause of the problem.
If the stat can't sense the temperature in the cylinder then the water will just get hotter until it reaches the boiler set temp.

 

[Gray0689]

No the stat not being cut in to insulation won't be the problem just fitted by a muppet so if they can't get that not right god nows what the problem could be
Sounds more a control problem than a plumbing problem
But impossible to be certain without seeing it IMHO

 

[mountainman]

Exactly Gray, 26 posts and no closer to resolution.
Time to get a pro in.