Cental Heating Help

[HelpThisDude]

Hello All, first post here and I really hope you can help me.
I’m no stranger to tools and meters, but I have no idea about household plumbing or CH systems.

The Problem:
Yesterday we had a strange vibrations running through the house, sounded like drilling. It was coming from the Airing cupboard. The pump installed for boost the bath/shower smelt and was causing the noise. No one was using the bath at the time.

The installers said that the motor on the pump had burnt out, because the water was too hot (max on pump was 65DegC). They will replace the pump, but want us to fix the water temp problem.
They blame the rectangular shape stat strapped to the side of the immersion heater/tank, (the electric part never used) made by Danfos. He explains that this is not regulating the temp of the tank.
Does what the bathroom shop guy said, make sense?

I have used a RS Thermometer to check the temp of the water (at the tap), and it is at 63.9 DegC. The stat is set to 55 DegC.
I have since turned it down to 45 DegC on the stat (let it for the night), and the temp of the water in the morning at the tap is reading 61.2 Deg C
When the dial on this stat is turned it does click in, and out. I have no idea of the best way to test it, or if a different component is faulty?

 

[doitmyself]

They blame the rectangular shape stat strapped to the side of the immersion heater/tank. He explains that this is not regulating the temp of the tank. Does what the bathroom shop guy said, make sense?

If you have the central heating ON, turn it OFF at the timer. If you turn the stat on the side of the cylinder up from Min until the boiler lights; note the temperature. Now turn it down slowly until the boiler goes out; note the temperature. There should be about 10C difference. If the boiler lights and goes out, the stat is basically OK, though it maybe out of calibration.

If this is OK, the fault must be elsewhere; but we need more info on your system to diagnose it.

How many motorized valves do you have - they will be near the hot water cylinder.

 

[crashndie]

hi mate, the stat is working ok by all accounts because you have a tall body of water to heat up the stat is normally 3/4 the way down the cylinder an set to around 60-65 deg. the problem you have is by the time the water 3/4 the way down the cylinder is 65 deg the water is a lot hotter at the top. if the stat is now set to 45 deg by the time you have ran 1/2 a bath of water, it will start running colder. the only thing i can think of to help you out an keep a decent hot water temp is a blender valve it will mix cold water with the hot to cool it down to a set temp. hope this helps mate

 

[HelpThisDude]

One, made by danfos again. The little metal lever is on Auto, the other side is Man.
I'll need to get an assistant to help with the boiler, its 2 floors down. There is no old style window to see a flame, just a status LED that changes colour, and is either solid or flashing. I'll dig out the book for it, and follow your suggestion. I just found it stange that it did not change the temp of the water even when the stat was turned down the night before.

Right, Heating was off anyway.
Turned water heating on at the Control panel, with the stat turened down to 20DecC.
The boiler stayed off.
As I turned the stat up it clicked at 50 Deg C, and the boiler kicked in.
As I turned the stat down it clicked at 40Deg, and the boiler stopped humming.
The measured temp of the tank is 60.1 DegC.
I guess this means the control system is ok, but out of calibration by 10 Deg C.
Am I on the right track?

hi mate, the stat is working ok by all accounts because you have a tall body of water to heat up the stat is normally 3/4 the way down the cylinder an set to around 60-65 deg. the problem you have is by the time the water 3/4 the way down the cylinder is 65 deg the water is a lot hotter at the top. if the stat is now set to 45 deg by the time you have ran 1/2 a bath of water, it will start running colder. the only thing i can think of to help you out an keep a decent hot water temp is a blender valve it will mix cold water with the hot to cool it down to a set temp. hope this helps mate

It seems silly then, that they have fitted a pump that has 'MAX 65DegC' on the label. If most systems are set to around 60, and the top is hotter, whats the point of a pump that cant handle it?
have they fitted the wrong pump? Are they to blame?

 

[crashndie]

could be just a cheap pump thats been fitted, do you have the install instructions for it ? if so have a flick tho an see if there's anything in it regarding fitting blending valves, 65 deg is the maximum temp you want flowing out your taps anyway am sure there's a building reg about it, the pump would not need to be made to take water hotter than what the reg's state ???. the boiler an valves sound like there working ok if you consered about the stat get a new one there about 30 quid max and have 2 or 3 wires easy swap

 

[HelpThisDude]

could be just a cheap pump thats been fitted, do you have the install instructions for it ? if so have a flick tho an see if there's anything in it regarding fitting blending valves, 65 deg is the maximum temp you want flowing out your taps anyway am sure there's a building reg about it, the pump would not need to be made to take water hotter than what the reg's state ???. the boiler an valves sound like there working ok if you consered about the stat get a new one there about 30 quid max and have 2 or 3 wires easy swap

Ok buddy, its a good point. Ill change the stat, what is the official name? will screwfix have one?

The reason I'm supprised at the max temp on the pump is because nothing ever runs near maximum.
I dont have the documentation for the pump, the installers have that sadly.

Thanks for the advice guys

 

[Puddle]

Confused you say the installers say the water is getting to hot then mention that the shop guy said something

The cylinder thermostat seems to be working ok you are going to get a variance between the cylinder thermostat and the top of the cylinder as hot water rises, top will always be hotter

One test you should do is make sure the temperature of the hot water stays with the results you have when the heating is on, as it could be the motorised valve for the hot water is letting bye slightly thus when turns off and heating still on, water will be continued to be heated
This would be a fault of the motorised valve ,not the cylinder thermostat, the cylinder thermostat is only |£10 so may be worth replacing anyway
If water is to hot it can damage the seals on the pump, the impellor if plastic and may cause excess aeration ,thus loss of water pressure from pump
However you mention the pump was staying on when no outlet was on and causing vibration, this sounds as though the pump flow switch was stuck in the on position, thus could of been due to hot water causing it to stick or just simply a faulty flow switch, you do not mention pump model or type
This is way I asked who said water was getting to hot and if you have had a site visit

 

[crashndie]

try this one should be a direct swap for you:
[DLMURL="http://www.NoLinkingToThis/app/sfd/cat/products.jsp?id=61083&ts=22367"]Danfoss ATC Cylinder Stat - NoLinkingToThis, Where the Trade Buys[/DLMURL]

was the pump running at all times ? or just wen the hot tap opened?

 

[HelpThisDude]

Sorry I should have been clear.
The Bathroom shop that installed the bathroom, also installed the shower pump. Its a little Salamander pump.
No one had used that bathroom all day, the drilling sound happened randomly, lasting about two min at a time.
The same bathroom installer was called, and he diagnosed the pump motor faulty. But blamed the water being too hot as a cause.

The pump only runs when the Hot or Cold tap is used in the bath or shower.

Thank you for the link to screw fix, I'll get on the site and check it out. I just hope that if the pump goes again, they wont use me as an excuse to not fix the pump a second time, using the excuse "an unqualified person fitted the stat".

 

[PlumbBobBob]

are you saying the pump is running the bath taps as well as the shower?

 

[crashndie]

humm salimanders ???? not the best pump in the world to start off with tbh. with out seeing what connections are on the pump you have got in at the moment id suggest one of these instead :
Grundfos Niagra 1.5 bar Shower Pump - Machine Mart

miles better an with proven record !
post the model of your up an will try and match it with something else with a better fit

 

[HelpThisDude]

Yes, it runs the bath taps and the shower in the same bathroom.

Salamanda CT50 TWIN is the model. They sold it to me as a "excellent quality" pump. I was charged £198+vat+fitting.
Live and learn.

 

[PlumbBobBob]

the bath taps shouldn't be run from a shower pump because both sides of the pump need to be run together. with bath taps you usually only run one at once. the bearings have probably worn out. shouldn't have been fitted as it was.

steve