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Plumberpro
Plumberpro, Plumber
Category: Plumbing
Satisfied Customers: 634
Experience:  Heating and plumbing answers. 20 years experience
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I have a rhino boiler house oil fired boiler. This heats water

Customer Question

I have a rhino boiler house oil fired boiler. This heats water in a water tank two floors up. last night and today, I have noticed the hot water is a lot hotter than it has been, yet none of the settings anywhere have been changed. I checked the thermostat on the boiler, which just seems to be a unit that clamps to the side of the boiler as opposed to having an element that goes within the tank. If I turn the dial, I can hear it 'clicking' on and off but I am unable yet to determine whether the boiler will cut in and out as I do that, I will be trying that over the weekend.
My first question is therefore:
1] the thermostat on the boiler is set to 70 degrees. can I assume that this is the maximum temperature the water will get to if left 'un-thermostated'?
2] Aside from efficiency, if I set the water to come on for a shorter time and assuming it is the water tank thermostat at fault, is it safe to use if the answer to question 1 is yes?
Submitted: 3 years ago.
Category: Plumbing
Expert:  Plumberpro replied 3 years ago.
Customer:

Hi . do you have a thermostat on the hot water tank? If you do and you turn it up and down , does it click on and off?

Customer:

If boiler set at 70 then that is the Max hot water temp will get to. You really need a thermostat on the hot water tank itself. So you can set the boiler high 80 for the heating . here are various hot water tank stats to suit every system , even wireless .

Customer:

You can just use the boiler stat but for safety its better to have the additional hot water tank stat

JACUSTOMER-y2ar9z57- :

Sorry, I typed my initial question wrongly in that I mixed up the boiler and water tank. Please allow me to edit:-

JACUSTOMER-y2ar9z57- :

Should have read "I checked the thermostat on the water tank, which just seems to be a unit that clamps to the side of the boiler as opposed to having an element that goes within the tank. If I turn the dial, I can hear it 'clicking' on and off but I am unable yet to determine whether the boiler will cut in and out as I do that.

JACUSTOMER-y2ar9z57- :

the thermostat on the boiler itself I have tried this morning, and it does indeed cut the boiler in and out as I vary it so I am sure that one is okay.

JACUSTOMER-y2ar9z57- :

damn, I have still typed it wrong!

JACUSTOMER-y2ar9z57- :

I checked the thermostat on the water tank, which just seems to be a unit that clamps to the side of the water tank as opposed to having an element that goes within the tank.

JACUSTOMER-y2ar9z57- :

so, in summary, I have yet to check if the water tank thermostat, although it does click when turned, actually cuts the boiler in and out. However, my real concern was that if the water tak thermostat is not working, that it is still safe as the water will not exceed the temperature set on the boiler.

Customer:

Hi , check the stat hasn't slipped down as thus will affect the temp as the water is hottest at top of tank. If thou think the stats working , raise it higher up he tank , it will shut off quicker and the water will be lower . usually it's a third of thecwayvupbtge tank , but sometimes you have to experiment . sorry I am just on vway out. Will be a couple of hours , if you don't mind

JACUSTOMER-y2ar9z57- :

the stat is set into a cutout shape in the foam sorround on the tank, so I know it has not moved

JACUSTOMER-y2ar9z57- :

but - its safe to use, right?

JACUSTOMER-y2ar9z57- :

I also have just had a 'eureka' moment. When I removed the thermostat from its place on the water tank and tested for 'clicking' when rotated, it was clicking at about 60 degrees, yet the tank was cool - cool enough that at the point where the thermostat touches the metal of the tank, I could feel it as lukewarm but not hot. Does this indicate then that my tank thermostat has stuck?

Customer:

Yes it may have to be honest I would replace it if in don't as its only 3 wires and cost a tenner.

Customer:

Regarding safety . if the hot water overheats to boiling it can cause the cold water storage tank to heat up too, eventually the plastic tank can deform and pour boiling hot water through the ceiling. Very rare but has happened .

JACUSTOMER-y2ar9z57- :

regarding safety - but if the thermostat on the boiler is only set to 70 degrees, then is this not the maximum temperature the water will achieve?

JACUSTOMER-y2ar9z57- :

oh, and I should have probably said that our hot water tank has a cold water tank at the top, also covered in the foam jacket - this is the header tank?

Customer:

Yes that's right. Its just that 2 are safer than one.. Yes that's the cold water storage tank which feeds the hot water tank

Customer:

But . I've been to hundreds of properties that just rely on the boiler stat and there has been no problem.

JACUSTOMER-y2ar9z57- :

ok, then I guess the first course of action is to obtain a new thermostat. I had not seen one that just 'clamps' to the side of the tank before, effectively measuning the tank temperature and not the actual water. I assumed that it would have something that actually went into the tank. Is this sort of clamp on variety common?

Customer:

Yes , that's the most common type . if there's foam on the hot water tank cut it to the size of stat , so its right up against the metal of the hw tank. If would need wiring in . tanks sent made any more with internal stats. The type that doesn't need wiring is one with a wire that goes to a valve , a bit like a thermostatic radiator valve and is fitted onto the return pipe and shuts flow from boiler to hw tank

JACUSTOMER-y2ar9z57- :

Well, I do hope that a stuck thermostst is my answer, as once I get into tracing cables through the walls to the control panel and out to the boiler house, it may get a bit too complicated for me!

JACUSTOMER-y2ar9z57- :

Thank you so much for your help, I really appreciate it. Just answer has been a godsend for me living so remote from anyone, and you have continued with the excellent service that I have always had.

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Customer: replied 3 years ago.

Just one more thing - I turned on the hot tap this morning and got hot water out. This would be fine except the hot water had not been on, the programmer was not set to heat water until later in the day.

Now, we have an outside boiler and single pump going to two seperate valves, operated by the electric 'head' units. I have not checked yet but I am wondering if the water valve has stuck open and will check this tonight. I am sure I am right on this next part but would appreciate you just confirming - if the programmer for the water is off, then regardless of the thermostat on the tank the electrically operated valve should be closed, right? And no electric current should be present at the valve until the programmer switches the water section on, right? lastly, I assume that the thermostat on the water tank does not actually switch off the boiler but instead closes the valve, is this correct?

Your help is appreciated!

Expert:  Plumberpro replied 3 years ago.

Hi .yes you are right if the programmer is off there should be no power to the valves and boiler. The circuit should work like this. Power from fused switch to programmer CH and hw . hw to cyl stat common . cyl stat 1 ( heat needed) cyl stat 1 to brown on motorised valve . the brown on the valve powers open the valve.

Grey on valve connected to live from anywhere , normally from wiring centre. Then as the switch opens it operates the switched orange which supplies power to boiler and pump

Customer: replied 3 years ago.

I found it, the answer.

I have Danfoss HPa2 actuators, and the heating one is fine but the water one is at fault.

When the timer cuts in, it opens the valve as required. However, when the timer/programmer cuts out, the actuator closes off as far as the power is concerned, but it seems the internal motor and the plastic spindle that fits over the valve head are not connecting in 'the turn off' mode, and although the switch is cutting off, it is leaving the valve open. Until you take off the actuator and put a screwdriver in the actuator and turn the spindle back to 'valve off' mode and turn the valve itself back to off, the water will keep running.

I found it by using the manual level on the actuator and the lever is not returning to the off position even though the power is cutting off, so essentially it is leaving the valve open and all the time the heaing is on, the water in the tank is also being heated. The thermostat is fine, and thinks it is turning off the water valve but if course, it is still open all the time.

I have ordered a new actuator, and hope this will do the trick! I do appreciate your help, and you can add this one to your experience in case anyone else asks again.

Expert:  Plumberpro replied 3 years ago.
That's great . I was going to suggest the hw valve must be open somehow , but its great you now know , all the best