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JamesI, Handyman
Category: Appliance
Satisfied Customers: 3124
Experience:  I have repaired and maintained numerous items over the years, from fridges to freezers, radios to TV's.
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I have a TP9000 central heating system with a Danfoss

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I have a TP9000 central heating system with a Danfoss thermostat programmer. For the last week, my rads have been firing up at the same time the water heater comes on, despite the house being no-where near cold enough. They’re programmed to come on at 15* but are firing up when the house temp is at 22*, along with the hot water tank, (which is supposed to come on). Can you advise me please?

Hi Lizzy, thank you for choosing Just Answer, my name is ***** ***** I will help with your query today.

Does the thermostat show a call for heat or is it showing central heating as off when the rads are getting hot turning a period the hot water is coming on?

Customer: replied 10 months ago.
Hi JamesNo, it appears to be off, as the internal temp is much higher than the programmed temp, but the rads are boiling. It turns off again after about ten mins.

Ok, there are two potential causes.

1. The thermostat is faulty and though its showing its not calling for heat its telling the boiler and rad valve to send heat to the rads.

2. There are two valves which the thermostat controls which sends water to the hot water tank and rads, and the rad valve may be stuck open.

Customer: replied 10 months ago.
Okay. I had a look in the cupboard where all the valves are, and it looked a bit too NASA for me, but everything’s labelled, so I’ll have a proper look.

Its worth starting by resetting the thermostat.

This is explained in the video here, let me know once this has been completed.

Customer: replied 10 months ago.
I did that twice this morning. It appears to reset, then reverts to the way it was. I’m assuming the settings should revert to the standard ones?
Customer: replied 10 months ago.
One of the little slidey valve things near the tank is quite sticky and doesn’t really move, now I come to look at it. I wonder if that’s the problem? The others move quite freely. There’s no hot water or heating on now, so I’d expect them to be the same.

The valve leavers should have resistance on them, if they are freely moving it sounds like its those ones at fault.

As you move the leaver you should hear a wirring sound which is the motor moving, if its not wirring it means the valve is already in an open position.

Customer: replied 10 months ago.
Okay. I’ll double check that. Back in a bit!

No problem

Just so we are clear the valve you looking for looks like the one here.

Customer: replied 10 months ago.
One lever is firmly in place, and I’d probably have to push it hard to move it. The two others, (we have two heating zones), are very loose and there was no whirring sound when I twiddled them.
Customer: replied 10 months ago.
sorry, I should have said: all three looked like your picture.

Great, that is strange as it suggests 2 of the three are in 'open positions', when you said your rads are on were both zones getting hot, if so that does explain why.

Customer: replied 10 months ago.
That’s good, I suppose, as all the rads heated up at the same time. Weird that two should go at the same time though. I guess I’m going to need it serviced again then. It was only done three months ago. ��

Do you have two room thermostats (as clearly you dont have the TP9000 controlling both zones).

Customer: replied 10 months ago.
there’s a second thermostat in a bedroom, but the main, downstairs, one programmes both zones. The second one just seems to show current and programmed temps, and allows an over-ride in zone two. I’ve always left that one alone at 13 degs. The main one seems to activate everything, you see.

Ok, in that case my guess is its the thermostat at fault, as its very unlikely for two valves to fail (especially at the same time).

Easy way to check is disconnect the main controller, give it a minute then see if the leavers are now stiff, if they are that confirm the controller is at fault.

Customer: replied 10 months ago.
Okay. I don’t know how to turn the main controller off, but if I turn the boiler main switch off, it’ll turn off. Will that do?
Customer: replied 10 months ago.
I just turned off the boiler and checked, and you’re right. If I push the two floppy levers along, they whirr back into place now. So it’ll be a new thermostat I need then. Drat!

Yes thats correct, a new thermostat is cheaper than two new valves though.

Please let me know if you need anything further

Customer: replied 10 months ago.
Thanks, ***** ***** was afraid that would be it, so thanks very much for confirming it.

No problem so I can mark the question as resolved please rate the service using the star rating at the top of this page

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