Radiators not heating up


Postby keithm » Wed Sep 23, 2009 3:10 pm

After the summer break I have turned on the Heating switch on my Honeywell timer but none of the radiators are heating up. Boiler comes on ok and the pump runs for a while until the water in the tank reaches the temperature on the tank thermostat. Each of the radiators has its own thermostatic control and I have removed these and checked that the pinmoves in and out ok. I have also tried bleeding each of the radiators and I get water out of all of them. Yesterday I thought it may have been the three way valve (Honeywell Y plan) but last night I checked this and the temperature is the same on all three pipes - hot. There is no separate room thermostat so I am not sure what would stop the pump pushing the water round the radiator system when all the valves are open.

Any ideas?
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Postby plumbbob » Wed Sep 23, 2009 9:52 pm

I am not sure what would stop the pump either, from what you say, it doesn't make sense.

I would guess the three way valve is not opening properly. The fact that all pipes are hot is I think a bit misleading.

On the end of the honeywell valve is a little lever. Manually push it along the slot and hook it in to the groove at the end of it's travel. When the heating is on, this lever should flop about without any resistance. If the lever is stiff or grates, the valve is faulty. If it moves smoothly, and you can feel the gears turning, you have an electrical fault.

Moving the lever fully to the right opens the valve manually.
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Postby keithm » Sat Sep 26, 2009 7:50 am

Thanks for the information.

I have now tried moving the lever. It moves about two thirds of the way across and then is stiff and I can feel cogs turning. At the end of the travel the pump turns on and by holding it there all the radiators heat up so at least there is no blockage.

So is that ba sign of the valve needing replacement or an electrical fault?
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Postby plumbbob » Sat Sep 26, 2009 8:51 am

With the power off, you should be able to press the lever hard and make the gears "rev". When you release the lever the motor should return within a couple of seconds. If the gears feel and sound smooth then it is not a mechanical fault with the valve.

Repeat the procedure with the heat on. Does the lever stay in the end position or does it return and switch the heating off again? If it does it is an electrical fault.

Remember when at the end of its travel, you can hook the lever in to a little slot which will allow the heat to stay on regardless of the fault.
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Postby keithm » Tue Sep 29, 2009 11:54 am

Looks as though it may be electrical then.

Both with power off and on I can push the lever through the gears (turning on the pump) and it returns after about 30 seconds and the pump goes off.

I notice on the timer if I go from off to on for hot water the boiler fires up but if I do this for the heating the boiler does not unless I push the lever up on the valve.

I have also noticed that since I first moved the lever last Saturday that when the boiler goes on with the timer first thing in the morning for heating up the hot water that the radiators do heat up during that time which seeems to imply to me that when the pump is running the hot water flows round the heating system now, where it did not a week ago.

Are there any checks I can do on the electrics or should I get an electrician/plumber in?
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Postby plumbbob » Tue Sep 29, 2009 5:37 pm

Actually, your description of the valve isn't how I expect correct operation to be. With the power off, the valve should return to rest at about the same speed you can push it over manually at ie, one or two seconds not 30.

"I have also noticed that since I first moved the lever last Saturday that when the boiler goes on with the timer first thing in the morning for heating up the hot water that the radiators do heat up" This also suggests the valve is not returning to rest properly leaving it partially open.

These symptoms could suggest a seized valve which caused the motor to burn out.

Operating the lever manually should trigger the pump and boiler so from that respect, it's fine. (You can hook the lever in a slot at the end of its travel to force manual operation of the heating by the way.)

An electrical test needs a voltmeter to determine there is 230 volts between the white and blue wires that lead to the valve when heat is being called for. You must use a meter as there will be a lower voltage present even if the programmer is set to off.
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Postby bd3cc » Tue Sep 29, 2009 10:13 pm

I cant see why the system would develop an electrical fault whilst turned of over the summer, unless something has been altered.
I would change the motorised valve head, replacing the electrical connectios like for like.
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Postby keithm » Wed Oct 28, 2009 9:54 am

Heating system now fixed. It was the the 3-way valve. Got a man in to do it as I was not confident myself. He thought to start with that it might just be a burnt out motor but it was the whole valve being faulty. Luckily he could replace the mechanism without changing the whole plumbed in valve as he said that would have been a nightmare with the different size pipes I had and the confined space.

Thanks for the advice
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