CH conundrum.

[Daftbat]

Hello to all, hope you can help.

We've an oil fueled Potterton central heating system, with two zone valves opened by Drayton ZA5 actuators, (one for CH, one for HW) and controlled by a Danfoss Lifestyle LP522 controller and Grundfoss Alpha+ pump.

In the last months and very occasionally we've noticed the downstairs radiators not getting warm, it's been intermittent but gradually got worse and in the last few days the downstairs rads have not got warm at all. The upstairs one's have always got warm as has the hot water from the taps.

The gradual pattern of failure has been rather strange in that the downstairs rads would get warm in the mornings but not get warm in the evenings - now the upstairs rads don't get warm at all when the system switches on, morning or evening.

The boiler has been serviced and given a clean bill of health and I've changed the actuator and checked the valve is easy to operate on the CH side of the system, the hot water actuator and valve works perfectly. I've also put a new Lifestyle LP522 controller on and still have the problem of downstairs rads not getting warm.

When the controller calls for everything to switch on both actuators move to their open position and the "switched on" indicator light on the pump comes on, however I can't perceive any vibration or noise from the pump to indicate it's working.

So my question is - despite it's light coming on is it likely to be the pump at fault or could it be something else ?

Many thanks.

 

[Johntheo5]

How old is the Alpha, if fairly modern it will display the power, watts, as W or/and some display the flowrate in m3/hr, so check for this and whether they are displayed or not, post a photo of the LEDs (running!!) and also check for the pump model like below, it will/should be either 45W or 35W.

Is the CH system sealed or open vented with a Feed & Expansion cistern in the attic?

 

[Johntheo5]

You said you pump is the Alpha + so probably a fairly old pump with no LED display etc, if its set to either II or III on the fixed speed mode then should be plenty of pump head to circulate the water. You could shut the pump isolating valves (but only if they are the gate type), remove the pump head and clean out the impeller vanes with a tie wrap and back flush the pump inlet and outlet ports, there should be a venting screw on the front of the pump, you can remove this to see if the pump shaft is rotating, just hold a cloth under it while checking it, you won't get much leakage.

Is this your pump? the pump shown was made in week 47 year 2006, PC:0647.

 

[Daftbat]

Hello John,

Many thanks for your response.

Yes it's a vented type system with a small feed and expansion tank in the loft.

You've also got the type of pump correct too - I've checked the manufactured date and it's 0515 so built 2005.

Please see a picture of the installation looks like there's a gate valve top and bottom so the pump can be isolated.

Bearing in mind it's age would it be better to replace with new and if so is it a simple matter ?

Sorry don't seem able to download a pic - I've resized it four times to below 500kb and it still says it's too big - the pump is identical to the one above except it's an Alpha+ 15-60 130, PN 59526495.

 

[Harry Bloomfield]

Please see a picture of the installation looks like there's a gate valve top and bottom so the pump can be isolated.

Bearing in mind it's age would it be better to replace with new and if so is it a simple matter ?

If both of the gate valves work, and the top and bottom unions are not seized, then replacing the pump is a fairly simple matter.

 

[Johntheo5]

Hello John,

Many thanks for your response.

Yes it's a vented type system with a small feed and expansion tank in the loft.

You've also got the type of pump correct too - I've checked the manufactured date and it's 0515 so built 2005.

Please see a picture of the installation looks like there's a gate valve top and bottom so the pump can be isolated.

Bearing in mind it's age would it be better to replace with new and if so is it a simple matter ?

Sorry don't seem able to download a pic - I've resized it four times to below 500kb and it still says it's too big - the pump is identical to the one above except it's an Alpha+ 15-60 130, PN 59526495.

Yes, I suppose, no harm in spending a few quid now after 20 years or so, would suggest a DAB Evosta 3 (not the Evosta 2) or, like my own, a 6M Wilo Yodos Pico, both of which display the power in watts and the flowrate in m3/hr, very useful.

What setting is your present pump on.

 

[Daftbat]

Traditionally it's been at the mid point - in other words the narrow point of the grey pointer on your picture above has been pointing left (west) and in that position the heating has seemed perfectly adequate.

I have though in these last weeks turned it clockwise to the point the one in your picure is - I assume thats maximum.

 

[Johntheo5]

Yes, try it on that, I is the lowest speed/head, if Rads not heating up fully, try it on II, if nothing changes install a new pump.

 

[Daftbat]

Many thanks for the responses, will change the pump and report back.

 

[Johntheo5]

Did changing the setting not do anything??