Central heating pump becomes hot and makes a noise

greensleeves · 4 Oct 2006

I have a 28 year old two-speed grundfos super 4 pump which has recently started making a noise and becoming hot. The central heating has been off over most of the summer. I had the boiler thermostat turned right down as this still heated the hot water satisfactorily(convection).
I have now turned up the boiler thermostat
as I thought I was maybe overworking the pump. It is still heating up and making a noise. Any causes for this, or is it most likely time for a new pump? Is this type of pump still available?

ChrisR · 4 Oct 2006

28 years is pretty good, time for a new one!
The standard type, which I expect yours is, has flanges 130mm apart.
(Connected to isolation valves which will either not work , or leak, or probably both, so expect to have to drain the system to replace the pump.)

greensleeves · 5 Oct 2006

thanks ChrisR. At least I know what a flange is now! Yes, two big nuts 130mm apart. It looks like you just unscrew these, put in the new pump, and screw them up again.

I don't seem to have any isolation valves so a system draining is called for. I did that a few times when installing my radiator thermostatic valves.

Looking round the pump world, I like the look of the Grundfos Alpha Pro. I'll need the /60 model as I have quite a big house. Some articles are quoting electrical savings of £42 a year, so could pay for itself in 3 years.

Better order one up and have it ready in case the pumps packs it in.

cheers

Gasguru · 5 Oct 2006

If the pump ran 24 Hrs a day consumption would be around £90/year.

The reality is a normal pump probably only consumes about £20 a year max.

Savings with a modulating pump are more like £5.00 a year so pay back is a long time!

These pumps are still too new to know the long term reliability.

There maybe benefits with undefloor heating systems and commercial sized pumps.

greensleeves · 5 Oct 2006

http://www.ukhomeideas.co.uk/ideas/...-new-alpha-pro-pump-can-cut-your-energy-bills

This link puts the cost of running the pump in an average house at £57 per annum, and reckons that reduces to £12 with the Alpha pro.

Anyway, I need a new pump, so payback perhaps is not relevant.

Gasguru · 5 Oct 2006

This is just an advertising site for manufacturers. They are always going to show their products in the best light.

£57.00 a year is garbage. A 6m pump consumes roughtly 100W. At 1p per hour that equates to 5700 Hours a year. An average system would run the run the pump a couple of hours a day to provide hot water ie. 730 Hours.

That leaves nearly 5000 Hours for a typical 8 month heating season. ie the pump is on another 21 Hours a day (average).

Do you really have your heating on (ie a demand from the room thermostat) for 21 hours a day for 8 months a year?

More un-substantiated claims by sponsored web sites. I see they are also making wild claims for solar and wind energy products.

greensleeves · 6 Oct 2006

you could be right gasguru.

http://mail.mtprog.com/CD_Layout/Da...nal.pdf#search="central heating pump wattage"

This link gives the average annual pump usage as 124kwh, and the saving from this type of pump at 62%. As I have probably an above average house the annual saving would be £7-£10 approx.

Gasguru · 6 Oct 2006

Good hunting greensleeves.

They say a standard pump is around 124kwh or roughly £12.40 a year so minimal savings will be obtained with a modulating pump.

Ive nothing against these high efficiency pumps, it's just the misleading information about them. That pump is going to have to be very reliable to get any saving from it. Think of the energy used in that service visit to replace it, that fact that the old pump will end up in landfill etc etc.

Standard pumps have a simple winding and a capacitor. High efficiency pumps have permanent magnets (often sintered at high temperatures-high enery use), highly complex control systems for the stator windings. Look at the size of the control box on the side.

Unfortunately electronics+heating industry are not generally that reliable.

greensleeves · 6 Oct 2006

thanks gasguru. I agree that it doesn't make sense to replace a working pump with a high efficiency one. However, its probably 50-50 when
replacing a faulty one. Yes, slight risk that the new technology is unproven long term. As mine looks like it is on the way out, I needed to order something. I will take care to do a little more research when I visit web sites however.

The noise sounds like it is being caused by gentle vibration. I'm assuming the bearings are going, which is causing the heat and vibration. Can't say I know anything about the internals though.

greensleeves · 11 Oct 2006

Just had another look at the flanges 130mm apart. I see the metal pipe above the top one and below the bottom one has a screw with the screwdriver slot in the vertical position. Would these be the isolating valves by any chance? Needless to say they won't turn (at the moment) with a screwdriver.

Gasguru · 12 Oct 2006

Drain system and replace the ball type pump valves with quality gate valve types. The screwdriver slot is notorioous for leaking if they are disturbed.

greensleeves · 12 Oct 2006

thanks gasguru. I'll leave this one to a plumber. I have BG coming on Monday to quote on a condensing boiler. I may need one as my hot water cylinder is now leaking. I'll see what they say. If its under 2 grand I'll probably go for that. Will I still need my new Grundfoss Alpha pro pump, or do I get to sell that on abay?

Gasguru · 12 Oct 2006

Highly unlikely you'll get a qoute of BG for under £2000. Can't see why anyone should object to fitting your new pump.

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Central heating pump becomes hot and makes a noise

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