Remote Radiators starved of heat


Postby theglenhotel » Sun Dec 14, 2008 9:49 am

We have a small hotel althought there are 30 radiators in our chs.
For the past month, radiators in 2 of the rooms (furthest from the boiler) are tepid at best. We thought sludge was the problem and asked local advice which confirmed the same. We had the system flushed but the problem remains the same. If we close all radiators except the 2 rooms in question, then the radiators heat up fine. We now believe there may be a problem with the pump. This is very frustrating as 3 independant heating engineers have all assured us it's just a "flushing out" problem. ANy comments would be most welcome.
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Postby stoneyboy » Sun Dec 14, 2008 1:51 pm

theglenhotel,
There is a good chance that the pump is on its way out. With 30 radiators I suspect a specialist pump is fitted which will cost a fortune to replace.
You may find that a standard pump something like the Grundfos Series 100 pump will be adequate for the job but it will be borderline.
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Postby simon@hwch » Sun Dec 14, 2008 10:12 pm

If you had stated the boiler used a pump recommendation could be made.

How do you heat your HW in the hotel? Is the HW zone valve jammed open?

Do you have a bypass fitted and has it been adjusted?

All these things you need to look at before condemning the pump.
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Postby stoneyboy » Mon Dec 15, 2008 10:23 am

theglenhotel,
A daft question but do you have non adjustable (without tools) lockshield valves on all radiators? If not could one of your guests have been making adjustments which creates a short circuit through one of the radiators?
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Postby theglenhotel » Mon Dec 15, 2008 3:52 pm

Thanks for that so far.

Our hot water supply is a seperate boiler/system completely.

The existing chs system has a Grundfos UPS 25-80 pump which has worked well for >15 years. I spoke with Grundfos and they think (given all the facts as stated above) that the pump is on it's way out, e.g. impellers not functioning correctly, etc. Can I replace the pump easily enough? There's isolating valves either side of the pump but do I need to do anything other than disconnecting the old one and replacing with the new one? Or should I get someone in? Thanks for your advice so far.
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Postby Steve the gas » Tue Dec 16, 2008 5:40 am

Hi,

If you feel able -- do it . Close pump valves and replace inc wiring like for like, careful some water = rags.
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Postby theglenhotel » Thu Dec 18, 2008 8:06 am

Well, that's the ne pump fitted and guess what? Same problem. Extreme radiators still starved of heat. A new problem has also occurred in that the highest radiators (2 out of 4) have insfficient pressure. I can take off the actual bleed valve fitting without water pumping out of the radiator.
Any ideas anyone?
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Postby Steve the gas » Fri Dec 19, 2008 5:34 am

Hi,

Only bleed rads with system off.
Did you say if you have tanks in loft perhaps?
One could be empty - low water symptom - could you check for us?

Steve
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Postby nitro23456 » Fri Dec 19, 2008 1:38 pm

Sounds like either a blockage or more likely that there isnt actually enough water in the system.... check for a stuck ball cock in F/E tank

Did you change the pump yourself? has anything been drained down at all?
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Postby stoneyboy » Sat Dec 20, 2008 12:07 pm

theglenhotel,
We don't know how well informed you are:
What setting is the pump on?
Now that you have bled the system with the pump running you may have introduced air into the system. Try bleeding again with the system off.
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