Hot water circulation pump


Postby greengrass » Wed Feb 13, 2008 5:58 pm

Red Grundfoss hot water circulation pump not working.
Bungalow: hot water system comprise hot water storage tank in airing cupboard in shower room, next door is the bathroom and those hot taps work fine even though pump not working. The circulation to the kitchen tap is something to be desired as it takes so long before hot reaches the tap.


Q: Do these pumps work on the principal of a built in 'flow switch' that operates the pump when a hot tap is turned on?
If this is so I would expect that the power feed cable to be permanently
'Live' and it isn't.
It has been checked with a reliable tester and his equipment , he is an electrical test technician mate who checks industrial elecs as well as domestic all his testers give same reading zilch power on the pumps cable.

This has been on going for some time and it's about time it was sorted but I've had some horrendous estimates, one £200 'as it needs new pump' he said, so have decided to ask for advice before calling in the big boys, or girls [I'm not Deleted], who know to fix it. Any advice would be welcome other than proverbials.
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Postby roger196 » Wed Feb 13, 2008 8:17 pm

I am assuming you do not have a combi boiler.
Normally the pump only operates to (a) heat the hot water cylinder on an indirect basis and (b) the central heating. The pump will come on when the thermostat on the hot water cylinder calls for heat or the room stat for the CH rads.
First check that the timer on the boiler is set to ON for DHW and CH. Then check that the roomstat and cylinder thermostat are turned up.
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Postby uk_ducati » Wed Feb 13, 2008 8:38 pm

hi
i have a couple of questions.
did the pump used to come on whenever you turned the taps on or is it a recirculating pump that used to be constantly on ( or timed to come on in the day)?
either way it should have constant live (unless it was a recirculating pump with a timer.)
are you certain that this pump is for pumping hot water to the taps and not for the hot water from the boiler to the hot water tank and central heating? just thinking this because if it is for the central heating and hot water there could have been a chance that when you tested the live the central heating was turned off or the room thermostat was off so there would no be a live to the pump. also this pump will have nothing to do with the pressure at the taps.

cheers
paul
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Postby greengrass » Thu Feb 14, 2008 2:15 am

Sorry should have said
standard boiler not combi. Bungalow hence pumped hot water, well it would be if the b****y pump worked.
Blue pump fitted by British Gas last year for the central heating that comes on obviously when heating switches on. No room stat just rads with TRV's. On the red pump 22mm piipe from around 2/3rds up the H.Tank to the pump then down through the floor. Two of, what appears to be motorised valves on it seems the heating circuit, I know one for definate is as that was also replaced by British gas when the old one broke 18 months past.
Don't know for sure what the other one is for [same size] with a window in the casing and the name satchwell on the window plastic.
The cables from both pumps and mortized valves enter what looks like a slightly enlarged surface 13 amp J.Box. NO timers in cupboard and heating /water on off controls are in the utiliy room right next to the boiler. Any closer and I would have refered to them as the 'little and large twins. I might take a chance and take the cover of and have a look to see in the pump cable and see if one lead has come out, hoping of course Idon't cuse a fault.
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Postby uk_ducati » Thu Feb 14, 2008 12:49 pm

hi
the red pump still sounds like the central heating and hot water pump to me. the tap hot water should come out of the top of the tank in 22mm pipe assuming it is a gravity fedd system.
is there a cold water tank in the attic?
the 2 motorised valve will be for turning the hot water and heating on together or one at a time.
have a quick look under the junction box cover. all you should find is a bank of 10 block connectors with all the wires comming together. have a look to see if any wires have come loose as you suggested.
is there any chance you could take some pics of the set up as i am only assuming things at the mo and could be giving you the wrong info.
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Postby greengrass » Thu Feb 14, 2008 2:58 pm

It's not gravity fed
The cold tank in the loft feeds into the bottom of the hot tank the hot comes out in 22mm around 300mm from top of the tanke to the red pump.
The central heating has its own pump blue.
And British gas renewed the blue but wouldn't touch the red one as my heating cover with them does not cover hot water systems only central heating so they told me the hot water is pumped because the tank is on same level it cannot gravity feed as such, and £120 to sort it out.
There are no room stats only TRV's on each radiator and a timer control for heating and hot water at the side of my Potterton neataheat boiler and what happens to the cables that leave the junction box is anyones guess as I cannot trace them.

send email to robertwhiting76@hotmail.com and I'll send pictures, as DIY DOC says I can't post them there is no facility for that on this site.
The pictures will make it a lot clearer.
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Postby roger196 » Fri Feb 15, 2008 11:26 am

Pending receipt of the photos, may provisional views are:-
The cold feed from the loft is the pipe which goes into the bottom of the hot water cylinder. The hot feed to the hot tap should come out of the top of the cylinder. This can be checked by gently holding this pipe about 20 inches from the cylinder and getting someone else to turn on the hot tap.
The pipe coming out 300mm from the top is the feed from the boiler to the indirect coil inside the cylinder. There will be another pipe coming out of the cylinder about 600mm from the top which is the return pipe to the boiler. Have a look for this pipe which may be round the back.
There should be a thermostat on the cylinder about one third up from the base. It is this thermostat which should turn the red pump on and off.
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Postby roger196 » Sat Feb 16, 2008 7:51 pm

Having looked at your diagram, I am concerned that there appears to be no expansion pipe for either the CH or DHW as the water heats up. There should be a small tank( as oppose to a much larger one for cold water storage) in the loft for the feed and expansion part of the CH system. These are safety issues which should be addressed immediately.
The black pipe is probably part of the bypass system. This allows a small quantity of water to circulate in the CH system when all the TRV's are closed to remove latent heat in the boiler.
I am not sure why you need the red pump at all. The hot water flows out of the hot water cylinder by virtue of the pressure of cold water from the tank in the loft feeding into the bottom of the cylinder.
I am still puzzled by your system, so am unwilling to offer advice on how to remedy your problem.
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Postby greengrass » Thu Feb 21, 2008 11:06 pm

Thanks for your help have found out from replies that the hot feed is in fact on the top of the tank combine with the expansion pipe to the cold water tank in the loft. Each hot tap turned on letting pipe cool for each one and turning on each tap in turn the pipe got hot.
The pipe from tank to Grundfoss pump is obviously hot, the pipe from the pump that goes into the floor is cold. Cannot lift floor it’s a chipboard panel and too many pipes in the way. All pipe work must have been installed before the main part of the flooring was laid. So its anybody’s guess what the Grundfoss feeds/fed. I think best to leave it alone as it’s not leaking. The only problem would be turning off the stop valves they have jammed. It’s confusing and b***y annoying I can’t lift the floor.
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