Very hot water booster pump

[Brad93]

Combiboiler Gravity system. Combiboiler downstairs pumping up to Tank directly above kitchen which has 100-150L sink for washing utensils/mixing bowls etc.

Water very slow to flow out but scalding hot, but no pressure. Using the mixer tap, the minute you switch on some cold you get no hot at all.

£150 booster pump has lasted about 3 months.

Now looking for something better.

However, all the pumps i'm looking at seem to be about 65°C max. I reckon their boiler may be set hotter than that. Many only can run for limited time also. They can be in the kitchen for two hours using the water for 30 minutes at a time.

May be possible to convince them to reduce the boiler temperature.

Any recommendations

 

[8ob]

Pump the cold feed to the combi instead of the hot out of it, just thoughts.

Bob

 

[knighty]

wait.... comb boiler and hot water tank? that doesn't make sense?

swap the hot water tank for a mains pressure hot water tank (just search unvented tank)

 

[Brad93]

I have no idea i'm not really into plumbing i've just been asked to look into it.

As far as i know, there's a combi boiler downstairs, probably about 20m away. Upstairs is probably 3-4m head, there's a tank of some description, but no red pressure tank like you see on some home systems.
The bakery engineer and I fitted a plastic, fairly cheap looking booster, that sensed demand and powered up, on the tank outlet, which goes straight down through the ceiling to a big sink.

 

[Brad93]

Pump the cold feed to the combi instead of the hot out of it, just thoughts.

Bob

I think it's the run and the head basically the hot water gets up there then there is only gravity pressure back down?

 

[Gareth J]

I've a salamander pump that coped reasonably well with very hot water. The seal on the hot side went eventually but was over 10yrs.

 

[Brad93]

I've a salamander pump that coped reasonably well with very hot water. The seal on the hot side went eventually but was over 10yrs.

I think we'd be happy with a year

 

[gaz1]

Pump the cold feed to the combi instead of the hot out of it, just thoughts.

Bob

8ob is right you need to pump on the cold feed from the tank whilst keeping the pump cold

I have no idea i'm not really into plumbing i've just been asked to look into it.

As far as i know, there's a combi boiler downstairs, probably about 20m away. Upstairs is probably 3-4m head, there's a tank of some description, but no red pressure tank like you see on some home systems.
The bakery engineer and I fitted a plastic, fairly cheap looking booster, that sensed demand and powered up, on the tank outlet, which goes straight down through the ceiling to a big sink.

see above reference most plumbers fit from the feed side from the hot tank but as you have found out heated water destroys pumps for fun as they over heat rather well

you can fit the pump on the feed pipe closest to the tank it dosnt need to be in the loft just incase your not sure wheres best just make sure that water tank has enough water to feed into the hot water system to flow enough water down the pipes to where its been called too

other alternative that you can do is run in 25mm hot water pipe or 28mm get as close to the tap point then reduce to a smaller amount

the red pressure tank is used more on a closed pressure system not suitable for open tank systems

other alternative is pipe closer to a heated tank with the central heating and the tank feed from upstairs within a dual feed to get away from the run of the hot water

 

[Brad93]

8ob is right you need to pump on the cold feed from the tank whilst keeping the pump cold

see above reference most plumbers fit from the feed side from the hot tank but as you have found out heated water destroys pumps for fun as they over heat rather well

the red pressure tank is used more on a closed pressure system not suitable for open tank systems

other alternative is pipe closer to a heated tank with the central heating and the tank feed from upstairs within a dual feed to get away from the run of the hot water

It's a bakery, no central heating

 

[Maker]

Brewing pumps are the only pumps I know that'll take seriously hot (Boiling) water. They're hard to come by, which suggests it's only really a problem brewers have. It shouldn't take a pump with specially engineered seals to fill a sink, there has to be something wrong with their setup.

 

[gaz1]

the tank still is heated by the boilers central heating pipes it makes no difference if you add a tee and pipe over to another tank

both systems gravity fed and the red pressure vessel both tanks filled from the gravity fed system

 

[gaz1]

from the combi boiler you will have 2 pipes running to the hot water cylinder coils
these 2 pipes can be run the same way to another hot water tank via a pump like the above drawing where the radiators change to a hot water cylinder with it being 20m away the waters hotter for start off

that means that tank will only call for heat when its needed after use or every odd other day to reheat back up too temp

instead of trying to feed a 20m pipe of hot water from the tank so you loose half of the water in the tank that needs reheating again

the option is yours but cost for cost it might be easier just to fit another tank in and feed flow and return pipes i know its a cost now but it does pay for itself as they will be less usage on reheating half of a tank

the other alternative that you can do if you have a good feed cold tank is fit another combi or hot water heater so you only need gas there and a cold feed and have it closer to the point where its needed

 

[JimmyS]

It sounds like you have a combi boiler that's being used just as a ordinary boiler serving a open vented hot water cylinder which won't have a expansion vessel etc but should have a header tank either as part of the cinder or a bit higher up. If that's the case you wont be able to boost the cold water service as the tank will pump over into the header tank as its open vented. You would have to go with what you have and fit a new pump. You get 2 types of boosters of that type either pressure switch operated or flow switch operated which is the cheaper one and probably what's fitted. I would think the cold to the kitchen sink is coming off the main and the reason you get no flow from the hot is that the mains pressure is probably higher than the hot and either there's no check valves on the mixer or they are knackered and you are getting reverse flow up the hot water pipe which means the flow switch doesn't open and the pump doesn't run.

 

[dobbslc]

Stuart Turner pumps with the green motor and brass pump ends are almost indestructible. Spares are still available.

 

[JimmyS]

Probably best to set to 65 deg water temp and maybe use something like a Stuart Turner monsoon pump. If the reason the temp on the cylinder is higher than 65 is to get more hot water as can mix down with mains water at the sink then you could fit a thermostatic mixing valve to mix the cold feed into the hot before the pump which would possibly help. Issue is the mixing valve needs to be one that works OK on gravity system some need mains pressure to get decent flow and might be more bother than it's worth if it stops flow switch triggering and might cause cavitation at the pump inlet etc. The Turner pumps have a 5 yr warranty I think.

 

[JimmyS]

As dobsslc said, I type too slow lol

 

[Brad93]

It sounds like you have a combi boiler that's being used just as a ordinary boiler serving a open vented hot water cylinder which won't have a expansion vessel etc but should have a header tank either as part of the cinder or a bit higher up. If that's the case you wont be able to boost the cold water service as the tank will pump over into the header tank as its open vented. You would have to go with what you have and fit a new pump. You get 2 types of boosters of that type either pressure switch operated or flow switch operated which is the cheaper one and probably what's fitted. I would think the cold to the kitchen sink is coming off the main and the reason you get no flow from the hot is that the mains pressure is probably higher than the hot and either there's no check valves on the mixer or they are knackered and you are getting reverse flow up the hot water pipe which means the flow switch doesn't open and the pump doesn't run.

There is a header tank now come to think of it, like what you'd have in a loft

 

[JimmyS]

The header tank will be doing the cold feed to the bottom of your cylinder. Other option would be to get shot of tank and possibly header tank and fit an unvented cylinder using the mains water feed to the header tank float valve. Gets rid of pump as well but wouldn't want to run it too hot.as pressure/temp safety valve would lift. Feed to header will probably just be 1/2" but if your only serving one sink it should be fine if mains pressure is OK. In long run better than having to boost a hot water feed.

 

[Sergei Slovenija]

+110 C https://product-selection.grundfos.com/uk/categories/pumps/circulator-pumps?tab=categories

 

[RichardM]

Just a thought!
Bakery for washing down. Is the hot water supposed to be potable, certifiable against bacteria / legionella? Do any regulations cover it as it's in the food industry?