central heating pump

[Pete & Helen]

How long can you keep your CH pump running? I have a solid fuel stove with back boiler and want to keep a fire in but worried that the pump isn't man enough to stay running all the time. its a standard domestic 240v pump

[NMEA]

How long can you keep your CH pump running? I have a solid fuel stove with back boiler and want to keep a fire in but worried that the pump isn't man enough to stay running all the time. its a standard domestic 240v pump

Assuming you have power for it then almost indefinately, they run for years without issue.

[Alf27]

I think it depends on your batteries rather than your pump ! our household ch pump often runs 24/7 we have been here 11 years so far, without problems, the pump on the boat is an Aldi unit on the ch boiler which also runs the water around which is heated by the back boiler, this also runs 24/7 during the heating season without problem.

The only thing I have found with back boilers is a build up of air in the system, which if left unvented could be a problem.

Edited October 12, 2013 by Alf27

[mango]

My domestic CH pump is over 30 years old and has worked faultlessly. Having run it on batteries via an inverter during an extended power cut, I know it uses quite a lot more power than a small 12 volt pump.

[Pete & Helen]

Hi, thanks for the reassuring comments. I'm on shore power so not a problems with the battery at the moment but will have to give that issue some thought when cruising. Its a standard Grundfos domestic CH pump. Might have to think about changing to, or running a parallel 12 volt pump. Any suggestions on manufacturer/model. My system is Morse Squirrel with back boiler feeding 2 rads at the back of the boat (57ft) and then through the hot water tank.

 

Thanks Pete

[Ex- Member]

We have a Wilo 240v CH smart pump A efficiency it draws just 0.4 amps on our amp meter, which I recall when I contacted the manufacturer when purchasing several years ago they also quoted 0.4 amps. We only need the lowest setting too so it will unlikely go over that. Considering the stove is 50f/t away from the batteries I really wonder if 12v is any more efficient.

[George94]

We have a Wilo 240v CH smart pump A efficiency it draws just 0.4 amps on our amp meter, which I recall when I contacted the manufacturer when purchasing several years ago they also quoted 0.4 amps. We only need the lowest setting too so it will unlikely go over that. Considering the stove is 50f/t away from the batteries I really wonder if 12v is any more efficient.

 

0.4 amps at 240 volts = 8 amps at 12 volts. I think my pump is more like 2. A boat doesn't need such a powerful pump as a house does.

[bizzard]

Solid fuel stoves are an uncontrollable heat source unlike oil, gas ect. so you really need to have the hot water cylinder or calorifier (primary circuit) plumbed in by the thermo-syphon method using as large a feed pipes as possible as a bit of safety heat sink. If its not and is pumped and the pump fails for whatever reason the whole lot can boil and erupt causing a big mess. Ideally its best for the radiators to thermo-syphon too for added safety but these can be pumped.

If you rely on a pump to keep the whole system happy I'd keep a big bag of salt handy to chuck on the fire to kill it in an emergency if the pump fails.

[Pete & Helen]

Current measured on mine is about 140-160mA AC. It is a worry having a pump failure so have been contemplating a change to thermo-syphon. although its piped with 25 or 28mm copper the runs are low level and the calorifier is at the opposite end of the boat and opposite side to the back boiler. As the rads are on the same side I was thinking of having the rads thermo-syphon and the calorifer on a pump, which would also help the rads but if it failed all I would loose is hot water. I think I have only got about 30cm between the top of the back boiler top connection and the rads, Q. would that sort of rise give me thermo-syphoning?

[Supertramp]

As bizzard says, a back boiler can get nasty if the pump fails on a 'non' syphon system.

I have the 240v Wilo pump, works great and is virtually silent.

As a backup, I have a Jabesco 12v pump in line as well.

 

My dog is sometimes on the boat alone with the fire and back boiler hot. - so to protect her -

I have added a couple of relays and remote thermostatic switches which ensure the 240v pump runs when required, but if the mains fails or is unavailable, the 12v pump switches in.

An additional separate safety circuit switches in the 12v pump if the boiler reaches a higher temp, - this covers the 240v pump failing.

[bizzard]

Current measured on mine is about 140-160mA AC. It is a worry having a pump failure so have been contemplating a change to thermo-syphon. although its piped with 25 or 28mm copper the runs are low level and the calorifier is at the opposite end of the boat and opposite side to the back boiler. As the rads are on the same side I was thinking of having the rads thermo-syphon and the calorifer on a pump, which would also help the rads but if it failed all I would loose is hot water. I think I have only got about 30cm between the top of the back boiler top connection and the rads, Q. would that sort of rise give me thermo-syphoning?

Ideally the calorifier needs to be mounted higher than the stoves back boiler,(say in an airing cupboard) for the most reliable and best therm-syphon circulation and avoid sharp right angled elbow bends they impede the flow and act like brakes on the circulations flow, bend the pipe or use large radius elbows.

[Pete & Helen]

Ideally the calorifier needs to be mounted higher than the stoves back boiler,(say in an airing cupboard) for the most reliable and best therm-syphon circulation and avoid sharp right angled elbow bends they impede the flow and act like brakes on the circulations flow, bend the pipe or use large radius elbows.

Cant manage that as the caorifier is opposite corner and the pipes would have to run under the rear doorway so at best would only be half the height of the back boiler and would need at least 1 90 bend. I'm hoping that the rads will give enough flow in the case of pump failure

[bizzard]

Cant manage that as the caorifier is opposite corner and the pipes would have to run under the rear doorway so at best would only be half the height of the back boiler and would need at least 1 90 bend. I'm hoping that the rads will give enough flow in the case of pump failure.

 

 

Keep the bag of salt handy.

[smileypete]

There's 12V 100°C solar circulation pumps on Ebay from about £15-25, cheap enough to have a spare and don't need an inverter, eg:

 

http://www.ebay.co.uk/itm/12V-DC-Electric-Centrifugal-Brushless-Water-Pump-Low-Noise-f-Aquarium-Hot-Water-/290985553141

http://www.ebay.co.uk/itm/12-Volt-Hot-Water-Pump-12v-10w-PV-Solar-Panel-Brewing-Boat-Irrigation-etc-/141080192704?pt=UK_Sound_Vision_Other

 

If air tends to collect in the pipes a mains pump should be powerful enough to push it out, so maybe worth retaining it as a backup and put a 12V one inline with it.

 

cheers, Pete.

~smpt~

Edited October 14, 2013 by smileypete

[Pete & Helen]

Thanks all for the info and words of wisdom

[MtB]

Keep the bag of salt handy.

Why do you specify salt? Surely sand is just as effective and a whole lot easier to obtain in the large quantity needed to extinguish a roaring stove.

 

Are you suggesting salt interferes with combustion chemically perhaps?

 

 

MtB

[Alastair]

I think he meant as in "A very very very large pinch of salt".

 

The pumps that SmileyPete linked to would be dangerous:

 

"The pump will automatically slow to protect itself when the motor temperature increases beyond rated temperature (95°C /203°F)"

[MtB]

I think he meant as in "A very very very large pinch of salt".

 

 

I don't think so, Bizz has mentioned before using salt to extinguish a runaway stove. I disagree and think sand is better, having had to do it for real once!

 

MtB

[bizzard]

 

I don't think so, Bizz has mentioned before using salt to extinguish a runaway stove. I disagree and think sand is better, having had to do it for real once!

 

MtB

Agree sand is as good but unless its been bought in specially for that purpose, and most people don't think ahead like that, but they would almost always have a packet seasoning salt onboard. Large polythene bags of table salt can be bought quite cheaply at supermarkets.

[smileypete]

I think he meant as in "A very very very large pinch of salt".

 

The pumps that SmileyPete linked to would be dangerous:

 

"The pump will automatically slow to protect itself when the motor temperature increases beyond rated temperature (95°C /203°F)"

 

Well spotted, I only added the second linky to that one as an afterthought as I thought it would be a better quality option

 

Of course it's best not to have pumped only in the first place, but if needs must it'd be well worth having a second pump plumbed in and ready in case the first fails.

 

I don't really like advising on something that isn't done the generally accepted 'best way', it just ends up trying to reliably solve the shortcomings on something which may never be as good as it could or should be.

 

cheers, Pete.

~smpt~

Edited October 14, 2013 by smileypete

[Alastair]

Yeah, I have to agree, Pete.

There is a reason why those traditional methods are 'traditional'.

[Pete & Helen]

Yeah, I have to agree, Pete.

There is a reason why those traditional methods are 'traditional'.

Had I had the choice so would I but the CH came like that when I purchased the boat, and like other boat modifications its not always an easy job

[smileypete]

Yeah, I have to agree, Pete.

There is a reason why those traditional methods are 'traditional'.

 

Don't get me wrong, I love experimental stuff and new ideas, but best do so when the *rse kicking consequences aren't too great!

 

Had I had the choice so would I but the CH came like that when I purchased the boat, and like other boat modifications its not always an easy job

 

Yeah, not easy when buying a not new boat, they're rarely perfect to say the least...

 

cheers, Pete.

~smpt~

Edited October 14, 2013 by smileypete

[George94]

Keep the bag of salt handy.

 

Flour works well too, if you don't have any salt. However, if you don't use enough to quench the fire, it will become fuel too.

[Alastair]

Flour! Seriously, that has to be one of the worst suggestions I've ever heard.

 

No, No and No.