Central heating set up issues

[Katie]

29 minutes ago, Tony Brooks said:

Back to the OP's question.

 

Being a mains pump that often drive the impeller by magnetic induction, I wonder if it has seized up, our one at home use to over the summer and needed a thump to get it spinning. Even when stuck, it used to hum at mains frequency. If this has happened, maybe the hum makes the OP think it's running.

Well I had already ordered a new pump as seemed most likely thing that was wrong so was going to get a plumber friend to fit that but I am now awaiting a quote to refit the system to be gravity fed as I much prefer the sound of this if it’s easy enough to do. I never liked the idea that I had to have enough battery to run my stove safely, especially as it’s 240v. I don’t think this set up is that unsafe but would prefer one less thing to worry about. 
 

Unfortunately having never worked on a boat before or fit a gravity fed system my friend isn’t keen on messing about with my boat so will have to pay to get someone in but worth it for safer (working) heating! 
 

will have to see if I can send back the new pump if gravity pipe work is successfully installed. 
 

thanks for all the input folks. I’m sure the pump system would be fine if I got it running properly but may aswell change it to what would work best for me while I’m having to fix it anyway. 

[Ronaldo47]

In 1976, before putting in central heating in my first house, I read all the books on the subject in my local.public library. One was an excellent DIY guide written by the National Coal Board, who were apparently pioneers in domestic small bore central heating. The book included extensive  information about designing gravity central heating systems,  mostly based on using back boilers. I do not remember the title. 

 

 

 

 

[Tracy D'arth]

26 minutes ago, Ronaldo47 said:

In 1976, before putting in central heating in my first house, I read all the books on the subject in my local.public library. One was an excellent DIY guide written by the National Coal Board, who were apparently pioneers in domestic small bore central heating. The book included extensive  information about designing gravity central heating systems,  mostly based on using back boilers. I do not remember the title. 

 

 

 

 

The solid fuel advisory body ran courses for heating engineers which we used as part of out training program. It was an excellent course, defining good practice and accurate design through detailed heat loss calculation and accurate pipe and radiator sizing. 

Systems were both pumped and gravity, accurate sizing guaranteeing proper safe performance. 

 

[Ronaldo47]

In the book I read, iron pipework was used. No check valves were used on the rads, and to balance the system, the pipe diameters were selected to provide the necessary flow resistances in each branch. 

[Tracy D'arth]

16 minutes ago, Ronaldo47 said:

In the book I read, iron pipework was used. No check valves were used on the rads, and to balance the system, the pipe diameters were selected to provide the necessary flow resistances in each branch. 

True but dated. That would apply to large systems where the availability of many sizes in iron pipe were the norm.

We are discussing tiny heating systems on boats, not massive municipal heating systems.

 

But the rules do apply to a lesser extent. The use of balancing lock shield valves on radiators mitigates much of the sizing design.

 

The flow resistance of pipework is  a limiting factor in gravity circulation systems which leads in instances of sloppy design to the use of seriously oversized pipes.

I have very rarely had to resort to using 28mm pipe in any boat installation that I have designed, 22mm and 15mm being the only sizes used.

[Ronaldo47]

The book was specifically directed at the d.i.y. installer of domestic heating systems using solid fuel back boilers  with, from memory, pipe sizes from 1 1/4" down to 1/4" for a small bedroom rad which would only require minimal heating.  

 

I found I got gravity circulstion in my pumped system with the pump turned off, and a heating engineer I spoke to said that smooth copper pipes have a much lower flow resistance than internally-rough iron pipes of  the same internal diameter. I could have fitted a spring-loaded valve  to prevent gravity flow,  but I had fitted  thermostatic radiator valves to the upstairs rooms anyway, and turning off the pump provided enough  gentle  background heating for the downstairs hall radiator (the only one with top and bottom flow and return connections) to take the chill off.  

 

I had designed my system in the 1970's oil crisis and 3 day week power cuts era, and had designed my pipework ( 22mm, with 15mm  branches to the rads ) on gravity circulation principles (continuous fall of pipes rather than horizontal, and slow bends wherever possible by bending the pipes rather than using sharp right angle elbows)  so that some heating would still be available by powering the gas back-boiler's 24V electrics from a battery and  not using the pump.  In the event the energy crisis was over by the time I had finished putting the system in, but manually switching off the pump demonstrated that my  design was sound.

Edited September 24, 2021 by Ronaldo47
typos