Posted: Fri Mar 21, 2014 1:39pm

Hi, The narrow boat we've just brought doesn't have central heating, which is not a problem, but I would like to have a heated towel rail/radiator in the bathroom. I would like something simple and not too expensive so think using the hot water from the engine or calorifier is probably the best way to go. I know this will mean that the rail is only heated when the engine is running, but that is better than nothing. What would be the best way to achieve this? Would it also be possible to insert a small radiator, in the pipe run to the towel rail, at the bottom of the area we hang our coats to help air/dry them? Regards John

Posted: Fri Mar 21, 2014 2:52pm

First of all please understand that most engines, but not all, take the hot water to heat the calorifier from the engine side of the thermostat so the more things like radiators and towel rails you put in that circuit the greater the chance that you will overcool the engine so it is not operating at optimum efficiency and it may reduce the engine’s life. However some common engines that normally run with an 80 degree + thermostats in general use appear perfectly satisfactory using a 62 degree one. If by any chance your boat is one of the many with an undersized skin tank size then doing so may be an advantage. This does not apply to the few engines that use twin thermostats to control the flow to the skin tank and calorifier. Next you need to consider how far away from the engine the towel rail and radiator will be. The further away the less likely it is that you will have a satisfactory outcome. It will be important that the pipes you use are at least 22mm and larger still will be better. This is to reduce the resistance the engine water pump has to work against to circulate the water through the system. You will need the engine header tank water level to be higher that the bleed point on the radiator, towel rail and any you insert into high points in the new pipework. Otherwise it may well prove impossible to bleed the air out of that circuit. There may be ways around this but they are likely to introduce more problems. If you do try it then send the hot water to the calorifier first and then organise a valve so you can isolate the rail and radiator in the summer yet still return the flow to the engine for re-heating. There are alternatives that involve another header tank, a pump, and heat exchanger but what you propose is the simplest. If by chance your engine has a heat exchanger core in its manifold (or you can buy one) you could use this to heat the water for the radiator etc but it will need another pump and its own header tank. Tony Brooks

Posted: Tue Mar 25, 2014 9:31pm

Hi Tony, Thank you for your response. More questions and issues to think about than answers, but that is good. I was aware of overheating an engine, but had never heard of over-cooling it. Although I said I was looking for something simple and not too expensive I would rather spend a couple of hundred pounds than risk a damaged engine. I assume that using a heat exchanger and separate pump would work? and as the water feeding the towel rail would be in a closed system, separate from the water in the engine, there would be no problem with the engine or the engine water pump. If this type of system is OK would the heat exchanger go in the pipe between the calorifier and the skin tank? does it matter where in the system the pump was fitted? Could the pump be wired to the ignition system, so that it ran when the engine was switched on? I also assume that a header tank is still needed and the system should be filled with an antifreeze mixture? Sorry for all these questions, but I don't want to keep coming back with follow up questions so hope I've covered everything.

Posted: Wed Mar 26, 2014 4:38pm

Before you go planning to spend loads of money please ponder on the fact that when you ask for a written answer I have to protect myself and the magazine by pointing out possible pitfalls. Please think about why I told you that some "marine" engines run with 62 degree thermostats perfectly happily when the same engine in another application would run with an 82 degree thermostat. Ostensibly that marine version is being overcooled but it seems to cause few in any discernible problems. It is simply not prudent for me to tell you to go ahead and try your plan and everything will be OK because it possibly may not be. Especially as you have not told me anything about your engine so I have no idea if its one of those twin thermostat ones would make the potential over-cooling cease to exist ones. You have also given me no idea about length of pipe runs involved or the height of the bleed points on the towel rail and radiator relative to the engine header tank. My duty of care to you means that I have to caution you about the pitfalls so you can make an informed decision. If you are intent on pursuing this project you will have lost nothing by trying the simple set-up first and see how well it works and what temperature the engine actually runs at. You will also find out if the engine actually produces enough heat when on canals to serve the calorifier, radiator and towel rail. If there is not enough heat (nothing gets as hot as it should) then you could loose the radiator. You would only have to go to the complications of a heat exchanger in the main keel cooling circuit, extra header tank & pump If the engine did run excessively cool. I know what I would do in your shoes but I simply can not assurer you that all will be fine.

Posted: Sun Mar 30, 2014 5:02pm

Hi Tony, Thanks again for your considered response. My engine is a Barrus Shire (2005) 40hp, which does have a twin thermostat. The skin tank is 7 sq ft (which I understand is slightly undersized for a 40hp engine). The pipe run is about 25ft in each direction say 60 foot in total, allowing for the length of tubing in the towel rail. I am prepared to try the system and see if it works OK. I just have one final question and please excuse my ignorance, but how would I measure the operating temperature of the engine?

Posted: Sun Mar 30, 2014 7:26pm

I am pleased you made this decision. I don't believe in spending more money that necessary. Use 22mm pipe for the new runs. I have absolutely no worries about the engine operating temperature, the twin thermostat should ensure it does not over-cool. I would have thought a Barrus Shire would have come supplied with an engine temperature gauge but if not look out for a cheap infra-red thermometer that you can "point" at the cylinder head. Give it a go, keep the top of the radiator and towel rail below the header tank level and I am sure it will all be fine. Tony Brooks