Installing a small radiator/towel rail in my hot water piping system

[Karen Lea Rainey]

Hi All,

There is currently no heating on my trad boat with the exception of a multi fuel stove, the bathroom in the middle of the boat needs a bit of warmth adding.

The engine is a Lister HRW2 with a small calorifier fitted, the piping from the calorifier routes through the bathroom at  skirting board height en route to the bathroom tap and galley hot water taps, and I'm thinking I might be able to put a small towel rail in the bathroom by re routing the flow of water via the towel rail.

Obviously it the hot tap system.

Currently the hot water is piping hot even after an hour of running the engine, there is a skin tank on the  other side of the boat and the engine is in it's own mid boat room.

And if so should I 'T off' the radiator/ towel rail so that it can be isolated/ turned off if necessary.

[David Mack]

If you do that the radiator will only get warm when you run a hot tap. Better to fit the radiator in the return pipe from the calorifier back to the engine, as discussed in this thread.

 

[Karen Lea Rainey]

Would the radiator not get any radial heat, the rubber hose inside the skirting board certainly feels quite warm when the engine has been running.

To put the radiator into the engine return hose, ( would I then need to T off that hose in 2 joints) with a flow and return pipe?

I understand that car heater hose would probably do the job, but want to avoid to many hoses coming through the engine room wall/inner bulkhead frame.

[Alan de Enfield]

But you will then be running your potable water thru a (potentially) rusty radiator (as you obviously cannot put antifreeze and rust inhibitor in the system)

Not what I'd consider to be a good idea. Have a shower and get a coating of rust, wash the pots and get rusty streaks on them.

Edited December 7, 2022 by Alan de Enfield

[Tony Brooks]

23 minutes ago, Karen Lea Rainey said:

Would the radiator not get any radial heat, the rubber hose inside the skirting board certainly feels quite warm when the engine has been running.

To put the radiator into the engine return hose, ( would I then need to T off that hose in 2 joints) with a flow and return pipe?

I understand that car heater hose would probably do the job, but want to avoid to many hoses coming through the engine room wall/inner bulkhead frame.

 

The problem in your post is that it is far from clear that you understand how your system works/is piped up.

 

Your calorifier will have four pipes/hoses on it. One very low down and that is the cold domestic water inlet. One very high up which is the domestic hot water outlet. There may also be a hose on a PRV with a plastic knob on it. None of these hoses will do what you want.

 

There will be two more hoses/pipes connected close to the center of the calorifier. These direct hot coolant to the calorifier and back to the engine. Your radiator needs to go into the return one as David M says. To identify it, it will be the hose that connects to the engine in a position that allows it to join the main coolant flow back into the engine water pump. Alternatively feel the pipes on the claorifier while the engine is warming up. One will be close to engine temperature and one will be much cooler to start with. That cooler one is the one to break into for the radiator.

 

I would comment that to make it easier to bleed the top of the radiator/towel rain should be lower than the coolant level in the engine header tank (possibly the exhaust manifold).

 

 

Edited December 7, 2022 by Tony Brooks

[Alan de Enfield]

5 minutes ago, Tony Brooks said:

The problem in your post is that it is far from clear that you underpants how your system works/is piped up.

 

Ain't predictive spelling a wonderful thing.

[Tony Brooks]

Thanks both, now corrected.

[jonathanA]

I would suggest that the problem with what Tony is suggesting is that you will not be able to turn off the radiator only and if you do the calorifier won't get hot either (or won't continue to heat up). 

It may be better to fit the radiator across the calorifier coil so that you can turn the radiator on and off as required. Doing this will potentially slow down how quickly the hot water comes up to temp and you may need to adjust the flow through the rad by closing down one of the rad valves (lock shield valve usually) to balance this. Of course you can just turn the rad off until the hot water is heated. 

This is probably easier to do too as all you need to do is fit a tee in the engine coolant to calorifier pipes and run new pipes from the tees to rad.  

[David Mack]

3 hours ago, Karen Lea Rainey said:

To put the radiator into the engine return hose, ( would I then need to T off that hose in 2 joints) with a flow and return pipe?

If you T off you will need valves to control whether the hot water goes through the radiator (when you want heat in the bathroom) or bypasses it (when you don't). Or you could just plumb it in series with the calorifier so it is always on. Simpler, but not ideal. Or you could fit a fan heater as in the thread I linked to earlier, which could be plumbed in series, with the fan only switched on when you want heat.

[jonathanA]

Exactly as I suggested in the post above yours...

 

The valves will be on the radiator simples 

Edited December 7, 2022 by jonathanA

[Karen Lea Rainey]

Thanks all,

I understand now how to fit the towel rail in the system,

'On return to engine from calorifier ' T 'off with a open /close valve for when not in use.

Thank you for your knowledge guys.

[David Mack]

41 minutes ago, jonathanA said:

Exactly as I suggested in the post above yours...

 

The valves will be on the radiator simples 

You will also need a valve on the short cut past the radiator, otherwise most of the hot water will go straight past.

[Tony Brooks]

9 minutes ago, David Mack said:

You will also need a valve on the short cut past the radiator, otherwise most of the hot water will go straight past.

 

In fact you might not, it will all depend upon flow. After all we don't put a valve in the calorifier pipe yet in most cases the skin tank does not short out the calorifier (I know the engine thermostat will play a part, but not with a hot engine when you have drawn off a lot of hot water).

 

Very much suck it and see. Also we find having a heated towel rail to keep keep the towels dry and warm, even in summer, is nice. If it gets too hot then just drape more towels over to to keep the heat in.

[Bod]

11 hours ago, Karen Lea Rainey said:

Hi All,

There is currently no heating on my trad boat with the exception of a multi fuel stove, the bathroom in the middle of the boat needs a bit of warmth adding.

The engine is a Lister HRW2 with a small calorifier fitted, the piping from the calorifier routes through the bathroom at  skirting board height en route to the bathroom tap and galley hot water taps, and I'm thinking I might be able to put a small towel rail in the bathroom by re routing the flow of water via the towel rail.

Obviously it the hot tap system.

Currently the hot water is piping hot even after an hour of running the engine, there is a skin tank on the  other side of the boat and the engine is in it's own mid boat room.

And if so should I 'T off' the radiator/ towel rail so that it can be isolated/ turned off if necessary.

There are only 2 ways of doing what you want.

1. putting the rad in the hot water tap pipes.  The rad will only heat up when a hot tap is running.

2. putting the rad in the calorifier heating circuit.  The rad will only heat up whilst the engine is running, and may drain heat away from the hot water tank when the engine is not running.

 

Bod

[Tony Brooks]

9 hours ago, Bod said:

may drain heat away from the hot water tank when the engine is not running.

 

That should have been resolved already, otherwise the engine would be draining heat from the calorifier. Sometimes reversing the in and out hoses on the calorifier sorts it or a correctly orientated NRV in the circuit sorts it.

[Tracy D'arth]

10 hours ago, Bod said:

There are only 2 ways of doing what you want.

1. putting the rad in the hot water tap pipes.  The rad will only heat up when a hot tap is running.

2. putting the rad in the calorifier heating circuit.  The rad will only heat up whilst the engine is running, and may drain heat away from the hot water tank when the engine is not running.

 

Bod

Oh NO!     Don't do it!  If you put the rad in a fresh water pipe, hot or not it will rot away in days and put rust in the system. Steel radiators will not work on fresh water.

1 hour ago, Tony Brooks said:

 

That should have been resolved already, otherwise the engine would be draining heat from the calorifier. Sometimes reversing the in and out hoses on the calorifier sorts it or a correctly orientated NRV in the circuit sorts it.

If the flow pipe is taken to the lower connection of the coil, you will not get reverse circulation and the coil will vent air much easier.

[cuthound]

On 07/12/2022 at 11:25, Karen Lea Rainey said:

Hi All,

There is currently no heating on my trad boat with the exception of a multi fuel stove, the bathroom in the middle of the boat needs a bit of warmth adding.

The engine is a Lister HRW2 with a small calorifier fitted, the piping from the calorifier routes through the bathroom at  skirting board height en route to the bathroom tap and galley hot water taps, and I'm thinking I might be able to put a small towel rail in the bathroom by re routing the flow of water via the towel rail.

Obviously it the hot tap system.

Currently the hot water is piping hot even after an hour of running the engine, there is a skin tank on the  other side of the boat and the engine is in it's own mid boat room.

And if so should I 'T off' the radiator/ towel rail so that it can be isolated/ turned off if necessary.

 

I fitted a Screwfix chrome heated towel rail to my youngest son's flat. Within 5 years the chrome was rusting badly and Screwfix claimed it wasn't covered by the warranty because it had been used in a damp environment! Not sure where you are supposed to use them if not in bathrooms.

 

Anyway I replaced it with a stainless steel towel rail which cost 5 times the price, which after a further 5 years still looks as good as new.

[Alan de Enfield]

1 minute ago, cuthound said:

 

I fitted a Screwfix chrome heated towel rail to my youngest son's flat. Within 5 years the chrome was rusting badly and Screwfix claimed it wasn't covered by the warranty because it had been used in a damp environment! Not sure where you are supposed to use them if not in bathrooms.

 

Anyway I replaced it with a stainless steel towel rail which cost 5 times the price, which after a further 5 years still looks as good as new.

 

Many years ago when we had a static caravan at the coast, No1 Son wanted to camp-out with a couple of friends and as they were there for the Summer Holidays we bought a tent and pitched it in front of the caravan but the other side of the stream so it was 'on a desert island'.

Anyway - long story short - after about 3 weeks the tent started to fall apart as the material 'sort of shredded'. Contacted the shop we bought it from and they said, sorry, it has been used in Sunlight and man-made materials (it was Nylon) degrade in Sunlight. No warranty.

[David Mack]

I remember my mother taking my sister's new school shoes back to the shop as they were beginning to fall apart after a few days. "Well, your daughter has been wearing them in the rain, hasn't she" was the shop's response!

[Karen Lea Rainey]

Hi All, radiator fitted to the wall,  5/8  16mm heater hose purchased, T pieces 16mm, circlips and small piece of 15mm copper pipe purchased to join the valves to the hose at the radiator.

My final question before cutting into the return pipe from the calorifier to the water pump is,

 

Do I put 2 T piece joints into the return coil hose from the calorifier, i.e 1 hose coming from either end of the radiator ?

(Would this increase the chance of water flow through the radiator ?)

Or do I put 1 T piece joint in the return coil hose, then T off a single pipe route either side of the radiator ?

 

I'm  just struggling to understand how any flow of hot water going through the radiator can be achieved by T ing into a single return hose to the engine.

Will it just be a case of 'radiated' heat finding it's way into the additional water capacity of the engine, coil, radiator and skin tank.

 

Thank you for your replies, keith

Edited January 11, 2023 by Karen Lea Rainey
Spelling

[Tacet]

Two pipes from the return should work but one is unlikely to be effective.

If you want to be posh you could put a full bore valve in the bit of pipe that bypasses the rad.  If it is sluggish to warm it then gives the option of throttling back to increase the flow though the rad, but it should be ok without.

[Tracy D'arth]

2 tees into the return pipe as far apart as the valves on the radiator. You may need to put a full flow valve into the return pipe between the tees that you can close down to throttle the flow in that pipe to increase the water going through the radiator but try it without first.

The radiator will work better if the tee at the end closest to the calorifier is connected to the top tapping on the radiator rather than the bottom. I would try it with that thermostatic valve but suspect it may be better with a manual valve.

[ditchcrawler]

47 minutes ago, Tacet said:

 

If you want to be posh you could put a full bore valve in the bit of pipe that bypasses the rad.  

I wouldnt do that if they keep the thermostatic valve on the rad as when the bathroom is hot you would throttle the flow through the colorifier

[jonathanA]

Which is why I advocated connecting the rad in parallel across the cauliflower. Simples....

 

 

 

 

 

 

[Sea Dog]

4 hours ago, jonathanA said:

Which is why I advocated connecting the rad in parallel across the cauliflower. Simples....

 

 

 

 

 

 

My engine heated bathroom towel rail type rad is in the return line after the cauliflower using 2 tees. I sized the rad height to ensure I wasn't introducing a high spot above the rest of the system to prevent an airlock.

 

Between the tees is a full bore valve so that the flow through the rad can be full or adjusted for balance. The full flow could also be opened  to give full bypass should the rad valves be closed, either because the heat is not required or for maintenance. This bypass also gave me the option to be quickly revert to stock if my idea didn't work.

 

In practice I was surprised to find the rad works perfectly with the full bore bypass valve fully open so there it has stayed along with all the others and the rad is effectively simply added in parallel with the return line.  The engine is quite happy and so is the rad which remains in use all year round.