Jump to content

Radiator system not functioning well


Daltonia

Featured Posts

In my boat, a Webasto Thermo Top C supplies heat to the radiator system. There are six radiators plus a towel rack. The header tank, in the gas locker, is topped up with water/antifreeze. The Webasto appears to be functioning OK but only some of the radiators are heating, and they heat up slowly. Below is an image of one that is not heating. The radiator two taps are both turned on fully. When I bleed it (at 1) the water that emerges only drips very slowly (i.e. very little pressure). The pipe at 2 gets hot. The pipe at 3 stays cold, as does the radiator. Any ideas on how I may find the problem please?

post-25277-0-03840100-1475168376_thumb.jpg

Link to comment
Share on other sites

Well if that was a domestic system then I would suspect gunk blocking the rads and pipes or the pump not functioning properly. Problem is domestic systems are much easier to fault and more importantly cheaper to sort out. What I used to do with my radiators on my boat, when I had it, was to back flush the system. having said that I only two radiators on my boat that I had installed. The heat came from the engine cooling system directly and I had installed isolating valves so that when my heating system stopped working I could just turn off the valves, disconnect the pipes and connect a couple of hoses and turn on the shorline tap. That would backflush all the gunk out.

Link to comment
Share on other sites

Bearing in mind your other thread, I suggest that loop to the calorifier has the gate valve wide open so all the circulation is going round the calorifier. Shut that valve right down and try again. What is the height difference between the top of the radiator and the header tank? If it's in the gas locker then perhaps it's only slightly above the radiator top?

Edited by nicknorman
Link to comment
Share on other sites

Bearing in mind your other thread, I suggest that loop to the calorifier has the gate valve wide open so all the circulation is going round the calorifier. Shut that valve right down and try again.

Yes, I tried that after reading your other post, but no difference.

 

What is the height difference between the top of the radiator and the header tank? If it's in the gas locker then perhaps it's only slightly above the radiator top?

The highest point in the radiator system is the top of the towel rack. The top of the towel rack lies about 30 cm below the current water level in the header tank. The top of most of the radiators lies about 50 cm below the current water level in the header tank.

Link to comment
Share on other sites

The highest point in the radiator system is the top of the towel rack. The top of the towel rack lies about 30 cm below the current water level in the header tank. The top of most of the radiators lies about 50 cm below the current water level in the header tank.

That perhaps explains why you don't get much flow out of the bleed valve, 30-50cm is not a huge head, although imsuppose it depends on what you mean by a dribble.

 

Do you know that age of the plumbing / radiators? Unless they are pretty old I'd doubt it's all gunged up.

 

Anyway a few thoughts: there is quite a volume of water in the system and it might take 30 mins or so to get properly hot.

 

The heat has to be going somewhere so is the heater running steadily, or cutting in and out? If the former, it's probably just that it takes longer than you think to heat up. If the latter, something is blocked.

 

We have seen the gate valve that throttles the calorifier loop but perhaps there is a similar valve elsewhere that throttles the radiator loop - if so maybe this valve is not fully open?

 

Radiators are typically plumbed in parallel and so there can be poor flow to the distant radiators. This is what the second valve in each radiator is for - balancing the system. Typically the radiator nearest the heater would be quite well shut down, progressively further away rads more opened until finally the furthest rad would be set fully open. If one rad won't heat up, try partially closing the vales on the rads that do get hot.

 

Finally, that silencer is dangerous. Do you have a CO alarm? If not please get one! And if you don't, don't run the heater until you get the silencer repaired.

Edited by nicknorman
Link to comment
Share on other sites

I would be minded to shut the valves on the calorifier circuit and on all but the furthest radiator, and see if the furthest radiator gets hot that way. If it doesn't you definitely have an air lock or a blockage somewhere.

 

If does get hot, then open the valves on the other radiators, with successively less opening the closer you get to the boiler. All radiators should get hot (or warm). Compare the outlet pipe temperatures - if cooler than the rest open the valve a fraction, if hotter, close it a bit until all the outlets are at the same temperature. Then you should have a balanced system.

Link to comment
Share on other sites

Many thanks for the replies. In response to the various queries:

The boat is only two years old.

The heater is cutting in and out when running, heating for a few minutes then cutting out for a few minutes.

I cannot find a gate valve that throttles the radiator loop.

 

I shut off the calorifier loop and all radiators except the very furthest. On this last radiator the inlet and outlet pipes heat up and the bottom of the radiator. The top of the radiator is warm, but not as hot as the bottom. When I open the bleed valve nothing comes out, neither air nor water.

 

Whilst fiddling with the radiators and switching the heating on and off I have noticed the water level in the header tank going up and down by 10 cm or more, sometimes overflowing into the gas locker.

 

Any further thoughts please?

Link to comment
Share on other sites

I agree - there is an airlock in the system. Are the bleed valves towards the stern of the boat? Most narrow boats sit nose-up, stern down. If the bleed valves are towards the stern, it is possible that air is trapped at the other ends of the radiators and you will not get it out without either changing the boat to nose down, stern up or reversing the radiators. Can you change the boat's attitude?

Link to comment
Share on other sites

Sounds like its riding on air. I'd turn the heater up to full to get the system as hot as possible and to get a bit of pressure up and then bleed the rads, start from the nearest rad and work to the furthest away. start the engine up too to help heat the colorifier if you can't switch the Webasto circuit out of it. Then balance the rads.

Link to comment
Share on other sites

Is a Webasto Thermo Top C big enough to power 6 radiators like this + a towel rail + a calorifier?

Obviously that would depend on the spec of the rads, but if around 6kw (calorifier irrelevant) then plenty man enough.

Personally I'd be dumping the header and converting to a proper pressurised system, also what concentration is the A/F?

Link to comment
Share on other sites

Personally I'd be dumping the header and converting to a proper pressurised system, also what concentration is the A/F?

Well, after fiddling for hours trying to get air out of this gravity system, and still at it, a pressurised system sounds very appealing indeed. What kit would be needed for a conversion? The water/antifreeze mixture I have put in is 75/25, as suggested by the Webasto manual. I've no idea what was put in before I bought the boat. I guess if I bleed a sample of fluid off the system, the overall antifreeze concentraiton could be checked somehow?

Link to comment
Share on other sites

What I find interesting is how a boater with basic tools can test and the refill as required a pressurised system. You are not filling with pure water like you do the pressure vessels on domestic boilers.

 

Personally I would avoid an boat based boiler that demanded a pressurised system. However I seem to recall seeing what NMEA say in manufacturers documents.

 

I can not see how pressurising the system would help with bleeding trapped air. It would be far more effective to find out where the air is trapped and fit a bleed point there. If a pressurised system is fitted we come back to how it is to be topped up using basic tools.

Link to comment
Share on other sites

Well, after fiddling for hours trying to get air out of this gravity system, and still at it, a pressurised system sounds very appealing indeed. What kit would be needed for a conversion? The water/antifreeze mixture I have put in is 75/25, as suggested by the Webasto manual. I've no idea what was put in before I bought the boat. I guess if I bleed a sample of fluid off the system, the overall antifreeze concentraiton could be checked somehow?

Did you drain it before adding the antifreeze?

Link to comment
Share on other sites

No, I mixed water/antifreeze (75/25) and added it via the header tank as the water level dropped when bleeding air from the radiators.

That could be part of your problem as the different densities of liquid in the radiator its self, especially if the inlet to the radiator is getting hot.

Link to comment
Share on other sites

Has it always been bad, or is it a change. If always poor performance, maybe you need a pumped system, though it does sound like you have an air lock. I would drain out lots of liquid from the highest point, keeping the header tank full to ensure the air bubble is found and eliminated.

Link to comment
Share on other sites

 

What I find interesting is how a boater with basic tools can test and the refill as required a pressurised system. You are not filling with pure water like you do the pressure vessels on domestic boilers.

 

Personally I would avoid an boat based boiler that demanded a pressurised system. However I seem to recall seeing what NMEA say in manufacturers documents.

 

I can not see how pressurising the system would help with bleeding trapped air. It would be far more effective to find out where the air is trapped and fit a bleed point there. If a pressurised system is fitted we come back to how it is to be topped up using basic tools.

 

It's very simple Tony, on install one fills the rads and tube with the AF mixture via the 1/2" openings at the top before installing the blank and bleed screw, the pressure system is just for pressurising and very little water is used during that process. Draining down when it's time to change the A/F is just the same. Inhibitor top up is again simple using a pressurised disposable canister. No special tools are ever needed and all that is required of the owner is to check the pressure gauge and top up from time to time if need be, but if there are no leaks re pressurising is rarely needed after the first few days.

Link to comment
Share on other sites

Well, after fiddling for hours trying to get air out of this gravity system, and still at it, a pressurised system sounds very appealing indeed. What kit would be needed for a conversion?

You just need a pressure vessel and filling loop kit which you tee into the return tube close to the heater if possible and also teed into the potable supply, kits are available, cheaper than a Webaso or Eber header tank into the bargain. I like pressurised systems for many reasons, not least because the siting of radiators is not governed by the height of the tank which gives more choice and better use of space, even up to fitting cieling height but narrow radiators and tall towel rads.

https://www.mrcentralheating.co.uk/evolve-expansion-vessel-kit?utm_source=google_shopping&gclid=Cj0KEQjw4MK_BRC1n6KTtezikbIBEiQA872hYboHgtlbU4ATgasQXhhZz0YY9AijmDo1Ra4WJ2de8jYaAhbt8P8HAQ#.V_DfFSgrIuE

 

And

https://www.mrcentralheating.co.uk/expansion-vessel-heating-5-litre#.V_DfhigrIuE

Edited by NMEA
Link to comment
Share on other sites

 

Deleted.

 

I still think its a lot of messing about for little gain.

 

Much more than a little gain Tony, frees one up to plan the install without any positioning and height constraints. I wouldn't use anything else for a new install.

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.