Calorifier Servicing

Urquhart

Urquhart

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I am doing some servicing in preparation for the season ahead, and to gain access to some pipework, I removed my calorifier from its mounted position. Having found it necessary to disconnect the pipework and electrical connections to do this, I thought it would be a good idea to remove the calorifier from the boat and service it. I've given it a general clean-up on the outside, but am at a slight loss to know how best to go about de-scaling it.

Does anyone have advice about a suitable product and/or method?

...and has anyone tried fitting a de-scaling supply line to enable the introduction of water with de-scaler directly into the calorifier in situ without contaminating the potable water system?

(Neither a 'search' here, nor consultation of Nigel Calder's excellent books yielded suitable answers).
 
I've never heard of anyone descaling a calorifier and, to be honest, I'm not convinced it would need it. How often do you descale your hot water tank at home?
 
Thank you both.

Yes, it is the same scale. But there are differences:

First, there will be a lot of it;
Secondly, domestic products work best if the appliance is brought up to operating temperature, hence my thought about additional plumbing to facilitate flushing with a suitable agent while the calorifier is in service. I would be very interested if anyone has tried this out.
 
pvb,

The quantity of scale which came out when it was simply inverted and flushed was most impressive. I seek to gain the best from my sailing, and that includes being assured of the readiest access to plentiful hot water. My home hot water tanks are not routinely descaled; perhaps they should be, in the interests of efficiency..?
 
Thank you, paladin, that may be a worthwhile resource. However, the page seems to load incorrectly and then crashes. Perhaps I will telephone them tomorrow.
 
[ QUOTE ]
My home hot water tanks are not routinely descaled; perhaps they should be, in the interests of efficiency..?

[/ QUOTE ]Yes, I think you should address that as a matter of urgency. /forums/images/graemlins/wink.gif
 
[ QUOTE ]
I've never heard of anyone descaling a calorifier and, to be honest, I'm not convinced it would need it. How often do you descale your hot water tank at home?

[/ QUOTE ]
I recently had to open up my calorifier to fix a leak and it was absolutely choked with limescale. Had been fitted about 10 years ago according to the date of manufacture. I used a combination of chipping and dilute hydrochloric acid that worked well - but the hot water is still discoloured /forums/images/graemlins/frown.gif
 
As one of the previous posts suggested, the best descaler IMO is Fernox DS-3 - see the following link:

http://www.fernox.com/index.php?cccpage=ds3

But do be careful and follow the instructions well, descaling can sometimes remove deposits that seal crevices and leaks! Fill the cylinder to test for leaks before re-installing once de-scaled.

I certainly wouldn't bother with any passive/active descaling system, just descale and thoroughly flush through every 2-3 years! Depends on local water conditions of course.
 
John,

In order to descale every two or three years, have you fitted any additional plumbing? Or do you disconnect the inlet side hose? Or do you de-scale the entire water system? If so, how?

I am considering installing an extra branch, to a tap, on the cold water inlet of the calorifier, so that I might attach a suitable funnel and introduce de-scaler routinely, without disturbing the permanent plumbing, or contaminating the potable water side with chemicals.
 
I have never descaled my entire HW system, I would not expect to do so unless I was certain there was a problem.

But to answer your question, you could always do something simple like this:

Descale.jpg


1) Close A and B and Open DOC (Drain Off Cock) to relieve system pressure and drain the cylinder, when initial pressure is relieved open C to let air in until most of the water is drained from cylinder.

2) Close DOC and fill cylinder with descale solution until full, then close C. I suppose you could then open the taps and B to allow descaler to enter the pipe system. You may need to open A to drive it through but then close it and top up descaler if necessary. Close A as soon as you can to stop any back flow (I dont like the idea of opening A much just to fill pipes!)

3) When descaler has done its job flush the system through thoroughly by opening taps, B then A.

There are other fancy methods using pumps and dosing pots but the above should suffice IMO. /forums/images/graemlins/cool.gif
 
John,

I'm very grateful to you. You drew more or less exactly what I had in mind - and a picture paints a thousand words!

I have re-installed the calorifier and it is working well. I shall probably modify the plumbing when I have a little more free time.

To close this discussion, I have one further question. I assumed that the coolant which circulates to the calorifier is the same coolant which resides in the engine header tank, and that having lost some fluid whern I removed the calorifier, I needed to top off the header tank and wait for it to drain down.

However, following a brief engine run this evening, there is no evidence of the additional coolant in the header tank flowing down into the calorifier. All pipes became appropriately hot with the engine running.

The engine is a Volvo MD22, the yacht is a Beneteau.

Can anyone help?
 
[ QUOTE ]
However, following a brief engine run this evening, there is no evidence of the additional coolant in the header tank flowing down into the calorifier. All pipes became appropriately hot with the engine running.

The engine is a Volvo MD22, the yacht is a Beneteau.

Can anyone help?

[/ QUOTE ]
I have the same engine and after refitting my calorifier and running the engine the coolant level had hardly dropped at all which suggests that the volume in the calorifier pipes is a very small proportion of the whole.

My calorifier also had a lot of limey sludge that may not be totally dissolved by descalant. I would suggest your drain/flushing taps should be large enough to cope. I would also be very reluctant to flush all that gunge through the normal pipework.
 
Thank you for that good input.

When I next take the calorifier out, I shall measure the quantity. For now I guess it is about 250-500 ml, and this would be in accord with your observation.

I spoke to a reputable marine engineer today, who suggested bleeding the system as follows:

Be cautious thoughout the process which follows that the engine and pipework do not reach temperatures which may be injurious:

Start engine;
Release upper coolant connection on calorifier until definite flow presents, then resecure;
Release LOWER coolant connection on engine until definite flow presents, then resecure;
Top up coolant.

I am not content with this process, as the business of breaking the seals on properly made up hose connections is unprofessional. Bleeding should be done with bleed screws and the like, designed in at the apropriate positions on the system.

However, if my present approach (letting nature take its course and topping up the coolant from time to time) seems wanting, I shall revisit it.

When I re-organise the plumbing, I shall make provision for workmanlike bleeding of the coolant circuit.

My final thought for now is that, with a horizontally-mounted calorifier, it will be almost impossible to bleed the consumer water side properly; there will always be a void above the hot water, and the losses involved (in terms of efficiency and volume of hot water) must be considerable. I am surprised that the estimable Mr Calder does not make mention of this in his excellent books, and I may be moved to write to him about it.

Thank you all again for your helpful comments.
 
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