Heater casing refurbishment

[stag-gered]

Hi,

I am fairly new to the forum, so I think I am making a few mistakes. I posted some further queries (below) on the heater refurbishment on a thread that is four years old and have not received any comments or help after almost a week, so perhaps this is wrong of me to attempt this on an old thread. Although perhaps no one has any suggestions/thoughts/advice.

The old thread answered some of my queries that I had following a strip down of my heater and casing (1969 Morris) - those on fan direction being the same regardless of which way it is connected and helpful advice on type of foam to use as replacements.

No one has mentioned the sealant/seal used between the parts on re-assembly of the casing - the rear section enclosing the fan. On dismantling there was a sealant present, but it wasn't clear if this is a square section strip or just a mastic that has formed itself into a square over time. What are members using to reseal the casing please?

Secondly, I has some 'hard' foam sections fall out on dismantling - these are approx 1/2" in section and not too much of it and in short pieces - about an 1" in length. No idea where they come from, although reading Gavin's comments and reference to the Moss catalogue I wonder if they are the remnants of the 'seal - motor to casing' - Part Nr 84. Any thoughts?

Thanks,
Alan

[geoberni]

I must admit I saw it, but I have no experience of stripping a heater so carried on past.
I think since Covid, there has been a drop off in Forum posting, not just here but in general. Many people seem to have gone to more instantaneous gratification, such as fb, twitter or other platforms.

Perhaps some of our more experienced and knowledgable members will contribute...

[kevin s]

Stripping the heater is pretty straight forward just undo the screws and pull it apart, I don't remember any sealer between the halves, there is foam sealing around the matrix which sounds like your description, the foam on the flaps also falls to pieces, but it's pretty simple to glue some new foam on

[ManyMinors]

Like Kevin. I have never found any "sealant". There is some foam strip stuck here and there which could easily be sourced from a DIY store.
The same heater was used in the Mini of the same period. I'm sure that one of the Mini forums will have a tutorial on heater refurbishment?

[stag-gered]

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Thanks for your comments.

I may (or may not) have attached a couple of photos. The larger pieces are those that fell out of the heater on dismantling - they are hard but presumably once upon a time were a foam or rubber. I have all the foam strips that encompass the heater matrix and also the pieces attached to the flap. It these larger section pieces that give no clue as to their origin.

The second photo has the remnants of the sealant. I assume this was to make the compartment of the heater casing containing the fan air tight in terms of directing all the air out through the hoses and flap rather than leaking around the casing.

If I have not attached photos, could someone please explain how to do this and I will have another go!

Thanks,
Alan

[taupe]

Those are the heater foam seals as shown in the parts manual BP6 and plate P4 they are simple to replace with self adhesive foam seal available everywhere ....ebay diy stores...hardware stores etc....this sort of thing..


https://www.ebay.co.uk/itm/353746274077 ... SwkXBhesd2

Measure your crusty hardened seal as a guide to the size required....

The circular one is the motor seal 17H8612 the other seal comes with the heater matrix..there are also die cut seals on the hinged air flap

t

[stag-gered]

Thank you. It was the circular one that I was particularly uncertain of, but you have confirmed it is the motor seal and presumably closes the space between the rotating fan and the white plastic inlet pipe/tube.

Thanks again.

[engineer]

I noticed a comment on here that heater fan rotation is the same even when earth polarity is changed and that the same fresh air heater was used on Minis. I beg to differ. My S ll has had a fresh air heater from a Mini installed since 1986. I've recently converted to negative earth & the fan goes the opposite direction (found out when servicing the heater). My problem now it that I can't remember which way it should spin. Someone please tell me?

[kevin s]

It's a centrifugal fan so it works either way round which is probably what people mean when saying polarity doesn't need changing. Forward curved blades usually give a slightly better flow which would mean anti clockwise as you look at the fan, but given it earths through the case it may be easier to leave as is.

[don58van]

There are comments on here about wiring of the fan motor. There is some disagreement about whether which way the wires are connected (polarity) matters in terms of making the motor rotate in the correct direction to make the fan blow correctly.
In the case of the box-shaped Minor heaters, the answer is that it does not matter which way the wires are connected. These heaters have a motor mounted to the outside of the box. On the other hand, the Mini heaters, although looking fairly similar, have their motor mounted on the inside of the box.

Here is how the website mgguru explains why the type of Smiths motor mounted to the outside of the heater boxes will always rotate in the one (correct) direction regardless of the polarity of the connections:

When power is on, electrical current flows in one black wire, through one field coil, then through the armature, and then through the second field coil, and finally back out the other black lead wire (all in series, which is where the motor type gets its name). Changing the polarity of the input power changes the polarity of all of the magnetic fields in this motor at the same time, so the motor would continue to run in the same direction. You cannot reverse the rotation of the motor by swapping the power leads, so both of the lead wires are black, because polarity doesn't matter.

I have demonstrated this myself when restoring a Minor heater.

It may be that the internally-mounted Mini heater motor is polarity-sensitive, but I don't have information on that.

BTW, I am not persuaded by the argument that it doesn't matter which direction the motor turns because it is a centrifugal fan. Surely the blades in the squirrel cage are angled in on direction for a reason.
Don

[jaekl]

There was a time period when the ADO16s and probably Minis had heaters that had + and - marked connections. The one used depend on how the battery was earthed so that the motors ran in the correct direction. The fan motors must have had permanent magnets for the fields or something similar making the direction of the current critical. Centrifugal fans are unique in that the air flow is the in the same direction regardless of the direction of rotation, but the rate of flow is much better when rotating correctly.

[engineer]

That rings completely true . My car has a Mini heater, with the fan motor marked + & -. If the fan spins Anticlockwise (viewed on fan end) the air velocity (measured by anemometer fixed in the centre of the intake) is about 10 to 15% more than when turning clockwise. I have now assembled & fitted my heater. It may have run the wrong way since 1987 when I fitted it in place of the round recirc type.

[oliver90owner]

It's a centrifugal fan so it works either way round which is probably what people mean when saying polarity doesn't need changing. Forward curved blades usually give a slightly better flow which would mean anti clockwise as you look at the fan, but given it earths through the case it may be easier to leave as is.

Fan blades do not work the same when running backwards if they are axial blowers. Engine fan blades are the same - they should be fitted the correct way round. They still flow in the correct direction but are less efficient. Impellor fans will depend on the type of motor fitted. They won’t pump well if reversed - think typical water pumps.

[kevin s]

There are a number of papers written about the shape of blades on centrifugal fans, forward curved blades generaly give the highest flow (which as I suggested would mean the fan rotating anti clockwise) but reverse and straight also have uses and still flow a reasonable amount.

Using the motor out of something more modern would probably be a good upgrade, the TR7 one is powerfull and looks similar.