Reversed Flow Through Oil Fired Boiler

John T Carroll

Neighbour got a new Grant SE Boiler and new circ pump installed 6 years ago. He had mentioned to me a few times that he would find the Boiler tripped on the overtemperature stat which had/has to be reset by removing a small cover and pressing the reset. The problem had got more frequent last year, mainly when he would come to fire it up in the morning. I had a look at it a few weeks ago and found that the circ pump, installed in the outlet (Flow) from the Boiler was actually pumping into the Boiler, this resulted in the Return being the hottest and of course as the boiler thermostat was now at the "wrong" end resulted in the odd trip or two. I wouldnt say that this is the first or last time that this has happened but the neighbour is a bit worried if it had any adverse effect on the life of the Boiler, I told him probably not as it was still forced circulation, the heat was still being removed, the only other difference that I can see is that his hot water cylinder coil was heating from the bottom up. Needles to say, he got the pump (flow) reversed and has had no more trips over the past ten days or so.

Dtp1979

John T Carroll wrote: »

Neighbour got a new Grant SE Boiler and new circ pump installed 6 years ago. He had mentioned to me a few times that he would find the Boiler tripped on the overtemperature stat which had/has to be reset by removing a small cover and pressing the reset. The problem had got more frequent last year, mainly when he would come to fire it up in the morning. I had a look at it a few weeks ago and found that the circ pump, installed in the outlet (Flow) from the Boiler was actually pumping into the Boiler, this resulted in the Return being the hottest and of course as the boiler thermostat was now at the "wrong" end resulted in the odd trip or two. I wouldnt say that this is the first or last time that this has happened but the neighbour is a bit worried if it had any adverse effect on the life of the Boiler, I told him probably not as it was still forced circulation, the heat was still being removed, the only other difference that I can see is that his hot water cylinder coil was heating from the bottom up. Needles to say, he got the pump (flow) reversed and has had no more trips over the past ten days or so.

Your best bet would be to ring Grant themselves and explain this to them. If you do, please let us know what they said.

John T Carroll

Dtp1979 wrote: »

Your best bet would be to ring Grant themselves and explain this to them. If you do, please let us know what they said.

The guy I spoke to at Grants this morning wasn't worried about the boiler he said, it was the system pipework that might fail if the water temperature(s) reached 110C which is the high level (over) temperature trip setting. My neighbours system is gravity fed so the maximum head at the boiler is in the region of 20 Feet or 0.6 Bar at 15C which is about 0.57 Bar at 110C. there is approx. 1 meter of copper pipe on both the Flow and Return, the rest is Qualpex who say that their product is good for 92C at 3 Bar "with short term overload temperatures up to 114C".

Wearb

Grant aren't worried about their boiler, that isn't the same as saying that it's ok to do it this way.
I am just adding this info lest some thinks that Grant are suggesting that it's ok to plumb it that way. They aren't saying that that sort of plumbing is ok. They are just saying that their boiler can stand up to that abuse.

John T Carroll

Wearb wrote: »

Grant aren't worried about their boiler, that isn't the same as saying that it's ok to do it this way.
I am just adding this info lest some thinks that Grant are suggesting that it's ok to plumb it that way. They aren't saying that that sort of plumbing is ok. They are just saying that their boiler can stand up to that abuse.

Yes Wearb, I should have clearly emphasised that, so thanks for doing so. I suppose installers have their own method of checking that they have installed the pump correctly as due to space restrictions etc it can be very difficult to see the directional arrow or the bottom of the pump which will identify the inlet branch, the problem can be a bit insidious. When I looked at the installation involved, the pump label was "right way up" and I couldnt see the arrow but by feeling the back of the pump I could determine that it was wrong way round, it was then very easy to confirm this by firing up the boiler for ten minutes or so and just feeling the flow and return.

Wearb

John T Carroll wrote: »

Wearb wrote: »

Grant aren't worried about their boiler, that isn't the same as saying that it's ok to do it this way.
I am just adding this info lest some thinks that Grant are suggesting that it's ok to plumb it that way. They aren't saying that that sort of plumbing is ok. They are just saying that their boiler can stand up to that abuse.

Yes Wearb, I should have clearly emphasised that, so thanks for doing so. I suppose installers have their own method of checking that they have installed the pump correctly as due to space restrictions etc it can be very difficult to see the directional arrow or the bottom of the pump which will identify the inlet branch, the problem can be a bit insidious. When I looked at the installation involved, the pump label was "right way up" and I couldnt see the arrow but by feeling the back of the pump I could determine that it was wrong way round, it was then very easy to confirm this by firing up the boiler for ten minutes or so and just feeling the flow and return.

A sort of dentists mirror came with some bit of gear that I bought and can be handy for looking in hard to see places.
As for my post, reading back on it, it was sort of unnecessary. Your post was clear enough.